Diff: rfc9114.form.xml

	rfc9114.form.xml	rfc9114.xml

	<?xml version="1.0" encoding="UTF-8"?>	<?xml version='1.0' encoding='UTF-8'?>
		<!DOCTYPE rfc [
	<!-- [CS] updated by Chris 03/25/21 -->	<!ENTITY nbsp " ">
		<!ENTITY zwsp "">
	<!-- [rfced] draft submitted in xml v3 -->	<!ENTITY nbhy "‑">
		<!ENTITY wj "⁠">
	<!-- generated by https://github.com/cabo/kramdown-rfc2629 version 1.3.24 -->	]>
		<rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft
	<!DOCTYPE rfc SYSTEM "rfc2629-xhtml.ent">	-ietf-quic-http-34" number="9114" obsoletes="" updates="" submissionType="IETF"
		category="std" consensus="true" xml:lang="en" tocInclude="true"
	<?rfc toc="yes"?>
	<?rfc sortrefs="yes"?>
	<?rfc symrefs="yes"?>
	<?rfc docmapping="yes"?>

	<rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft
	-ietf-quic-http-34" number="0000" obsoletes="" updates="" submissionType="IETF"
	category="std" consensus="true" xml:lang="en" tocInclude="true"
	sortRefs="true" symRefs="true" version="3">	sortRefs="true" symRefs="true" version="3">

		<link href='https://datatracker.ietf.org/doc/draft-ietf-quic-http-latest' rel=
	<!-- xml2rfc v2v3 conversion 3.5.0 -->	'prev'/>
	<front>	<front>

	<title abbrev="HTTP/3">Hypertext Transfer Protocol Version 3 (HTTP/3)</title	<title>HTTP/3</title>
	>	<seriesInfo name='RFC' value='9114'/>
	<seriesInfo name="RFC" value="0000"/>	<author fullname='Mike Bishop' initials='M.' role='editor' surname='Bishop'>
	<author initials="M." surname="Bishop" fullname="Mike Bishop" role="editor">
	<organization>Akamai</organization>	<organization>Akamai</organization>
	<address>	<address>
	<email>mbishop@evequefou.be</email>	<email>mbishop@evequefou.be</email>
	</address>	</address>
	</author>	</author>

	<date year="2021" month="March"/>	<date month='May' year='2022'/>
	<area>Transport</area>	<area>Transport</area>
	<workgroup>QUIC</workgroup>	<workgroup>QUIC</workgroup>

		<keyword>HTTP/2</keyword>
	<!-- [rfced] Please insert any keywords (beyond those that appear in the	<keyword>HPACK</keyword>
	title) for use on https://www.rfc-editor.org/search. -->	<keyword>QPACK</keyword>
		<keyword>Web</keyword>
	<keyword>example</keyword>

	<abstract>	<abstract>
	<t>The QUIC transport protocol has several features that are desirable in a	<t>The QUIC transport protocol has several features that are desirable in a
	transport for HTTP, such as stream multiplexing, per-stream flow control, and	transport for HTTP, such as stream multiplexing, per-stream flow control, and
	low-latency connection establishment. This document describes a mapping of HTTP	low-latency connection establishment. This document describes a mapping of HTTP
	semantics over QUIC. This document also identifies HTTP/2 features that are	semantics over QUIC. This document also identifies HTTP/2 features that are

	subsumed by QUIC, and describes how HTTP/2 extensions can be ported to HTTP/3.</ t>	subsumed by QUIC and describes how HTTP/2 extensions can be ported to HTTP/3.</t >
	</abstract>	</abstract>

	<note>
	<name>DO NOT DEPLOY THIS VERSION OF HTTP</name>
	<t>DO NOT DEPLOY THIS VERSION OF HTTP/3 UNTIL IT IS IN AN RFC. This versio
	n is
	still a work in progress. For trial deployments, please use earlier versions.</t
	>
	</note>
	<note>
	<name>Note to Readers</name>
	<t>Discussion of this draft takes place on the QUIC working group mailing
	list
	(quic@ietf.org), which is archived at
	<eref target="https://mailarchive.ietf.org/arch/search/?email_list=quic"/>.</t>
	<t>Working Group information can be found at <eref target="https://github.
	com/quicwg"/>; source
	code and issues list for this draft can be found at
	<eref target="https://github.com/quicwg/base-drafts/labels/-http"/>.</t>
	</note>
	</front>	</front>
	<middle>	<middle>

	<section anchor="introduction" numbered="true" toc="default">	<section anchor='introduction'>
	<name>Introduction</name>	<name>Introduction</name>

	<t>HTTP semantics (<xref target="RFCYYY4" format="default"/>) are used for	<t>HTTP semantics (<xref target='RFC9110'/>) are used for a broad range of
	a broad	services on the
	range of services on the Internet. These semantics have most commonly been used	Internet. These semantics have most commonly been used with HTTP/1.1 and HTTP/2.
	with HTTP/1.1 and HTTP/2. HTTP/1.1 has been used over a variety of transport	HTTP/1.1 has been used over a variety of transport and session layers, while
	and session layers, while HTTP/2 has been used primarily with TLS over TCP.	HTTP/2 has been used primarily with TLS over TCP. HTTP/3 supports the same
	HTTP/3 supports the same semantics over a new transport protocol, QUIC.</t>	semantics over a new transport protocol: QUIC.</t>
	<section anchor="prior-versions-of-http" numbered="true" toc="default">	<section anchor='prior-versions-of-http'>
	<name>Prior versions of HTTP</name>	<name>Prior Versions of HTTP</name>
	<t>HTTP/1.1 (<xref target="I-D.ietf-httpbis-messaging" format="default"/	<t>HTTP/1.1 (<xref target='RFC9112'/>) uses whitespace-delimited text fi
	>) uses whitespace-delimited text	elds to convey HTTP
	fields to convey HTTP messages. While these exchanges are human-readable, using	messages. While these exchanges are human readable, using whitespace for
	whitespace for message formatting leads to parsing complexity and excessive	message formatting leads to parsing complexity and excessive tolerance of
	tolerance of variant behavior.</t>	variant behavior.</t>
	<t>Because HTTP/1.1 does not include a multiplexing layer, multiple TCP connections	<t>Because HTTP/1.1 does not include a multiplexing layer, multiple TCP connections
	are often used to service requests in parallel. However, that has a negative	are often used to service requests in parallel. However, that has a negative
	impact on congestion control and network efficiency, since TCP does not share	impact on congestion control and network efficiency, since TCP does not share
	congestion control across multiple connections.</t>	congestion control across multiple connections.</t>

	<t>HTTP/2 (<xref target="RFC7540" format="default"/>) introduced a binar y framing and multiplexing layer	<t>HTTP/2 (<xref target='RFC9113'/>) introduced a binary framing and mul tiplexing layer
	to improve latency without modifying the transport layer. However, because the	to improve latency without modifying the transport layer. However, because the
	parallel nature of HTTP/2's multiplexing is not visible to TCP's loss recovery	parallel nature of HTTP/2's multiplexing is not visible to TCP's loss recovery
	mechanisms, a lost or reordered packet causes all active transactions to	mechanisms, a lost or reordered packet causes all active transactions to
	experience a stall regardless of whether that transaction was directly impacted	experience a stall regardless of whether that transaction was directly impacted
	by the lost packet.</t>	by the lost packet.</t>
	</section>	</section>

	<section anchor="delegation-to-quic" numbered="true" toc="default">	<section anchor='delegation-to-quic'>
	<name>Delegation to QUIC</name>	<name>Delegation to QUIC</name>
	<t>The QUIC transport protocol incorporates stream multiplexing and per- stream flow	<t>The QUIC transport protocol incorporates stream multiplexing and per- stream flow
	control, similar to that provided by the HTTP/2 framing layer. By providing	control, similar to that provided by the HTTP/2 framing layer. By providing
	reliability at the stream level and congestion control across the entire	reliability at the stream level and congestion control across the entire
	connection, QUIC has the capability to improve the performance of HTTP compared	connection, QUIC has the capability to improve the performance of HTTP compared

	to a TCP mapping. QUIC also incorporates TLS 1.3 (<xref target="RFC8446" format ="default"/>) at the	to a TCP mapping. QUIC also incorporates TLS 1.3 (<xref target='TLS'/>) at the
	transport layer, offering comparable confidentiality and integrity to running	transport layer, offering comparable confidentiality and integrity to running
	TLS over TCP, with the improved connection setup latency of TCP Fast Open	TLS over TCP, with the improved connection setup latency of TCP Fast Open

	(<xref target="RFC7413" format="default"/>).</t>	(<xref target='TFO'/>).</t>
	<t>This document defines HTTP/3, a mapping of HTTP semantics over the QU	<t>This document defines HTTP/3: a mapping of HTTP semantics over the QU
	IC	IC
	transport protocol, drawing heavily on the design of HTTP/2. HTTP/3 relies on	transport protocol, drawing heavily on the design of HTTP/2. HTTP/3 relies on
	QUIC to provide confidentiality and integrity protection of data; peer	QUIC to provide confidentiality and integrity protection of data; peer
	authentication; and reliable, in-order, per-stream delivery. While delegating	authentication; and reliable, in-order, per-stream delivery. While delegating

	stream lifetime and flow control issues to QUIC, a binary framing similar to the	stream lifetime and flow-control issues to QUIC, a binary framing similar to the
	HTTP/2 framing is used on each stream. Some HTTP/2 features are subsumed by	HTTP/2 framing is used on each stream. Some HTTP/2 features are subsumed by
	QUIC, while other features are implemented atop QUIC.</t>	QUIC, while other features are implemented atop QUIC.</t>

	<t>QUIC is described in <xref target="RFCYYY1" format="default"/>. For	<t>QUIC is described in <xref target='QUIC-TRANSPORT'/>. For a full des
	a full description of HTTP/2, see	cription of
	<xref target="RFC7540" format="default"/>.</t>	HTTP/2, see <xref target='RFC9113'/>.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="http3-protocol-overview" numbered="true" toc="default">	<section anchor='http3-protocol-overview'>
	<name>HTTP/3 Protocol Overview</name>	<name>HTTP/3 Protocol Overview</name>
	<t>HTTP/3 provides a transport for HTTP semantics using the QUIC transport protocol	<t>HTTP/3 provides a transport for HTTP semantics using the QUIC transport protocol
	and an internal framing layer similar to HTTP/2.</t>	and an internal framing layer similar to HTTP/2.</t>
	<t>Once a client knows that an HTTP/3 server exists at a certain endpoint, it opens	<t>Once a client knows that an HTTP/3 server exists at a certain endpoint, it opens
	a QUIC connection. QUIC provides protocol negotiation, stream-based	a QUIC connection. QUIC provides protocol negotiation, stream-based
	multiplexing, and flow control. Discovery of an HTTP/3 endpoint is described in	multiplexing, and flow control. Discovery of an HTTP/3 endpoint is described in

	<xref target="discovery" format="default"/>.</t>	<xref target='discovery'/>.</t>
	<t>Within each stream, the basic unit of HTTP/3 communication is a frame	<t>Within each stream, the basic unit of HTTP/3 communication is a frame

	(<xref target="frames" format="default"/>). Each frame type serves a different	(<xref target='frames'/>). Each frame type serves a different purpose. For exa
	purpose. For example, HEADERS	mple, <xref format='none' target='frame-headers'>HEADERS</xref><iref item='HEADE
	and DATA frames form the basis of HTTP requests and responses	RS'/>
	(<xref target="request-response" format="default"/>). Frames that apply to the	and <xref format='none' target='frame-data'>DATA</xref><iref item='DATA'/> frame
	entire connection are	s form the basis of HTTP requests and responses
	conveyed on a dedicated control stream.</t>	(<xref target='request-response'/>). Frames that apply to the entire connection
	<t>Multiplexing of requests is performed using the QUIC stream abstraction	are
	,	conveyed on a dedicated <xref format='none' target='control-streams'>control str
	described in <xref section="2" sectionFormat="of" target="RFCYYY1" format="defau	eam</xref><iref item='control stream'/>.</t>
	lt"/>. Each request-response pair	<t>Multiplexing of requests is performed using the QUIC stream abstraction
		, which
		is described in <xref section='2' sectionFormat='of' target='QUIC-TRANSPORT'/>.
		Each request-response pair
	consumes a single QUIC stream. Streams are independent of each other, so one	consumes a single QUIC stream. Streams are independent of each other, so one
	stream that is blocked or suffers packet loss does not prevent progress on other	stream that is blocked or suffers packet loss does not prevent progress on other
	streams.</t>	streams.</t>

	<t>Server push is an interaction mode introduced in HTTP/2 (<xref target=" RFC7540" format="default"/>) that	<t>Server push is an interaction mode introduced in HTTP/2 (<xref target=' RFC9113'/>) that
	permits a server to push a request-response exchange to a client in anticipation	permits a server to push a request-response exchange to a client in anticipation
	of the client making the indicated request. This trades off network usage	of the client making the indicated request. This trades off network usage
	against a potential latency gain. Several HTTP/3 frames are used to manage	against a potential latency gain. Several HTTP/3 frames are used to manage

	server push, such as PUSH_PROMISE, MAX_PUSH_ID, and CANCEL_PUSH.</t>	server push, such as <xref format='none' target='frame-push-promise'>PUSH_PROMIS E</xref><iref item='PUSH_PROMISE'/>, <xref format='none' target='frame-max-push- id'>MAX_PUSH_ID</xref><iref item='MAX_PUSH_ID'/>, and <xref format='none' target ='frame-cancel-push'>CANCEL_PUSH</xref><iref item='CANCEL_PUSH'/>.</t>
	<t>As in HTTP/2, request and response fields are compressed for transmissi on.	<t>As in HTTP/2, request and response fields are compressed for transmissi on.

	Because HPACK (<xref target="RFC7541" format="default"/>) relies on in-order tra nsmission of	Because HPACK (<xref target='HPACK'/>) relies on in-order transmission of
	compressed field sections (a guarantee not provided by QUIC), HTTP/3 replaces	compressed field sections (a guarantee not provided by QUIC), HTTP/3 replaces

	HPACK with QPACK (<xref target="RFCYYY2" format="default"/>). QPACK uses separat e unidirectional streams to	HPACK with QPACK (<xref target='RFC9204'/>). QPACK uses separate unidirectional streams to
	modify and track field table state, while encoded field sections refer to the	modify and track field table state, while encoded field sections refer to the
	state of the table without modifying it.</t>	state of the table without modifying it.</t>

	<section anchor="document-organization" numbered="true" toc="default">	<section anchor='document-organization'>
	<name>Document Organization</name>	<name>Document Organization</name>
	<t>The following sections provide a detailed overview of the lifecycle o f an HTTP/3	<t>The following sections provide a detailed overview of the lifecycle o f an HTTP/3
	connection:</t>	connection:</t>

	<ul spacing="normal">	<ul spacing='normal'>
	<li>Connection Setup and Management (<xref target="connection-setup" f	<li>"<xref format='title' target='connection-setup'/>" (<xref target='
	ormat="default"/>) covers how an HTTP/3	connection-setup'/>) covers how an HTTP/3
	endpoint is discovered and an HTTP/3 connection is established.</li>	endpoint is discovered and an HTTP/3 connection is established.</li>

	<li>HTTP Request Lifecycle (<xref target="http-request-lifecycle" form at="default"/>) describes how HTTP	<li>"<xref format='title' target='http-request-lifecycle'/>" (<xref ta rget='http-request-lifecycle'/>) describes how HTTP
	semantics are expressed using frames.</li>	semantics are expressed using frames.</li>

	<li>Connection Closure (<xref target="connection-closure" format="defa	<li>"<xref format='title' target='connection-closure'/>" (<xref target
	ult"/>) describes how HTTP/3 connections	='connection-closure'/>) describes how HTTP/3
	are terminated, either gracefully or abruptly.</li>	connections are terminated, either gracefully or abruptly.</li>
	</ul>	</ul>
	<t>The details of the wire protocol and interactions with the transport are	<t>The details of the wire protocol and interactions with the transport are
	described in subsequent sections:</t>	described in subsequent sections:</t>

	<ul spacing="normal">	<ul spacing='normal'>
	<li>Stream Mapping and Usage (<xref target="stream-mapping" format="de	<li>"<xref format='title' target='stream-mapping'/>" (<xref target='st
	fault"/>) describes the way QUIC streams	ream-mapping'/>) describes the way QUIC streams
	are used.</li>	are used.</li>

	<li>HTTP Framing Layer (<xref target="http-framing-layer" format="defa	<li>"<xref format='title' target='http-framing-layer'/>" (<xref target
	ult"/>) describes the frames used on	='http-framing-layer'/>) describes the frames used
	most streams.</li>	on most streams.</li>
	<li>Error Handling (<xref target="errors" format="default"/>) describe	<li>"<xref format='title' target='errors'/>" (<xref target='errors'/>)
	s how error conditions are handled and	describes how error conditions are handled and
	expressed, either on a particular stream or for the connection as a whole.</li>	expressed, either on a particular stream or for the connection as a whole.</li>
	</ul>	</ul>
	<t>Additional resources are provided in the final sections:</t>	<t>Additional resources are provided in the final sections:</t>

	<ul spacing="normal">	<ul spacing='normal'>
	<li>Extensions to HTTP/3 (<xref target="extensions" format="default"/>	<li>"<xref format='title' target='extensions'/>" (<xref target='extens
	) describes how new capabilities can be	ions'/>) describes how new capabilities can be
	added in future documents.</li>	added in future documents.</li>
	<li>A more detailed comparison between HTTP/2 and HTTP/3 can be found in	<li>A more detailed comparison between HTTP/2 and HTTP/3 can be found in

	<xref target="h2-considerations" format="default"/>.</li>	<xref target='h2-considerations'/>.</li>
	</ul>	</ul>
	</section>	</section>

	<section anchor="conventions-and-terminology" numbered="true" toc="default ">	<section anchor='conventions-and-terminology'>
	<name>Conventions and Terminology</name>	<name>Conventions and Terminology</name>
	<t>The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp 14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL	<t>The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp 14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
	NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECO MMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",	NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECO MMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
	"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to be i nterpreted as	"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to be i nterpreted as
	described in BCP 14 <xref target="RFC2119" format="default"/> <xref target= "RFC8174" format="default"/> when, and only when, they	described in BCP 14 <xref target="RFC2119" format="default"/> <xref target= "RFC8174" format="default"/> when, and only when, they
	appear in all capitals, as shown here.</t>	appear in all capitals, as shown here.</t>
	<t>This document uses the variable-length integer encoding from	<t>This document uses the variable-length integer encoding from

	<xref target="RFCYYY1" format="default"/>.</t>	<xref target='QUIC-TRANSPORT'/>.</t>
	<t>The following terms are used:</t>	<t>The following terms are used:</t>
	<dl>	<dl>

	<dt>	<dt>abort:</dt>
	abort: </dt>
	<dd>	<dd>
	<t>An abrupt termination of a connection or stream, possibly due to an error	<t>An abrupt termination of a connection or stream, possibly due to an error
	condition.</t>	condition.</t>
	</dd>	</dd>

	<dt>	<dt>client:</dt>
	client: </dt>
	<dd>	<dd>
	<t>The endpoint that initiates an HTTP/3 connection. Clients send H TTP requests	<t>The endpoint that initiates an HTTP/3 connection. Clients send H TTP requests
	and receive HTTP responses.</t>	and receive HTTP responses.</t>
	</dd>	</dd>

	<dt>	<dt>connection:</dt>
	connection: </dt>
	<dd>	<dd>

	<t>A transport-layer connection between two endpoints, using QUIC as the	<t>A transport-layer connection between two endpoints using QUIC as the
	transport protocol.</t>	transport protocol.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='errors'>connection error</xref><iref i
	connection error: </dt>	tem='connection error'/>:</dt>
	<dd>	<dd>
	<t>An error that affects the entire HTTP/3 connection.</t>	<t>An error that affects the entire HTTP/3 connection.</t>
	</dd>	</dd>

	<dt>	<dt>endpoint:</dt>
	endpoint: </dt>
	<dd>	<dd>
	<t>Either the client or server of the connection.</t>	<t>Either the client or server of the connection.</t>
	</dd>	</dd>

	<dt>	<dt>frame:</dt>
	frame: </dt>
	<dd>	<dd>
	<t>The smallest unit of communication on a stream in HTTP/3, consist ing of a	<t>The smallest unit of communication on a stream in HTTP/3, consist ing of a
	header and a variable-length sequence of bytes structured according to the	header and a variable-length sequence of bytes structured according to the

	frame type.	frame type.</t>
	</t>
	<t>Protocol elements called "frames" exist in both this document and	<t>Protocol elements called "frames" exist in both this document and

	<xref target="RFCYYY1" format="default"/>. Where frames from <xref target="RFCYY	<xref target='QUIC-TRANSPORT'/>. Where frames from <xref target='QUIC-TRANSPORT'
	Y1" format="default"/> are referenced, the	/> are referenced, the
	frame name will be prefaced with "QUIC." For example, "QUIC CONNECTION_CLOSE	frame name will be prefaced with "QUIC". For example, "QUIC CONNECTION_CLOSE
	frames." References without this preface refer to frames defined in	frames". References without this preface refer to frames defined in
	<xref target="frames" format="default"/>.</t>	<xref target='frames'/>.</t>
	</dd>	</dd>

	<dt>	<dt>HTTP/3 connection:</dt>
	HTTP/3 connection: </dt>
	<dd>	<dd>
	<t>A QUIC connection where the negotiated application protocol is HT TP/3.</t>	<t>A QUIC connection where the negotiated application protocol is HT TP/3.</t>
	</dd>	</dd>

	<dt>	<dt>peer:</dt>
	peer: </dt>
	<dd>	<dd>
	<t>An endpoint. When discussing a particular endpoint, "peer" refer s to the	<t>An endpoint. When discussing a particular endpoint, "peer" refer s to the
	endpoint that is remote to the primary subject of discussion.</t>	endpoint that is remote to the primary subject of discussion.</t>
	</dd>	</dd>

	<dt>	<dt>receiver:</dt>
	receiver: </dt>
	<dd>	<dd>
	<t>An endpoint that is receiving frames.</t>	<t>An endpoint that is receiving frames.</t>
	</dd>	</dd>

	<dt>	<dt>sender:</dt>
	sender: </dt>
	<dd>	<dd>
	<t>An endpoint that is transmitting frames.</t>	<t>An endpoint that is transmitting frames.</t>
	</dd>	</dd>

	<dt>	<dt>server:</dt>
	server: </dt>
	<dd>	<dd>
	<t>The endpoint that accepts an HTTP/3 connection. Servers receive HTTP requests	<t>The endpoint that accepts an HTTP/3 connection. Servers receive HTTP requests
	and send HTTP responses.</t>	and send HTTP responses.</t>
	</dd>	</dd>

	<dt>	<dt>stream:</dt>
	stream: </dt>
	<dd>	<dd>
	<t>A bidirectional or unidirectional bytestream provided by the QUIC transport.	<t>A bidirectional or unidirectional bytestream provided by the QUIC transport.

	All streams within an HTTP/3 connection can be considered "HTTP/3 streams,"	All streams within an HTTP/3 connection can be considered "HTTP/3 streams",
	but multiple stream types are defined within HTTP/3.</t>	but multiple stream types are defined within HTTP/3.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='errors'>stream error</xref><iref item=
	stream error: </dt>	'stream error'/>:</dt>
	<dd>	<dd>
	<t>An application-level error on the individual stream.</t>	<t>An application-level error on the individual stream.</t>
	</dd>	</dd>
	</dl>	</dl>

	<t>The term "content" is defined in <xref section="6.4" sectionFormat="o f" target="RFCYYY4" format="default"/>.</t>	<t>The term "content" is defined in <xref section='6.4' sectionFormat='o f' target='RFC9110'/>.</t>
	<t>Finally, the terms "resource", "message", "user agent", "origin serve r",	<t>Finally, the terms "resource", "message", "user agent", "origin serve r",

	"gateway", "intermediary", "proxy", and "tunnel" are defined in <xref section="3 " sectionFormat="of" target="RFCYYY4" format="default"/>.</t>	"gateway", "intermediary", "proxy", and "tunnel" are defined in <xref section='3 ' sectionFormat='of' target='RFC9110'/>.</t>
	<t>Packet diagrams in this document use the format defined in	<t>Packet diagrams in this document use the format defined in

	<xref section="1.3" sectionFormat="of" target="RFCYYY1" format="default"/> to il lustrate the order and size of fields.</t>	<xref section='1.3' sectionFormat='of' target='QUIC-TRANSPORT'/> to illustrate t he order and size of fields.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="connection-setup" numbered="true" toc="default">	<section anchor='connection-setup'>
	<name>Connection Setup and Management</name>	<name>Connection Setup and Management</name>

	<section anchor="discovery" numbered="true" toc="default">	<section anchor='discovery'>
	<name>Discovering an HTTP/3 Endpoint</name>	<name>Discovering an HTTP/3 Endpoint</name>
	<t>HTTP relies on the notion of an authoritative response: a response th at has been	<t>HTTP relies on the notion of an authoritative response: a response th at has been
	determined to be the most appropriate response for that request given the state	determined to be the most appropriate response for that request given the state
	of the target resource at the time of response message origination by (or at the	of the target resource at the time of response message origination by (or at the
	direction of) the origin server identified within the target URI. Locating an	direction of) the origin server identified within the target URI. Locating an

	authoritative server for an HTTP URI is discussed in	authoritative server for an HTTP URI is discussed in <xref section='4.3' section
	<xref section="4.3" sectionFormat="of" target="RFCYYY4" format="default"/>.</t>	Format='of' target='RFC9110'/>.</t>
	<t>The "https" scheme associates authority with possession of a certific ate that	<t>The "https" scheme associates authority with possession of a certific ate that
	the client considers to be trustworthy for the host identified by the authority	the client considers to be trustworthy for the host identified by the authority
	component of the URI. Upon receiving a server certificate in the TLS handshake,	component of the URI. Upon receiving a server certificate in the TLS handshake,

	the client <bcp14>MUST</bcp14> verify that the certificate is an acceptable matc	the client <bcp14>MUST</bcp14>
	h for the URI's	verify that the certificate is an acceptable match for the URI's
	origin server using the process described in <xref section="4.3.4" sectionFormat	origin server using the process described in <xref section='4.3.4' sectionFormat
	="of" target="RFCYYY4" format="default"/>. If	='of' target='RFC9110'/>. If
	the certificate cannot be verified with respect to the URI's origin server, the	the certificate cannot be verified with respect to the URI's origin server, the

	client <bcp14>MUST NOT</bcp14> consider the server authoritative for that origin	client <bcp14>MUST NOT</bcp14>
	.</t>	consider the server authoritative for that origin.</t>
	<t>A client <bcp14>MAY</bcp14> attempt access to a resource with an "htt	<t>A client <bcp14>MAY</bcp14>
	ps" URI by resolving the	attempt access to a resource with an "https" URI by resolving the
	host identifier to an IP address, establishing a QUIC connection to that address	host identifier to an IP address, establishing a QUIC connection to that address
	on the indicated port (including validation of the server certificate as	on the indicated port (including validation of the server certificate as
	described above), and sending an HTTP/3 request message targeting the URI	described above), and sending an HTTP/3 request message targeting the URI
	to the server over that secured connection. Unless some other mechanism is used	to the server over that secured connection. Unless some other mechanism is used

	to select HTTP/3, the token "h3" is used in the Application Layer Protocol	to select HTTP/3, the token "h3" is used in the Application-Layer Protocol
	Negotiation (ALPN; see <xref target="RFC7301" format="default"/>) extension duri	Negotiation (ALPN; see <xref target='RFC7301'/>) extension during the TLS handsh
	ng the TLS handshake.</t>	ake.</t>
	<t>Connectivity problems (e.g., blocking UDP) can result in QUIC connect	<t>Connectivity problems (e.g., blocking UDP) can result in a failure to
	ion	establish
	establishment failure; clients <bcp14>SHOULD</bcp14> attempt to use TCP-based ve	a QUIC connection; clients <bcp14>SHOULD</bcp14>
	rsions of HTTP	attempt to use TCP-based versions of HTTP
	in this case.</t>	in this case.</t>

	<t>Servers <bcp14>MAY</bcp14> serve HTTP/3 on any UDP port; an alternati	<t>Servers <bcp14>MAY</bcp14>
	ve service advertisement	serve HTTP/3 on any UDP port; an alternative service advertisement
	always includes an explicit port, and URIs contain either an explicit port or a	always includes an explicit port, and URIs contain either an explicit port or a
	default port associated with the scheme.</t>	default port associated with the scheme.</t>

	<section anchor="alt-svc" numbered="true" toc="default">	<section anchor='alt-svc'>
	<name>HTTP Alternative Services</name>	<name>HTTP Alternative Services</name>
	<t>An HTTP origin can advertise the availability of an equivalent HTTP /3 endpoint	<t>An HTTP origin can advertise the availability of an equivalent HTTP /3 endpoint
	via the Alt-Svc HTTP response header field or the HTTP/2 ALTSVC frame	via the Alt-Svc HTTP response header field or the HTTP/2 ALTSVC frame

	(<xref target="RFC7838" format="default"/>), using the "h3" ALPN token.</t>	(<xref target='ALTSVC'/>) using the "h3" ALPN token.</t>
	<t>For example, an origin could indicate in an HTTP response that HTTP /3 was	<t>For example, an origin could indicate in an HTTP response that HTTP /3 was
	available on UDP port 50781 at the same hostname by including the following	available on UDP port 50781 at the same hostname by including the following

	header field:</t>	header field:</t>
		<sourcecode type='http-message'><![CDATA[
	<artwork type="drawing" name="" align="left" alt=""><![CDATA[
	Alt-Svc: h3=":50781"	Alt-Svc: h3=":50781"

	]]></artwork>	]]></sourcecode>
	<t>On receipt of an Alt-Svc record indicating HTTP/3 support, a client	<t>On receipt of an Alt-Svc record indicating HTTP/3 support, a client
	<bcp14>MAY</bcp14> attempt	<bcp14>MAY</bcp14>
		attempt
	to establish a QUIC connection to the indicated host and port; if this	to establish a QUIC connection to the indicated host and port; if this
	connection is successful, the client can send HTTP requests using the mapping	connection is successful, the client can send HTTP requests using the mapping
	described in this document.</t>	described in this document.</t>
	</section>	</section>

	<section anchor="other-schemes" numbered="true" toc="default">	<section anchor='other-schemes'>
	<name>Other Schemes</name>	<name>Other Schemes</name>
	<t>Although HTTP is independent of the transport protocol, the "http" scheme	<t>Although HTTP is independent of the transport protocol, the "http" scheme
	associates authority with the ability to receive TCP connections on the	associates authority with the ability to receive TCP connections on the
	indicated port of whatever host is identified within the authority component.	indicated port of whatever host is identified within the authority component.
	Because HTTP/3 does not use TCP, HTTP/3 cannot be used for direct access to the	Because HTTP/3 does not use TCP, HTTP/3 cannot be used for direct access to the
	authoritative server for a resource identified by an "http" URI. However,	authoritative server for a resource identified by an "http" URI. However,

	protocol extensions such as <xref target="RFC7838" format="default"/> permit the authoritative server	protocol extensions such as <xref target='ALTSVC'/> permit the authoritative ser ver
	to identify other services that are also authoritative and that might be	to identify other services that are also authoritative and that might be
	reachable over HTTP/3.</t>	reachable over HTTP/3.</t>

	<t>Prior to making requests for an origin whose scheme is not "https",	<t>Prior to making requests for an origin whose scheme is not "https",
	the client	the client <bcp14>MUST</bcp14>
	<bcp14>MUST</bcp14> ensure the server is willing to serve that scheme. For origi	ensure the server is willing to serve that scheme. For origins whose scheme
	ns whose scheme
	is "http", an experimental method to accomplish this is described in	is "http", an experimental method to accomplish this is described in

	<xref target="RFC8164" format="default"/>. Other mechanisms might be defined for various schemes in the	<xref target='RFC8164'/>. Other mechanisms might be defined for various schemes in the
	future.</t>	future.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="connection-establishment" numbered="true" toc="default">	<section anchor='connection-establishment'>
	<name>Connection Establishment</name>	<name>Connection Establishment</name>
	<t>HTTP/3 relies on QUIC version 1 as the underlying transport. The use of other	<t>HTTP/3 relies on QUIC version 1 as the underlying transport. The use of other

	QUIC transport versions with HTTP/3 <bcp14>MAY</bcp14> be defined by future spec	QUIC transport versions with HTTP/3 <bcp14>MAY</bcp14>
	ifications.</t>	be defined by future specifications.</t>
	<t>QUIC version 1 uses TLS version 1.3 or greater as its handshake proto col.	<t>QUIC version 1 uses TLS version 1.3 or greater as its handshake proto col.

	HTTP/3 clients <bcp14>MUST</bcp14> support a mechanism to indicate the target ho	HTTP/3 clients <bcp14>MUST</bcp14>
	st to the	support a mechanism to indicate the target host to the
	server during the TLS handshake. If the server is identified by a domain name	server during the TLS handshake. If the server is identified by a domain name

	(<xref target="RFC8499" format="default"/>), clients <bcp14>MUST</bcp14> send th	(<xref target='DNS-TERMS'/>), clients <bcp14>MUST</bcp14>
	e Server Name Indication (SNI;	send the Server Name Indication (SNI;
	<xref target="RFC6066" format="default"/>) TLS extension unless an alternative m	<xref target='RFC6066'/>) TLS extension unless an alternative mechanism to indic
	echanism to indicate the	ate the
	target host is used.</t>	target host is used.</t>

	<t>QUIC connections are established as described in <xref target="RFCYYY 1" format="default"/>. During	<t>QUIC connections are established as described in <xref target='QUIC-T RANSPORT'/>. During
	connection establishment, HTTP/3 support is indicated by selecting the ALPN	connection establishment, HTTP/3 support is indicated by selecting the ALPN

	token "h3" in the TLS handshake. Support for other application-layer protocols	token "h3" in the TLS handshake. Support for other application-layer protocols
	<bcp14>MAY</bcp14> be offered in the same handshake.</t>	<bcp14>MAY</bcp14>
		be offered in the same handshake.</t>
	<t>While connection-level options pertaining to the core QUIC protocol a re set in	<t>While connection-level options pertaining to the core QUIC protocol a re set in

	the initial crypto handshake, HTTP/3-specific settings are conveyed in the	the initial crypto handshake, settings specific to HTTP/3 are conveyed in the
	SETTINGS frame. After the QUIC connection is established, a SETTINGS frame	<xref format='none' target='frame-settings'>SETTINGS</xref><iref item='SETTINGS'
	(<xref target="frame-settings" format="default"/>) <bcp14>MUST</bcp14> be sent b	/> frame. After the QUIC connection is established, a
	y each endpoint as the initial frame of their	<xref format='none' target='frame-settings'>SETTINGS</xref><iref item='SETTINGS'
	respective HTTP control stream; see <xref target="control-streams" format="defau	/> frame <bcp14>MUST</bcp14>
	lt"/>.</t>	be sent by each endpoint as the initial frame of their
		respective HTTP <xref format='none' target='control-streams'>control stream</xre
		f><iref item='control stream'/>.</t>
	</section>	</section>

	<section anchor="connection-reuse" numbered="true" toc="default">	<section anchor='connection-reuse'>
	<name>Connection Reuse</name>	<name>Connection Reuse</name>
	<t>HTTP/3 connections are persistent across multiple requests. For best	<t>HTTP/3 connections are persistent across multiple requests. For best
	performance, it is expected that clients will not close connections until it is	performance, it is expected that clients will not close connections until it is
	determined that no further communication with a server is necessary (for	determined that no further communication with a server is necessary (for
	example, when a user navigates away from a particular web page) or until the	example, when a user navigates away from a particular web page) or until the
	server closes the connection.</t>	server closes the connection.</t>

	<t>Once a connection exists to a server endpoint, this connection <bcp14	<t>Once a connection to a server endpoint exists, this connection
	>MAY</bcp14> be reused for	<bcp14>MAY</bcp14>
		be reused for
	requests with multiple different URI authority components. To use an existing	requests with multiple different URI authority components. To use an existing

	connection for a new origin, clients <bcp14>MUST</bcp14> validate the certificat	connection for a new origin, clients <bcp14>MUST</bcp14>
	e presented by	validate the certificate presented by
	the server for the new origin server using the process described in <xref sectio	the server for the new origin server using the process described in <xref sectio
	n="4.3.4" sectionFormat="of" target="RFCYYY4" format="default"/>. This implies	n='4.3.4' sectionFormat='of' target='RFC9110'/>. This implies that clients will
	that clients will need to retain the	need to retain the
	server certificate and any additional information needed to verify that	server certificate and any additional information needed to verify that

	certificate; clients which do not do so will be unable to reuse the connection	certificate; clients that do not do so will be unable to reuse the connection
	for additional origins.</t>	for additional origins.</t>
	<t>If the certificate is not acceptable with regard to the new origin fo r any	<t>If the certificate is not acceptable with regard to the new origin fo r any

	reason, the connection <bcp14>MUST NOT</bcp14> be reused and a new connection <b	reason, the connection <bcp14>MUST NOT</bcp14>
	cp14>SHOULD</bcp14> be	be reused and a new connection <bcp14>SHOULD</bcp14>
		be
	established for the new origin. If the reason the certificate cannot be	established for the new origin. If the reason the certificate cannot be
	verified might apply to other origins already associated with the connection,	verified might apply to other origins already associated with the connection,

	the client <bcp14>SHOULD</bcp14> re-validate the server certificate for those or	the client <bcp14>SHOULD</bcp14>
	igins. For	revalidate the server certificate for those origins. For
	instance, if validation of a certificate fails because the certificate has	instance, if validation of a certificate fails because the certificate has
	expired or been revoked, this might be used to invalidate all other origins for	expired or been revoked, this might be used to invalidate all other origins for
	which that certificate was used to establish authority.</t>	which that certificate was used to establish authority.</t>

	<t>Clients <bcp14>SHOULD NOT</bcp14> open more than one HTTP/3 connectio	<t>Clients <bcp14>SHOULD NOT</bcp14>
	n to a given IP address	open more than one HTTP/3 connection to a given IP address
	and UDP port, where the IP address and port might be derived from a URI, a	and UDP port, where the IP address and port might be derived from a URI, a

	selected alternative service (<xref target="RFC7838" format="default"/>), a conf	selected alternative service (<xref target='ALTSVC'/>), a configured proxy, or n
	igured proxy, or name	ame
	resolution of any of these. A client <bcp14>MAY</bcp14> open multiple HTTP/3 con	resolution of any of these. A client <bcp14>MAY</bcp14>
	nections to the	open multiple HTTP/3 connections to the
	same IP address and UDP port using different transport or TLS configurations but	same IP address and UDP port using different transport or TLS configurations but
	<bcp14>SHOULD</bcp14> avoid creating multiple connections with the same configur	<bcp14>SHOULD</bcp14>
	ation.</t>	avoid creating multiple connections with the same configuration.</t>
	<t>Servers are encouraged to maintain open HTTP/3 connections for as lon g as	<t>Servers are encouraged to maintain open HTTP/3 connections for as lon g as
	possible but are permitted to terminate idle connections if necessary. When	possible but are permitted to terminate idle connections if necessary. When

	either endpoint chooses to close the HTTP/3 connection, the terminating endpoint	either endpoint chooses to close the HTTP/3 connection, the terminating endpoint
	<bcp14>SHOULD</bcp14> first send a GOAWAY frame (<xref target="connection-shutdo	<bcp14>SHOULD</bcp14>
	wn" format="default"/>) so that both	first send a <xref format='none' target='frame-goaway'>GOAWAY</xref><iref item=
		'GOAWAY'/> frame (<xref target='connection-shutdown'/>) so that both
	endpoints can reliably determine whether previously sent frames have been	endpoints can reliably determine whether previously sent frames have been
	processed and gracefully complete or terminate any necessary remaining tasks.</t >	processed and gracefully complete or terminate any necessary remaining tasks.</t >
	<t>A server that does not wish clients to reuse HTTP/3 connections for a particular	<t>A server that does not wish clients to reuse HTTP/3 connections for a particular
	origin can indicate that it is not authoritative for a request by sending a 421	origin can indicate that it is not authoritative for a request by sending a 421

	(Misdirected Request) status code in response to the request; see <xref section= "7.4" sectionFormat="of" target="RFCYYY4" format="default"/>.</t>	(Misdirected Request) status code in response to the request; see <xref section= '7.4' sectionFormat='of' target='RFC9110'/>.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="http-request-lifecycle" numbered="true" toc="default">	<section anchor='http-request-lifecycle'>
	<name>HTTP Request Lifecycle</name>	<name>Expressing HTTP Semantics in HTTP/3</name>
	<section anchor="request-response" numbered="true" toc="default">	<section anchor='request-response'>
	<name>HTTP Message Exchanges</name>	<name>HTTP Message Framing</name>
	<t>A client sends an HTTP request on a request stream, which is a client	<t>A client sends an HTTP request on a <xref format='none' target='reque
	-initiated	st-streams'>request stream</xref><iref item='request stream'/>, which is a clien
	bidirectional QUIC stream; see <xref target="request-streams" format="default"/>	t-initiated
	. A client <bcp14>MUST</bcp14> send only a	bidirectional QUIC stream; see <xref target='request-streams'/>. A client
		<bcp14>MUST</bcp14>
		send only a
	single request on a given stream. A server sends zero or more interim HTTP	single request on a given stream. A server sends zero or more interim HTTP
	responses on the same stream as the request, followed by a single final HTTP	responses on the same stream as the request, followed by a single final HTTP

	response, as detailed below. See <xref section="15" sectionFormat="of" target="R FCYYY4" format="default"/> for a description	response, as detailed below. See <xref section='15' sectionFormat='of' target='R FC9110'/> for a description
	of interim and final HTTP responses.</t>	of interim and final HTTP responses.</t>
	<t>Pushed responses are sent on a server-initiated unidirectional QUIC s tream; see	<t>Pushed responses are sent on a server-initiated unidirectional QUIC s tream; see

	<xref target="push-streams" format="default"/>. A server sends zero or more int erim HTTP responses, followed	<xref target='push-streams'/>. A server sends zero or more interim HTTP respons es, followed
	by a single final HTTP response, in the same manner as a standard response.	by a single final HTTP response, in the same manner as a standard response.

	Push is described in more detail in <xref target="server-push" format="default"/ >.</t>	Push is described in more detail in <xref target='server-push'/>.</t>
	<t>On a given stream, receipt of multiple requests or receipt of an addi tional HTTP	<t>On a given stream, receipt of multiple requests or receipt of an addi tional HTTP

	response following a final HTTP response <bcp14>MUST</bcp14> be treated as malfo	response following a final HTTP response <bcp14>MUST</bcp14>
	rmed	be treated as <xref format='none' target='malformed'>malformed</xref><iref item
	(<xref target="malformed" format="default"/>).</t>	='malformed'/>.</t>
	<t>An HTTP message (request or response) consists of:</t>	<t>An HTTP message (request or response) consists of:</t>

	<ol spacing="normal" type="1"><li>the header section, sent as a single H	<ol spacing='normal' type='1'>
	EADERS frame (see <xref target="frame-headers" format="default"/>),</li>	<li>the header section, including message control data, sent as a sing
	<li>optionally, the content, if present, sent as a series of DATA fram	le <xref format='none' target='frame-headers'>HEADERS</xref><iref item='HEADERS'
	es	/>
	(see <xref target="frame-data" format="default"/>), and</li>	frame,</li>
	<li>optionally, the trailer section, if present, sent as a single HEAD	<li>optionally, the content, if present, sent as a series of <xref for
	ERS frame.</li>	mat='none' target='frame-data'>DATA</xref><iref item='DATA'/> frames, and</li>
		<li>optionally, the trailer section, if present, sent as a single <xre
		f format='none' target='frame-headers'>HEADERS</xref><iref item='HEADERS'/> fram
		e.</li>
	</ol>	</ol>

	<t>Header and trailer sections are described in Sections <xref target="R	<t>Header and trailer sections are described in Sections <xref section='
	FCYYY4" section="6.3" sectionFormat="bare" format="default"/> and <xref target="	6.3' sectionFormat='bare' target='RFC9110'/> and <xref section='6.5' sectionForm
	RFCYYY4" section="6.5" sectionFormat="bare" format="default"/> of <xref target="	at='bare' target='RFC9110'/> of <xref target='RFC9110'/>; the content is describ
	RFCYYY4" format="default"/>; the content is described in <xref section="6.4" sec	ed in <xref section='6.4' sectionFormat='of' target='RFC9110'/>.</t>
	tionFormat="of" target="RFCYYY4" format="default"/>.</t>	<t>Receipt of an invalid sequence of frames <bcp14>MUST</bcp14>
	<t>Receipt of an invalid sequence of frames <bcp14>MUST</bcp14> be treat	be treated as a <xref format='none' target='errors'>connection error</xref><ire
	ed as a connection error	f item='connection error'/>
	of type H3_FRAME_UNEXPECTED; see <xref target="errors" format="default"/>. In p	of type <xref format='none' target='H3_FRAME_UNEXPECTED'>H3_FRAME_UNEXPECTED</xr
	articular, a DATA frame before	ef><iref item='H3_FRAME_UNEXPECTED'/>. In particular, a <xref format='none' tar
	any HEADERS frame, or a HEADERS or DATA frame after the trailing HEADERS frame,	get='frame-data'>DATA</xref><iref item='DATA'/> frame before
		any <xref format='none' target='frame-headers'>HEADERS</xref><iref item='HEADERS
		'/> frame, or a <xref format='none' target='frame-headers'>HEADERS</xref><iref i
		tem='HEADERS'/> or <xref format='none' target='frame-data'>DATA</xref><iref item
		='DATA'/> frame after the trailing <xref format='none' target='frame-headers'>HE
		ADERS</xref><iref item='HEADERS'/> frame,
	is considered invalid. Other frame types, especially unknown frame types,	is considered invalid. Other frame types, especially unknown frame types,

	might be permitted subject to their own rules; see <xref target="extensions" for	might be permitted subject to their own rules; see <xref target='extensions'/>.<
	mat="default"/>.</t>	/t>
	<t>A server <bcp14>MAY</bcp14> send one or more PUSH_PROMISE frames (<xr	<t>A server <bcp14>MAY</bcp14>
	ef target="frame-push-promise" format="default"/>)	send one or more <xref format='none' target='frame-push-promise'>PUSH_PROMISE</
		xref><iref item='PUSH_PROMISE'/> frames
	before, after, or interleaved with the frames of a response message. These	before, after, or interleaved with the frames of a response message. These

	PUSH_PROMISE frames are not part of the response; see <xref target="server-push"	<xref format='none' target='frame-push-promise'>PUSH_PROMISE</xref><iref item='P
	format="default"/> for more	USH_PROMISE'/> frames are not part of the response; see <xref target='server-pus
	details. PUSH_PROMISE frames are not permitted on push streams; a pushed	h'/> for more
	response that includes PUSH_PROMISE frames <bcp14>MUST</bcp14> be treated as a c	details. <xref format='none' target='frame-push-promise'>PUSH_PROMISE</xref><ir
	onnection error	ef item='PUSH_PROMISE'/> frames are not permitted on <xref format='none' target=
	of type H3_FRAME_UNEXPECTED; see <xref target="errors" format="default"/>.</t>	'push-streams'>push streams</xref><iref item='push stream'/>; a pushed
	<t>Frames of unknown types (<xref target="extensions" format="default"/>	response that includes <xref format='none' target='frame-push-promise'>PUSH_PROM
	), including reserved frames	ISE</xref><iref item='PUSH_PROMISE'/> frames <bcp14>MUST</bcp14>
	(<xref target="frame-reserved" format="default"/>) <bcp14>MAY</bcp14> be sent on	be treated as a <xref format='none' target='errors'>connection error</xref><ire
	a request or push stream before, after, or	f item='connection error'/>
		of type <xref format='none' target='H3_FRAME_UNEXPECTED'>H3_FRAME_UNEXPECTED</xr
		ef><iref item='H3_FRAME_UNEXPECTED'/>.</t>
		<t>Frames of unknown types (<xref target='extensions'/>), including rese
		rved frames
		(<xref target='frame-reserved'/>) <bcp14>MAY</bcp14>
		be sent on a request or <xref format='none' target='push-streams'>push stream</
		xref><iref item='push stream'/> before, after, or
	interleaved with other frames described in this section.</t>	interleaved with other frames described in this section.</t>

	<t>The HEADERS and PUSH_PROMISE frames might reference updates to the QP ACK dynamic	<t>The <xref format='none' target='frame-headers'>HEADERS</xref><iref it em='HEADERS'/> and <xref format='none' target='frame-push-promise'>PUSH_PROMISE< /xref><iref item='PUSH_PROMISE'/> frames might reference updates to the QPACK dy namic
	table. While these updates are not directly part of the message exchange, they	table. While these updates are not directly part of the message exchange, they
	must be received and processed before the message can be consumed. See	must be received and processed before the message can be consumed. See

	<xref target="header-formatting" format="default"/> for more details.</t>	<xref target='header-formatting'/> for more details.</t>
	<t>Transfer codings (see <xref section="6.1" sectionFormat="of" target="	<t>Transfer codings (see <xref section='7' sectionFormat='of' target='RF
	I-D.ietf-httpbis-messaging" format="default"/>) are not defined for HTTP/3;	C9112'/>) are not defined for HTTP/3;
	the Transfer-Encoding header field <bcp14>MUST NOT</bcp14> be used.</t>	the Transfer-Encoding header field <bcp14>MUST NOT</bcp14>
	<t>A response <bcp14>MAY</bcp14> consist of multiple messages when and o	be used.</t>
	nly when one or more	<t>A response <bcp14>MAY</bcp14>
	interim responses (1xx; see <xref section="15.2" sectionFormat="of" target="RFCY	consist of multiple messages when and only when one or more
	YY4" format="default"/>) precede a final	interim responses (1xx; see <xref section='15.2' sectionFormat='of' target='RFC9
		110'/>) precede a final
	response to the same request. Interim responses do not contain content	response to the same request. Interim responses do not contain content
	or trailer sections.</t>	or trailer sections.</t>
	<t>An HTTP request/response exchange fully consumes a client-initiated	<t>An HTTP request/response exchange fully consumes a client-initiated

	bidirectional QUIC stream. After sending a request, a client <bcp14>MUST</bcp14>	bidirectional QUIC stream. After sending a request, a client <bcp14>MUS
	close the	T</bcp14>
	stream for sending. Unless using the CONNECT method (see <xref target="connect"	close the
	format="default"/>), clients	stream for sending. Unless using the CONNECT method (see <xref target='connect'
	<bcp14>MUST NOT</bcp14> make stream closure dependent on receiving a response to	/>), clients <bcp14>MUST NOT</bcp14>
	their request.	make stream closure dependent on receiving a response to their request.
	After sending a final response, the server <bcp14>MUST</bcp14> close the stream	After sending a final response, the server <bcp14>MUST</bcp14>
	for sending. At	close the stream for sending. At
	this point, the QUIC stream is fully closed.</t>	this point, the QUIC stream is fully closed.</t>
	<t>When a stream is closed, this indicates the end of the final HTTP mes sage.	<t>When a stream is closed, this indicates the end of the final HTTP mes sage.

	Because some messages are large or unbounded, endpoints <bcp14>SHOULD</bcp14> be	Because some messages are large or unbounded, endpoints <bcp14>SHOULD</
	gin processing	bcp14>
		begin processing
	partial HTTP messages once enough of the message has been received to make	partial HTTP messages once enough of the message has been received to make
	progress. If a client-initiated stream terminates without enough of the HTTP	progress. If a client-initiated stream terminates without enough of the HTTP

	message to provide a complete response, the server <bcp14>SHOULD</bcp14> abort i	message to provide a complete response, the server <bcp14>SHOULD</bcp14
	ts response	>
	stream with the error code H3_REQUEST_INCOMPLETE; see <xref target="errors" form	abort its response
	at="default"/>.</t>	stream with the error code <xref format='none' target='H3_REQUEST_INCOMPLETE'>H3
		_REQUEST_INCOMPLETE</xref><iref item='H3_REQUEST_INCOMPLETE'/>.</t>
	<t>A server can send a complete response prior to the client sending an entire	<t>A server can send a complete response prior to the client sending an entire
	request if the response does not depend on any portion of the request that has	request if the response does not depend on any portion of the request that has
	not been sent and received. When the server does not need to receive the	not been sent and received. When the server does not need to receive the

	remainder of the request, it <bcp14>MAY</bcp14> abort reading the request stream	remainder of the request, it <bcp14>MAY</bcp14>
	, send a	abort reading the <xref format='none' target='request-streams'>request stream</
		xref><iref item='request stream'/>, send a
	complete response, and cleanly close the sending part of the stream. The error	complete response, and cleanly close the sending part of the stream. The error

	code H3_NO_ERROR <bcp14>SHOULD</bcp14> be used when requesting that the client s	code <xref format='none' target='H3_NO_ERROR'>H3_NO_ERROR</xref><iref item='H3_N
	top sending on	O_ERROR'/> <bcp14>SHOULD</bcp14>
	the request stream. Clients <bcp14>MUST NOT</bcp14> discard complete responses	be used when requesting that the client stop sending on
	as a result of	the <xref format='none' target='request-streams'>request stream</xref><iref item
		='request stream'/>. Clients <bcp14>MUST NOT</bcp14>
		discard complete responses as a result of
	having their request terminated abruptly, though clients can always discard	having their request terminated abruptly, though clients can always discard
	responses at their discretion for other reasons. If the server sends a partial	responses at their discretion for other reasons. If the server sends a partial

	or complete response but does not abort reading the request, clients <bcp14>SHOU	or complete response but does not abort reading the request, clients <b
	LD</bcp14>	cp14>SHOULD</bcp14>
	continue sending the body of the request and close the stream normally.</t>
	<section anchor="header-formatting" numbered="true" toc="default">	continue sending the content of the request and close the stream normally.</t>
	<name>Field Formatting and Compression</name>	<section anchor='request-cancellation'>
	<t>HTTP messages carry metadata as a series of key-value pairs called
	HTTP fields;
	see Sections <xref target="RFCYYY4" section="6.3" sectionFormat="bare" format="d
	efault"/> and <xref target="RFCYYY4" section="6.5" sectionFormat="bare" format="
	default"/> of <xref target="RFCYYY4" format="default"/>. For a listing of regist
	ered HTTP
	fields, see the "Hypertext Transfer Protocol (HTTP) Field Name Registry"
	maintained at <eref target="https://www.iana.org/assignments/http-fields/"/>.</t
	>
	<ul empty="true" spacing="normal">
	<li>
	<strong>Note:</strong> This registry will not exist until <xref t
	arget="RFCYYY4" format="default"/> is approved.
	<strong>RFC Editor</strong>, please remove this note prior to publication.</li>
	</ul>
	<t>Field names are strings containing a subset of ASCII characters. Pr
	operties of
	HTTP field names and values are discussed in more detail in <xref section="5.1"
	sectionFormat="of" target="RFCYYY4" format="default"/>. As in HTTP/2, characters
	in field names <bcp14>MUST</bcp14> be converted to
	lowercase prior to their encoding. A request or response containing uppercase
	characters in field names <bcp14>MUST</bcp14> be treated as malformed (<xref tar
	get="malformed" format="default"/>).</t>
	<t>Like HTTP/2, HTTP/3 does not use the Connection header field to ind
	icate
	connection-specific fields; in this protocol, connection-specific metadata is
	conveyed by other means. An endpoint <bcp14>MUST NOT</bcp14> generate an HTTP/3
	field section
	containing connection-specific fields; any message containing
	connection-specific fields <bcp14>MUST</bcp14> be treated as malformed (<xref ta
	rget="malformed" format="default"/>).</t>
	<t>The only exception to this is the TE header field, which <bcp14>MAY
	</bcp14> be present in an
	HTTP/3 request header; when it is, it <bcp14>MUST NOT</bcp14> contain any value
	other than
	"trailers".</t>
	<t>An intermediary transforming an HTTP/1.x message to HTTP/3 <bcp14>M
	UST</bcp14> remove
	connection-specific header fields as discussed in <xref section="7.6.1" sectionF
	ormat="of" target="RFCYYY4" format="default"/>, or their messages will be treate
	d by other HTTP/3 endpoints as
	malformed (<xref target="malformed" format="default"/>).</t>
	<section anchor="pseudo-header-fields" numbered="true" toc="default">
	<name>Pseudo-Header Fields</name>
	<t>Like HTTP/2, HTTP/3 employs a series of pseudo-header fields wher
	e the field
	name begins with the ':' character (ASCII 0x3a). These pseudo-header fields
	convey the target URI, the method of the request, and the status code for the
	response.</t>
	<t>Pseudo-header fields are not HTTP fields. Endpoints <bcp14>MUST
	NOT</bcp14> generate
	pseudo-header fields other than those defined in this document; however, an
	extension could negotiate a modification of this restriction; see
	<xref target="extensions" format="default"/>.</t>
	<t>Pseudo-header fields are only valid in the context in which they
	are defined.
	Pseudo-header fields defined for requests <bcp14>MUST NOT</bcp14> appear in resp
	onses;
	pseudo-header fields defined for responses <bcp14>MUST NOT</bcp14> appear in req
	uests.
	Pseudo-header fields <bcp14>MUST NOT</bcp14> appear in trailer sections. Endpoin
	ts <bcp14>MUST</bcp14> treat a
	request or response that contains undefined or invalid pseudo-header fields as
	malformed (<xref target="malformed" format="default"/>).</t>
	<t>All pseudo-header fields <bcp14>MUST</bcp14> appear in the header
	section before regular header
	fields. Any request or response that contains a pseudo-header field that
	appears in a header section after a regular header field <bcp14>MUST</bcp14> be
	treated as
	malformed (<xref target="malformed" format="default"/>).</t>
	<t>The following pseudo-header fields are defined for requests:</t>
	<dl>
	<dt>
	":method": </dt>
	<dd>
	<t>Contains the HTTP method (<xref section="9" sectionFormat="of
	" target="RFCYYY4" format="default"/>)</t>
	</dd>
	<dt>
	":scheme": </dt>
	<dd>
	<t>Contains the scheme portion of the target URI (<xref section=
	"3.1" sectionFormat="of" target="RFC3986" format="default"/>)</t>
	</dd>
	<dt/>
	<dd>
	<t>":scheme" is not restricted to URIs with scheme "http" and "h
	ttps".
	A proxy or
	gateway can translate requests for non-HTTP schemes, enabling the use of
	HTTP to interact with non-HTTP services.</t>
	</dd>
	<dt/>
	<dd>
	<t>See <xref target="other-schemes" format="default"/> for guida
	nce on using a scheme other than "https".</t>
	</dd>
	<dt>
	":authority": </dt>
	<dd>
	<t>Contains the authority portion of the target URI (<xref secti
	on="3.2" sectionFormat="of" target="RFC3986" format="default"/>).
	The authority <bcp14>MUST NOT</bcp14> include the deprecated "userinfo"
	subcomponent for URIs of scheme "http" or "https".</t>
	</dd>
	<dt/>
	<dd>
	<t>To ensure that the HTTP/1.1 request line can be reproduced ac
	curately, this
	pseudo-header field <bcp14>MUST</bcp14> be omitted when translating from an HTTP
	/1.1
	request that has a request target in origin or asterisk form; see <xref section=
	"7.1" sectionFormat="of" target="RFCYYY4" format="default"/>. Clients that gene
	rate HTTP/3 requests directly
	<bcp14>SHOULD</bcp14> use the ":authority" pseudo-header field instead of the Ho
	st field.
	An intermediary that converts an HTTP/3 request to HTTP/1.1 <bcp14>MUST</bcp14>
	create a
	Host field if one is not present in a request by copying the value of the
	":authority" pseudo-header field.</t>
	</dd>
	<dt>
	":path": </dt>
	<dd>
	<t>Contains the path and query parts of the target URI (the "pat
	h-absolute"
	production and optionally a '?' character followed by the "query"
	production; see Sections <xref target="RFC3986" section="3.3" sectionFormat="bar
	e" format="default"/> and <xref target="RFC3986" section="3.4" sectionFormat="ba
	re" format="default"/> of <xref target="RFC3986" format="default"/>. A request
	in
	asterisk form includes the value '*' for the ":path" pseudo-header field.</t>
	</dd>
	<dt/>
	<dd>
	<t>This pseudo-header field <bcp14>MUST NOT</bcp14> be empty for
	"http" or "https" URIs;
	"http" or "https" URIs that do not contain a path component <bcp14>MUST</bcp14>
	include a
	value of '/'. The exception to this rule is an OPTIONS request for an
	"http" or "https" URI that does not include a path component; these <bcp14>MUST<
	/bcp14>
	include a ":path" pseudo-header field with a value of '*'; see
	<xref section="7.1" sectionFormat="of" target="RFCYYY4" format="default"/>.</t>
	</dd>
	</dl>
	<t>All HTTP/3 requests <bcp14>MUST</bcp14> include exactly one value
	for the ":method", ":scheme",
	and ":path" pseudo-header fields, unless it is a CONNECT request; see
	<xref target="connect" format="default"/>.</t>
	<t>If the ":scheme" pseudo-header field identifies a scheme that has
	a mandatory
	authority component (including "http" and "https"), the request <bcp14>MUST</bcp
	14> contain
	either an ":authority" pseudo-header field or a "Host" header field. If these
	fields are present, they <bcp14>MUST NOT</bcp14> be empty. If both fields are p
	resent, they
	<bcp14>MUST</bcp14> contain the same value. If the scheme does not have a manda
	tory authority
	component and none is provided in the request target, the request <bcp14>MUST NO
	T</bcp14>
	contain the ":authority" pseudo-header or "Host" header fields.</t>
	<t>An HTTP request that omits mandatory pseudo-header fields or cont
	ains invalid
	values for those pseudo-header fields is malformed (<xref target="malformed" for
	mat="default"/>).</t>
	<t>HTTP/3 does not define a way to carry the version identifier that
	is included in
	the HTTP/1.1 request line.</t>
	<t>For responses, a single ":status" pseudo-header field is defined
	that carries
	the HTTP status code; see <xref section="15" sectionFormat="of" target="RFCYYY4"
	format="default"/>. This pseudo-header
	field <bcp14>MUST</bcp14> be included in all responses; otherwise, the response
	is malformed
	(<xref target="malformed" format="default"/>).</t>
	<t>HTTP/3 does not define a way to carry the version or reason phras
	e that is
	included in an HTTP/1.1 status line.</t>
	</section>
	<section anchor="field-compression" numbered="true" toc="default">
	<name>Field Compression</name>
	<t><xref target="RFCYYY2" format="default"/> describes a variation o
	f HPACK that gives an encoder some control over
	how much head-of-line blocking can be caused by compression. This allows an
	encoder to balance compression efficiency with latency. HTTP/3 uses QPACK to
	compress header and trailer sections, including the pseudo-header fields present
	in the header section.</t>
	<t>To allow for better compression efficiency, the "Cookie" field (<
	xref target="RFC6265" format="default"/>)
	<bcp14>MAY</bcp14> be split into separate field lines, each with one or more coo
	kie-pairs,
	before compression. If a decompressed field section contains multiple cookie
	field lines, these <bcp14>MUST</bcp14> be concatenated into a single byte string
	using the
	two-byte delimiter of 0x3b, 0x20 (the ASCII string "; ") before being passed
	into a context other than HTTP/2 or HTTP/3, such as an HTTP/1.1 connection, or a
	generic HTTP server application.</t>
	</section>
	<section anchor="header-size-constraints" numbered="true" toc="default
	">
	<name>Header Size Constraints</name>
	<t>An HTTP/3 implementation <bcp14>MAY</bcp14> impose a limit on the
	maximum size of the message
	header it will accept on an individual HTTP message. A server that receives a
	larger header section than it is willing to handle can send an HTTP 431 (Request
	Header Fields Too Large) status code (<xref target="RFC6585" format="default"/>)
	. A client can discard
	responses that it cannot process. The size of a field list is calculated based
	on the uncompressed size of fields, including the length of the name and value
	in bytes plus an overhead of 32 bytes for each field.</t>
	<t>If an implementation wishes to advise its peer of this limit, it
	can be conveyed
	as a number of bytes in the SETTINGS_MAX_FIELD_SECTION_SIZE parameter. An
	implementation that has received this parameter <bcp14>SHOULD NOT</bcp14> send a
	n HTTP message
	header that exceeds the indicated size, as the peer will likely refuse to
	process it. However, an HTTP message can traverse one or more intermediaries
	before reaching the origin server; see <xref section="3.7" sectionFormat="of" ta
	rget="RFCYYY4" format="default"/>. Because
	this limit is applied separately by each implementation which processes the
	message, messages below this limit are not guaranteed to be accepted.</t>
	</section>
	</section>
	<section anchor="request-cancellation" numbered="true" toc="default">
	<name>Request Cancellation and Rejection</name>	<name>Request Cancellation and Rejection</name>

	<t>Once a request stream has been opened, the request <bcp14>MAY</bcp1	<t>Once a <xref format='none' target='request-streams'>request stream<
	4> be cancelled by either	/xref><iref item='request stream'/> has been opened, the request <bcp
		14>MAY</bcp14>
		be cancelled by either
	endpoint. Clients cancel requests if the response is no longer of interest;	endpoint. Clients cancel requests if the response is no longer of interest;
	servers cancel requests if they are unable to or choose not to respond. When	servers cancel requests if they are unable to or choose not to respond. When

	possible, it is <bcp14>RECOMMENDED</bcp14> that servers send an HTTP response wi	possible, it is <bcp14>RECOMMENDED</bcp14>
	th an	that servers send an HTTP response with an
	appropriate status code rather than canceling a request it has already begun	appropriate status code rather than cancelling a request it has already begun
	processing.</t>	processing.</t>

	<t>Implementations <bcp14>SHOULD</bcp14> cancel requests by abruptly t	<t>Implementations <bcp14>SHOULD</bcp14>
	erminating any	cancel requests by abruptly terminating any directions of
	directions of a stream that are still open. This means resetting the	a stream that are still open. To do so, an implementation resets the sending
	sending parts of streams and aborting reading on receiving parts of streams;	parts of streams and aborts reading on the receiving parts of streams; see
	see <xref section="2.4" sectionFormat="of" target="RFCYYY1" format="default"/>.<	<xref section='2.4' sectionFormat='of' target='QUIC-TRANSPORT'/>.</t>
	/t>
	<t>When the server cancels a request without performing any applicatio n processing,	<t>When the server cancels a request without performing any applicatio n processing,

	the request is considered "rejected." The server <bcp14>SHOULD</bcp14> abort it	the request is considered "rejected". The server <bcp14>SHOULD</bcp1
	s response	4>
	stream with the error code H3_REQUEST_REJECTED. In this context, "processed"	abort its response
		stream with the error code <xref format='none' target='H3_REQUEST_REJECTED'>H3_R
		EQUEST_REJECTED</xref><iref item='H3_REQUEST_REJECTED'/>. In this context, "proc
		essed"
	means that some data from the stream was passed to some higher layer of software	means that some data from the stream was passed to some higher layer of software
	that might have taken some action as a result. The client can treat requests	that might have taken some action as a result. The client can treat requests
	rejected by the server as though they had never been sent at all, thereby	rejected by the server as though they had never been sent at all, thereby
	allowing them to be retried later.</t>	allowing them to be retried later.</t>

	<t>Servers <bcp14>MUST NOT</bcp14> use the H3_REQUEST_REJECTED error c	<t>Servers <bcp14>MUST NOT</bcp14>
	ode for requests that were	use the <xref format='none' target='H3_REQUEST_REJECTED'>H3_REQUEST_REJECTED</x
		ref><iref item='H3_REQUEST_REJECTED'/> error code for requests that were
	partially or fully processed. When a server abandons a response after partial	partially or fully processed. When a server abandons a response after partial

	processing, it <bcp14>SHOULD</bcp14> abort its response stream with the error co	processing, it <bcp14>SHOULD</bcp14>
	de	abort its response stream with the error code
	H3_REQUEST_CANCELLED.</t>	<xref format='none' target='H3_REQUEST_CANCELLED'>H3_REQUEST_CANCELLED</xref><ir
	<t>Client <bcp14>SHOULD</bcp14> use the error code H3_REQUEST_CANCELLE	ef item='H3_REQUEST_CANCELLED'/>.</t>
	D to cancel requests. Upon	<t>Client <bcp14>SHOULD</bcp14>
	receipt of this error code, a server <bcp14>MAY</bcp14> abruptly terminate the r	use the error code <xref format='none' target='H3_REQUEST_CANCELLED'>H3_REQUEST
	esponse using	_CANCELLED</xref><iref item='H3_REQUEST_CANCELLED'/> to cancel requests. Upon
	the error code H3_REQUEST_REJECTED if no processing was performed. Clients <bcp	receipt of this error code, a server <bcp14>MAY</bcp14>
	14>MUST	abruptly terminate the response using
	NOT</bcp14> use the H3_REQUEST_REJECTED error code, except when a server has req	the error code <xref format='none' target='H3_REQUEST_REJECTED'>H3_REQUEST_REJEC
	uested	TED</xref><iref item='H3_REQUEST_REJECTED'/> if no processing was performed. Cl
	closure of the request stream with this error code.</t>	ients <bcp14>MUST
	<t>If a stream is canceled after receiving a complete response, the cl	NOT</bcp14>
	ient <bcp14>MAY</bcp14>	use the <xref format='none' target='H3_REQUEST_REJECTED'>H3_REQUEST_REJECTED</x
		ref><iref item='H3_REQUEST_REJECTED'/> error code, except when a server has requ
		ested
		closure of the <xref format='none' target='request-streams'>request stream</xref
		><iref item='request stream'/> with this error code.</t>
		<t>If a stream is cancelled after receiving a complete response, the c
		lient <bcp14>MAY</bcp14>

	ignore the cancellation and use the response. However, if a stream is cancelled	ignore the cancellation and use the response. However, if a stream is cancelled

	after receiving a partial response, the response <bcp14>SHOULD NOT</bcp14> be us	after receiving a partial response, the response <bcp14>SHOULD NOT</b
	ed. Only	cp14>
	idempotent actions such as GET, PUT, or DELETE can be safely retried; a client	be used. Only
	<bcp14>SHOULD NOT</bcp14> automatically retry a request with a non-idempotent me	idempotent actions such as GET, PUT, or DELETE can be safely retried; a client
	thod unless it	<bcp14>SHOULD NOT</bcp14>
		automatically retry a request with a non-idempotent method unless it
	has some means to know that the request semantics are idempotent	has some means to know that the request semantics are idempotent
	independent of the method or some means to detect that the original request was	independent of the method or some means to detect that the original request was

	never applied. See <xref section="9.2.2" sectionFormat="of" target="RFCYYY4" fo rmat="default"/> for more details.</t>	never applied. See <xref section='9.2.2' sectionFormat='of' target='RFC9110'/> for more details.</t>
	</section>	</section>

	<section anchor="malformed" numbered="true" toc="default">	<section anchor='malformed'>
	<name>Malformed Requests and Responses</name>	<name>Malformed Requests and Responses</name><iref item='malformed' pr
		imary='true'/>
	<t>A malformed request or response is one that is an otherwise valid s equence of	<t>A malformed request or response is one that is an otherwise valid s equence of
	frames but is invalid due to:</t>	frames but is invalid due to:</t>

	<ul spacing="normal">	<ul spacing='normal'>
	<li>the presence of prohibited fields or pseudo-header fields,</li>	<li>the presence of prohibited fields or pseudo-header fields,</li>
	<li>the absence of mandatory pseudo-header fields,</li>	<li>the absence of mandatory pseudo-header fields,</li>
	<li>invalid values for pseudo-header fields,</li>	<li>invalid values for pseudo-header fields,</li>
	<li>pseudo-header fields after fields,</li>	<li>pseudo-header fields after fields,</li>
	<li>an invalid sequence of HTTP messages,</li>	<li>an invalid sequence of HTTP messages,</li>
	<li>the inclusion of uppercase field names, or</li>	<li>the inclusion of uppercase field names, or</li>
	<li>the inclusion of invalid characters in field names or values.</l i>	<li>the inclusion of invalid characters in field names or values.</l i>
	</ul>	</ul>
	<t>A request or response that is defined as having content when it con tains a	<t>A request or response that is defined as having content when it con tains a

	Content-Length header field (<xref section="6.4.1" sectionFormat="of" target="RF	Content-Length header field (<xref section='8.6' sectionFormat='of' target='RFC9
	CYYY4" format="default"/>),	110'/>) is malformed if the
	is malformed if the value of a Content-Length header field does not equal the	value of the Content-Length header field does not equal the sum of the <xref for
	sum of the DATA frame lengths received. A response that is defined as never	mat='none' target='frame-data'>DATA</xref><iref item='DATA'/>
	having content, even when a Content-Length is present, can have a non-zero	frame lengths received. A response that is defined as never having content, even
	Content-Length field even though no content is included in DATA frames.</t>	when a Content-Length is present, can have a non-zero Content-Length header
		field even though no content is included in <xref format='none' target='frame-da
		ta'>DATA</xref><iref item='DATA'/> frames.</t>
	<t>Intermediaries that process HTTP requests or responses (i.e., any i ntermediary	<t>Intermediaries that process HTTP requests or responses (i.e., any i ntermediary

	not acting as a tunnel) <bcp14>MUST NOT</bcp14> forward a malformed request or r	not acting as a tunnel) <bcp14>MUST NOT</bcp14>
	esponse.	forward a malformed request or response.
	Malformed requests or responses that are detected <bcp14>MUST</bcp14> be treated	Malformed requests or responses that are detected <bcp14>MUST</bcp14>
	as a stream	be treated as a <xref format='none' target='errors'>stream
	error (<xref target="errors" format="default"/>) of type H3_MESSAGE_ERROR.</t>	error</xref><iref item='stream error'/> of type <xref format='none' target='H3_M
	<t>For malformed requests, a server <bcp14>MAY</bcp14> send an HTTP re	ESSAGE_ERROR'>H3_MESSAGE_ERROR</xref><iref item='H3_MESSAGE_ERROR'/>.</t>
	sponse indicating the error	<t>For malformed requests, a server <bcp14>MAY</bcp14>
	prior to closing or resetting the stream. Clients <bcp14>MUST NOT</bcp14> accep	send an HTTP response indicating the error
	t a malformed	prior to closing or resetting the stream. Clients <bcp14>MUST NOT</b
		cp14>
		accept a malformed
	response. Note that these requirements are intended to protect against several	response. Note that these requirements are intended to protect against several
	types of common attacks against HTTP; they are deliberately strict because being	types of common attacks against HTTP; they are deliberately strict because being
	permissive can expose implementations to these vulnerabilities.</t>	permissive can expose implementations to these vulnerabilities.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="connect" numbered="true" toc="default">	<section anchor='header-formatting'>
		<name>HTTP Fields</name>
		<t>HTTP messages carry metadata as a series of key-value pairs called "H
		TTP
		fields"; see Sections <xref section='6.3' sectionFormat='bare' target='RFC9110'/
		> and <xref section='6.5' sectionFormat='bare' target='RFC9110'/> of <xref targe
		t='RFC9110'/>. For a listing of registered
		HTTP fields, see the "Hypertext Transfer Protocol (HTTP) Field Name Registry"
		maintained at <eref brackets='angle' target='https://www.iana.org/assignments/ht
		tp-fields/'/>. Like HTTP/2, HTTP/3 has additional considerations related to
		the use of characters in field names, the Connection header field, and
		pseudo-header fields.</t>
		<t>Field names are strings containing a subset of ASCII characters. Prop
		erties of
		HTTP field names and values are discussed in more detail in <xref section='5.1'
		sectionFormat='of' target='RFC9110'/>. Characters in field names <bcp14
		>MUST</bcp14>
		be converted to lowercase prior to
		their encoding. A request or response containing uppercase characters in field
		names <bcp14>MUST</bcp14>
		be treated as <xref format='none' target='malformed'>malformed</xref><iref item
		='malformed'/>.</t>
		<t>HTTP/3 does not use the Connection header field to indicate connectio
		n-specific
		fields; in this protocol, connection-specific metadata is conveyed by other
		means. An endpoint <bcp14>MUST NOT</bcp14>
		generate an HTTP/3 field section containing
		connection-specific fields; any message containing connection-specific fields
		<bcp14>MUST</bcp14>
		be treated as <xref format='none' target='malformed'>malformed</xref><iref item
		='malformed'/>.</t>
		<t>The only exception to this is the TE header field, which <bc
		p14>MAY</bcp14>
		be present in an
		HTTP/3 request header; when it is, it <bcp14>MUST NOT</bcp14>
		contain any value other than
		"trailers".</t>
		<t>An intermediary transforming an HTTP/1.x message to HTTP/3 <
		bcp14>MUST</bcp14>
		remove
		connection-specific header fields as discussed in <xref section='7.6.1' sectionF
		ormat='of' target='RFC9110'/>, or their messages will be treated by other HTTP/3
		endpoints as
		<xref format='none' target='malformed'>malformed</xref><iref item='malformed'/>.
		</t>
		<section anchor='field-compression'>
		<name>Field Compression</name>
		<t><xref target='RFC9204'/> describes a variation of HPACK that gives
		an encoder some control
		over how much head-of-line blocking can be caused by compression. This allows
		an encoder to balance compression efficiency with latency. HTTP/3 uses QPACK to
		compress header and trailer sections, including the control data present in the
		header section.</t>
		<t>To allow for better compression efficiency, the Cookie header field
		(<xref target='COOKIES'/>) <bcp14>MAY</bcp14>
		be split into separate field lines, each with one or
		more cookie-pairs, before compression. If a decompressed field section contains
		multiple cookie field lines, these <bcp14>MUST</bcp14>
		be concatenated into a single byte
		string using the two-byte delimiter of "<tt>; </tt>" (ASCII 0x3b, 0x20) bef
		ore being
		passed into a context other than HTTP/2 or HTTP/3, such as an HTTP/1.1
		connection, or a generic HTTP server application.</t>
		</section>
		<section anchor='header-size-constraints'>
		<name>Header Size Constraints</name>
		<t>An HTTP/3 implementation <bcp14>MAY</bcp14>
		impose a limit on the maximum size of the message
		header it will accept on an individual HTTP message. A server that receives a
		larger header section than it is willing to handle can send an HTTP 431 (Request
		Header Fields Too Large) status code (<xref target='RFC6585'/>). A client can d
		iscard
		responses that it cannot process. The size of a field list is calculated based
		on the uncompressed size of fields, including the length of the name and value
		in bytes plus an overhead of 32 bytes for each field.</t>
		<t>If an implementation wishes to advise its peer of this limit, it ca
		n be conveyed
		as a number of bytes in the <xref format='none' target='SETTINGS_MAX_FIELD_SECTI
		ON_SIZE'>SETTINGS_MAX_FIELD_SECTION_SIZE</xref><iref item='SETTINGS_MAX_FIELD_SE
		CTION_SIZE'/> parameter. An
		implementation that has received this parameter <bcp14>SHOULD NOT</bc
		p14>
		send an HTTP message
		header that exceeds the indicated size, as the peer will likely refuse to
		process it. However, an HTTP message can traverse one or more intermediaries
		before reaching the origin server; see <xref section='3.7' sectionFormat='of' ta
		rget='RFC9110'/>. Because
		this limit is applied separately by each implementation that processes the
		message, messages below this limit are not guaranteed to be accepted.</t>
		</section>
		</section>
		<section anchor='http-control-data'>
		<name>HTTP Control Data</name>
		<t>Like HTTP/2, HTTP/3 employs a series of pseudo-header fields, where t
		he field
		name begins with the <tt>:</tt> character (ASCII 0x3a). These pseudo-header fie
		lds
		convey message control data; see <xref section='6.2' sectionFormat='of' target='
		RFC9110'/>.</t>
		<t>Pseudo-header fields are not HTTP fields. Endpoints <bcp14>
		MUST NOT</bcp14>
		generate
		pseudo-header fields other than those defined in this document. However, an
		extension could negotiate a modification of this restriction; see
		<xref target='extensions'/>.</t>
		<t>Pseudo-header fields are only valid in the context in which they are
		defined.
		Pseudo-header fields defined for requests <bcp14>MUST NOT</bcp14>
		appear in responses;
		pseudo-header fields defined for responses <bcp14>MUST NOT</bcp14>
		appear in requests.
		Pseudo-header fields <bcp14>MUST NOT</bcp14>
		appear in trailer sections. Endpoints <bcp14>MUST</bcp14>
		treat a
		request or response that contains undefined or invalid pseudo-header fields as
		<xref format='none' target='malformed'>malformed</xref><iref item='malformed'/>.
		</t>
		<t>All pseudo-header fields <bcp14>MUST</bcp14>
		appear in the header section before regular header
		fields. Any request or response that contains a pseudo-header field that
		appears in a header section after a regular header field <bcp14>MUST</b
		cp14>
		be treated as
		<xref format='none' target='malformed'>malformed</xref><iref item='malformed'/>.
		</t>
		<section anchor='request-pseudo-header-fields'>
		<name>Request Pseudo-Header Fields</name>
		<t>The following pseudo-header fields are defined for requests:</t>
		<dl>
		<dt>":method":</dt>
		<dd>
		<t>Contains the HTTP method (<xref section='9' sectionFormat='of'
		target='RFC9110'/>)</t>
		</dd>
		<dt>":scheme":</dt>
		<dd>
		<t>Contains the scheme portion of the target URI (<xref section='3
		.1' sectionFormat='of' target='URI'/>).</t>
		</dd>
		<dt/>
		<dd>
		<t>The :scheme pseudo-header is not restricted to URIs with scheme
		"http" and
		"https". A proxy or gateway can translate requests for non-HTTP schemes,
		enabling the use of HTTP to interact with non-HTTP services.</t>
		</dd>
		<dt/>
		<dd>
		<t>See <xref target='other-schemes'/> for guidance on using a sche
		me other than "https".</t>
		</dd>
		<dt>":authority":</dt>
		<dd>
		<t>Contains the authority portion of the target URI (<xref section
		='3.2' sectionFormat='of' target='URI'/>).
		The authority <bcp14>MUST NOT</bcp14>
		include the deprecated userinfo
		subcomponent for URIs of scheme "http" or "https".</t>
		</dd>
		<dt/>
		<dd>
		<t>To ensure that the HTTP/1.1 request line can be reproduced accu
		rately, this
		pseudo-header field <bcp14>MUST</bcp14>
		be omitted when translating from an HTTP/1.1
		request that has a request target in a method-specific form; see <xref section='
		7.1' sectionFormat='of' target='RFC9110'/>. Clients that generate HTTP/3 reques
		ts directly <bcp14>SHOULD</bcp14>
		use
		the :authority pseudo-header field instead of the Host header field. An
		intermediary that converts an HTTP/3 request to HTTP/1.1 <bcp14>M
		UST</bcp14>
		create a Host
		field if one is not present in a request by copying the value of the
		:authority pseudo-header field.</t>
		</dd>
		<dt>":path":</dt>
		<dd>
		<t>Contains the path and query parts of the target URI (the "path-
		absolute"
		production and optionally a <tt>?</tt> character (ASCII 0x3f) followed by the
		"query" production; see Sections <xref section='3.3' sectionFormat='bare' target
		='URI'/> and <xref section='3.4' sectionFormat='bare' target='URI'/> of <xref ta
		rget='URI'/>.</t>
		</dd>
		<dt/>
		<dd>
		<t>This pseudo-header field <bcp14>MUST NOT</bcp14>
		be empty for "http" or "https" URIs;
		"http" or "https" URIs that do not contain a path component <bcp1
		4>MUST</bcp14>
		include a
		value of <tt>/</tt> (ASCII 0x2f). An OPTIONS request that does not include a pa
		th
		component includes the value <tt>*</tt> (ASCII 0x2a) for the :path pseudo-header
		field; see <xref section='7.1' sectionFormat='of' target='RFC9110'/>.</t>
		</dd>
		</dl>
		<t>All HTTP/3 requests <bcp14>MUST</bcp14>
		include exactly one value for the :method, :scheme,
		and :path pseudo-header fields, unless the request is a CONNECT request; see
		<xref target='connect'/>.</t>
		<t>If the :scheme pseudo-header field identifies a scheme that has a m
		andatory
		authority component (including "http" and "https"), the request <bcp1
		4>MUST</bcp14>
		contain
		either an :authority pseudo-header field or a Host header field. If these
		fields are present, they <bcp14>MUST NOT</bcp14>
		be empty. If both fields are present, they <bcp14>MUST</bcp14>
		contain the same value. If the scheme does not have a mandatory authority
		component and none is provided in the request target, the request <bc
		p14>MUST NOT</bcp14>

		contain the :authority pseudo-header or Host header fields.</t>
		<t>An HTTP request that omits mandatory pseudo-header fields or contai
		ns invalid
		values for those pseudo-header fields is <xref format='none' target='malformed'>
		malformed</xref><iref item='malformed'/>.</t>
		<t>HTTP/3 does not define a way to carry the version identifier that i
		s included in
		the HTTP/1.1 request line. HTTP/3 requests implicitly have a protocol version
		of "3.0".</t>
		</section>
		<section anchor='response-pseudo-header-fields'>
		<name>Response Pseudo-Header Fields</name>
		<t>For responses, a single ":status" pseudo-header field is defined th
		at carries
		the HTTP status code; see <xref section='15' sectionFormat='of' target='RFC9110'
		/>. This pseudo-header
		field <bcp14>MUST</bcp14>
		be included in all responses; otherwise, the response is <xref format='none' ta
		rget='malformed'>malformed</xref><iref item='malformed'/>
		(see <xref target='malformed'/>).</t>
		<t>HTTP/3 does not define a way to carry the version or reason phrase
		that is
		included in an HTTP/1.1 status line. HTTP/3 responses implicitly have a protocol
		version of "3.0".</t>
		</section>
		</section>
		<section anchor='connect'>
	<name>The CONNECT Method</name>	<name>The CONNECT Method</name>
	<t>The CONNECT method requests that the recipient establish a tunnel to the	<t>The CONNECT method requests that the recipient establish a tunnel to the

	destination origin server identified by the request-target; see <xref section="9 .3.6" sectionFormat="of" target="RFCYYY4" format="default"/>. It is primarily us ed with HTTP proxies to establish a TLS	destination origin server identified by the request-target; see <xref section='9 .3.6' sectionFormat='of' target='RFC9110'/>. It is primarily used with HTTP prox ies to establish a TLS
	session with an origin server for the purposes of interacting with "https"	session with an origin server for the purposes of interacting with "https"
	resources.</t>	resources.</t>
	<t>In HTTP/1.x, CONNECT is used to convert an entire HTTP connection int o a tunnel	<t>In HTTP/1.x, CONNECT is used to convert an entire HTTP connection int o a tunnel
	to a remote host. In HTTP/2 and HTTP/3, the CONNECT method is used to establish	to a remote host. In HTTP/2 and HTTP/3, the CONNECT method is used to establish
	a tunnel over a single stream.</t>	a tunnel over a single stream.</t>

	<t>A CONNECT request <bcp14>MUST</bcp14> be constructed as follows:</t>	<t>A CONNECT request <bcp14>MUST</bcp14>
	<ul spacing="normal">	be constructed as follows:</t>
	<li>The ":method" pseudo-header field is set to "CONNECT"</li>	<ul spacing='normal'>
	<li>The ":scheme" and ":path" pseudo-header fields are omitted</li>	<li>The :method pseudo-header field is set to "CONNECT"</li>
	<li>The ":authority" pseudo-header field contains the host and port to	<li>The :scheme and :path pseudo-header fields are omitted</li>
	connect to	<li>The :authority pseudo-header field contains the host and port to c
		onnect to
	(equivalent to the authority-form of the request-target of CONNECT requests;	(equivalent to the authority-form of the request-target of CONNECT requests;

	see <xref section="7.1" sectionFormat="of" target="RFCYYY4" format="default"/>)< /li>	see <xref section='7.1' sectionFormat='of' target='RFC9110'/>).</li>
	</ul>	</ul>

	<t>The request stream remains open at the end of the request to carry th e data to	<t>The <xref format='none' target='request-streams'>request stream</xref ><iref item='request stream'/> remains open at the end of the request to carry t he data to
	be transferred. A CONNECT request that does not conform to these restrictions	be transferred. A CONNECT request that does not conform to these restrictions

	is malformed; see <xref target="malformed" format="default"/>.</t>	is <xref format='none' target='malformed'>malformed</xref><iref item='malformed'
	<t>A proxy that supports CONNECT establishes a TCP connection (<xref tar	/>.</t>
	get="RFC0793" format="default"/>) to the	<t>A proxy that supports CONNECT establishes a TCP connection (<xref tar
	server identified in the ":authority" pseudo-header field. Once this connection	get='RFC0793'/>) to the
	is successfully established, the proxy sends a HEADERS frame containing a 2xx	server identified in the :authority pseudo-header field. Once this connection
	series status code to the client, as defined in <xref section="15.3" sectionForm	is successfully established, the proxy sends a <xref format='none' target='frame
	at="of" target="RFCYYY4" format="default"/>.</t>	-headers'>HEADERS</xref><iref item='HEADERS'/> frame containing a 2xx
	<t>All DATA frames on the stream correspond to data sent or received on	series status code to the client, as defined in <xref section='15.3' sectionForm
	the TCP	at='of' target='RFC9110'/>.</t>
	connection. The payload of any DATA frame sent by the client is transmitted by	<t>All <xref format='none' target='frame-data'>DATA</xref><iref item='DA
		TA'/> frames on the stream correspond to data sent or received on the TCP
		connection. The payload of any <xref format='none' target='frame-data'>DATA</xre
		f><iref item='DATA'/> frame sent by the client is transmitted by
	the proxy to the TCP server; data received from the TCP server is packaged into	the proxy to the TCP server; data received from the TCP server is packaged into

	DATA frames by the proxy. Note that the size and number of TCP segments is not	<xref format='none' target='frame-data'>DATA</xref><iref item='DATA'/> frames by
	guaranteed to map predictably to the size and number of HTTP DATA or QUIC STREAM	the proxy. Note that the size and number of TCP segments is not
		guaranteed to map predictably to the size and number of HTTP <xref format='none'
		target='frame-data'>DATA</xref><iref item='DATA'/> or QUIC STREAM
	frames.</t>	frames.</t>

	<t>Once the CONNECT method has completed, only DATA frames are permitted	<t>Once the CONNECT method has completed, only <xref format='none' targe
	to be sent	t='frame-data'>DATA</xref><iref item='DATA'/> frames are permitted to be sent
	on the stream. Extension frames <bcp14>MAY</bcp14> be used if specifically perm	on the stream. Extension frames <bcp14>MAY</bcp14>
	itted by the	be used if specifically permitted by the
	definition of the extension. Receipt of any other known frame type <bcp14>MUST<	definition of the extension. Receipt of any other known frame type <bc
	/bcp14> be	p14>MUST</bcp14>
	treated as a connection error of type H3_FRAME_UNEXPECTED; see <xref target="err	be
	ors" format="default"/>.</t>	treated as a <xref format='none' target='errors'>connection error</xref><iref it
		em='connection error'/> of type <xref format='none' target='H3_FRAME_UNEXPECTED'
		>H3_FRAME_UNEXPECTED</xref><iref item='H3_FRAME_UNEXPECTED'/>.</t>
	<t>The TCP connection can be closed by either peer. When the client ends the	<t>The TCP connection can be closed by either peer. When the client ends the

	request stream (that is, the receive stream at the proxy enters the "Data Recvd"	<xref format='none' target='request-streams'>request stream</xref><iref item='re quest stream'/> (that is, the receive stream at the proxy enters the "Data Recvd "
	state), the proxy will set the FIN bit on its connection to the TCP server. When	state), the proxy will set the FIN bit on its connection to the TCP server. When
	the proxy receives a packet with the FIN bit set, it will close the send stream	the proxy receives a packet with the FIN bit set, it will close the send stream

	that it sends to the client. TCP connections that remain half-closed in a	that it sends to the client. TCP connections that remain half closed in a
	single direction are not invalid, but are often handled poorly by servers, so	single direction are not invalid, but are often handled poorly by servers, so

	clients <bcp14>SHOULD NOT</bcp14> close a stream for sending while they still ex	clients <bcp14>SHOULD NOT</bcp14>
	pect to receive	close a stream for sending while they still expect to receive
	data from the target of the CONNECT.</t>	data from the target of the CONNECT.</t>

	<t>A TCP connection error is signaled by abruptly terminating the stream . A proxy	<t>A TCP <xref format='none' target='errors'>connection error</xref><ire f item='connection error'/> is signaled by abruptly terminating the stream. A pr oxy
	treats any error in the TCP connection, which includes receiving a TCP segment	treats any error in the TCP connection, which includes receiving a TCP segment

	with the RST bit set, as a stream error of type H3_CONNECT_ERROR; see	with the RST bit set, as a <xref format='none' target='errors'>stream error</xre
	<xref target="errors" format="default"/>. Correspondingly, if a proxy detects a	f><iref item='stream error'/> of type <xref format='none' target='H3_CONNECT_ERR
	n error with the stream or the	OR'>H3_CONNECT_ERROR</xref><iref item='H3_CONNECT_ERROR'/>.</t>
	QUIC connection, it <bcp14>MUST</bcp14> close the TCP connection. If the underl	<t>Correspondingly, if a proxy detects an error with the stream or the Q
	ying TCP	UIC
	implementation permits it, the proxy <bcp14>SHOULD</bcp14> send a TCP segment wi	connection, it <bcp14>MUST</bcp14>
	th the RST bit	close the TCP connection. If the proxy detects that the
	set.</t>	client has reset the stream or aborted reading from the stream, it <bcp
		14>MUST</bcp14>
		close
		the TCP connection. If the stream is reset or reading is aborted by the client,
		a proxy <bcp14>SHOULD</bcp14>
		perform the same operation on the other direction in order to
		ensure that both directions of the stream are cancelled. In all these cases, if
		the underlying TCP implementation permits it, the proxy <bcp14>SHOULD</
		bcp14>
		send a TCP
		segment with the RST bit set.</t>
	<t>Since CONNECT creates a tunnel to an arbitrary server, proxies that s upport	<t>Since CONNECT creates a tunnel to an arbitrary server, proxies that s upport

	CONNECT <bcp14>SHOULD</bcp14> restrict its use to a set of known ports or a list	CONNECT <bcp14>SHOULD</bcp14>
	of safe	restrict its use to a set of known ports or a list of safe
	request targets; see <xref section="9.3.6" sectionFormat="of" target="RFCYYY4" f	request targets; see <xref section='9.3.6' sectionFormat='of' target='RFC9110'/>
	ormat="default"/> for more detail.</t>	for more details.</t>
	</section>	</section>

	<section anchor="http-upgrade" numbered="true" toc="default">	<section anchor='http-upgrade'>
	<name>HTTP Upgrade</name>	<name>HTTP Upgrade</name>

	<t>HTTP/3 does not support the HTTP Upgrade mechanism (<xref section="7.	<t>HTTP/3 does not support the HTTP Upgrade mechanism (<xref section='7.
	8" sectionFormat="of" target="RFCYYY4" format="default"/>) or 101 (Switching Pro	8' sectionFormat='of' target='RFC9110'/>) or the 101 (Switching Protocols) infor
	tocols) informational status code (<xref section="15.2.2" sectionFormat="of" tar	mational status code
	get="RFCYYY4" format="default"/>).</t>	(<xref section='15.2.2' sectionFormat='of' target='RFC9110'/>).</t>
	</section>	</section>

	<section anchor="server-push" numbered="true" toc="default">	<section anchor='server-push'>
	<name>Server Push</name>	<name>Server Push</name><iref item='push ID' primary='true'/>
	<t>Server push is an interaction mode that permits a server to push a	<t>Server push is an interaction mode that permits a server to push a
	request-response exchange to a client in anticipation of the client making the	request-response exchange to a client in anticipation of the client making the
	indicated request. This trades off network usage against a potential latency	indicated request. This trades off network usage against a potential latency
	gain. HTTP/3 server push is similar to what is described in	gain. HTTP/3 server push is similar to what is described in

	<xref section="8.2" sectionFormat="of" target="RFC7540" format="default"/>, but	<xref section='8.2' sectionFormat='of' target='RFC9113'/>, but it uses different
	uses different mechanisms.</t>	mechanisms.</t>
	<t>Each server push is assigned a unique Push ID by the server. The Pus	<t>Each server push is assigned a unique push ID by the server. The pus
	h ID is	h ID is
	used to refer to the push in various contexts throughout the lifetime of the	used to refer to the push in various contexts throughout the lifetime of the
	HTTP/3 connection.</t>	HTTP/3 connection.</t>

	<t>The Push ID space begins at zero, and ends at a maximum value set by	<t>The push ID space begins at zero and ends at a maximum value set by t
	the	he
	MAX_PUSH_ID frame; see <xref target="frame-max-push-id" format="default"/>. In	<xref format='none' target='frame-max-push-id'>MAX_PUSH_ID</xref><iref item='MAX
	particular, a server is not	_PUSH_ID'/> frame. In particular, a server is not
	able to push until after the client sends a MAX_PUSH_ID frame. A client sends	able to push until after the client sends a <xref format='none' target='frame-ma
	MAX_PUSH_ID frames to control the number of pushes that a server can promise. A	x-push-id'>MAX_PUSH_ID</xref><iref item='MAX_PUSH_ID'/> frame. A client sends
	server <bcp14>SHOULD</bcp14> use Push IDs sequentially, beginning from zero. A	<xref format='none' target='frame-max-push-id'>MAX_PUSH_ID</xref><iref item='MAX
	client <bcp14>MUST</bcp14>	_PUSH_ID'/> frames to control the number of pushes that a server can promise. A
	treat receipt of a push stream as a connection error of type H3_ID_ERROR	server <bcp14>SHOULD</bcp14>
	(<xref target="errors" format="default"/>) when no MAX_PUSH_ID frame has been se	use push IDs sequentially, beginning from zero. A client <bcp14>MUST<
	nt or when the stream	/bcp14>
	references a Push ID that is greater than the maximum Push ID.</t>
	<t>The Push ID is used in one or more PUSH_PROMISE frames (<xref target=	treat receipt of a <xref format='none' target='push-streams'>push stream</xref><
	"frame-push-promise" format="default"/>)	iref item='push stream'/> as a <xref format='none' target='errors'>connection er
	that carry the header section of the request message. These frames are sent on	ror</xref><iref item='connection error'/> of type <xref format='none' target='H3
	the request stream that generated the push. This allows the server push to be	_ID_ERROR'>H3_ID_ERROR</xref><iref item='H3_ID_ERROR'/>
	associated with a client request. When the same Push ID is promised on multiple	when no <xref format='none' target='frame-max-push-id'>MAX_PUSH_ID</xref><iref i
	request streams, the decompressed request field sections <bcp14>MUST</bcp14> con	tem='MAX_PUSH_ID'/> frame has been sent or when the stream
	tain the same	references a push ID that is greater than the maximum push ID.</t>
	fields in the same order, and both the name and the value in each field <bcp14>M	<t>The push ID is used in one or more <xref format='none' target='frame-
	UST</bcp14> be	push-promise'>PUSH_PROMISE</xref><iref item='PUSH_PROMISE'/> frames that carry t
		he control
		data and header fields of the request message. These frames are sent on the
		<xref format='none' target='request-streams'>request stream</xref><iref item='re
		quest stream'/> that generated the push. This allows the server push to be
		associated with a client request. When the same push ID is promised on multiple
		<xref format='none' target='request-streams'>request streams</xref><iref item='r
		equest stream'/>, the decompressed request field sections <bcp14>MUST</
		bcp14>
		contain the same
		fields in the same order, and both the name and the value in each field
		<bcp14>MUST</bcp14>
		be
	identical.</t>	identical.</t>

	<t>The Push ID is then included with the push stream that ultimately ful	<t>The push ID is then included with the <xref format='none' target='pus
	fills	h-streams'>push stream</xref><iref item='push stream'/> that ultimately fulfills
	those promises; see <xref target="push-streams" format="default"/>. The push st	those promises. The <xref format='none' target='push-streams'>push stream</xref
	ream identifies the Push ID of	><iref item='push stream'/> identifies the push ID of
	the promise that it fulfills, then contains a response to the promised request	the promise that it fulfills, then contains a response to the promised request

	as described in <xref target="request-response" format="default"/>.</t>	as described in <xref target='request-response'/>.</t>
	<t>Finally, the Push ID can be used in CANCEL_PUSH frames; see	<t>Finally, the push ID can be used in <xref format='none' target='frame
	<xref target="frame-cancel-push" format="default"/>. Clients use this frame to	-cancel-push'>CANCEL_PUSH</xref><iref item='CANCEL_PUSH'/> frames; see
	indicate they do not wish to	<xref target='frame-cancel-push'/>. Clients use this frame to indicate they do
		not wish to
	receive a promised resource. Servers use this frame to indicate they will not	receive a promised resource. Servers use this frame to indicate they will not
	be fulfilling a previous promise.</t>	be fulfilling a previous promise.</t>

	<t>Not all requests can be pushed. A server <bcp14>MAY</bcp14> push req	<t>Not all requests can be pushed. A server <bcp14>MAY</bcp14>
	uests that have the	push requests that have the
	following properties:</t>	following properties:</t>

	<ul spacing="normal">	<ul spacing='normal'>
	<li>cacheable; see <xref section="9.2.3" sectionFormat="of" target="RF	<li>cacheable; see <xref section='9.2.3' sectionFormat='of' target='RF
	CYYY4" format="default"/></li>	C9110'/></li>
	<li>safe; see <xref section="9.2.1" sectionFormat="of" target="RFCYYY4	<li>safe; see <xref section='9.2.1' sectionFormat='of' target='RFC9110
	" format="default"/></li>	'/></li>
	<li>does not include a request body or trailer section</li>	<li>does not include request content or a trailer section</li>
	</ul>	</ul>

	<t>The server <bcp14>MUST</bcp14> include a value in the ":authority" ps	<t>The server <bcp14>MUST</bcp14>
	eudo-header field for	include a value in the :authority pseudo-header field for
	which the server is authoritative. If the client has not yet validated the	which the server is authoritative. If the client has not yet validated the

	connection for the origin indicated by the pushed request, it <bcp14>MUST</bcp14	connection for the origin indicated by the pushed request, it <bcp14>MU
	> perform the	ST</bcp14>
		perform the
	same verification process it would do before sending a request for that origin	same verification process it would do before sending a request for that origin

	on the connection; see <xref target="connection-reuse" format="default"/>. If t	on the connection; see <xref target='connection-reuse'/>. If this verification
	his verification fails,	fails,
	the client <bcp14>MUST NOT</bcp14> consider the server authoritative for that or	the client <bcp14>MUST NOT</bcp14>
	igin.</t>	consider the server authoritative for that origin.</t>
	<t>Clients <bcp14>SHOULD</bcp14> send a CANCEL_PUSH frame upon receipt o	<t>Clients <bcp14>SHOULD</bcp14>
	f a PUSH_PROMISE frame	send a <xref format='none' target='frame-cancel-push'>CANCEL_PUSH</xref><iref i
		tem='CANCEL_PUSH'/> frame upon receipt of a <xref format='none' target='frame-pu
		sh-promise'>PUSH_PROMISE</xref><iref item='PUSH_PROMISE'/> frame
	carrying a request that is not cacheable, is not known to be safe, that	carrying a request that is not cacheable, is not known to be safe, that

	indicates the presence of a request body, or for which it does not consider the	indicates the presence of request content, or for which it does not consider the
	server authoritative. Any corresponding responses <bcp14>MUST NOT</bcp14> be us	server authoritative. Any corresponding responses <bcp14>MUST NOT</bcp
	ed or cached.</t>	14>
		be used or cached.</t>
	<t>Each pushed response is associated with one or more client requests. The push	<t>Each pushed response is associated with one or more client requests. The push

	is associated with the request stream on which the PUSH_PROMISE frame was	is associated with the <xref format='none' target='request-streams'>request stre am</xref><iref item='request stream'/> on which the <xref format='none' target=' frame-push-promise'>PUSH_PROMISE</xref><iref item='PUSH_PROMISE'/> frame was
	received. The same server push can be associated with additional client	received. The same server push can be associated with additional client

	requests using a PUSH_PROMISE frame with the same Push ID on multiple request	requests using a <xref format='none' target='frame-push-promise'>PUSH_PROMISE</x
	streams. These associations do not affect the operation of the protocol, but	ref><iref item='PUSH_PROMISE'/> frame with the same push ID on multiple <xref fo
	<bcp14>MAY</bcp14> be considered by user agents when deciding how to use pushed	rmat='none' target='request-streams'>request
	resources.</t>	streams</xref><iref item='request stream'/>. These associations do not affect t
	<t>Ordering of a PUSH_PROMISE frame in relation to certain parts of the	he operation of the protocol, but
	response is	they <bcp14>MAY</bcp14>
	important. The server <bcp14>SHOULD</bcp14> send PUSH_PROMISE frames prior to se	be considered by user agents when deciding how to use pushed resources.</t>
	nding HEADERS	<t>Ordering of a <xref format='none' target='frame-push-promise'>PUSH_PR
	or DATA frames that reference the promised responses. This reduces the chance	OMISE</xref><iref item='PUSH_PROMISE'/> frame in relation to certain parts of th
		e response is
		important. The server <bcp14>SHOULD</bcp14>
		send <xref format='none' target='frame-push-promise'>PUSH_PROMISE</xref><iref i
		tem='PUSH_PROMISE'/> frames prior to sending <xref format='none' target='frame-h
		eaders'>HEADERS</xref><iref item='HEADERS'/>
		or <xref format='none' target='frame-data'>DATA</xref><iref item='DATA'/> frames
		that reference the promised responses. This reduces the chance
	that a client requests a resource that will be pushed by the server.</t>	that a client requests a resource that will be pushed by the server.</t>

	<t>Due to reordering, push stream data can arrive before the correspondi	<t>Due to reordering, <xref format='none' target='push-streams'>push str
	ng	eam</xref><iref item='push stream'/> data can arrive before the corresponding
	PUSH_PROMISE frame. When a client receives a new push stream with an	<xref format='none' target='frame-push-promise'>PUSH_PROMISE</xref><iref item='P
	as-yet-unknown Push ID, both the associated client request and the pushed	USH_PROMISE'/> frame. When a client receives a new <xref format='none' target='
		push-streams'>push stream</xref><iref item='push stream'/> with an
		as-yet-unknown push ID, both the associated client request and the pushed
	request header fields are unknown. The client can buffer the stream data in	request header fields are unknown. The client can buffer the stream data in

	expectation of the matching PUSH_PROMISE. The client can use stream flow control	expectation of the matching <xref format='none' target='frame-push-promise'>PUSH
	(see <xref section="4.1" sectionFormat="of" target="RFCYYY1" format="default"/>)	_PROMISE</xref><iref item='PUSH_PROMISE'/>. The client can use stream flow contr
	to limit the amount of data a server may	ol
	commit to the pushed stream.</t>	(<xref section='4.1' sectionFormat='of' target='QUIC-TRANSPORT'/>) to limit the
	<t>Push stream data can also arrive after a client has canceled a push.	amount of data a server may
	In this	commit to the pushed stream. Clients <bcp14>SHOULD</bcp14>
		abort reading and discard data
		already read from <xref format='none' target='push-streams'>push streams</xref><
		iref item='push stream'/> if no corresponding <xref format='none' target='frame-
		push-promise'>PUSH_PROMISE</xref><iref item='PUSH_PROMISE'/> frame is
		processed in a reasonable amount of time.</t>
		<t>Push stream data can also arrive after a client has cancelled a push.
		In this
	case, the client can abort reading the stream with an error code of	case, the client can abort reading the stream with an error code of

	H3_REQUEST_CANCELLED. This asks the server not to transfer additional data and	<xref format='none' target='H3_REQUEST_CANCELLED'>H3_REQUEST_CANCELLED</xref><ir ef item='H3_REQUEST_CANCELLED'/>. This asks the server not to transfer additiona l data and
	indicates that it will be discarded upon receipt.</t>	indicates that it will be discarded upon receipt.</t>

	<t>Pushed responses that are cacheable (see <xref section="3" sectionFor mat="of" target="RFCYYY3" format="default"/>) can be	<t>Pushed responses that are cacheable (see <xref section='3' sectionFor mat='of' target='RFC9111'/>) can be
	stored by the client, if it implements an HTTP cache. Pushed responses are	stored by the client, if it implements an HTTP cache. Pushed responses are
	considered successfully validated on the origin server (e.g., if the "no-cache"	considered successfully validated on the origin server (e.g., if the "no-cache"

	cache response directive is present; see <xref section="5.2.2.3" sectionFormat=" of" target="RFCYYY3" format="default"/>) at the	cache response directive is present; see <xref section='5.2.2.4' sectionFormat=' of' target='RFC9111'/>) at the
	time the pushed response is received.</t>	time the pushed response is received.</t>

	<t>Pushed responses that are not cacheable <bcp14>MUST NOT</bcp14> be st	<t>Pushed responses that are not cacheable <bcp14>MUST NOT</bcp
	ored by any HTTP cache.	14>
	They <bcp14>MAY</bcp14> be made available to the application separately.</t>	be stored by any HTTP cache.
		They <bcp14>MAY</bcp14>
		be made available to the application separately.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="connection-closure" numbered="true" toc="default">	<section anchor='connection-closure'>
	<name>Connection Closure</name>	<name>Connection Closure</name>
	<t>Once established, an HTTP/3 connection can be used for many requests an d	<t>Once established, an HTTP/3 connection can be used for many requests an d
	responses over time until the connection is closed. Connection closure can	responses over time until the connection is closed. Connection closure can
	happen in any of several different ways.</t>	happen in any of several different ways.</t>

	<section anchor="idle-connections" numbered="true" toc="default">	<section anchor='idle-connections'>
	<name>Idle Connections</name>	<name>Idle Connections</name>
	<t>Each QUIC endpoint declares an idle timeout during the handshake. If the QUIC	<t>Each QUIC endpoint declares an idle timeout during the handshake. If the QUIC
	connection remains idle (no packets received) for longer than this duration, the	connection remains idle (no packets received) for longer than this duration, the
	peer will assume that the connection has been closed. HTTP/3 implementations	peer will assume that the connection has been closed. HTTP/3 implementations
	will need to open a new HTTP/3 connection for new requests if the existing	will need to open a new HTTP/3 connection for new requests if the existing
	connection has been idle for longer than the idle timeout negotiated during the	connection has been idle for longer than the idle timeout negotiated during the

	QUIC handshake, and <bcp14>SHOULD</bcp14> do so if approaching the idle timeout;	QUIC handshake, and they <bcp14>SHOULD</bcp14>
	see <xref section="10.1" sectionFormat="of" target="RFCYYY1" format="default"/>	do so if approaching the idle timeout; see
	.</t>	<xref section='10.1' sectionFormat='of' target='QUIC-TRANSPORT'/>.</t>
	<t>HTTP clients are expected to request that the transport keep connecti ons open	<t>HTTP clients are expected to request that the transport keep connecti ons open
	while there are responses outstanding for requests or server pushes, as	while there are responses outstanding for requests or server pushes, as

	described in <xref section="10.1.2" sectionFormat="of" target="RFCYYY1" format=" default"/>. If the client is not	described in <xref section='10.1.2' sectionFormat='of' target='QUIC-TRANSPORT'/> . If the client is not
	expecting a response from the server, allowing an idle connection to time out is	expecting a response from the server, allowing an idle connection to time out is
	preferred over expending effort maintaining a connection that might not be	preferred over expending effort maintaining a connection that might not be

	needed. A gateway <bcp14>MAY</bcp14> maintain connections in anticipation of ne	needed. A gateway <bcp14>MAY</bcp14>
	ed rather than	maintain connections in anticipation of need rather than
	incur the latency cost of connection establishment to servers. Servers <bcp14>SH	incur the latency cost of connection establishment to servers. Servers
	OULD	<bcp14>SHOULD
	NOT</bcp14> actively keep connections open.</t>	NOT</bcp14>
		actively keep connections open.</t>
	</section>	</section>

	<section anchor="connection-shutdown" numbered="true" toc="default">	<section anchor='connection-shutdown'>
	<name>Connection Shutdown</name>	<name>Connection Shutdown</name>
	<t>Even when a connection is not idle, either endpoint can decide to sto p using the	<t>Even when a connection is not idle, either endpoint can decide to sto p using the
	connection and initiate a graceful connection close. Endpoints initiate the	connection and initiate a graceful connection close. Endpoints initiate the

	graceful shutdown of an HTTP/3 connection by sending a GOAWAY frame	graceful shutdown of an HTTP/3 connection by sending a <xref format='none' targe
	(<xref target="frame-goaway" format="default"/>). The GOAWAY frame contains an i	t='frame-goaway'>GOAWAY</xref><iref item='GOAWAY'/> frame. The <xref format='non
	dentifier that indicates to	e' target='frame-goaway'>GOAWAY</xref><iref item='GOAWAY'/>
	the receiver the range of requests or pushes that were or might be processed in	frame contains an identifier that indicates to the receiver the range of
	this connection. The server sends a client-initiated bidirectional Stream ID;	requests or pushes that were or might be processed in this connection. The
	the client sends a Push ID (<xref target="server-push" format="default"/>). Req	server sends a client-initiated bidirectional stream ID; the client sends a <xre
	uests or pushes with the	f format='none' target='server-push'>push
	indicated identifier or greater are rejected (<xref target="request-cancellation	ID</xref><iref item='push ID'/>. Requests or pushes with the indicated identifi
	" format="default"/>) by the	er or greater are rejected
	sender of the GOAWAY. This identifier <bcp14>MAY</bcp14> be zero if no requests	(<xref target='request-cancellation'/>) by the sender of the <xref format='none'
	or pushes were	target='frame-goaway'>GOAWAY</xref><iref item='GOAWAY'/>. This identifier
	processed.</t>	<bcp14>MAY</bcp14>
	<t>The information in the GOAWAY frame enables a client and server to ag	be
	ree on	zero if no requests or pushes were processed.</t>
		<t>The information in the <xref format='none' target='frame-goaway'>GOAW
		AY</xref><iref item='GOAWAY'/> frame enables a client and server to agree on
	which requests or pushes were accepted prior to the shutdown of the HTTP/3	which requests or pushes were accepted prior to the shutdown of the HTTP/3

	connection. Upon sending a GOAWAY frame, the endpoint <bcp14>SHOULD</bcp14> expl	connection. Upon sending a <xref format='none' target='frame-goaway'>GOAWAY</xre
	icitly cancel	f><iref item='GOAWAY'/> frame, the endpoint <bcp14>SHOULD</bcp14>
	(see <xref target="request-cancellation" format="default"/> and <xref target="fr	explicitly cancel
	ame-cancel-push" format="default"/>) any requests or pushes	(see Sections <xref format='counter' target='request-cancellation'/> and <xref f
	that have identifiers greater than or equal to that indicated, in order to clean	ormat='counter' target='frame-cancel-push'/>) any requests
	up transport state for the affected streams. The endpoint <bcp14>SHOULD</bcp14>	or pushes that have identifiers greater than or equal to the one indicated, in
	continue to do	order to clean up transport state for the affected streams. The endpoint
	so as more requests or pushes arrive.</t>	<bcp14>SHOULD</bcp14>
	<t>Endpoints <bcp14>MUST NOT</bcp14> initiate new requests or promise ne
	w pushes on the connection	continue to do so as more requests or pushes arrive.</t>
	after receipt of a GOAWAY frame from the peer. Clients <bcp14>MAY</bcp14> estab	<t>Endpoints <bcp14>MUST NOT</bcp14>
	lish a new	initiate new requests or promise new pushes on the connection
		after receipt of a <xref format='none' target='frame-goaway'>GOAWAY</xref><iref
		item='GOAWAY'/> frame from the peer. Clients <bcp14>MAY</bcp14>
		establish a new
	connection to send additional requests.</t>	connection to send additional requests.</t>
	<t>Some requests or pushes might already be in transit:</t>	<t>Some requests or pushes might already be in transit:</t>

	<ul spacing="normal">	<ul spacing='normal'>
	<li>	<li>

	<t>Upon receipt of a GOAWAY frame, if the client has already sent re	<t>Upon receipt of a <xref format='none' target='frame-goaway'>GOAWA
	quests with	Y</xref><iref item='GOAWAY'/> frame, if the client has already sent requests wit
	a Stream ID greater than or equal to the identifier contained in the GOAWAY	h
		a stream ID greater than or equal to the identifier contained in the <xref forma
		t='none' target='frame-goaway'>GOAWAY</xref><iref item='GOAWAY'/>
	frame, those requests will not be processed. Clients can safely retry	frame, those requests will not be processed. Clients can safely retry
	unprocessed requests on a different HTTP connection. A client that is	unprocessed requests on a different HTTP connection. A client that is
	unable to retry requests loses all requests that are in flight when the	unable to retry requests loses all requests that are in flight when the

	server closes the connection. </t>	server closes the connection.</t>
	<t>	<t>Requests on stream IDs less than the stream ID in a <xref format=
	Requests on Stream IDs less than the Stream ID in a GOAWAY frame from the	'none' target='frame-goaway'>GOAWAY</xref><iref item='GOAWAY'/> frame from the
	server might have been processed; their status cannot be known until a	server might have been processed; their status cannot be known until a

	response is received, the stream is reset individually, another GOAWAY is	response is received, the stream is reset individually, another <xref format='no
	received with a lower Stream ID than that of the request in question,	ne' target='frame-goaway'>GOAWAY</xref><iref item='GOAWAY'/> is
	or the connection terminates. </t>	received with a lower stream ID than that of the request in question,
	<t>	or the connection terminates.</t>
	Servers <bcp14>MAY</bcp14> reject individual requests on streams below the indic	<t>Servers <bcp14>MAY</bcp14>
	ated ID if	reject individual requests on streams below the indicated ID if
	these requests were not processed.</t>	these requests were not processed.</t>
	</li>	</li>

	<li>If a server receives a GOAWAY frame after having promised pushes w	<li>If a server receives a <xref format='none' target='frame-goaway'>G
	ith a Push	OAWAY</xref><iref item='GOAWAY'/> frame after having promised pushes with a <xre
	ID greater than or equal to the identifier contained in the GOAWAY frame,	f format='none' target='server-push'>push
		ID</xref><iref item='push ID'/> greater than or equal to the identifier containe
		d in the <xref format='none' target='frame-goaway'>GOAWAY</xref><iref item='GOAW
		AY'/> frame,
	those pushes will not be accepted.</li>	those pushes will not be accepted.</li>
	</ul>	</ul>

	<t>Servers <bcp14>SHOULD</bcp14> send a GOAWAY frame when the closing of	<t>Servers <bcp14>SHOULD</bcp14>
	a connection is known	send a <xref format='none' target='frame-goaway'>GOAWAY</xref><iref item='GOAWA
		Y'/> frame when the closing of a connection is known
	in advance, even if the advance notice is small, so that the remote peer can	in advance, even if the advance notice is small, so that the remote peer can

	know whether a request has been partially processed or not. For example, if an	know whether or not a request has been partially processed. For example, if an
	HTTP client sends a POST at the same time that a server closes a QUIC	HTTP client sends a POST at the same time that a server closes a QUIC
	connection, the client cannot know if the server started to process that POST	connection, the client cannot know if the server started to process that POST

	request if the server does not send a GOAWAY frame to indicate what streams it	request if the server does not send a <xref format='none' target='frame-goaway'> GOAWAY</xref><iref item='GOAWAY'/> frame to indicate what streams it
	might have acted on.</t>	might have acted on.</t>

	<t>An endpoint <bcp14>MAY</bcp14> send multiple GOAWAY frames indicating	<t>An endpoint <bcp14>MAY</bcp14>
	different identifiers,	send multiple <xref format='none' target='frame-goaway'>GOAWAY</xref><iref item
	but the identifier in each frame <bcp14>MUST NOT</bcp14> be greater than the ide	='GOAWAY'/> frames indicating different identifiers,
	ntifier in any	but the identifier in each frame <bcp14>MUST NOT</bcp14>
		be greater than the identifier in any
	previous frame, since clients might already have retried unprocessed requests on	previous frame, since clients might already have retried unprocessed requests on

	another HTTP connection. Receiving a GOAWAY containing a larger identifier than	another HTTP connection. Receiving a <xref format='none' target='frame-goaway'>
	previously received <bcp14>MUST</bcp14> be treated as a connection error of type	GOAWAY</xref><iref item='GOAWAY'/> containing a larger identifier than
	H3_ID_ERROR;	previously received <bcp14>MUST</bcp14>
	see <xref target="errors" format="default"/>.</t>	be treated as a <xref format='none' target='errors'>connection error</xref><ire
		f item='connection error'/> of type <xref format='none' target='H3_ID_ERROR'>H3_
		ID_ERROR</xref><iref item='H3_ID_ERROR'/>.</t>
	<t>An endpoint that is attempting to gracefully shut down a connection c an send a	<t>An endpoint that is attempting to gracefully shut down a connection c an send a

	GOAWAY frame with a value set to the maximum possible value (2<sup>62</sup>-4	<xref format='none' target='frame-goaway'>GOAWAY</xref><iref item='GOAWAY'/> fra me with a value set to the maximum possible value (2<sup>62</sup>-4
	for servers, 2<sup>62</sup>-1 for clients). This ensures that the peer stops	for servers, 2<sup>62</sup>-1 for clients). This ensures that the peer stops
	creating new requests or pushes. After allowing time for any in-flight requests	creating new requests or pushes. After allowing time for any in-flight requests

	or pushes to arrive, the endpoint can send another GOAWAY frame indicating which	or pushes to arrive, the endpoint can send another <xref format='none' target='f rame-goaway'>GOAWAY</xref><iref item='GOAWAY'/> frame indicating which
	requests or pushes it might accept before the end of the connection. This	requests or pushes it might accept before the end of the connection. This
	ensures that a connection can be cleanly shut down without losing requests.</t>	ensures that a connection can be cleanly shut down without losing requests.</t>

	<t>A client has more flexibility in the value it chooses for the Push ID	<t>A client has more flexibility in the value it chooses for the Push ID
	in a	field in a
	GOAWAY that it sends. A value of 2<sup>62</sup>-1 indicates that the server can	<xref format='none' target='frame-goaway'>GOAWAY</xref><iref item='GOAWAY'/> tha
		t it sends. A value of 2<sup>62</sup>-1 indicates that the server can
	continue fulfilling pushes that have already been promised. A smaller value	continue fulfilling pushes that have already been promised. A smaller value

	indicates the client will reject pushes with Push IDs greater than or equal to	indicates the client will reject pushes with push IDs greater than or equal to
	this value. Like the server, the client <bcp14>MAY</bcp14> send subsequent GOAW	this value. Like the server, the client <bcp14>MAY</bcp14>
	AY frames so	send subsequent <xref format='none' target='frame-goaway'>GOAWAY</xref><iref it
	long as the specified Push ID is no greater than any previously sent value.</t>	em='GOAWAY'/> frames so
	<t>Even when a GOAWAY indicates that a given request or push will not be	long as the specified <xref format='none' target='server-push'>push ID</xref><ir
	processed	ef item='push ID'/> is no greater than any previously sent value.</t>
		<t>Even when a <xref format='none' target='frame-goaway'>GOAWAY</xref><i
		ref item='GOAWAY'/> indicates that a given request or push will not be processed
	or accepted upon receipt, the underlying transport resources still exist. The	or accepted upon receipt, the underlying transport resources still exist. The
	endpoint that initiated these requests can cancel them to clean up transport	endpoint that initiated these requests can cancel them to clean up transport
	state.</t>	state.</t>
	<t>Once all accepted requests and pushes have been processed, the endpoi nt can	<t>Once all accepted requests and pushes have been processed, the endpoi nt can

	permit the connection to become idle, or <bcp14>MAY</bcp14> initiate an immediat	permit the connection to become idle, or it <bcp14>MAY</bcp14>
	e closure of	initiate an immediate closure of
	the connection. An endpoint that completes a graceful shutdown <bcp14>SHOULD</b	the connection. An endpoint that completes a graceful shutdown <bcp14>
	cp14> use the	SHOULD</bcp14>
	H3_NO_ERROR error code when closing the connection.</t>	use the
		<xref format='none' target='H3_NO_ERROR'>H3_NO_ERROR</xref><iref item='H3_NO_ERR
		OR'/> error code when closing the connection.</t>
	<t>If a client has consumed all available bidirectional stream IDs with requests,	<t>If a client has consumed all available bidirectional stream IDs with requests,

	the server need not send a GOAWAY frame, since the client is unable to make	the server need not send a <xref format='none' target='frame-goaway'>GOAWAY</xre f><iref item='GOAWAY'/> frame, since the client is unable to make
	further requests.</t>	further requests.</t>
	</section>	</section>

	<section anchor="immediate-application-closure" numbered="true" toc="defau lt">	<section anchor='immediate-application-closure'>
	<name>Immediate Application Closure</name>	<name>Immediate Application Closure</name>
	<t>An HTTP/3 implementation can immediately close the QUIC connection at any time.	<t>An HTTP/3 implementation can immediately close the QUIC connection at any time.
	This results in sending a QUIC CONNECTION_CLOSE frame to the peer indicating	This results in sending a QUIC CONNECTION_CLOSE frame to the peer indicating
	that the application layer has terminated the connection. The application error	that the application layer has terminated the connection. The application error
	code in this frame indicates to the peer why the connection is being closed.	code in this frame indicates to the peer why the connection is being closed.

	See <xref target="errors" format="default"/> for error codes that can be used wh en closing a connection in	See <xref target='errors'/> for error codes that can be used when closing a conn ection in
	HTTP/3.</t>	HTTP/3.</t>

	<t>Before closing the connection, a GOAWAY frame <bcp14>MAY</bcp14> be s	<t>Before closing the connection, a <xref format='none' target='frame-go
	ent to allow the client to	away'>GOAWAY</xref><iref item='GOAWAY'/> frame <bcp14>MAY</bcp14>
	retry some requests. Including the GOAWAY frame in the same packet as the QUIC	be sent to allow the client to
		retry some requests. Including the <xref format='none' target='frame-goaway'>GO
		AWAY</xref><iref item='GOAWAY'/> frame in the same packet as the QUIC
	CONNECTION_CLOSE frame improves the chances of the frame being received by	CONNECTION_CLOSE frame improves the chances of the frame being received by
	clients.</t>	clients.</t>
	<t>If there are open streams that have not been explicitly closed, they are	<t>If there are open streams that have not been explicitly closed, they are
	implicitly closed when the connection is closed; see	implicitly closed when the connection is closed; see

	<xref section="10.2" sectionFormat="of" target="RFCYYY1" format="default"/>.</t>	<xref section='10.2' sectionFormat='of' target='QUIC-TRANSPORT'/>.</t>
	</section>	</section>

	<section anchor="transport-closure" numbered="true" toc="default">	<section anchor='transport-closure'>
	<name>Transport Closure</name>	<name>Transport Closure</name>
	<t>For various reasons, the QUIC transport could indicate to the applica tion layer	<t>For various reasons, the QUIC transport could indicate to the applica tion layer
	that the connection has terminated. This might be due to an explicit closure	that the connection has terminated. This might be due to an explicit closure
	by the peer, a transport-level error, or a change in network topology that	by the peer, a transport-level error, or a change in network topology that
	interrupts connectivity.</t>	interrupts connectivity.</t>

	<t>If a connection terminates without a GOAWAY frame, clients <bcp14>MUS	<t>If a connection terminates without a <xref format='none' target='fram
	T</bcp14> assume that any	e-goaway'>GOAWAY</xref><iref item='GOAWAY'/> frame, clients <bcp14>MUST
		</bcp14>
		assume that any
	request that was sent, whether in whole or in part, might have been processed.</ t>	request that was sent, whether in whole or in part, might have been processed.</ t>
	</section>	</section>
	</section>	</section>

	<section anchor="stream-mapping" numbered="true" toc="default">	<section anchor='stream-mapping'>
	<name>Stream Mapping and Usage</name>	<name>Stream Mapping and Usage</name>
	<t>A QUIC stream provides reliable in-order delivery of bytes, but makes n o	<t>A QUIC stream provides reliable in-order delivery of bytes, but makes n o
	guarantees about order of delivery with regard to bytes on other streams. In	guarantees about order of delivery with regard to bytes on other streams. In
	version 1 of QUIC, the stream data containing HTTP frames is carried by QUIC	version 1 of QUIC, the stream data containing HTTP frames is carried by QUIC
	STREAM frames, but this framing is invisible to the HTTP framing layer. The	STREAM frames, but this framing is invisible to the HTTP framing layer. The
	transport layer buffers and orders received stream data, exposing a reliable	transport layer buffers and orders received stream data, exposing a reliable
	byte stream to the application. Although QUIC permits out-of-order delivery	byte stream to the application. Although QUIC permits out-of-order delivery
	within a stream, HTTP/3 does not make use of this feature.</t>	within a stream, HTTP/3 does not make use of this feature.</t>
	<t>QUIC streams can be either unidirectional, carrying data only from init iator to	<t>QUIC streams can be either unidirectional, carrying data only from init iator to

	receiver, or bidirectional. Streams can be initiated by either the client or	receiver, or bidirectional, carrying data in both directions. Streams can be
	the server. For more detail on QUIC streams, see	initiated by either the client or the server. For more detail on QUIC streams,
	<xref section="2" sectionFormat="of" target="RFCYYY1" format="default"/>.</t>	see <xref section='2' sectionFormat='of' target='QUIC-TRANSPORT'/>.</t>
	<t>When HTTP fields and data are sent over QUIC, the QUIC layer handles mo st of	<t>When HTTP fields and data are sent over QUIC, the QUIC layer handles mo st of
	the stream management. HTTP does not need to do any separate multiplexing when	the stream management. HTTP does not need to do any separate multiplexing when

	using QUIC - data sent over a QUIC stream always maps to a particular HTTP	using QUIC: data sent over a QUIC stream always maps to a particular HTTP
	transaction or to the entire HTTP/3 connection context.</t>	transaction or to the entire HTTP/3 connection context.</t>

	<section anchor="request-streams" numbered="true" toc="default">	<section anchor='request-streams'>
	<name>Bidirectional Streams</name>	<name>Bidirectional Streams</name><iref item='request stream' primary='t
		rue'/>
	<t>All client-initiated bidirectional streams are used for HTTP requests and	<t>All client-initiated bidirectional streams are used for HTTP requests and
	responses. A bidirectional stream ensures that the response can be readily	responses. A bidirectional stream ensures that the response can be readily
	correlated with the request. These streams are referred to as request streams.< /t>	correlated with the request. These streams are referred to as request streams.< /t>
	<t>This means that the client's first request occurs on QUIC stream 0, w ith	<t>This means that the client's first request occurs on QUIC stream 0, w ith

	subsequent requests on stream 4, 8, and so on. In order to permit these streams	subsequent requests on streams 4, 8, and so on. In order to permit these streams
	to open, an HTTP/3 server <bcp14>SHOULD</bcp14> configure non-zero minimum value	to open, an HTTP/3 server <bcp14>SHOULD</bcp14>
	s for the	configure non-zero minimum values for the
	number of permitted streams and the initial stream flow control window. So as	number of permitted streams and the initial stream flow-control window. So as
	to not unnecessarily limit parallelism, at least 100 request streams <bcp14>SHOU	to not unnecessarily limit parallelism, at least 100 request streams <b
	LD</bcp14> be	cp14>SHOULD</bcp14>
		be
	permitted at a time.</t>	permitted at a time.</t>
	<t>HTTP/3 does not use server-initiated bidirectional streams, though an extension	<t>HTTP/3 does not use server-initiated bidirectional streams, though an extension

	could define a use for these streams. Clients <bcp14>MUST</bcp14> treat receipt	could define a use for these streams. Clients <bcp14>MUST</bcp14>
	of a	treat receipt of a
	server-initiated bidirectional stream as a connection error of type	server-initiated bidirectional stream as a <xref format='none' target='errors'>c
	H3_STREAM_CREATION_ERROR (<xref target="errors" format="default"/>) unless such	onnection error</xref><iref item='connection error'/> of type
	an extension has been	<xref format='none' target='H3_STREAM_CREATION_ERROR'>H3_STREAM_CREATION_ERROR</
		xref><iref item='H3_STREAM_CREATION_ERROR'/> unless such an extension has been
	negotiated.</t>	negotiated.</t>
	</section>	</section>

	<section anchor="unidirectional-streams" numbered="true" toc="default">	<section anchor='unidirectional-streams'>
	<name>Unidirectional Streams</name>	<name>Unidirectional Streams</name>
	<t>Unidirectional streams, in either direction, are used for a range of purposes.	<t>Unidirectional streams, in either direction, are used for a range of purposes.
	The purpose is indicated by a stream type, which is sent as a variable-length	The purpose is indicated by a stream type, which is sent as a variable-length
	integer at the start of the stream. The format and structure of data that	integer at the start of the stream. The format and structure of data that
	follows this integer is determined by the stream type.</t>	follows this integer is determined by the stream type.</t>

	<figure anchor="fig-stream-header">	<figure>
	<name>Unidirectional Stream Header</name>	<name>Unidirectional Stream Header</name>

	<artwork type="drawing" name="" align="left" alt=""><![CDATA[	<artwork type='ascii-art'><![CDATA[
	Unidirectional Stream Header {	Unidirectional Stream Header {
	Stream Type (i),	Stream Type (i),
	}	}
	]]></artwork>	]]></artwork>
	</figure>	</figure>

	<t>Two stream types are defined in this document: control streams	<t>Two stream types are defined in this document: <xref format='none' ta
	(<xref target="control-streams" format="default"/>) and push streams (<xref targ	rget='control-streams'>control streams</xref><iref item='control stream'/>
	et="push-streams" format="default"/>). <xref target="RFCYYY2" format="default"/>	(<xref target='control-streams'/>) and <xref format='none' target='push-streams'
	defines	>push streams</xref><iref item='push stream'/> (<xref target='push-streams'/>).
		<xref target='RFC9204'/> defines
	two additional stream types. Other stream types can be defined by extensions to	two additional stream types. Other stream types can be defined by extensions to

	HTTP/3; see <xref target="extensions" format="default"/> for more details. Some	HTTP/3; see <xref target='extensions'/> for more details. Some stream types are
	stream types are reserved	reserved
	(<xref target="stream-grease" format="default"/>).</t>	(<xref target='stream-grease'/>).</t>
	<t>The performance of HTTP/3 connections in the early phase of their lif etime is	<t>The performance of HTTP/3 connections in the early phase of their lif etime is
	sensitive to the creation and exchange of data on unidirectional streams.	sensitive to the creation and exchange of data on unidirectional streams.

	Endpoints that excessively restrict the number of streams or the flow control	Endpoints that excessively restrict the number of streams or the flow-control
	window of these streams will increase the chance that the remote peer reaches	window of these streams will increase the chance that the remote peer reaches
	the limit early and becomes blocked. In particular, implementations should	the limit early and becomes blocked. In particular, implementations should
	consider that remote peers may wish to exercise reserved stream behavior	consider that remote peers may wish to exercise reserved stream behavior

	(<xref target="stream-grease" format="default"/>) with some of the unidirectiona	(<xref target='stream-grease'/>) with some of the unidirectional streams they ar
	l streams they are permitted	e permitted
	to use. To avoid blocking, the transport parameters sent by both clients and	to use.</t>
	servers <bcp14>MUST</bcp14> allow the peer to create at least one unidirectional	<t>Each endpoint needs to create at least one unidirectional stream for
	stream for the	the HTTP
	HTTP control stream plus the number of unidirectional streams required by	<xref format='none' target='control-streams'>control stream</xref><iref item='co
	mandatory extensions (three being the minimum number required for the base	ntrol stream'/>. QPACK requires two additional unidirectional streams, and other
	HTTP/3 protocol and QPACK), and <bcp14>SHOULD</bcp14> provide at least 1,024 byt	extensions might require further streams. Therefore, the transport parameters
	es of flow	sent by both clients and servers <bcp14>MUST</bcp14>
	control credit to each stream.</t>	allow the peer to create at least three
		unidirectional streams. These transport parameters <bcp14>SHOULD</bcp14
		>
		also provide at least
		1,024 bytes of flow-control credit to each unidirectional stream.</t>
	<t>Note that an endpoint is not required to grant additional credits to create more	<t>Note that an endpoint is not required to grant additional credits to create more
	unidirectional streams if its peer consumes all the initial credits before	unidirectional streams if its peer consumes all the initial credits before

	creating the critical unidirectional streams. Endpoints <bcp14>SHOULD</bcp14> cr	creating the critical unidirectional streams. Endpoints <bcp14>SHOULD</
	eate the HTTP	bcp14>
	control stream as well as the unidirectional streams required by mandatory	create the HTTP
		<xref format='none' target='control-streams'>control stream</xref><iref item='co
		ntrol stream'/> as well as the unidirectional streams required by mandatory
	extensions (such as the QPACK encoder and decoder streams) first, and then	extensions (such as the QPACK encoder and decoder streams) first, and then
	create additional streams as allowed by their peer.</t>	create additional streams as allowed by their peer.</t>
	<t>If the stream header indicates a stream type that is not supported by the	<t>If the stream header indicates a stream type that is not supported by the
	recipient, the remainder of the stream cannot be consumed as the semantics are	recipient, the remainder of the stream cannot be consumed as the semantics are

	unknown. Recipients of unknown stream types <bcp14>MAY</bcp14> abort reading of	unknown. Recipients of unknown stream types <bcp14>MUST</bcp14>
	the stream with	either abort reading of the
	an error code of H3_STREAM_CREATION_ERROR or a reserved error code	stream or discard incoming data without further processing. If reading is
	(<xref target="http-error-codes" format="default"/>), but <bcp14>MUST NOT</bcp14	aborted, the recipient <bcp14>SHOULD</bcp14>
	> consider such streams to be a connection	use the <xref format='none' target='H3_STREAM_CREATION_ERROR'>H3_STREAM_CREATIO
	error of any kind.</t>	N_ERROR</xref><iref item='H3_STREAM_CREATION_ERROR'/> error code or a
	<t>Implementations <bcp14>MAY</bcp14> send stream types before knowing w	reserved error code (<xref target='http-error-codes'/>). The recipient
	hether the peer supports	<bcp14>MUST NOT</bcp14>
		consider
		unknown stream types to be a <xref format='none' target='errors'>connection erro
		r</xref><iref item='connection error'/> of any kind.</t>
		<t>As certain stream types can affect connection state, a recipient
		<bcp14>SHOULD NOT</bcp14>

		discard data from incoming unidirectional streams prior to reading the stream
		type.</t>
		<t>Implementations <bcp14>MAY</bcp14>
		send stream types before knowing whether the peer supports
	them. However, stream types that could modify the state or semantics of	them. However, stream types that could modify the state or semantics of

	existing protocol components, including QPACK or other extensions, <bcp14>MUST N	existing protocol components, including QPACK or other extensions, <bcp
	OT</bcp14> be	14>MUST NOT</bcp14>
		be
	sent until the peer is known to support them.</t>	sent until the peer is known to support them.</t>
	<t>A sender can close or reset a unidirectional stream unless otherwise specified.	<t>A sender can close or reset a unidirectional stream unless otherwise specified.

	A receiver <bcp14>MUST</bcp14> tolerate unidirectional streams being closed or r	A receiver <bcp14>MUST</bcp14>
	eset prior to	tolerate unidirectional streams being closed or reset prior to
	the reception of the unidirectional stream header.</t>	the reception of the unidirectional stream header.</t>

	<section anchor="control-streams" numbered="true" toc="default">	<section anchor='control-streams'>
	<name>Control Streams</name>	<name>Control Streams</name><iref item='control stream' primary='true'
		/>
	<t>A control stream is indicated by a stream type of 0x00. Data on th is stream	<t>A control stream is indicated by a stream type of 0x00. Data on th is stream

	consists of HTTP/3 frames, as defined in <xref target="frames" format="default"/	consists of HTTP/3 frames, as defined in <xref target='frames'/>.</t>
	>.</t>	<t>Each side <bcp14>MUST</bcp14>
	<t>Each side <bcp14>MUST</bcp14> initiate a single control stream at t	initiate a single control stream at the beginning of the
	he beginning of the	connection and send its <xref format='none' target='frame-settings'>SETTINGS</xr
	connection and send its SETTINGS frame as the first frame on this stream. If	ef><iref item='SETTINGS'/> frame as the first frame on this stream. If
	the first frame of the control stream is any other frame type, this <bcp14>MUST<	the first frame of the control stream is any other frame type, this <
	/bcp14> be	bcp14>MUST</bcp14>
	treated as a connection error of type H3_MISSING_SETTINGS. Only one control	be
		treated as a <xref format='none' target='errors'>connection error</xref><iref it
		em='connection error'/> of type <xref format='none' target='H3_MISSING_SETTINGS'
		>H3_MISSING_SETTINGS</xref><iref item='H3_MISSING_SETTINGS'/>. Only one control
	stream per peer is permitted; receipt of a second stream claiming to be a	stream per peer is permitted; receipt of a second stream claiming to be a

	control stream <bcp14>MUST</bcp14> be treated as a connection error of type	control stream <bcp14>MUST</bcp14>
	H3_STREAM_CREATION_ERROR. The sender <bcp14>MUST NOT</bcp14> close the control	be treated as a <xref format='none' target='errors'>connection error</xref><ire
	stream, and the	f item='connection error'/> of type
	receiver <bcp14>MUST NOT</bcp14> request that the sender close the control strea	<xref format='none' target='H3_STREAM_CREATION_ERROR'>H3_STREAM_CREATION_ERROR</
	m. If either	xref><iref item='H3_STREAM_CREATION_ERROR'/>. The sender <bcp14>MUST
	control stream is closed at any point, this <bcp14>MUST</bcp14> be treated as a	NOT</bcp14>
	connection	close the control stream, and the
	error of type H3_CLOSED_CRITICAL_STREAM. Connection errors are described in	receiver <bcp14>MUST NOT</bcp14>
	<xref target="errors" format="default"/>.</t>	request that the sender close the control stream. If either
		control stream is closed at any point, this <bcp14>MUST</bcp14>
		be treated as a <xref format='none' target='errors'>connection
		error</xref><iref item='connection error'/> of type <xref format='none' target='
		H3_CLOSED_CRITICAL_STREAM'>H3_CLOSED_CRITICAL_STREAM</xref><iref item='H3_CLOSED
		_CRITICAL_STREAM'/>. Connection errors are described in
		<xref target='errors'/>.</t>
	<t>Because the contents of the control stream are used to manage the b ehavior of	<t>Because the contents of the control stream are used to manage the b ehavior of

	other streams, endpoints <bcp14>SHOULD</bcp14> provide enough flow control credi	other streams, endpoints <bcp14>SHOULD</bcp14>
	t to keep the	provide enough flow-control credit to keep the
	peer's control stream from becoming blocked.</t>	peer's control stream from becoming blocked.</t>
	<t>A pair of unidirectional streams is used rather than a single bidir ectional	<t>A pair of unidirectional streams is used rather than a single bidir ectional
	stream. This allows either peer to send data as soon as it is able. Depending	stream. This allows either peer to send data as soon as it is able. Depending
	on whether 0-RTT is available on the QUIC connection, either client or server	on whether 0-RTT is available on the QUIC connection, either client or server
	might be able to send stream data first.</t>	might be able to send stream data first.</t>
	</section>	</section>

	<section anchor="push-streams" numbered="true" toc="default">	<section anchor='push-streams'>
	<name>Push Streams</name>	<name>Push Streams</name><iref item='push stream' primary='true'/>
	<t>Server push is an optional feature introduced in HTTP/2 that allows a server to	<t>Server push is an optional feature introduced in HTTP/2 that allows a server to

	initiate a response before a request has been made. See <xref target="server-pu sh" format="default"/> for	initiate a response before a request has been made. See <xref target='server-pu sh'/> for
	more details.</t>	more details.</t>

	<t>A push stream is indicated by a stream type of 0x01, followed by th e Push ID	<t>A push stream is indicated by a stream type of 0x01, followed by th e <xref format='none' target='server-push'>push ID</xref><iref item='push ID'/>
	of the promise that it fulfills, encoded as a variable-length integer. The	of the promise that it fulfills, encoded as a variable-length integer. The
	remaining data on this stream consists of HTTP/3 frames, as defined in	remaining data on this stream consists of HTTP/3 frames, as defined in

	<xref target="frames" format="default"/>, and fulfills a promised server push by zero or more interim HTTP	<xref target='frames'/>, and fulfills a promised server push by zero or more int erim HTTP
	responses followed by a single final HTTP response, as defined in	responses followed by a single final HTTP response, as defined in

	<xref target="request-response" format="default"/>. Server push and Push IDs ar	<xref target='request-response'/>. Server push and push IDs are described in
	e described in	<xref target='server-push'/>.</t>
	<xref target="server-push" format="default"/>.</t>	<t>Only servers can push; if a server receives a client-initiated push
	<t>Only servers can push; if a server receives a client-initiated push	stream, this <bcp14>MUST</bcp14>
	stream, this	be treated as a <xref format='none' target='errors'>connection error</xref><ire
	<bcp14>MUST</bcp14> be treated as a connection error of type H3_STREAM_CREATION_	f item='connection error'/> of type <xref format='none' target='H3_STREAM_CREATI
	ERROR; see	ON_ERROR'>H3_STREAM_CREATION_ERROR</xref><iref item='H3_STREAM_CREATION_ERROR'/>
	<xref target="errors" format="default"/>.</t>	.</t>
	<figure anchor="fig-push-stream-header">	<figure>
	<name>Push Stream Header</name>	<name>Push Stream Header</name>

	<artwork type="drawing" name="" align="left" alt=""><![CDATA[	<artwork type='ascii-art'><![CDATA[
	Push Stream Header {	Push Stream Header {
	Stream Type (i) = 0x01,	Stream Type (i) = 0x01,
	Push ID (i),	Push ID (i),
	}	}
	]]></artwork>	]]></artwork>
	</figure>	</figure>

	<t>Each Push ID <bcp14>MUST</bcp14> only be used once in a push stream	<t>A client <bcp14>SHOULD NOT</bcp14>
	header. If a push stream	abort reading on a push stream prior to reading the push
	header includes a Push ID that was used in another push stream header, the	stream header, as this could lead to disagreement between client and server on
	client <bcp14>MUST</bcp14> treat this as a connection error of type H3_ID_ERROR;	which push IDs have already been consumed.</t>
	see	<t>Each <xref format='none' target='server-push'>push ID</xref><iref i
	<xref target="errors" format="default"/>.</t>	tem='push ID'/> <bcp14>MUST</bcp14>
		only be used once in a push stream header. If a client detects
		that a push stream header includes a <xref format='none' target='server-push'>pu
		sh ID</xref><iref item='push ID'/> that was used in another push
		stream header, the client <bcp14>MUST</bcp14>
		treat this as a <xref format='none' target='errors'>connection error</xref><ire
		f item='connection error'/> of type
		<xref format='none' target='H3_ID_ERROR'>H3_ID_ERROR</xref><iref item='H3_ID_ERR
		OR'/>.</t>
	</section>	</section>

	<section anchor="stream-grease" numbered="true" toc="default">	<section anchor='stream-grease'>
	<name>Reserved Stream Types</name>	<name>Reserved Stream Types</name>
	<t>Stream types of the format <tt>0x1f * N + 0x21</tt> for non-negativ e integer values of	<t>Stream types of the format <tt>0x1f * N + 0x21</tt> for non-negativ e integer values of

	N are reserved to exercise the requirement that unknown types be ignored. These	<tt>N</tt> are reserved to exercise the requirement that unknown types be ignore
	streams have no semantics, and can be sent when application-layer padding is	d.
	desired. They <bcp14>MAY</bcp14> also be sent on connections where no data is cu	These streams have no semantics, and they can be sent when application-layer
	rrently being	padding is desired. They <bcp14>MAY</bcp14>
	transferred. Endpoints <bcp14>MUST NOT</bcp14> consider these streams to have an	also be sent on connections where no data is
	y meaning upon	currently being transferred. Endpoints <bcp14>MUST NOT</bcp14>
	receipt.</t>	consider these streams to have
		any meaning upon receipt.</t>
	<t>The payload and length of the stream are selected in any manner the sending	<t>The payload and length of the stream are selected in any manner the sending

	implementation chooses. When sending a reserved stream type, the implementation	implementation chooses. When sending a reserved stream type, the implementation
	<bcp14>MAY</bcp14> either terminate the stream cleanly or reset it. When resett	<bcp14>MAY</bcp14>
	ing the stream,	either terminate the stream cleanly or reset it. When resetting the stream,
	either the H3_NO_ERROR error code or a reserved error code	either the <xref format='none' target='H3_NO_ERROR'>H3_NO_ERROR</xref><iref item
	(<xref target="http-error-codes" format="default"/>) <bcp14>SHOULD</bcp14> be us	='H3_NO_ERROR'/> error code or a reserved error code
	ed.</t>	(<xref target='http-error-codes'/>) <bcp14>SHOULD</bcp14>
		be used.</t>
	</section>	</section>
	</section>	</section>
	</section>	</section>

	<section anchor="http-framing-layer" numbered="true" toc="default">	<section anchor='http-framing-layer'>
	<name>HTTP Framing Layer</name>	<name>HTTP Framing Layer</name>

	<t>HTTP frames are carried on QUIC streams, as described in <xref target="	<t>HTTP frames are carried on QUIC streams, as described in <xref target='
	stream-mapping" format="default"/>.	stream-mapping'/>.
	HTTP/3 defines three stream types: control stream, request stream, and push	HTTP/3 defines three stream types: <xref format='none' target='control-streams'>
	stream. This section describes HTTP/3 frame formats and their permitted stream	control stream</xref><iref item='control stream'/>, <xref format='none' target='
	types; see <xref target="stream-frame-mapping" format="default"/> for an overvie	request-streams'>request stream</xref><iref item='request stream'/>, and <xref f
	w. A comparison between	ormat='none' target='push-streams'>push
	HTTP/2 and HTTP/3 frames is provided in <xref target="h2-frames" format="default	stream</xref><iref item='push stream'/>. This section describes HTTP/3 frame for
	"/>.</t>	mats and their permitted stream
	<table anchor="stream-frame-mapping" align="center">	types; see <xref target='stream-frame-mapping'/> for an overview. A comparison
		between
		HTTP/2 and HTTP/3 frames is provided in <xref target='h2-frames'/>.</t>
		<table anchor='stream-frame-mapping'>
	<name>HTTP/3 Frames and Stream Type Overview</name>	<name>HTTP/3 Frames and Stream Type Overview</name>
	<thead>	<thead>
	<tr>	<tr>

	<th align="left">Frame</th>	<th align='left'>Frame</th>
	<th align="left">Control Stream</th>	<th align='left'>Control Stream</th>
	<th align="left">Request Stream</th>	<th align='left'>Request Stream</th>
	<th align="left">Push Stream</th>	<th align='left'>Push Stream</th>
	<th align="left">Section</th>	<th align='left'>Section</th>
	</tr>	</tr>
	</thead>	</thead>
	<tbody>	<tbody>
	<tr>	<tr>

	<td align="left">DATA</td>	<td align='left'><xref format='none' target='frame-data'>DATA</xref>
	<td align="left">No</td>	<iref item='DATA'/></td>
	<td align="left">Yes</td>	<td align='left'>No</td>
	<td align="left">Yes</td>	<td align='left'>Yes</td>
	<td align="left">	<td align='left'>Yes</td>
	<xref target="frame-data" format="default"/></td>	<td align='left'><xref target='frame-data'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">HEADERS</td>	<td align='left'><xref format='none' target='frame-headers'>HEADERS<
	<td align="left">No</td>	/xref><iref item='HEADERS'/></td>
	<td align="left">Yes</td>	<td align='left'>No</td>
	<td align="left">Yes</td>	<td align='left'>Yes</td>
	<td align="left">	<td align='left'>Yes</td>
	<xref target="frame-headers" format="default"/></td>	<td align='left'><xref target='frame-headers'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">CANCEL_PUSH</td>	<td align='left'><xref format='none' target='frame-cancel-push'>CANC
	<td align="left">Yes</td>	EL_PUSH</xref><iref item='CANCEL_PUSH'/></td>
	<td align="left">No</td>	<td align='left'>Yes</td>
	<td align="left">No</td>	<td align='left'>No</td>
	<td align="left">	<td align='left'>No</td>
	<xref target="frame-cancel-push" format="default"/></td>	<td align='left'><xref target='frame-cancel-push'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">SETTINGS</td>	<td align='left'><xref format='none' target='frame-settings'>SETTING
	<td align="left">Yes (1)</td>	S</xref><iref item='SETTINGS'/></td>
	<td align="left">No</td>	<td align='left'>Yes (1)</td>
	<td align="left">No</td>	<td align='left'>No</td>
	<td align="left">	<td align='left'>No</td>
	<xref target="frame-settings" format="default"/></td>	<td align='left'><xref target='frame-settings'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">PUSH_PROMISE</td>	<td align='left'><xref format='none' target='frame-push-promise'>PUS
	<td align="left">No</td>	H_PROMISE</xref><iref item='PUSH_PROMISE'/></td>
	<td align="left">Yes</td>	<td align='left'>No</td>
	<td align="left">No</td>	<td align='left'>Yes</td>
	<td align="left">	<td align='left'>No</td>
	<xref target="frame-push-promise" format="default"/></td>	<td align='left'><xref target='frame-push-promise'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">GOAWAY</td>	<td align='left'><xref format='none' target='frame-goaway'>GOAWAY</x
	<td align="left">Yes</td>	ref><iref item='GOAWAY'/></td>
	<td align="left">No</td>	<td align='left'>Yes</td>
	<td align="left">No</td>	<td align='left'>No</td>
	<td align="left">	<td align='left'>No</td>
	<xref target="frame-goaway" format="default"/></td>	<td align='left'><xref target='frame-goaway'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">MAX_PUSH_ID</td>	<td align='left'><xref format='none' target='frame-max-push-id'>MAX_
	<td align="left">Yes</td>	PUSH_ID</xref><iref item='MAX_PUSH_ID'/></td>
	<td align="left">No</td>	<td align='left'>Yes</td>
	<td align="left">No</td>	<td align='left'>No</td>
	<td align="left">	<td align='left'>No</td>
	<xref target="frame-max-push-id" format="default"/></td>	<td align='left'><xref target='frame-max-push-id'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">Reserved</td>	<td align='left'>Reserved</td>
	<td align="left">Yes</td>	<td align='left'>Yes</td>
	<td align="left">Yes</td>	<td align='left'>Yes</td>
	<td align="left">Yes</td>	<td align='left'>Yes</td>
	<td align="left">	<td align='left'><xref target='frame-reserved'/></td>
	<xref target="frame-reserved" format="default"/></td>
	</tr>	</tr>
	</tbody>	</tbody>
	</table>	</table>

	<t>The SETTINGS frame can only occur as the first frame of a Control strea	<t>The <xref format='none' target='frame-settings'>SETTINGS</xref><iref it
	m; this	em='SETTINGS'/> frame can only occur as the first frame of a Control stream; thi
	is indicated in <xref target="stream-frame-mapping" format="default"/> with a (1	s
	). Specific guidance	is indicated in <xref target='stream-frame-mapping'/> with a (1). Specific guid
		ance
	is provided in the relevant section.</t>	is provided in the relevant section.</t>
	<t>Note that, unlike QUIC frames, HTTP/3 frames can span multiple packets. </t>	<t>Note that, unlike QUIC frames, HTTP/3 frames can span multiple packets. </t>

	<section anchor="frame-layout" numbered="true" toc="default">	<section anchor='frame-layout'>
	<name>Frame Layout</name>	<name>Frame Layout</name>
	<t>All frames have the following format:</t>	<t>All frames have the following format:</t>

	<figure anchor="fig-frame">	<figure>
	<name>HTTP/3 Frame Format</name>	<name>HTTP/3 Frame Format</name>

	<artwork type="drawing" name="" align="left" alt=""><![CDATA[	<artwork type='ascii-art'><![CDATA[
	HTTP/3 Frame Format {	HTTP/3 Frame Format {
	Type (i),	Type (i),
	Length (i),	Length (i),
	Frame Payload (..),	Frame Payload (..),
	}	}
	]]></artwork>	]]></artwork>
	</figure>	</figure>
	<t>A frame includes the following fields:</t>	<t>A frame includes the following fields:</t>
	<dl>	<dl>

	<dt>	<dt>Type:</dt>
	Type: </dt>
	<dd>	<dd>
	<t>A variable-length integer that identifies the frame type.</t>	<t>A variable-length integer that identifies the frame type.</t>
	</dd>	</dd>

	<dt>	<dt>Length:</dt>
	Length: </dt>
	<dd>	<dd>
	<t>A variable-length integer that describes the length in bytes of	<t>A variable-length integer that describes the length in bytes of
	the Frame Payload.</t>	the Frame Payload.</t>
	</dd>	</dd>

	<dt>	<dt>Frame Payload:</dt>
	Frame Payload: </dt>
	<dd>	<dd>
	<t>A payload, the semantics of which are determined by the Type fiel d.</t>	<t>A payload, the semantics of which are determined by the Type fiel d.</t>
	</dd>	</dd>
	</dl>	</dl>

	<t>Each frame's payload <bcp14>MUST</bcp14> contain exactly the fields i	<t>Each frame's payload <bcp14>MUST</bcp14>
	dentified in its	contain exactly the fields identified in its
	description. A frame payload that contains additional bytes after the	description. A frame payload that contains additional bytes after the
	identified fields or a frame payload that terminates before the end of the	identified fields or a frame payload that terminates before the end of the

	identified fields <bcp14>MUST</bcp14> be treated as a connection error of type	identified fields <bcp14>MUST</bcp14>
	H3_FRAME_ERROR; see <xref target="errors" format="default"/>. In particular, re	be treated as a <xref format='none' target='errors'>connection error</xref><ire
	dundant length encodings <bcp14>MUST</bcp14>	f item='connection error'/> of type
	be verified to be self-consistent; see <xref target="frame-parsing" format="defa	<xref format='none' target='H3_FRAME_ERROR'>H3_FRAME_ERROR</xref><iref item='H3_
	ult"/>.</t>	FRAME_ERROR'/>. In particular, redundant length encodings <bcp14>MUST<
		/bcp14>

		be verified to be self-consistent; see <xref target='frame-parsing'/>.</t>
	<t>When a stream terminates cleanly, if the last frame on the stream was truncated,	<t>When a stream terminates cleanly, if the last frame on the stream was truncated,

	this <bcp14>MUST</bcp14> be treated as a connection error of type H3_FRAME_ERROR	this <bcp14>MUST</bcp14>
	; see	be treated as a <xref format='none' target='errors'>connection error</xref><ire
	<xref target="errors" format="default"/>. Streams that terminate abruptly may be	f item='connection error'/> of type <xref format='none' target='H3_FRAME_ERROR'>
	reset at any point in a	H3_FRAME_ERROR</xref><iref item='H3_FRAME_ERROR'/>. Streams that
	frame.</t>	terminate abruptly may be reset at any point in a frame.</t>
	</section>	</section>

	<section anchor="frames" numbered="true" toc="default">	<section anchor='frames'>
	<name>Frame Definitions</name>	<name>Frame Definitions</name>

	<section anchor="frame-data" numbered="true" toc="default">	<section anchor='frame-data'>
	<name>DATA</name>	<name>DATA</name><iref item='DATA' primary='true'/>
	<t>DATA frames (type=0x0) convey arbitrary, variable-length sequences	<t>DATA frames (type=0x00) convey arbitrary, variable-length sequences
	of bytes	of bytes
	associated with HTTP request or response content.</t>	associated with HTTP request or response content.</t>

	<t>DATA frames <bcp14>MUST</bcp14> be associated with an HTTP request	<t>DATA frames <bcp14>MUST</bcp14>
	or response. If a DATA	be associated with an HTTP request or response. If a DATA
	frame is received on a control stream, the recipient <bcp14>MUST</bcp14> respond	frame is received on a <xref format='none' target='control-streams'>control stre
	with a	am</xref><iref item='control stream'/>, the recipient <bcp14>MUST</bc
	connection error of type H3_FRAME_UNEXPECTED; see <xref target="errors" format="	p14>
	default"/>.</t>	respond with a
	<figure anchor="fig-data">	<xref format='none' target='errors'>connection error</xref><iref item='connectio
		n error'/> of type <xref format='none' target='H3_FRAME_UNEXPECTED'>H3_FRAME_UNE
		XPECTED</xref><iref item='H3_FRAME_UNEXPECTED'/>.</t>
		<figure>
	<name>DATA Frame</name>	<name>DATA Frame</name>

	<artwork type="drawing" name="" align="left" alt=""><![CDATA[	<artwork type='ascii-art'><![CDATA[
	DATA Frame {	DATA Frame {

	Type (i) = 0x0,	Type (i) = 0x00,
	Length (i),	Length (i),
	Data (..),	Data (..),
	}	}
	]]></artwork>	]]></artwork>
	</figure>	</figure>
	</section>	</section>

	<section anchor="frame-headers" numbered="true" toc="default">	<section anchor='frame-headers'>
	<name>HEADERS</name>	<name>HEADERS</name><iref item='HEADERS' primary='true'/>
	<t>The HEADERS frame (type=0x1) is used to carry an HTTP field section	<t>The HEADERS frame (type=0x01) is used to carry an HTTP field sectio
	, encoded	n that is
	using QPACK. See <xref target="RFCYYY2" format="default"/> for more details.</t>	encoded using QPACK. See <xref target='RFC9204'/> for more details.</t>
	<figure anchor="fig-headers">	<figure>
	<name>HEADERS Frame</name>	<name>HEADERS Frame</name>

	<artwork type="drawing" name="" align="left" alt=""><![CDATA[	<artwork type='ascii-art'><![CDATA[
	HEADERS Frame {	HEADERS Frame {

	Type (i) = 0x1,	Type (i) = 0x01,
	Length (i),	Length (i),
	Encoded Field Section (..),	Encoded Field Section (..),
	}	}
	]]></artwork>	]]></artwork>
	</figure>	</figure>

	<t>HEADERS frames can only be sent on request or push streams. If a H	<t>HEADERS frames can only be sent on <xref format='none' target='requ
	EADERS frame	est-streams'>request streams</xref><iref item='request stream'/> or <xref format
	is received on a control stream, the recipient <bcp14>MUST</bcp14> respond with	='none' target='push-streams'>push streams</xref><iref item='push stream'/>. If
	a connection	a
	error (<xref target="errors" format="default"/>) of type H3_FRAME_UNEXPECTED.</t	HEADERS frame is received on a <xref format='none' target='control-streams'>cont
	>	rol stream</xref><iref item='control stream'/>, the recipient <bcp14>
		MUST</bcp14>
		respond with a
		<xref format='none' target='errors'>connection error</xref><iref item='connectio
		n error'/> of type <xref format='none' target='H3_FRAME_UNEXPECTED'>H3_FRAME_UNE
		XPECTED</xref><iref item='H3_FRAME_UNEXPECTED'/>.</t>
	</section>	</section>

	<section anchor="frame-cancel-push" numbered="true" toc="default">	<section anchor='frame-cancel-push'>
	<name>CANCEL_PUSH</name>	<name>CANCEL_PUSH</name><iref item='CANCEL_PUSH' primary='true'/>
	<t>The CANCEL_PUSH frame (type=0x3) is used to request cancellation of	<t>The CANCEL_PUSH frame (type=0x03) is used to request cancellation o
	a server	f a server
	push prior to the push stream being received. The CANCEL_PUSH frame identifies	push prior to the <xref format='none' target='push-streams'>push stream</xref><i
	a server push by Push ID (see <xref target="server-push" format="default"/>), en	ref item='push stream'/> being received. The CANCEL_PUSH frame identifies
	coded as a variable-length	a server push by <xref format='none' target='server-push'>push ID</xref><iref it
		em='push ID'/> (see <xref target='server-push'/>), encoded as a variable-length
	integer.</t>	integer.</t>

	<t>When a client sends CANCEL_PUSH, it is indicating that it does not	<t>When a client sends a CANCEL_PUSH frame, it is indicating that it d
	wish to	oes not wish
	receive the promised resource. The server <bcp14>SHOULD</bcp14> abort sending t	to receive the promised resource. The server <bcp14>SHOULD</bcp14>
	he resource,	abort sending the resource,
	but the mechanism to do so depends on the state of the corresponding push	but the mechanism to do so depends on the state of the corresponding <xref forma
	stream. If the server has not yet created a push stream, it does not create	t='none' target='push-streams'>push
	one. If the push stream is open, the server <bcp14>SHOULD</bcp14> abruptly term	stream</xref><iref item='push stream'/>. If the server has not yet created a <x
	inate that	ref format='none' target='push-streams'>push stream</xref><iref item='push strea
	stream. If the push stream has already ended, the server <bcp14>MAY</bcp14> sti	m'/>, it does not create
	ll abruptly	one. If the <xref format='none' target='push-streams'>push stream</xref><iref i
	terminate the stream or <bcp14>MAY</bcp14> take no action.</t>	tem='push stream'/> is open, the server <bcp14>SHOULD</bcp14>
	<t>A server sends CANCEL_PUSH to indicate that it will not be fulfilli	abruptly terminate that
	ng a promise	stream. If the <xref format='none' target='push-streams'>push stream</xref><ire
	which was previously sent. The client cannot expect the corresponding promise	f item='push stream'/> has already ended, the server <bcp14>MAY</bcp1
	to be fulfilled, unless it has already received and processed the promised	4>
	response. Regardless of whether a push stream has been opened, a server	still abruptly
	<bcp14>SHOULD</bcp14> send a CANCEL_PUSH frame when it determines that promise w	terminate the stream or <bcp14>MAY</bcp14>
	ill not be	take no action.</t>
	fulfilled. If a stream has already been opened, the server can	<t>A server sends a CANCEL_PUSH frame to indicate that it will not be
	abort sending on the stream with an error code of H3_REQUEST_CANCELLED.</t>	fulfilling a
	<t>Sending a CANCEL_PUSH frame has no direct effect on the state of ex	promise that was previously sent. The client cannot expect the corresponding
	isting push	promise to be fulfilled, unless it has already received and processed the
	streams. A client <bcp14>SHOULD NOT</bcp14> send a CANCEL_PUSH frame when it has	promised response. Regardless of whether a <xref format='none' target='push-stre
	already	ams'>push stream</xref><iref item='push stream'/> has been opened, a server
	received a corresponding push stream. A push stream could arrive after a client	<bcp14>SHOULD</bcp14>
		send a CANCEL_PUSH frame when it determines that promise will not be
		fulfilled. If a stream has already been opened, the server can abort sending on
		the stream with an error code of <xref format='none' target='H3_REQUEST_CANCELLE
		D'>H3_REQUEST_CANCELLED</xref><iref item='H3_REQUEST_CANCELLED'/>.</t>
		<t>Sending a CANCEL_PUSH frame has no direct effect on the state of ex
		isting <xref format='none' target='push-streams'>push
		streams</xref><iref item='push stream'/>. A client <bcp14>SHOULD NOT<
		/bcp14>
		send a CANCEL_PUSH frame when it has already
		received a corresponding <xref format='none' target='push-streams'>push stream</
		xref><iref item='push stream'/>. A <xref format='none' target='push-streams'>pu
		sh stream</xref><iref item='push stream'/> could arrive after a client
	has sent a CANCEL_PUSH frame, because a server might not have processed the	has sent a CANCEL_PUSH frame, because a server might not have processed the

	CANCEL_PUSH. The client <bcp14>SHOULD</bcp14> abort reading the stream with an e	CANCEL_PUSH. The client <bcp14>SHOULD</bcp14>
	rror code of	abort reading the stream with an error code of
	H3_REQUEST_CANCELLED.</t>	<xref format='none' target='H3_REQUEST_CANCELLED'>H3_REQUEST_CANCELLED</xref><ir
	<t>A CANCEL_PUSH frame is sent on the control stream. Receiving a CAN	ef item='H3_REQUEST_CANCELLED'/>.</t>
	CEL_PUSH	<t>A CANCEL_PUSH frame is sent on the <xref format='none' target='cont
	frame on a stream other than the control stream <bcp14>MUST</bcp14> be treated a	rol-streams'>control stream</xref><iref item='control stream'/>. Receiving a CA
	s a connection	NCEL_PUSH
	error of type H3_FRAME_UNEXPECTED.</t>	frame on a stream other than the <xref format='none' target='control-streams'>co
	<figure anchor="fig-cancel-push">	ntrol stream</xref><iref item='control stream'/> <bcp14>MUST</bcp14>
		be treated as a <xref format='none' target='errors'>connection
		error</xref><iref item='connection error'/> of type <xref format='none' target='
		H3_FRAME_UNEXPECTED'>H3_FRAME_UNEXPECTED</xref><iref item='H3_FRAME_UNEXPECTED'/
		>.</t>
		<figure>
	<name>CANCEL_PUSH Frame</name>	<name>CANCEL_PUSH Frame</name>

	<artwork type="drawing" name="" align="left" alt=""><![CDATA[	<artwork type='ascii-art'><![CDATA[
	CANCEL_PUSH Frame {	CANCEL_PUSH Frame {

	Type (i) = 0x3,	Type (i) = 0x03,
	Length (i),	Length (i),
	Push ID (i),	Push ID (i),
	}	}
	]]></artwork>	]]></artwork>
	</figure>	</figure>

	<t>The CANCEL_PUSH frame carries a Push ID encoded as a variable-lengt	<t>The CANCEL_PUSH frame carries a <xref format='none' target='server-
	h integer.	push'>push ID</xref><iref item='push ID'/> encoded as a variable-length integer.
	The Push ID identifies the server push that is being cancelled; see	The Push ID field identifies the server push that is being cancelled; see
	<xref target="server-push" format="default"/>. If a CANCEL_PUSH frame is receiv	<xref target='server-push'/>. If a CANCEL_PUSH frame is received that reference
	ed that references a Push ID	s a <xref format='none' target='server-push'>push ID</xref><iref item='push ID'/
	greater than currently allowed on the connection, this <bcp14>MUST</bcp14> be tr	>
	eated as a	greater than currently allowed on the connection, this <bcp14>MUST</b
	connection error of type H3_ID_ERROR.</t>	cp14>
	<t>If the client receives a CANCEL_PUSH frame, that frame might identi	be treated as a
	fy a Push ID	<xref format='none' target='errors'>connection error</xref><iref item='connectio
	that has not yet been mentioned by a PUSH_PROMISE frame due to reordering. If a	n error'/> of type <xref format='none' target='H3_ID_ERROR'>H3_ID_ERROR</xref><i
	server receives a CANCEL_PUSH frame for a Push ID that has not yet been	ref item='H3_ID_ERROR'/>.</t>
	mentioned by a PUSH_PROMISE frame, this <bcp14>MUST</bcp14> be treated as a conn	<t>If the client receives a CANCEL_PUSH frame, that frame might identi
	ection error of	fy a <xref format='none' target='server-push'>push ID</xref><iref item='push ID'
	type H3_ID_ERROR.</t>	/>
		that has not yet been mentioned by a <xref format='none' target='frame-push-prom
		ise'>PUSH_PROMISE</xref><iref item='PUSH_PROMISE'/> frame due to reordering. If
		a
		server receives a CANCEL_PUSH frame for a <xref format='none' target='server-pus
		h'>push ID</xref><iref item='push ID'/> that has not yet been
		mentioned by a <xref format='none' target='frame-push-promise'>PUSH_PROMISE</xre
		f><iref item='PUSH_PROMISE'/> frame, this <bcp14>MUST</bcp14>
		be treated as a <xref format='none' target='errors'>connection error</xref><ire
		f item='connection error'/> of
		type <xref format='none' target='H3_ID_ERROR'>H3_ID_ERROR</xref><iref item='H3_I
		D_ERROR'/>.</t>
	</section>	</section>

	<section anchor="frame-settings" numbered="true" toc="default">	<section anchor='frame-settings'>
	<name>SETTINGS</name>	<name>SETTINGS</name><iref item='SETTINGS' primary='true'/>
	<t>The SETTINGS frame (type=0x4) conveys configuration parameters that	<t>The SETTINGS frame (type=0x04) conveys configuration parameters tha
	affect how	t affect how
	endpoints communicate, such as preferences and constraints on peer behavior.	endpoints communicate, such as preferences and constraints on peer behavior.
	Individually, a SETTINGS parameter can also be referred to as a "setting"; the	Individually, a SETTINGS parameter can also be referred to as a "setting"; the
	identifier and value of each setting parameter can be referred to as a "setting	identifier and value of each setting parameter can be referred to as a "setting
	identifier" and a "setting value".</t>	identifier" and a "setting value".</t>
	<t>SETTINGS frames always apply to an entire HTTP/3 connection, never a single	<t>SETTINGS frames always apply to an entire HTTP/3 connection, never a single

	stream. A SETTINGS frame <bcp14>MUST</bcp14> be sent as the first frame of each	stream. A SETTINGS frame <bcp14>MUST</bcp14>
	control stream	be sent as the first frame of each <xref format='none' target='control-streams'
	(see <xref target="control-streams" format="default"/>) by each peer, and <bcp14	>control stream</xref><iref item='control stream'/>
	>MUST NOT</bcp14> be sent subsequently. If an	(see <xref target='control-streams'/>) by each peer, and it <bcp14>MU
	endpoint receives a second SETTINGS frame on the control stream, the endpoint	ST NOT</bcp14>
	<bcp14>MUST</bcp14> respond with a connection error of type H3_FRAME_UNEXPECTED.	be sent subsequently. If
	</t>	an endpoint receives a second SETTINGS frame on the <xref format='none' target='
	<t>SETTINGS frames <bcp14>MUST NOT</bcp14> be sent on any stream other	control-streams'>control stream</xref><iref item='control stream'/>, the endpoin
	than the control stream.	t <bcp14>MUST</bcp14>
	If an endpoint receives a SETTINGS frame on a different stream, the endpoint	respond with a <xref format='none' target='errors'>connection error</xref><iref
	<bcp14>MUST</bcp14> respond with a connection error of type H3_FRAME_UNEXPECTED.	item='connection error'/> of type <xref format='none' target='H3_FRAME_UNEXPECT
	</t>	ED'>H3_FRAME_UNEXPECTED</xref><iref item='H3_FRAME_UNEXPECTED'/>.</t>
		<t>SETTINGS frames <bcp14>MUST NOT</bcp14>
		be sent on any stream other than the <xref format='none' target='control-stream
		s'>control stream</xref><iref item='control stream'/>.
		If an endpoint receives a SETTINGS frame on a different stream, the endpoint
		<bcp14>MUST</bcp14>
		respond with a <xref format='none' target='errors'>connection error</xref><iref
		item='connection error'/> of type <xref format='none' target='H3_FRAME_UNEXPECT
		ED'>H3_FRAME_UNEXPECTED</xref><iref item='H3_FRAME_UNEXPECTED'/>.</t>
	<t>SETTINGS parameters are not negotiated; they describe characteristi cs of the	<t>SETTINGS parameters are not negotiated; they describe characteristi cs of the
	sending peer that can be used by the receiving peer. However, a negotiation	sending peer that can be used by the receiving peer. However, a negotiation

	can be implied by the use of SETTINGS - each peer uses SETTINGS to advertise a	can be implied by the use of SETTINGS: each peer uses SETTINGS to advertise a
	set of supported values. The definition of the setting would describe how each	set of supported values. The definition of the setting would describe how each
	peer combines the two sets to conclude which choice will be used. SETTINGS does	peer combines the two sets to conclude which choice will be used. SETTINGS does
	not provide a mechanism to identify when the choice takes effect.</t>	not provide a mechanism to identify when the choice takes effect.</t>
	<t>Different values for the same parameter can be advertised by each p eer. For	<t>Different values for the same parameter can be advertised by each p eer. For
	example, a client might be willing to consume a very large response field	example, a client might be willing to consume a very large response field
	section, while servers are more cautious about request size.</t>	section, while servers are more cautious about request size.</t>

	<t>The same setting identifier <bcp14>MUST NOT</bcp14> occur more than	<t>The same setting identifier <bcp14>MUST NOT</bcp14>
	once in the SETTINGS frame.	occur more than once in the SETTINGS frame.
	A receiver <bcp14>MAY</bcp14> treat the presence of duplicate setting identifier	A receiver <bcp14>MAY</bcp14>
	s as a	treat the presence of duplicate setting identifiers as a
	connection error of type H3_SETTINGS_ERROR.</t>	<xref format='none' target='errors'>connection error</xref><iref item='connectio
		n error'/> of type <xref format='none' target='H3_SETTINGS_ERROR'>H3_SETTINGS_ER
		ROR</xref><iref item='H3_SETTINGS_ERROR'/>.</t>
	<t>The payload of a SETTINGS frame consists of zero or more parameters . Each	<t>The payload of a SETTINGS frame consists of zero or more parameters . Each
	parameter consists of a setting identifier and a value, both encoded as QUIC	parameter consists of a setting identifier and a value, both encoded as QUIC
	variable-length integers.</t>	variable-length integers.</t>

	<figure anchor="fig-ext-settings">	<figure>
	<name>SETTINGS Frame</name>	<name>SETTINGS Frame</name>

	<artwork type="drawing" name="" align="left" alt=""><![CDATA[	<artwork type='ascii-art'><![CDATA[
	Setting {	Setting {
	Identifier (i),	Identifier (i),
	Value (i),	Value (i),
	}	}

	SETTINGS Frame {	SETTINGS Frame {

	Type (i) = 0x4,	Type (i) = 0x04,
	Length (i),	Length (i),
	Setting (..) ...,	Setting (..) ...,
	}	}
	]]></artwork>	]]></artwork>
	</figure>	</figure>

	<t>An implementation <bcp14>MUST</bcp14> ignore any parameter with an	<t>An implementation <bcp14>MUST</bcp14>
	identifier it does	ignore any parameter with an identifier it does
	not understand.</t>	not understand.</t>

	<section anchor="settings-parameters" numbered="true" toc="default">	<section anchor='settings-parameters'>
	<name>Defined SETTINGS Parameters</name>	<name>Defined SETTINGS Parameters</name>
	<t>The following settings are defined in HTTP/3:</t>	<t>The following settings are defined in HTTP/3:</t>
	<dl>	<dl>

	<dt>	<dt><xref format='none' target='SETTINGS_MAX_FIELD_SECTION_SIZE'>S
	SETTINGS_MAX_FIELD_SECTION_SIZE (0x6): </dt>	ETTINGS_MAX_FIELD_SECTION_SIZE</xref> (0x06)<iref item='SETTINGS_MAX_FIELD_SECTI
		ON_SIZE'/>:</dt>
	<dd>	<dd>

	<t>The default value is unlimited. See <xref target="header-siz e-constraints" format="default"/> for usage.</t>	<t anchor='SETTINGS_MAX_FIELD_SECTION_SIZE'>The default value is unlimited. See <xref target='header-size-constraints'/> for usage.</t>
	</dd>	</dd>
	</dl>	</dl>
	<t>Setting identifiers of the format <tt>0x1f * N + 0x21</tt> for no n-negative integer	<t>Setting identifiers of the format <tt>0x1f * N + 0x21</tt> for no n-negative integer

	values of N are reserved to exercise the requirement that unknown identifiers be	values of <tt>N</tt> are reserved to exercise the requirement that unknown ident
	ignored. Such settings have no defined meaning. Endpoints <bcp14>SHOULD</bcp14>	ifiers
	include at	be ignored. Such settings have no defined meaning. Endpoints <bcp1
	least one such setting in their SETTINGS frame. Endpoints <bcp14>MUST NOT</bcp14	4>SHOULD</bcp14>
	> consider such	include at
		least one such setting in their SETTINGS frame. Endpoints <bcp14>MU
		ST NOT</bcp14>
		consider such
	settings to have any meaning upon receipt.</t>	settings to have any meaning upon receipt.</t>
	<t>Because the setting has no defined meaning, the value of the sett ing can be any	<t>Because the setting has no defined meaning, the value of the sett ing can be any
	value the implementation selects.</t>	value the implementation selects.</t>

	<t>Setting identifiers which were defined in <xref target="RFC7540"	<t>Setting identifiers that were defined in <xref target='RFC9113'/>
	format="default"/> where there is no	where there is no
	corresponding HTTP/3 setting have also been reserved (<xref target="iana-setting	corresponding HTTP/3 setting have also been reserved (<xref target='iana-setting
	s" format="default"/>). These	s'/>). These
	reserved settings <bcp14>MUST NOT</bcp14> be sent, and their receipt <bcp14>MUST	reserved settings <bcp14>MUST NOT</bcp14>
	</bcp14> be treated as a	be sent, and their receipt <bcp14>MUST</bcp14>
	connection error of type H3_SETTINGS_ERROR.</t>	be treated as a
	<t>Additional settings can be defined by extensions to HTTP/3; see <	<xref format='none' target='errors'>connection error</xref><iref item='connectio
	xref target="extensions" format="default"/>	n error'/> of type <xref format='none' target='H3_SETTINGS_ERROR'>H3_SETTINGS_ER
		ROR</xref><iref item='H3_SETTINGS_ERROR'/>.</t>
		<t>Additional settings can be defined by extensions to HTTP/3; see <
		xref target='extensions'/>
	for more details.</t>	for more details.</t>
	</section>	</section>

	<section anchor="settings-initialization" numbered="true" toc="default ">	<section anchor='settings-initialization'>
	<name>Initialization</name>	<name>Initialization</name>

	<t>An HTTP implementation <bcp14>MUST NOT</bcp14> send frames or req	<t>An HTTP implementation <bcp14>MUST NOT</bcp14>
	uests that would be invalid	send frames or requests that would be invalid
	based on its current understanding of the peer's settings.</t>	based on its current understanding of the peer's settings.</t>

	<t>All settings begin at an initial value. Each endpoint <bcp14>SHO	<t>All settings begin at an initial value. Each endpoint
	ULD</bcp14> use these initial	<bcp14>SHOULD</bcp14>
		use these initial
	values to send messages before the peer's SETTINGS frame has arrived, as packets	values to send messages before the peer's SETTINGS frame has arrived, as packets
	carrying the settings can be lost or delayed. When the SETTINGS frame arrives,	carrying the settings can be lost or delayed. When the SETTINGS frame arrives,
	any settings are changed to their new values.</t>	any settings are changed to their new values.</t>
	<t>This removes the need to wait for the SETTINGS frame before sendi ng messages.	<t>This removes the need to wait for the SETTINGS frame before sendi ng messages.

	Endpoints <bcp14>MUST NOT</bcp14> require any data to be received from the peer	Endpoints <bcp14>MUST NOT</bcp14>
	prior to	require any data to be received from the peer prior to
	sending the SETTINGS frame; settings <bcp14>MUST</bcp14> be sent as soon as the	sending the SETTINGS frame; settings <bcp14>MUST</bcp14>
	transport is	be sent as soon as the transport is
	ready to send data.</t>	ready to send data.</t>
	<t>For servers, the initial value of each client setting is the defa ult value.</t>	<t>For servers, the initial value of each client setting is the defa ult value.</t>
	<t>For clients using a 1-RTT QUIC connection, the initial value of e ach server	<t>For clients using a 1-RTT QUIC connection, the initial value of e ach server
	setting is the default value. 1-RTT keys will always become available prior to	setting is the default value. 1-RTT keys will always become available prior to
	the packet containing SETTINGS being processed by QUIC, even if the server sends	the packet containing SETTINGS being processed by QUIC, even if the server sends

	SETTINGS immediately. Clients <bcp14>SHOULD NOT</bcp14> wait indefinitely for S	SETTINGS immediately. Clients <bcp14>SHOULD NOT</bcp14>
	ETTINGS to	wait indefinitely for SETTINGS to
	arrive before sending requests, but <bcp14>SHOULD</bcp14> process received datag	arrive before sending requests, but they <bcp14>SHOULD</bcp14>
	rams in order	process received datagrams in
	to increase the likelihood of processing SETTINGS before sending the first	order to increase the likelihood of processing SETTINGS before sending the first
	request.</t>	request.</t>
	<t>When a 0-RTT QUIC connection is being used, the initial value of each server	<t>When a 0-RTT QUIC connection is being used, the initial value of each server

	setting is the value used in the previous session. Clients <bcp14>SHOULD</bcp14>	setting is the value used in the previous session. Clients <bcp14>S
	store the	HOULD</bcp14>
		store the
	settings the server provided in the HTTP/3 connection where resumption	settings the server provided in the HTTP/3 connection where resumption

	information was provided, but <bcp14>MAY</bcp14> opt not to store settings in ce	information was provided, but they <bcp14>MAY</bcp14>
	rtain cases	opt not to store settings in certain
	(e.g., if the session ticket is received before the SETTINGS frame). A client	cases (e.g., if the session ticket is received before the SETTINGS frame). A
	<bcp14>MUST</bcp14> comply with stored settings -- or default values, if no valu	client <bcp14>MUST</bcp14>
	es are stored	comply with stored settings -- or default values if no values are
	comply with those values.</t>	stored -- when attempting 0-RTT. Once a server has provided new settings,
	<t>A server can remember the settings that it advertised, or store a	clients <bcp14>MUST</bcp14>
	n	comply with those values.</t>
		<t>A server can remember the settings that it advertised or store an
	integrity-protected copy of the values in the ticket and recover the information	integrity-protected copy of the values in the ticket and recover the information
	when accepting 0-RTT data. A server uses the HTTP/3 settings values in	when accepting 0-RTT data. A server uses the HTTP/3 settings values in
	determining whether to accept 0-RTT data. If the server cannot determine that	determining whether to accept 0-RTT data. If the server cannot determine that

	the settings remembered by a client are compatible with its current settings, it	the settings remembered by a client are compatible with its current settings, it
	<bcp14>MUST NOT</bcp14> accept 0-RTT data. Remembered settings are compatible i	<bcp14>MUST NOT</bcp14>
	f a client	accept 0-RTT data. Remembered settings are compatible if a client
	complying with those settings would not violate the server's current settings.</ t>	complying with those settings would not violate the server's current settings.</ t>

	<t>A server <bcp14>MAY</bcp14> accept 0-RTT and subsequently provide	<t>A server <bcp14>MAY</bcp14>
	different settings in its	accept 0-RTT and subsequently provide different settings in its
	SETTINGS frame. If 0-RTT data is accepted by the server, its SETTINGS frame <bcp	SETTINGS frame. If 0-RTT data is accepted by the server, its SETTINGS frame
	14>MUST	<bcp14>MUST
	NOT</bcp14> reduce any limits or alter any values that might be violated by the	NOT</bcp14>
	client	reduce any limits or alter any values that might be violated by the client
	with its 0-RTT data. The server <bcp14>MUST</bcp14> include all settings that d	with its 0-RTT data. The server <bcp14>MUST</bcp14>
	iffer from	include all settings that differ from
	their default values. If a server accepts 0-RTT but then sends settings that	their default values. If a server accepts 0-RTT but then sends settings that

	are not compatible with the previously specified settings, this <bcp14>MUST</bcp	are not compatible with the previously specified settings, this <bc
	14> be treated	p14>MUST</bcp14>
	as a connection error of type H3_SETTINGS_ERROR. If a server accepts 0-RTT but	be treated
		as a <xref format='none' target='errors'>connection error</xref><iref item='conn
		ection error'/> of type <xref format='none' target='H3_SETTINGS_ERROR'>H3_SETTIN
		GS_ERROR</xref><iref item='H3_SETTINGS_ERROR'/>. If a server accepts 0-RTT but
	then sends a SETTINGS frame that omits a setting value that the client	then sends a SETTINGS frame that omits a setting value that the client
	understands (apart from reserved setting identifiers) that was previously	understands (apart from reserved setting identifiers) that was previously

	specified to have a non-default value, this <bcp14>MUST</bcp14> be treated as a	specified to have a non-default value, this <bcp14>MUST</bcp14>
	connection	be treated as a <xref format='none' target='errors'>connection
	error of type H3_SETTINGS_ERROR.</t>	error</xref><iref item='connection error'/> of type <xref format='none' target='
		H3_SETTINGS_ERROR'>H3_SETTINGS_ERROR</xref><iref item='H3_SETTINGS_ERROR'/>.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="frame-push-promise" numbered="true" toc="default">	<section anchor='frame-push-promise'>
	<name>PUSH_PROMISE</name>	<name>PUSH_PROMISE</name><iref item='PUSH_PROMISE' primary='true'/>
	<t>The PUSH_PROMISE frame (type=0x5) is used to carry a promised reque	<t>The PUSH_PROMISE frame (type=0x05) is used to carry a promised requ
	st header	est header
	section from server to client on a request stream, as in HTTP/2.</t>	section from server to client on a <xref format='none' target='request-streams'>
	<figure anchor="fig-push-promise">	request stream</xref><iref item='request stream'/>.</t>
		<figure>
	<name>PUSH_PROMISE Frame</name>	<name>PUSH_PROMISE Frame</name>

	<artwork type="drawing" name="" align="left" alt=""><![CDATA[	<artwork type='ascii-art'><![CDATA[
	PUSH_PROMISE Frame {	PUSH_PROMISE Frame {

	Type (i) = 0x5,	Type (i) = 0x05,
	Length (i),	Length (i),
	Push ID (i),	Push ID (i),
	Encoded Field Section (..),	Encoded Field Section (..),
	}	}
	]]></artwork>	]]></artwork>
	</figure>	</figure>
	<t>The payload consists of:</t>	<t>The payload consists of:</t>
	<dl>	<dl>

	<dt>	<dt>Push ID:</dt>
	Push ID: </dt>
	<dd>	<dd>

	<t>A variable-length integer that identifies the server push opera	<t>A variable-length integer that identifies the server push opera
	tion. A Push	tion. A <xref format='none' target='server-push'>push
	ID is used in push stream headers (<xref target="server-push" format="default"/>	ID</xref><iref item='push ID'/> is used in <xref format='none' target='push-stre
	) and CANCEL_PUSH frames	ams'>push stream</xref><iref item='push stream'/> headers (<xref target='server-
	(<xref target="frame-cancel-push" format="default"/>).</t>	push'/>) and <xref format='none' target='frame-cancel-push'>CANCEL_PUSH</xref><i
		ref item='CANCEL_PUSH'/> frames.</t>
	</dd>	</dd>

	<dt>	<dt>Encoded Field Section:</dt>
	Encoded Field Section: </dt>
	<dd>	<dd>

	<t>QPACK-encoded request header fields for the promised response.	<t>QPACK-encoded request header fields for the promised response.
	See <xref target="RFCYYY2" format="default"/>	See
	for more details.</t>	<xref target='RFC9204'/> for more details.</t>
	</dd>	</dd>
	</dl>	</dl>

	<t>A server <bcp14>MUST NOT</bcp14> use a Push ID that is larger than	<t>A server <bcp14>MUST NOT</bcp14>
	the client has provided in a	use a <xref format='none' target='server-push'>push ID</xref><iref item='push I
	MAX_PUSH_ID frame (<xref target="frame-max-push-id" format="default"/>). A clien	D'/> that is larger than the client has provided in a
	t <bcp14>MUST</bcp14> treat receipt of a	<xref format='none' target='frame-max-push-id'>MAX_PUSH_ID</xref><iref item='MAX
	PUSH_PROMISE frame that contains a larger Push ID than the client has advertised	_PUSH_ID'/> frame (<xref target='frame-max-push-id'/>). A client <bcp
	as a connection error of H3_ID_ERROR.</t>	14>MUST</bcp14>
	<t>A server <bcp14>MAY</bcp14> use the same Push ID in multiple PUSH_P	treat receipt of a
	ROMISE frames. If so, the	PUSH_PROMISE frame that contains a larger <xref format='none' target='server-pus
	decompressed request header sets <bcp14>MUST</bcp14> contain the same fields in	h'>push ID</xref><iref item='push ID'/> than the client has advertised
	the same order,	as a <xref format='none' target='errors'>connection error</xref><iref item='conn
	and both the name and the value in each field <bcp14>MUST</bcp14> be exact match	ection error'/> of <xref format='none' target='H3_ID_ERROR'>H3_ID_ERROR</xref><i
	es. Clients	ref item='H3_ID_ERROR'/>.</t>
	<bcp14>SHOULD</bcp14> compare the request header sections for resources promised	<t>A server <bcp14>MAY</bcp14>
	multiple	use the same <xref format='none' target='server-push'>push ID</xref><iref item=
	times. If a client receives a Push ID that has already been promised and detects	'push ID'/> in multiple PUSH_PROMISE frames. If so, the
	a mismatch, it <bcp14>MUST</bcp14> respond with a connection error of type	decompressed request header sets <bcp14>MUST</bcp14>
	H3_GENERAL_PROTOCOL_ERROR. If the decompressed field sections match exactly, the	contain the same fields in the same order,
	client <bcp14>SHOULD</bcp14> associate the pushed content with each stream on wh	and both the name and the value in each field <bcp14>MUST</bcp14>
	ich a	be exact matches. Clients <bcp14>SHOULD</bcp14>
		compare the request header sections for resources promised multiple
		times. If a client receives a <xref format='none' target='server-push'>push ID</
		xref><iref item='push ID'/> that has already been promised and detects
		a mismatch, it <bcp14>MUST</bcp14>
		respond with a <xref format='none' target='errors'>connection error</xref><iref
		item='connection error'/> of type
		<xref format='none' target='H3_GENERAL_PROTOCOL_ERROR'>H3_GENERAL_PROTOCOL_ERROR
		</xref><iref item='H3_GENERAL_PROTOCOL_ERROR'/>. If the decompressed field secti
		ons match exactly, the
		client <bcp14>SHOULD</bcp14>
		associate the pushed content with each stream on which a
	PUSH_PROMISE frame was received.</t>	PUSH_PROMISE frame was received.</t>

	<t>Allowing duplicate references to the same Push ID is primarily to r	<t>Allowing duplicate references to the same <xref format='none' targe
	educe	t='server-push'>push ID</xref><iref item='push ID'/> is primarily to reduce
	duplication caused by concurrent requests. A server <bcp14>SHOULD</bcp14> avoid	duplication caused by concurrent requests. A server <bcp14>SHOULD</b
	reusing a Push	cp14>
	ID over a long period. Clients are likely to consume server push responses and	avoid reusing a <xref format='none' target='server-push'>push
		ID</xref><iref item='push ID'/> over a long period. Clients are likely to consu
		me server push responses and
	not retain them for reuse over time. Clients that see a PUSH_PROMISE frame that	not retain them for reuse over time. Clients that see a PUSH_PROMISE frame that

	uses a Push ID that they have already consumed and discarded are forced to	uses a <xref format='none' target='server-push'>push ID</xref><iref item='push I D'/> that they have already consumed and discarded are forced to
	ignore the promise.</t>	ignore the promise.</t>

	<t>If a PUSH_PROMISE frame is received on the control stream, the clie	<t>If a PUSH_PROMISE frame is received on the <xref format='none' targ
	nt <bcp14>MUST</bcp14>	et='control-streams'>control stream</xref><iref item='control stream'/>, the cli
	respond with a connection error of type H3_FRAME_UNEXPECTED; see <xref target="e	ent <bcp14>MUST</bcp14>
	rrors" format="default"/>.</t>
	<t>A client <bcp14>MUST NOT</bcp14> send a PUSH_PROMISE frame. A serv	respond with a <xref format='none' target='errors'>connection error</xref><iref
	er <bcp14>MUST</bcp14> treat the receipt of	item='connection error'/> of type <xref format='none' target='H3_FRAME_UNEXPECTE
	a PUSH_PROMISE frame as a connection error of type H3_FRAME_UNEXPECTED; see	D'>H3_FRAME_UNEXPECTED</xref><iref item='H3_FRAME_UNEXPECTED'/>.</t>
	<xref target="errors" format="default"/>.</t>	<t>A client <bcp14>MUST NOT</bcp14>
	<t>See <xref target="server-push" format="default"/> for a description	send a PUSH_PROMISE frame. A server <bcp14>MUST</bcp14>
	of the overall server push mechanism.</t>	treat the receipt of
		a PUSH_PROMISE frame as a <xref format='none' target='errors'>connection error</
		xref><iref item='connection error'/> of type <xref format='none' target='H3_FRAM
		E_UNEXPECTED'>H3_FRAME_UNEXPECTED</xref><iref item='H3_FRAME_UNEXPECTED'/>.</t>
		<t>See <xref target='server-push'/> for a description of the overall s
		erver push mechanism.</t>
	</section>	</section>

	<section anchor="frame-goaway" numbered="true" toc="default">	<section anchor='frame-goaway'>
	<name>GOAWAY</name>	<name>GOAWAY</name><iref item='GOAWAY' primary='true'/>
	<t>The GOAWAY frame (type=0x7) is used to initiate graceful shutdown o	<t>The GOAWAY frame (type=0x07) is used to initiate graceful shutdown
	f an HTTP/3	of an HTTP/3
	connection by either endpoint. GOAWAY allows an endpoint to stop accepting new	connection by either endpoint. GOAWAY allows an endpoint to stop accepting new
	requests or pushes while still finishing processing of previously received	requests or pushes while still finishing processing of previously received
	requests and pushes. This enables administrative actions, like server	requests and pushes. This enables administrative actions, like server
	maintenance. GOAWAY by itself does not close a connection.</t>	maintenance. GOAWAY by itself does not close a connection.</t>

	<figure anchor="fig-goaway">	<figure>
	<name>GOAWAY Frame</name>	<name>GOAWAY Frame</name>

	<artwork type="drawing" name="" align="left" alt=""><![CDATA[	<artwork type='ascii-art'><![CDATA[
	GOAWAY Frame {	GOAWAY Frame {

	Type (i) = 0x7,	Type (i) = 0x07,
	Length (i),	Length (i),

	Stream ID/Push ID (..),	Stream ID/Push ID (i),
	}	}
	]]></artwork>	]]></artwork>
	</figure>	</figure>

	<t>The GOAWAY frame is always sent on the control stream. In the serv	<t>The GOAWAY frame is always sent on the <xref format='none' target='
	er to client	control-streams'>control stream</xref><iref item='control stream'/>. In the ser
	direction, it carries a QUIC Stream ID for a client-initiated bidirectional	ver-to-client
	stream encoded as a variable-length integer. A client <bcp14>MUST</bcp14> treat	direction, it carries a QUIC stream ID for a client-initiated bidirectional
	receipt of a	stream encoded as a variable-length integer. A client <bcp14>MUST</b
	GOAWAY frame containing a Stream ID of any other type as a connection error of	cp14>
	type H3_ID_ERROR.</t>	treat receipt of a
	<t>In the client to server direction, the GOAWAY frame carries a Push	GOAWAY frame containing a stream ID of any other type as a <xref format='none' t
	ID encoded as	arget='errors'>connection error</xref><iref item='connection error'/> of
		type <xref format='none' target='H3_ID_ERROR'>H3_ID_ERROR</xref><iref item='H3_I
		D_ERROR'/>.</t>
		<t>In the client-to-server direction, the GOAWAY frame carries a <xref
		format='none' target='server-push'>push ID</xref><iref item='push ID'/> encoded
		as
	a variable-length integer.</t>	a variable-length integer.</t>
	<t>The GOAWAY frame applies to the entire connection, not a specific s tream. A	<t>The GOAWAY frame applies to the entire connection, not a specific s tream. A

	client <bcp14>MUST</bcp14> treat a GOAWAY frame on a stream other than the contr	client <bcp14>MUST</bcp14>
	ol stream as a	treat a GOAWAY frame on a stream other than the <xref format='none' target='con
	connection error of type H3_FRAME_UNEXPECTED; see <xref target="errors" format="	trol-streams'>control stream</xref><iref item='control stream'/> as a
	default"/>.</t>	<xref format='none' target='errors'>connection error</xref><iref item='connectio
	<t>See <xref target="connection-shutdown" format="default"/> for more	n error'/> of type <xref format='none' target='H3_FRAME_UNEXPECTED'>H3_FRAME_UNE
	information on the use of the GOAWAY frame.</t>	XPECTED</xref><iref item='H3_FRAME_UNEXPECTED'/>.</t>
		<t>See <xref target='connection-shutdown'/> for more information on th
		e use of the GOAWAY frame.</t>
	</section>	</section>

	<section anchor="frame-max-push-id" numbered="true" toc="default">	<section anchor='frame-max-push-id'>
	<name>MAX_PUSH_ID</name>	<name>MAX_PUSH_ID</name><iref item='MAX_PUSH_ID' primary='true'/>
	<t>The MAX_PUSH_ID frame (type=0xd) is used by clients to control the	<t>The MAX_PUSH_ID frame (type=0x0d) is used by clients to control the
	number of	number of
	server pushes that the server can initiate. This sets the maximum value for a	server pushes that the server can initiate. This sets the maximum value for a

	Push ID that the server can use in PUSH_PROMISE and CANCEL_PUSH frames.	<xref format='none' target='server-push'>push ID</xref><iref item='push ID'/> th
	Consequently, this also limits the number of push streams that the server can	at the server can use in <xref format='none' target='frame-push-promise'>PUSH_PR
		OMISE</xref><iref item='PUSH_PROMISE'/> and <xref format='none' target='frame-ca
		ncel-push'>CANCEL_PUSH</xref><iref item='CANCEL_PUSH'/> frames.
		Consequently, this also limits the number of <xref format='none' target='push-st
		reams'>push streams</xref><iref item='push stream'/> that the server can
	initiate in addition to the limit maintained by the QUIC transport.</t>	initiate in addition to the limit maintained by the QUIC transport.</t>

	<t>The MAX_PUSH_ID frame is always sent on the control stream. Receip	<t>The MAX_PUSH_ID frame is always sent on the <xref format='none' tar
	t of a	get='control-streams'>control stream</xref><iref item='control stream'/>. Recei
	MAX_PUSH_ID frame on any other stream <bcp14>MUST</bcp14> be treated as a connec	pt of a
	tion error of	MAX_PUSH_ID frame on any other stream <bcp14>MUST</bcp14>
	type H3_FRAME_UNEXPECTED.</t>	be treated as a <xref format='none' target='errors'>connection error</xref><ire
	<t>A server <bcp14>MUST NOT</bcp14> send a MAX_PUSH_ID frame. A clien	f item='connection error'/> of
	t <bcp14>MUST</bcp14> treat the receipt of	type <xref format='none' target='H3_FRAME_UNEXPECTED'>H3_FRAME_UNEXPECTED</xref>
	a MAX_PUSH_ID frame as a connection error of type H3_FRAME_UNEXPECTED.</t>	<iref item='H3_FRAME_UNEXPECTED'/>.</t>
	<t>The maximum Push ID is unset when an HTTP/3 connection is created,	<t>A server <bcp14>MUST NOT</bcp14>
	meaning that	send a MAX_PUSH_ID frame. A client <bcp14>MUST</bcp14>
		treat the receipt of
		a MAX_PUSH_ID frame as a <xref format='none' target='errors'>connection error</x
		ref><iref item='connection error'/> of type <xref format='none' target='H3_FRAME
		_UNEXPECTED'>H3_FRAME_UNEXPECTED</xref><iref item='H3_FRAME_UNEXPECTED'/>.</t>
		<t>The maximum <xref format='none' target='server-push'>push ID</xref>
		<iref item='push ID'/> is unset when an HTTP/3 connection is created, meaning th
		at
	a server cannot push until it receives a MAX_PUSH_ID frame. A client that	a server cannot push until it receives a MAX_PUSH_ID frame. A client that
	wishes to manage the number of promised server pushes can increase the maximum	wishes to manage the number of promised server pushes can increase the maximum

	Push ID by sending MAX_PUSH_ID frames as the server fulfills or cancels server	<xref format='none' target='server-push'>push ID</xref><iref item='push ID'/> by sending MAX_PUSH_ID frames as the server fulfills or cancels server
	pushes.</t>	pushes.</t>

	<figure anchor="fig-max-push">	<figure>
	<name>MAX_PUSH_ID Frame</name>	<name>MAX_PUSH_ID Frame</name>

	<artwork type="drawing" name="" align="left" alt=""><![CDATA[	<artwork type='ascii-art'><![CDATA[
	MAX_PUSH_ID Frame {	MAX_PUSH_ID Frame {

	Type (i) = 0xd,	Type (i) = 0x0d,
	Length (i),	Length (i),
	Push ID (i),	Push ID (i),
	}	}
	]]></artwork>	]]></artwork>
	</figure>	</figure>
	<t>The MAX_PUSH_ID frame carries a single variable-length integer that identifies	<t>The MAX_PUSH_ID frame carries a single variable-length integer that identifies

	the maximum value for a Push ID that the server can use; see <xref target="serve	the maximum value for a <xref format='none' target='server-push'>push ID</xref><
	r-push" format="default"/>. A	iref item='push ID'/> that the server can use; see <xref target='server-push'/>.
	MAX_PUSH_ID frame cannot reduce the maximum Push ID; receipt of a MAX_PUSH_ID	A
	frame that contains a smaller value than previously received <bcp14>MUST</bcp14>	MAX_PUSH_ID frame cannot reduce the maximum <xref format='none' target='server-p
	be treated as	ush'>push ID</xref><iref item='push ID'/>; receipt of a MAX_PUSH_ID
	a connection error of type H3_ID_ERROR.</t>	frame that contains a smaller value than previously received <bcp14>M
		UST</bcp14>
		be treated as
		a <xref format='none' target='errors'>connection error</xref><iref item='connect
		ion error'/> of type <xref format='none' target='H3_ID_ERROR'>H3_ID_ERROR</xref>
		<iref item='H3_ID_ERROR'/>.</t>
	</section>	</section>

	<section anchor="frame-reserved" numbered="true" toc="default">	<section anchor='frame-reserved'>
	<name>Reserved Frame Types</name>	<name>Reserved Frame Types</name>

	<t>Frame types of the format <tt>0x1f * N + 0x21</tt> for non-negative	<t>Frame types of the format <tt>0x1f * N + 0x21</tt> for non-negative
	integer values of N	integer values of
	are reserved to exercise the requirement that unknown types be ignored	<tt>N</tt> are reserved to exercise the requirement that unknown types be ignore
	(<xref target="extensions" format="default"/>). These frames have no semantics,	d
	and <bcp14>MAY</bcp14> be sent on any stream	(<xref target='extensions'/>). These frames have no semantics, and they
	where frames are allowed to be sent. This enables their use for	<bcp14>MAY</bcp14>
	application-layer padding. Endpoints <bcp14>MUST NOT</bcp14> consider these fra	be sent on any
	mes to have any	stream where frames are allowed to be sent. This enables their use for
		application-layer padding. Endpoints <bcp14>MUST NOT</bcp14>
		consider these frames to have any
	meaning upon receipt.</t>	meaning upon receipt.</t>
	<t>The payload and length of the frames are selected in any manner the	<t>The payload and length of the frames are selected in any manner the
	implementation chooses.</t>	implementation chooses.</t>
	<t>Frame types that were used in HTTP/2 where there is no correspondin g HTTP/3	<t>Frame types that were used in HTTP/2 where there is no correspondin g HTTP/3

	frame have also been reserved (<xref target="iana-frames" format="default"/>).	frame have also been reserved (<xref target='iana-frames'/>). These frame types
	These frame types <bcp14>MUST NOT</bcp14> be	<bcp14>MUST NOT</bcp14>
	sent, and their receipt <bcp14>MUST</bcp14> be treated as a connection error of	be
	type	sent, and their receipt <bcp14>MUST</bcp14>
	H3_FRAME_UNEXPECTED.</t>	be treated as a <xref format='none' target='errors'>connection error</xref><ire
		f item='connection error'/> of type
		<xref format='none' target='H3_FRAME_UNEXPECTED'>H3_FRAME_UNEXPECTED</xref><iref
		item='H3_FRAME_UNEXPECTED'/>.</t>
	</section>	</section>
	</section>	</section>
	</section>	</section>

	<section anchor="errors" numbered="true" toc="default">	<section anchor='errors'>
	<name>Error Handling</name>	<name>Error Handling</name><iref item='connection error' primary='true'/><
		iref item='stream error' primary='true'/>
	<t>When a stream cannot be completed successfully, QUIC allows the applica tion to	<t>When a stream cannot be completed successfully, QUIC allows the applica tion to

	abruptly terminate (reset) that stream and communicate a reason; see <xref secti on="2.4" sectionFormat="of" target="RFCYYY1" format="default"/>. This is referre d to as a "stream error." An HTTP/3	abruptly terminate (reset) that stream and communicate a reason; see <xref secti on='2.4' sectionFormat='of' target='QUIC-TRANSPORT'/>. This is referred to as a "stream error". An HTTP/3
	implementation can decide to close a QUIC stream and communicate the type of	implementation can decide to close a QUIC stream and communicate the type of

	error. Wire encodings of error codes are defined in <xref target="http-error-cod	error. Wire encodings of error codes are defined in <xref target='http-error-cod
	es" format="default"/>.	es'/>.
	Stream errors are distinct from HTTP status codes which indicate error	Stream errors are distinct from HTTP status codes that indicate error
	conditions. Stream errors indicate that the sender did not transfer or consume	conditions. Stream errors indicate that the sender did not transfer or consume
	the full request or response, while HTTP status codes indicate the result of a	the full request or response, while HTTP status codes indicate the result of a
	request that was successfully received.</t>	request that was successfully received.</t>
	<t>If an entire connection needs to be terminated, QUIC similarly provides	<t>If an entire connection needs to be terminated, QUIC similarly provides

	mechanisms to communicate a reason; see <xref section="5.3" sectionFormat="of" t	mechanisms to communicate a reason; see <xref section='5.3' sectionFormat='of' t
	arget="RFCYYY1" format="default"/>. This	arget='QUIC-TRANSPORT'/>. This
	is referred to as a "connection error." Similar to stream errors, an HTTP/3	is referred to as a "connection error". Similar to stream errors, an HTTP/3
	implementation can terminate a QUIC connection and communicate the reason using	implementation can terminate a QUIC connection and communicate the reason using

	an error code from <xref target="http-error-codes" format="default"/>.</t>	an error code from <xref target='http-error-codes'/>.</t>
	<t>Although the reasons for closing streams and connections are called "er	<t>Although the reasons for closing streams and connections are called "er
	rors,"	rors",
	these actions do not necessarily indicate a problem with the connection or	these actions do not necessarily indicate a problem with the connection or
	either implementation. For example, a stream can be reset if the requested	either implementation. For example, a stream can be reset if the requested
	resource is no longer needed.</t>	resource is no longer needed.</t>

	<t>An endpoint <bcp14>MAY</bcp14> choose to treat a stream error as a conn	<t>An endpoint <bcp14>MAY</bcp14>
	ection error under	choose to treat a stream error as a connection error under
	certain circumstances, closing the entire connection in response to a condition	certain circumstances, closing the entire connection in response to a condition
	on a single stream. Implementations need to consider the impact on outstanding	on a single stream. Implementations need to consider the impact on outstanding
	requests before making this choice.</t>	requests before making this choice.</t>

	<t>Because new error codes can be defined without negotiation (see <xref t arget="extensions" format="default"/>),	<t>Because new error codes can be defined without negotiation (see <xref t arget='extensions'/>),
	use of an error code in an unexpected context or receipt of an unknown error	use of an error code in an unexpected context or receipt of an unknown error

	code <bcp14>MUST</bcp14> be treated as equivalent to H3_NO_ERROR. However, clos	code <bcp14>MUST</bcp14>
	ing a stream	be treated as equivalent to <xref format='none' target='H3_NO_ERROR'>H3_NO_ERRO
		R</xref><iref item='H3_NO_ERROR'/>. However, closing a stream
	can have other effects regardless of the error code; for example, see	can have other effects regardless of the error code; for example, see

	<xref target="request-response" format="default"/>.</t>	<xref target='request-response'/>.</t>
	<section anchor="http-error-codes" numbered="true" toc="default">	<section anchor='http-error-codes'>
	<name>HTTP/3 Error Codes</name>	<name>HTTP/3 Error Codes</name>
	<t>The following error codes are defined for use when abruptly terminati ng streams,	<t>The following error codes are defined for use when abruptly terminati ng streams,
	aborting reading of streams, or immediately closing HTTP/3 connections.</t>	aborting reading of streams, or immediately closing HTTP/3 connections.</t>
	<dl>	<dl>

	<dt>	<dt><xref format='none' target='H3_NO_ERROR'>H3_NO_ERROR</xref> (0x010
	H3_NO_ERROR (0x100): </dt>	0)<iref item='H3_NO_ERROR'/>:</dt>
	<dd>	<dd>

	<t>No error. This is used when the connection or stream needs to be closed, but	<t anchor='H3_NO_ERROR'>No error. This is used when the connection or stream needs to be closed, but
	there is no error to signal.</t>	there is no error to signal.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_GENERAL_PROTOCOL_ERROR'>H3_GENERAL_
	H3_GENERAL_PROTOCOL_ERROR (0x101): </dt>	PROTOCOL_ERROR</xref> (0x0101)<iref item='H3_GENERAL_PROTOCOL_ERROR'/>:</dt>
	<dd>	<dd>

	<t>Peer violated protocol requirements in a way that does not match	<t anchor='H3_GENERAL_PROTOCOL_ERROR'>Peer violated protocol require
	a more	ments in a way that does not match a more
	specific error code, or endpoint declines to use the more specific error code.</	specific error code or endpoint declines to use the more specific error code.</t
	t>	>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_INTERNAL_ERROR'>H3_INTERNAL_ERROR</
	H3_INTERNAL_ERROR (0x102): </dt>	xref> (0x0102)<iref item='H3_INTERNAL_ERROR'/>:</dt>
	<dd>	<dd>

	<t>An internal error has occurred in the HTTP stack.</t>	<t anchor='H3_INTERNAL_ERROR'>An internal error has occurred in the HTTP stack.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_STREAM_CREATION_ERROR'>H3_STREAM_CR
	H3_STREAM_CREATION_ERROR (0x103): </dt>	EATION_ERROR</xref> (0x0103)<iref item='H3_STREAM_CREATION_ERROR'/>:</dt>
	<dd>	<dd>

	<t>The endpoint detected that its peer created a stream that it will not accept.</t>	<t anchor='H3_STREAM_CREATION_ERROR'>The endpoint detected that its peer created a stream that it will not accept.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_CLOSED_CRITICAL_STREAM'>H3_CLOSED_C
	H3_CLOSED_CRITICAL_STREAM (0x104): </dt>	RITICAL_STREAM</xref> (0x0104)<iref item='H3_CLOSED_CRITICAL_STREAM'/>:</dt>
	<dd>	<dd>

	<t>A stream required by the HTTP/3 connection was closed or reset.</ t>	<t anchor='H3_CLOSED_CRITICAL_STREAM'>A stream required by the HTTP/ 3 connection was closed or reset.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_FRAME_UNEXPECTED'>H3_FRAME_UNEXPECT
	H3_FRAME_UNEXPECTED (0x105): </dt>	ED</xref> (0x0105)<iref item='H3_FRAME_UNEXPECTED'/>:</dt>
	<dd>	<dd>

	<t>A frame was received that was not permitted in the current state or on the	<t anchor='H3_FRAME_UNEXPECTED'>A frame was received that was not pe rmitted in the current state or on the
	current stream.</t>	current stream.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_FRAME_ERROR'>H3_FRAME_ERROR</xref>
	H3_FRAME_ERROR (0x106): </dt>	(0x0106)<iref item='H3_FRAME_ERROR'/>:</dt>
	<dd>	<dd>

	<t>A frame that fails to satisfy layout requirements or with an inva lid size	<t anchor='H3_FRAME_ERROR'>A frame that fails to satisfy layout requ irements or with an invalid size
	was received.</t>	was received.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_EXCESSIVE_LOAD'>H3_EXCESSIVE_LOAD</
	H3_EXCESSIVE_LOAD (0x107): </dt>	xref> (0x0107)<iref item='H3_EXCESSIVE_LOAD'/>:</dt>
	<dd>	<dd>

	<t>The endpoint detected that its peer is exhibiting a behavior that might be	<t anchor='H3_EXCESSIVE_LOAD'>The endpoint detected that its peer is exhibiting a behavior that might be
	generating excessive load.</t>	generating excessive load.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_ID_ERROR'>H3_ID_ERROR</xref> (0x010
	H3_ID_ERROR (0x108): </dt>	8)<iref item='H3_ID_ERROR'/>:</dt>
	<dd>	<dd>

	<t>A Stream ID or Push ID was used incorrectly, such as exceeding a limit,	<t anchor='H3_ID_ERROR'>A stream ID or <xref format='none' target='s erver-push'>push ID</xref><iref item='push ID'/> was used incorrectly, such as e xceeding a limit,
	reducing a limit, or being reused.</t>	reducing a limit, or being reused.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_SETTINGS_ERROR'>H3_SETTINGS_ERROR</
	H3_SETTINGS_ERROR (0x109): </dt>	xref> (0x0109)<iref item='H3_SETTINGS_ERROR'/>:</dt>
	<dd>	<dd>

	<t>An endpoint detected an error in the payload of a SETTINGS frame. </t>	<t anchor='H3_SETTINGS_ERROR'>An endpoint detected an error in the p ayload of a <xref format='none' target='frame-settings'>SETTINGS</xref><iref ite m='SETTINGS'/> frame.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_MISSING_SETTINGS'>H3_MISSING_SETTIN
	H3_MISSING_SETTINGS (0x10a): </dt>	GS</xref> (0x010a)<iref item='H3_MISSING_SETTINGS'/>:</dt>
	<dd>	<dd>

	<t>No SETTINGS frame was received at the beginning of the control st ream.</t>	<t anchor='H3_MISSING_SETTINGS'>No <xref format='none' target='frame -settings'>SETTINGS</xref><iref item='SETTINGS'/> frame was received at the begi nning of the <xref format='none' target='control-streams'>control stream</xref>< iref item='control stream'/>.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_REQUEST_REJECTED'>H3_REQUEST_REJECT
	H3_REQUEST_REJECTED (0x10b): </dt>	ED</xref> (0x010b)<iref item='H3_REQUEST_REJECTED'/>:</dt>
	<dd>	<dd>

	<t>A server rejected a request without performing any application pr ocessing.</t>	<t anchor='H3_REQUEST_REJECTED'>A server rejected a request without performing any application processing.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_REQUEST_CANCELLED'>H3_REQUEST_CANCE
	H3_REQUEST_CANCELLED (0x10c): </dt>	LLED</xref> (0x010c)<iref item='H3_REQUEST_CANCELLED'/>:</dt>
	<dd>	<dd>

	<t>The request or its response (including pushed response) is cancel led.</t>	<t anchor='H3_REQUEST_CANCELLED'>The request or its response (includ ing pushed response) is cancelled.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_REQUEST_INCOMPLETE'>H3_REQUEST_INCO
	H3_REQUEST_INCOMPLETE (0x10d): </dt>	MPLETE</xref> (0x010d)<iref item='H3_REQUEST_INCOMPLETE'/>:</dt>
	<dd>	<dd>

	<t>The client's stream terminated without containing a fully-formed request.</t>	<t anchor='H3_REQUEST_INCOMPLETE'>The client's stream terminated wit hout containing a fully formed request.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_MESSAGE_ERROR'>H3_MESSAGE_ERROR</xr
	H3_MESSAGE_ERROR (0x10e): </dt>	ef> (0x010e)<iref item='H3_MESSAGE_ERROR'/>:</dt>
	<dd>	<dd>

	<t>An HTTP message was malformed and cannot be processed.</t>	<t anchor='H3_MESSAGE_ERROR'>An HTTP message was <xref format='none' target='malformed'>malformed</xref><iref item='malformed'/> and cannot be proce ssed.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_CONNECT_ERROR'>H3_CONNECT_ERROR</xr
	H3_CONNECT_ERROR (0x10f): </dt>	ef> (0x010f)<iref item='H3_CONNECT_ERROR'/>:</dt>
	<dd>	<dd>

	<t>The TCP connection established in response to a CONNECT request w as reset or	<t anchor='H3_CONNECT_ERROR'>The TCP connection established in respo nse to a CONNECT request was reset or
	abnormally closed.</t>	abnormally closed.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='H3_VERSION_FALLBACK'>H3_VERSION_FALLBA
	H3_VERSION_FALLBACK (0x110): </dt>	CK</xref> (0x0110)<iref item='H3_VERSION_FALLBACK'/>:</dt>
	<dd>	<dd>

	<t>The requested operation cannot be served over HTTP/3. The peer s hould	<t anchor='H3_VERSION_FALLBACK'>The requested operation cannot be se rved over HTTP/3. The peer should
	retry over HTTP/1.1.</t>	retry over HTTP/1.1.</t>
	</dd>	</dd>
	</dl>	</dl>

	<t>Error codes of the format <tt>0x1f * N + 0x21</tt> for non-negative i	<t>Error codes of the format <tt>0x1f * N + 0x21</tt> for non-negative i
	nteger values of N	nteger values of
	are reserved to exercise the requirement that unknown error codes be treated as	<tt>N</tt> are reserved to exercise the requirement that unknown error codes be
	equivalent to H3_NO_ERROR (<xref target="extensions" format="default"/>). Implem	treated
	entations <bcp14>SHOULD</bcp14> select an	as equivalent to <xref format='none' target='H3_NO_ERROR'>H3_NO_ERROR</xref><ire
		f item='H3_NO_ERROR'/> (<xref target='extensions'/>). Implementations <
		bcp14>SHOULD</bcp14>
		select an
	error code from this space with some probability when they would have sent	error code from this space with some probability when they would have sent

	H3_NO_ERROR.</t>	<xref format='none' target='H3_NO_ERROR'>H3_NO_ERROR</xref><iref item='H3_NO_ERR OR'/>.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="extensions" numbered="true" toc="default">	<section anchor='extensions'>
	<name>Extensions to HTTP/3</name>	<name>Extensions to HTTP/3</name>
	<t>HTTP/3 permits extension of the protocol. Within the limitations descr ibed in	<t>HTTP/3 permits extension of the protocol. Within the limitations descr ibed in
	this section, protocol extensions can be used to provide additional services or	this section, protocol extensions can be used to provide additional services or
	alter any aspect of the protocol. Extensions are effective only within the	alter any aspect of the protocol. Extensions are effective only within the
	scope of a single HTTP/3 connection.</t>	scope of a single HTTP/3 connection.</t>
	<t>This applies to the protocol elements defined in this document. This d oes not	<t>This applies to the protocol elements defined in this document. This d oes not
	affect the existing options for extending HTTP, such as defining new methods,	affect the existing options for extending HTTP, such as defining new methods,
	status codes, or fields.</t>	status codes, or fields.</t>

	<t>Extensions are permitted to use new frame types (<xref target="frames"	<t>Extensions are permitted to use new frame types (<xref target='frames'/
	format="default"/>), new settings	>), new settings
	(<xref target="settings-parameters" format="default"/>), new error codes (<xref	(<xref target='settings-parameters'/>), new error codes (<xref target='errors'/>
	target="errors" format="default"/>), or new unidirectional	), or new unidirectional
	stream types (<xref target="unidirectional-streams" format="default"/>). Regist	stream types (<xref target='unidirectional-streams'/>). Registries are establis
	ries are established for	hed for
	managing these extension points: frame types (<xref target="iana-frames" format=	managing these extension points: frame types (<xref target='iana-frames'/>), set
	"default"/>), settings	tings
	(<xref target="iana-settings" format="default"/>), error codes (<xref target="ia	(<xref target='iana-settings'/>), error codes (<xref target='iana-error-codes'/>
	na-error-codes" format="default"/>), and stream types	), and stream types
	(<xref target="iana-stream-types" format="default"/>).</t>	(<xref target='iana-stream-types'/>).</t>
	<t>Implementations <bcp14>MUST</bcp14> ignore unknown or unsupported value	<t>Implementations <bcp14>MUST</bcp14>
	s in all extensible	ignore unknown or unsupported values in all extensible
	protocol elements. Implementations <bcp14>MUST</bcp14> discard frames and abort	protocol elements. Implementations <bcp14>MUST</bcp14>
	reading on	discard data or abort reading on
	unidirectional streams that have unknown or unsupported types. This means that	unidirectional streams that have unknown or unsupported types. This means that
	any of these extension points can be safely used by extensions without prior	any of these extension points can be safely used by extensions without prior
	arrangement or negotiation. However, where a known frame type is required to be	arrangement or negotiation. However, where a known frame type is required to be

	in a specific location, such as the SETTINGS frame as the first frame of the	in a specific location, such as the <xref format='none' target='frame-settings'>
	control stream (see <xref target="control-streams" format="default"/>), an unkno	SETTINGS</xref><iref item='SETTINGS'/> frame as the first frame of the
	wn frame type does not satisfy	<xref format='none' target='control-streams'>control stream</xref><iref item='co
	that requirement and <bcp14>SHOULD</bcp14> be treated as an error.</t>	ntrol stream'/> (see <xref target='control-streams'/>), an unknown frame type do
	<t>Extensions that could change the semantics of existing protocol compone	es not satisfy
	nts <bcp14>MUST</bcp14>	that requirement and <bcp14>SHOULD</bcp14>
		be treated as an error.</t>
		<t>Extensions that could change the semantics of existing protocol compone
		nts <bcp14>MUST</bcp14>

	be negotiated before being used. For example, an extension that changes the	be negotiated before being used. For example, an extension that changes the

	layout of the HEADERS frame cannot be used until the peer has given a positive	layout of the <xref format='none' target='frame-headers'>HEADERS</xref><iref ite m='HEADERS'/> frame cannot be used until the peer has given a positive
	signal that this is acceptable. Coordinating when such a revised layout comes	signal that this is acceptable. Coordinating when such a revised layout comes
	into effect could prove complex. As such, allocating new identifiers for	into effect could prove complex. As such, allocating new identifiers for
	new definitions of existing protocol elements is likely to be more effective.</t >	new definitions of existing protocol elements is likely to be more effective.</t >
	<t>This document does not mandate a specific method for negotiating the us e of an	<t>This document does not mandate a specific method for negotiating the us e of an

	extension but notes that a setting (<xref target="settings-parameters" format="d	extension, but it notes that a setting (<xref target='settings-parameters'/>) co
	efault"/>) could be used for	uld be used
	that purpose. If both peers set a value that indicates willingness to use the	for that purpose. If both peers set a value that indicates willingness to use
	extension, then the extension can be used. If a setting is used for extension	the extension, then the extension can be used. If a setting is used for
	negotiation, the default value <bcp14>MUST</bcp14> be defined in such a fashion	extension negotiation, the default value <bcp14>MUST</bcp14>
	that the	be defined in such a fashion that
	extension is disabled if the setting is omitted.</t>	the extension is disabled if the setting is omitted.</t>
	</section>	</section>

	<section anchor="security-considerations" numbered="true" toc="default">	<section anchor='security-considerations'>
	<name>Security Considerations</name>	<name>Security Considerations</name>
	<t>The security considerations of HTTP/3 should be comparable to those of HTTP/2	<t>The security considerations of HTTP/3 should be comparable to those of HTTP/2

	with TLS. However, many of the considerations from <xref section="10" sectionFo	with TLS. However, many of the considerations from <xref section='10' sectionFo
	rmat="of" target="RFC7540" format="default"/>	rmat='of' target='RFC9113'/>
	apply to <xref target="RFCYYY1" format="default"/> and are discussed in that doc	apply to <xref target='QUIC-TRANSPORT'/> and are discussed in that document.</t>
	ument.</t>	<section anchor='server-authority'>
	<section anchor="server-authority" numbered="true" toc="default">
	<name>Server Authority</name>	<name>Server Authority</name>
	<t>HTTP/3 relies on the HTTP definition of authority. The security consi derations	<t>HTTP/3 relies on the HTTP definition of authority. The security consi derations

	of establishing authority are discussed in <xref section="17.1" sectionFormat="o f" target="RFCYYY4" format="default"/>.</t>	of establishing authority are discussed in <xref section='17.1' sectionFormat='o f' target='RFC9110'/>.</t>
	</section>	</section>

	<section anchor="cross-protocol-attacks" numbered="true" toc="default">	<section anchor='cross-protocol-attacks'>
	<name>Cross-Protocol Attacks</name>	<name>Cross-Protocol Attacks</name>
	<t>The use of ALPN in the TLS and QUIC handshakes establishes the target	<t>The use of ALPN in the TLS and QUIC handshakes establishes the target
	application protocol before application-layer bytes are processed. This ensures	application protocol before application-layer bytes are processed. This ensures
	that endpoints have strong assurances that peers are using the same protocol.</t >	that endpoints have strong assurances that peers are using the same protocol.</t >

	<t>This does not guarantee protection from all cross-protocol attacks. < xref section="21.5" sectionFormat="of" target="RFCYYY1" format="default"/> descr ibes some ways in which the plaintext of QUIC	<t>This does not guarantee protection from all cross-protocol attacks. < xref section='21.5' sectionFormat='of' target='QUIC-TRANSPORT'/> describes some ways in which the plaintext of QUIC
	packets can be used to perform request forgery against endpoints that don't use	packets can be used to perform request forgery against endpoints that don't use
	authenticated transports.</t>	authenticated transports.</t>
	</section>	</section>

	<section anchor="intermediary-encapsulation-attacks" numbered="true" toc="	<section anchor='intermediary-encapsulation-attacks'>
	default">	<name>Intermediary-Encapsulation Attacks</name>
	<name>Intermediary Encapsulation Attacks</name>
	<t>The HTTP/3 field encoding allows the expression of names that are not valid	<t>The HTTP/3 field encoding allows the expression of names that are not valid

	field names in the syntax used by HTTP (<xref section="5.1" sectionFormat="of" t	field names in the syntax used by HTTP (<xref section='5.1' sectionFormat='of' t
	arget="RFCYYY4" format="default"/>).	arget='RFC9110'/>). Requests or
	Requests or responses containing invalid field names <bcp14>MUST</bcp14> be trea	responses containing invalid field names <bcp14>MUST</bcp14>
	ted as	be treated as <xref format='none' target='malformed'>malformed</xref><iref item
	malformed (<xref target="malformed" format="default"/>). An intermediary theref	='malformed'/>.
	ore cannot translate an HTTP/3	Therefore, an intermediary cannot translate an HTTP/3 request or response
	request or response containing an invalid field name into an HTTP/1.1 message.</	containing an invalid field name into an HTTP/1.1 message.</t>
	t>
	<t>Similarly, HTTP/3 can transport field values that are not valid. Whil e most	<t>Similarly, HTTP/3 can transport field values that are not valid. Whil e most

	values that can be encoded will not alter field parsing, carriage return (CR,	values that can be encoded will not alter field parsing, carriage return (ASCII
	ASCII 0xd), line feed (LF, ASCII 0xa), and the zero character (NUL, ASCII 0x0)	0x0d), line feed (ASCII 0x0a), and the null character (ASCII 0x00) might be
	might be exploited by an attacker if they are translated verbatim. Any request	exploited by an attacker if they are translated verbatim. Any request or
	or response that contains a character not permitted in a field value <bcp14>MUST	response that contains a character not permitted in a field value <bcp1
	</bcp14> be	4>MUST</bcp14>
	treated as malformed (<xref target="malformed" format="default"/>). Valid chara	be
	cters are defined by the	treated as <xref format='none' target='malformed'>malformed</xref><iref item='ma
	"field-content" ABNF rule in <xref section="5.5" sectionFormat="of" target="RFCY	lformed'/>. Valid characters are defined by the
	YY4" format="default"/>.</t>	"field-content" ABNF rule in <xref section='5.5' sectionFormat='of' target='RFC9
		110'/>.</t>
	</section>	</section>

	<section anchor="cacheability-of-pushed-responses" numbered="true" toc="de fault">	<section anchor='cacheability-of-pushed-responses'>
	<name>Cacheability of Pushed Responses</name>	<name>Cacheability of Pushed Responses</name>
	<t>Pushed responses do not have an explicit request from the client; the request is	<t>Pushed responses do not have an explicit request from the client; the request is

	provided by the server in the PUSH_PROMISE frame.</t>	provided by the server in the <xref format='none' target='frame-push-promise'>PU SH_PROMISE</xref><iref item='PUSH_PROMISE'/> frame.</t>
	<t>Caching responses that are pushed is possible based on the guidance p rovided by	<t>Caching responses that are pushed is possible based on the guidance p rovided by
	the origin server in the Cache-Control header field. However, this can cause	the origin server in the Cache-Control header field. However, this can cause
	issues if a single server hosts more than one tenant. For example, a server	issues if a single server hosts more than one tenant. For example, a server
	might offer multiple users each a small portion of its URI space.</t>	might offer multiple users each a small portion of its URI space.</t>

	<t>Where multiple tenants share space on the same server, that server <b	<t>Where multiple tenants share space on the same server, that server
	cp14>MUST</bcp14> ensure	<bcp14>MUST</bcp14>
		ensure
	that tenants are not able to push representations of resources that they do not	that tenants are not able to push representations of resources that they do not
	have authority over. Failure to enforce this would allow a tenant to provide a	have authority over. Failure to enforce this would allow a tenant to provide a
	representation that would be served out of cache, overriding the actual	representation that would be served out of cache, overriding the actual
	representation that the authoritative tenant provides.</t>	representation that the authoritative tenant provides.</t>
	<t>Clients are required to reject pushed responses for which an origin s erver is	<t>Clients are required to reject pushed responses for which an origin s erver is

	not authoritative; see <xref target="server-push" format="default"/>.</t>	not authoritative; see <xref target='server-push'/>.</t>
	</section>	</section>

	<section anchor="denial-of-service-considerations" numbered="true" toc="de fault">	<section anchor='denial-of-service-considerations'>
	<name>Denial-of-Service Considerations</name>	<name>Denial-of-Service Considerations</name>
	<t>An HTTP/3 connection can demand a greater commitment of resources to operate	<t>An HTTP/3 connection can demand a greater commitment of resources to operate
	than an HTTP/1.1 or HTTP/2 connection. The use of field compression and flow	than an HTTP/1.1 or HTTP/2 connection. The use of field compression and flow
	control depend on a commitment of resources for storing a greater amount of	control depend on a commitment of resources for storing a greater amount of
	state. Settings for these features ensure that memory commitments for these	state. Settings for these features ensure that memory commitments for these
	features are strictly bounded.</t>	features are strictly bounded.</t>

	<t>The number of PUSH_PROMISE frames is constrained in a similar fashion	<t>The number of <xref format='none' target='frame-push-promise'>PUSH_PR
	. A client	OMISE</xref><iref item='PUSH_PROMISE'/> frames is constrained in a similar fashi
	that accepts server push <bcp14>SHOULD</bcp14> limit the number of Push IDs it i	on. A client
	ssues at a	that accepts server push <bcp14>SHOULD</bcp14>
		limit the number of push IDs it issues at a
	time.</t>	time.</t>
	<t>Processing capacity cannot be guarded as effectively as state capacit y.</t>	<t>Processing capacity cannot be guarded as effectively as state capacit y.</t>
	<t>The ability to send undefined protocol elements that the peer is requ ired to	<t>The ability to send undefined protocol elements that the peer is requ ired to
	ignore can be abused to cause a peer to expend additional processing time. This	ignore can be abused to cause a peer to expend additional processing time. This

	might be done by setting multiple undefined SETTINGS parameters, unknown frame	might be done by setting multiple undefined <xref format='none' target='frame-se ttings'>SETTINGS</xref><iref item='SETTINGS'/> parameters, unknown frame
	types, or unknown stream types. Note, however, that some uses are entirely	types, or unknown stream types. Note, however, that some uses are entirely
	legitimate, such as optional-to-understand extensions and padding to increase	legitimate, such as optional-to-understand extensions and padding to increase
	resistance to traffic analysis.</t>	resistance to traffic analysis.</t>
	<t>Compression of field sections also offers some opportunities to waste processing	<t>Compression of field sections also offers some opportunities to waste processing

	resources; see <xref section="7" sectionFormat="of" target="RFCYYY2" format="def ault"/> for more details on potential abuses.</t>	resources; see <xref section='7' sectionFormat='of' target='RFC9204'/> for more details on potential abuses.</t>
	<t>All these features -- i.e., server push, unknown protocol elements, f ield	<t>All these features -- i.e., server push, unknown protocol elements, f ield
	compression -- have legitimate uses. These features become a burden only when	compression -- have legitimate uses. These features become a burden only when
	they are used unnecessarily or to excess.</t>	they are used unnecessarily or to excess.</t>
	<t>An endpoint that does not monitor such behavior exposes itself to a r isk of	<t>An endpoint that does not monitor such behavior exposes itself to a r isk of

	denial-of-service attack. Implementations <bcp14>SHOULD</bcp14> track the use o	denial-of-service attack. Implementations <bcp14>SHOULD</bcp14>
	f these	track the use of these
	features and set limits on their use. An endpoint <bcp14>MAY</bcp14> treat acti	features and set limits on their use. An endpoint <bcp14>MAY</bcp14>
	vity that is	treat activity that is
	suspicious as a connection error of type H3_EXCESSIVE_LOAD (<xref target="errors	suspicious as a <xref format='none' target='errors'>connection error</xref><iref
	" format="default"/>), but	item='connection error'/> of type <xref format='none' target='H3_EXCESSIVE_LOAD
		'>H3_EXCESSIVE_LOAD</xref><iref item='H3_EXCESSIVE_LOAD'/>, but
	false positives will result in disrupting valid connections and requests.</t>	false positives will result in disrupting valid connections and requests.</t>

	<section anchor="limits-on-field-section-size" numbered="true" toc="defa ult">	<section anchor='limits-on-field-section-size'>
	<name>Limits on Field Section Size</name>	<name>Limits on Field Section Size</name>

	<t>A large field section (<xref target="request-response" format="defa ult"/>) can cause an implementation to	<t>A large field section (<xref target='request-response'/>) can cause an implementation to
	commit a large amount of state. Header fields that are critical for routing can	commit a large amount of state. Header fields that are critical for routing can
	appear toward the end of a header section, which prevents streaming of the	appear toward the end of a header section, which prevents streaming of the
	header section to its ultimate destination. This ordering and other reasons,	header section to its ultimate destination. This ordering and other reasons,
	such as ensuring cache correctness, mean that an endpoint likely needs to buffer	such as ensuring cache correctness, mean that an endpoint likely needs to buffer
	the entire header section. Since there is no hard limit to the size of a field	the entire header section. Since there is no hard limit to the size of a field
	section, some endpoints could be forced to commit a large amount of available	section, some endpoints could be forced to commit a large amount of available
	memory for header fields.</t>	memory for header fields.</t>

	<t>An endpoint can use the SETTINGS_MAX_FIELD_SECTION_SIZE	<t>An endpoint can use the <xref format='none' target='SETTINGS_MAX_FI
	(<xref target="header-size-constraints" format="default"/>) setting to advise pe	ELD_SECTION_SIZE'>SETTINGS_MAX_FIELD_SECTION_SIZE</xref><iref item='SETTINGS_MAX
	ers of limits that might apply	_FIELD_SECTION_SIZE'/>
	on the size of field sections. This setting is only advisory, so endpoints <bcp1	(<xref target='header-size-constraints'/>) setting to advise peers of limits tha
	4>MAY</bcp14>	t might apply
		on the size of field sections. This setting is only advisory, so endpoints
		<bcp14>MAY</bcp14>

	choose to send field sections that exceed this limit and risk having the request	choose to send field sections that exceed this limit and risk having the request

	or response being treated as malformed. This setting is specific to an HTTP/3	or response being treated as <xref format='none' target='malformed'>malformed</x ref><iref item='malformed'/>. This setting is specific to an HTTP/3
	connection, so any request or response could encounter a hop with a lower,	connection, so any request or response could encounter a hop with a lower,
	unknown limit. An intermediary can attempt to avoid this problem by passing on	unknown limit. An intermediary can attempt to avoid this problem by passing on
	values presented by different peers, but they are not obligated to do so.</t>	values presented by different peers, but they are not obligated to do so.</t>
	<t>A server that receives a larger field section than it is willing to handle can	<t>A server that receives a larger field section than it is willing to handle can

	send an HTTP 431 (Request Header Fields Too Large) status code (<xref target="RF C6585" format="default"/>).	send an HTTP 431 (Request Header Fields Too Large) status code (<xref target='RF C6585'/>).
	A client can discard responses that it cannot process.</t>	A client can discard responses that it cannot process.</t>
	</section>	</section>

	<section anchor="connect-issues" numbered="true" toc="default">	<section anchor='connect-issues'>
	<name>CONNECT Issues</name>	<name>CONNECT Issues</name>
	<t>The CONNECT method can be used to create disproportionate load on a proxy, since	<t>The CONNECT method can be used to create disproportionate load on a proxy, since
	stream creation is relatively inexpensive when compared to the creation and	stream creation is relatively inexpensive when compared to the creation and
	maintenance of a TCP connection. Therefore, a proxy that supports CONNECT might	maintenance of a TCP connection. Therefore, a proxy that supports CONNECT might
	be more conservative in the number of simultaneous requests it accepts.</t>	be more conservative in the number of simultaneous requests it accepts.</t>
	<t>A proxy might also maintain some resources for a TCP connection bey ond the	<t>A proxy might also maintain some resources for a TCP connection bey ond the
	closing of the stream that carries the CONNECT request, since the outgoing TCP	closing of the stream that carries the CONNECT request, since the outgoing TCP
	connection remains in the TIME_WAIT state. To account for this, a proxy might	connection remains in the TIME_WAIT state. To account for this, a proxy might
	delay increasing the QUIC stream limits for some time after a TCP connection	delay increasing the QUIC stream limits for some time after a TCP connection
	terminates.</t>	terminates.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="use-of-compression" numbered="true" toc="default">	<section anchor='use-of-compression'>
	<name>Use of Compression</name>	<name>Use of Compression</name>
	<t>Compression can allow an attacker to recover secret data when it is c ompressed	<t>Compression can allow an attacker to recover secret data when it is c ompressed
	in the same context as data under attacker control. HTTP/3 enables compression	in the same context as data under attacker control. HTTP/3 enables compression

	of fields (<xref target="header-formatting" format="default"/>); the following c	of fields (<xref target='header-formatting'/>); the following concerns also appl
	oncerns also apply to the use	y to the use
	of HTTP compressed content-codings; see <xref section="8.4.1" sectionFormat="of"	of HTTP compressed content-codings; see <xref section='8.4.1' sectionFormat='of'
	target="RFCYYY4" format="default"/>.</t>	target='RFC9110'/>.</t>
	<t>There are demonstrable attacks on compression that exploit the charac teristics	<t>There are demonstrable attacks on compression that exploit the charac teristics

	of the web (e.g., <xref target="BREACH" format="default"/>). The attacker induc es multiple requests	of the web (e.g., <xref target='BREACH'/>). The attacker induces multiple reque sts
	containing varying plaintext, observing the length of the resulting ciphertext	containing varying plaintext, observing the length of the resulting ciphertext
	in each, which reveals a shorter length when a guess about the secret is	in each, which reveals a shorter length when a guess about the secret is
	correct.</t>	correct.</t>

	<t>Implementations communicating on a secure channel <bcp14>MUST NOT</bc	<t>Implementations communicating on a secure channel <bcp14>MUS
	p14> compress content that	T NOT</bcp14>
		compress content that
	includes both confidential and attacker-controlled data unless separate	includes both confidential and attacker-controlled data unless separate

	compression contexts are used for each source of data. Compression <bcp14>MUST	compression contexts are used for each source of data. Compression <bc
	NOT</bcp14> be	p14>MUST NOT</bcp14>
		be
	used if the source of data cannot be reliably determined.</t>	used if the source of data cannot be reliably determined.</t>
	<t>Further considerations regarding the compression of field sections ar e	<t>Further considerations regarding the compression of field sections ar e

	described in <xref target="RFCYYY2" format="default"/>.</t>	described in <xref target='RFC9204'/>.</t>
	</section>	</section>

	<section anchor="padding-and-traffic-analysis" numbered="true" toc="defaul t">	<section anchor='padding-and-traffic-analysis'>
	<name>Padding and Traffic Analysis</name>	<name>Padding and Traffic Analysis</name>
	<t>Padding can be used to obscure the exact size of frame content and is provided	<t>Padding can be used to obscure the exact size of frame content and is provided
	to mitigate specific attacks within HTTP, for example, attacks where compressed	to mitigate specific attacks within HTTP, for example, attacks where compressed
	content includes both attacker-controlled plaintext and secret data (e.g.,	content includes both attacker-controlled plaintext and secret data (e.g.,

	<xref target="BREACH" format="default"/>).</t>	<xref target='BREACH'/>).</t>
	<t>Where HTTP/2 employs PADDING frames and Padding fields in other frame s to make a	<t>Where HTTP/2 employs PADDING frames and Padding fields in other frame s to make a
	connection more resistant to traffic analysis, HTTP/3 can either rely on	connection more resistant to traffic analysis, HTTP/3 can either rely on
	transport-layer padding or employ the reserved frame and stream types discussed	transport-layer padding or employ the reserved frame and stream types discussed

	in <xref target="frame-reserved" format="default"/> and <xref target="stream-gre	in Sections <xref format='counter' target='frame-reserved'/> and <xref format='c
	ase" format="default"/>. These methods of padding produce	ounter' target='stream-grease'/>. These methods of
	different results in terms of the granularity of padding, how padding is	padding produce different results in terms of the granularity of padding, how
	arranged in relation to the information that is being protected, whether padding	padding is arranged in relation to the information that is being protected,
	is applied in the case of packet loss, and how an implementation might control	whether padding is applied in the case of packet loss, and how an implementation
	padding.</t>	might control padding.</t>
	<t>Reserved stream types can be used to give the appearance of sending t raffic even	<t>Reserved stream types can be used to give the appearance of sending t raffic even
	when the connection is idle. Because HTTP traffic often occurs in bursts,	when the connection is idle. Because HTTP traffic often occurs in bursts,
	apparent traffic can be used to obscure the timing or duration of such bursts,	apparent traffic can be used to obscure the timing or duration of such bursts,
	even to the point of appearing to send a constant stream of data. However, as	even to the point of appearing to send a constant stream of data. However, as
	such traffic is still flow controlled by the receiver, a failure to promptly	such traffic is still flow controlled by the receiver, a failure to promptly

	drain such streams and provide additional flow control credit can limit the	drain such streams and provide additional flow-control credit can limit the
	sender's ability to send real traffic.</t>	sender's ability to send real traffic.</t>
	<t>To mitigate attacks that rely on compression, disabling or limiting c ompression	<t>To mitigate attacks that rely on compression, disabling or limiting c ompression
	might be preferable to padding as a countermeasure.</t>	might be preferable to padding as a countermeasure.</t>
	<t>Use of padding can result in less protection than might seem immediat ely	<t>Use of padding can result in less protection than might seem immediat ely
	obvious. Redundant padding could even be counterproductive. At best, padding	obvious. Redundant padding could even be counterproductive. At best, padding
	only makes it more difficult for an attacker to infer length information by	only makes it more difficult for an attacker to infer length information by
	increasing the number of frames an attacker has to observe. Incorrectly	increasing the number of frames an attacker has to observe. Incorrectly
	implemented padding schemes can be easily defeated. In particular, randomized	implemented padding schemes can be easily defeated. In particular, randomized
	padding with a predictable distribution provides very little protection;	padding with a predictable distribution provides very little protection;
	similarly, padding payloads to a fixed size exposes information as payload sizes	similarly, padding payloads to a fixed size exposes information as payload sizes
	cross the fixed-sized boundary, which could be possible if an attacker can	cross the fixed-sized boundary, which could be possible if an attacker can
	control plaintext.</t>	control plaintext.</t>
	</section>	</section>

	<section anchor="frame-parsing" numbered="true" toc="default">	<section anchor='frame-parsing'>
	<name>Frame Parsing</name>	<name>Frame Parsing</name>
	<t>Several protocol elements contain nested length elements, typically i n the form	<t>Several protocol elements contain nested length elements, typically i n the form
	of frames with an explicit length containing variable-length integers. This	of frames with an explicit length containing variable-length integers. This

	could pose a security risk to an incautious implementer. An implementation <bcp	could pose a security risk to an incautious implementer. An implementation
	14>MUST</bcp14>	<bcp14>MUST</bcp14>

	ensure that the length of a frame exactly matches the length of the fields it	ensure that the length of a frame exactly matches the length of the fields it
	contains.</t>	contains.</t>
	</section>	</section>

	<section anchor="early-data" numbered="true" toc="default">	<section anchor='early-data'>
	<name>Early Data</name>	<name>Early Data</name>
	<t>The use of 0-RTT with HTTP/3 creates an exposure to replay attack. T he	<t>The use of 0-RTT with HTTP/3 creates an exposure to replay attack. T he

	anti-replay mitigations in <xref target="RFC8470" format="default"/> <bcp14>MUST	anti-replay mitigations in <xref target='HTTP-REPLAY'/> <bcp14>MUST</bc
	</bcp14> be applied when using	p14>
	HTTP/3 with 0-RTT. When applying <xref target="RFC8470" format="default"/> to H	be applied when using
	TTP/3, references to the	HTTP/3 with 0-RTT. When applying <xref target='HTTP-REPLAY'/> to HTTP/3, refere
		nces to the
	TLS layer refer to the handshake performed within QUIC, while all references to	TLS layer refer to the handshake performed within QUIC, while all references to
	application data refer to the contents of streams.</t>	application data refer to the contents of streams.</t>
	</section>	</section>

	<section anchor="migration" numbered="true" toc="default">	<section anchor='migration'>
	<name>Migration</name>	<name>Migration</name>
	<t>Certain HTTP implementations use the client address for logging or	<t>Certain HTTP implementations use the client address for logging or
	access-control purposes. Since a QUIC client's address might change during a	access-control purposes. Since a QUIC client's address might change during a
	connection (and future versions might support simultaneous use of multiple	connection (and future versions might support simultaneous use of multiple
	addresses), such implementations will need to either actively retrieve the	addresses), such implementations will need to either actively retrieve the
	client's current address or addresses when they are relevant or explicitly	client's current address or addresses when they are relevant or explicitly
	accept that the original address might change.</t>	accept that the original address might change.</t>
	</section>	</section>

	<section anchor="privacy-considerations" numbered="true" toc="default">	<section anchor='privacy-considerations'>
	<name>Privacy Considerations</name>	<name>Privacy Considerations</name>
	<t>Several characteristics of HTTP/3 provide an observer an opportunity to	<t>Several characteristics of HTTP/3 provide an observer an opportunity to
	correlate actions of a single client or server over time. These include the	correlate actions of a single client or server over time. These include the
	value of settings, the timing of reactions to stimulus, and the handling of any	value of settings, the timing of reactions to stimulus, and the handling of any
	features that are controlled by settings.</t>	features that are controlled by settings.</t>
	<t>As far as these create observable differences in behavior, they could be used as	<t>As far as these create observable differences in behavior, they could be used as
	a basis for fingerprinting a specific client.</t>	a basis for fingerprinting a specific client.</t>
	<t>HTTP/3's preference for using a single QUIC connection allows correla tion of a	<t>HTTP/3's preference for using a single QUIC connection allows correla tion of a
	user's activity on a site. Reusing connections for different origins allows	user's activity on a site. Reusing connections for different origins allows
	for correlation of activity across those origins.</t>	for correlation of activity across those origins.</t>
	<t>Several features of QUIC solicit immediate responses and can be used by an	<t>Several features of QUIC solicit immediate responses and can be used by an
	endpoint to measure latency to their peer; this might have privacy implications	endpoint to measure latency to their peer; this might have privacy implications
	in certain scenarios.</t>	in certain scenarios.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="iana-considerations" numbered="true" toc="default">	<section anchor='iana-considerations'>
	<name>IANA Considerations</name>	<name>IANA Considerations</name>

	<t>This document registers a new ALPN protocol ID (<xref target="iana-alpn	<t>This document registers a new ALPN protocol ID (<xref target='iana-alpn
	" format="default"/>) and creates new	'/>) and creates new
	registries that manage the assignment of codepoints in HTTP/3.</t>	registries that manage the assignment of code points in HTTP/3.</t>
	<section anchor="iana-alpn" numbered="true" toc="default">	<section anchor='iana-alpn'>
	<name>Registration of HTTP/3 Identification String</name>	<name>Registration of HTTP/3 Identification String</name>
	<t>This document creates a new registration for the identification of	<t>This document creates a new registration for the identification of

	HTTP/3 in the "Application Layer Protocol Negotiation (ALPN)	HTTP/3 in the "TLS Application-Layer Protocol Negotiation (ALPN)
	Protocol IDs" registry established in <xref target="RFC7301" format="default"/>.	Protocol IDs" registry established in <xref target='RFC7301'/>.</t>
	</t>
	<t>The "h3" string identifies HTTP/3:</t>	<t>The "h3" string identifies HTTP/3:</t>
	<dl>	<dl>

	<dt>	<dt>Protocol:</dt>
	Protocol: </dt>
	<dd>	<dd>
	<t>HTTP/3</t>	<t>HTTP/3</t>
	</dd>	</dd>

	<dt>	<dt>Identification Sequence:</dt>
	Identification Sequence: </dt>
	<dd>	<dd>
	<t>0x68 0x33 ("h3")</t>	<t>0x68 0x33 ("h3")</t>
	</dd>	</dd>

	<dt>	<dt>Specification:</dt>
	Specification: </dt>
	<dd>	<dd>
	<t>This document</t>	<t>This document</t>
	</dd>	</dd>
	</dl>	</dl>
	</section>	</section>

	<section anchor="iana-policy" numbered="true" toc="default">	<section anchor='iana-policy'>
	<name>New Registries</name>	<name>New Registries</name>
	<t>New registries created in this document operate under the QUIC regist ration	<t>New registries created in this document operate under the QUIC regist ration

	policy documented in <xref section="22.1" sectionFormat="of" target="RFCYYY1" fo	policy documented in <xref section='22.1' sectionFormat='of' target='QUIC-TRANSP
	rmat="default"/>. These registries all	ORT'/>. These registries all
	include the common set of fields listed in <xref section="22.1.1" sectionFormat=	include the common set of fields listed in <xref section='22.1.1' sectionFormat=
	"of" target="RFCYYY1" format="default"/>.	'of' target='QUIC-TRANSPORT'/>.
	These registries [<bcp14>SHALL</bcp14> be/are] collected under a "Hypertext Tran	These registries are collected under the "Hypertext Transfer Protocol version 3
	sfer Protocol	(HTTP/3)" heading.</t>
	version 3 (HTTP/3) Parameters" heading.</t>	<t>The initial allocations in these registries are all assigned permanen
	<t>The initial allocations in these registries created in this document	t status
	are all	and list a change controller of the IETF and a contact of the HTTP working group
	assigned permanent status and list a change controller of the IETF and a contact	(ietf-http-wg@w3.org).</t>
	of the HTTP working group (ietf-http-wg@w3.org).</t>	<section anchor='iana-frames'>
	<section anchor="iana-frames" numbered="true" toc="default">
	<name>Frame Types</name>	<name>Frame Types</name>
	<t>This document establishes a registry for HTTP/3 frame type codes. T he "HTTP/3	<t>This document establishes a registry for HTTP/3 frame type codes. T he "HTTP/3

	Frame Type" registry governs a 62-bit space. This registry follows the QUIC	Frame Types" registry governs a 62-bit space. This registry follows the QUIC
	registry policy; see <xref target="iana-policy" format="default"/>. Permanent r	registry policy; see <xref target='iana-policy'/>. Permanent registrations in t
	egistrations in this registry	his registry
	are assigned using the Specification Required policy (<xref target="RFC8126" for	are assigned using the Specification Required policy (<xref target='RFC8126'/>),
	mat="default"/>), except for	except for
	values between 0x00 and 0x3f (in hexadecimal; inclusive), which are assigned	values between 0x00 and 0x3f (in hexadecimal; inclusive), which are assigned
	using Standards Action or IESG Approval as defined in	using Standards Action or IESG Approval as defined in

	Sections <xref target="RFC8126" section="4.9" sectionFormat="bare" format="defau lt"/> and <xref target="RFC8126" section="4.10" sectionFormat="bare" format="def ault"/> of <xref target="RFC8126" format="default"/>.</t>	Sections <xref section='4.9' sectionFormat='bare' target='RFC8126'/> and <xref s ection='4.10' sectionFormat='bare' target='RFC8126'/> of <xref target='RFC8126'/ >.</t>
	<t>While this registry is separate from the "HTTP/2 Frame Type" regist ry defined in	<t>While this registry is separate from the "HTTP/2 Frame Type" regist ry defined in

	<xref target="RFC7540" format="default"/>, it is preferable that the assignments	<xref target='RFC9113'/>, it is preferable that the assignments parallel each ot
	parallel each other where the	her where the
	code spaces overlap. If an entry is present in only one registry, every effort	code spaces overlap. If an entry is present in only one registry, every effort
	<bcp14>SHOULD</bcp14> be made to avoid assigning the corresponding value to an u	<bcp14>SHOULD</bcp14>
	nrelated	be made to avoid assigning the corresponding value to an unrelated
	operation. Expert reviewers <bcp14>MAY</bcp14> reject unrelated registrations w	operation. Expert reviewers <bcp14>MAY</bcp14>
	hich would	reject unrelated registrations that would
	conflict with the same value in the corresponding registry.</t>	conflict with the same value in the corresponding registry.</t>

	<t>In addition to common fields as described in <xref target="iana-pol	<t>In addition to common fields as described in <xref target='iana-pol
	icy" format="default"/>, permanent	icy'/>, permanent
	registrations in this registry <bcp14>MUST</bcp14> include the following field:<	registrations in this registry <bcp14>MUST</bcp14>
	/t>	include the following field:</t>
	<dl>	<dl>

	<dt>	<dt>Frame Type:</dt>
	Frame Type: </dt>
	<dd>	<dd>
	<t>A name or label for the frame type.</t>	<t>A name or label for the frame type.</t>
	</dd>	</dd>
	</dl>	</dl>

	<t>Specifications of frame types <bcp14>MUST</bcp14> include a descrip	<t>Specifications of frame types <bcp14>MUST</bcp14>
	tion of the frame layout and	include a description of the frame layout and
	its semantics, including any parts of the frame that are conditionally present.< /t>	its semantics, including any parts of the frame that are conditionally present.< /t>

	<t>The entries in <xref target="iana-frame-table" format="default"/> a	<t>The entries in <xref target='iana-frame-table'/> are registered by
	re registered by this document.</t>	this document.</t>
	<table anchor="iana-frame-table" align="center">	<table anchor='iana-frame-table'>
	<name>Initial HTTP/3 Frame Types</name>	<name>Initial HTTP/3 Frame Types</name>
	<thead>	<thead>
	<tr>	<tr>

	<th align="left">Frame Type</th>	<th align='left'>Frame Type</th>
	<th align="center">Value</th>	<th align='center'>Value</th>
	<th align="left">Specification</th>	<th align='left'>Specification</th>
	</tr>	</tr>
	</thead>	</thead>
	<tbody>	<tbody>
	<tr>	<tr>

	<td align="left">DATA</td>	<td align='left'><xref format='none' target='frame-data'>DATA</x
	<td align="center">0x0</td>	ref><iref item='DATA'/></td>
	<td align="left">	<td align='center'>0x00</td>
	<xref target="frame-data" format="default"/></td>	<td align='left'><xref target='frame-data'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">HEADERS</td>	<td align='left'><xref format='none' target='frame-headers'>HEAD
	<td align="center">0x1</td>	ERS</xref><iref item='HEADERS'/></td>
	<td align="left">	<td align='center'>0x01</td>
	<xref target="frame-headers" format="default"/></td>	<td align='left'><xref target='frame-headers'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">Reserved</td>	<td align='left'>Reserved</td>
	<td align="center">0x2</td>	<td align='center'>0x02</td>
	<td align="left">N/A</td>	<td align='left'>This document</td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">CANCEL_PUSH</td>	<td align='left'><xref format='none' target='frame-cancel-push'>
	<td align="center">0x3</td>	CANCEL_PUSH</xref><iref item='CANCEL_PUSH'/></td>
	<td align="left">	<td align='center'>0x03</td>
	<xref target="frame-cancel-push" format="default"/></td>	<td align='left'><xref target='frame-cancel-push'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">SETTINGS</td>	<td align='left'><xref format='none' target='frame-settings'>SET
	<td align="center">0x4</td>	TINGS</xref><iref item='SETTINGS'/></td>
	<td align="left">	<td align='center'>0x04</td>
	<xref target="frame-settings" format="default"/></td>	<td align='left'><xref target='frame-settings'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">PUSH_PROMISE</td>	<td align='left'><xref format='none' target='frame-push-promise'
	<td align="center">0x5</td>	>PUSH_PROMISE</xref><iref item='PUSH_PROMISE'/></td>
	<td align="left">	<td align='center'>0x05</td>
	<xref target="frame-push-promise" format="default"/></td>	<td align='left'><xref target='frame-push-promise'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">Reserved</td>	<td align='left'>Reserved</td>
	<td align="center">0x6</td>	<td align='center'>0x06</td>
	<td align="left">N/A</td>	<td align='left'>This document</td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">GOAWAY</td>	<td align='left'><xref format='none' target='frame-goaway'>GOAWA
	<td align="center">0x7</td>	Y</xref><iref item='GOAWAY'/></td>
	<td align="left">	<td align='center'>0x07</td>
	<xref target="frame-goaway" format="default"/></td>	<td align='left'><xref target='frame-goaway'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">Reserved</td>	<td align='left'>Reserved</td>
	<td align="center">0x8</td>	<td align='center'>0x08</td>
	<td align="left">N/A</td>	<td align='left'>This document</td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">Reserved</td>	<td align='left'>Reserved</td>
	<td align="center">0x9</td>	<td align='center'>0x09</td>
	<td align="left">N/A</td>	<td align='left'>This document</td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">MAX_PUSH_ID</td>	<td align='left'><xref format='none' target='frame-max-push-id'>
	<td align="center">0xd</td>	MAX_PUSH_ID</xref><iref item='MAX_PUSH_ID'/></td>
	<td align="left">	<td align='center'>0x0d</td>
	<xref target="frame-max-push-id" format="default"/></td>	<td align='left'><xref target='frame-max-push-id'/></td>
	</tr>	</tr>
	</tbody>	</tbody>
	</table>	</table>

	<t>Each code of the format <tt>0x1f * N + 0x21</tt> for non-negative i	<t>Each code of the format <tt>0x1f * N + 0x21</tt> for non-negative i
	nteger values of N	nteger values of <tt>N</tt>
	(that is, 0x21, 0x40, ..., through 0x3ffffffffffffffe) <bcp14>MUST NOT</bcp14> b	(that is, 0x21, 0x40, ..., through 0x3ffffffffffffffe) <bcp14>MUST NO
	e assigned by	T</bcp14>
	IANA and <bcp14>MUST NOT</bcp14> appear in the listing of assigned values.</t>	be assigned by
		IANA and <bcp14>MUST NOT</bcp14>
		appear in the listing of assigned values.</t>
	</section>	</section>

	<section anchor="iana-settings" numbered="true" toc="default">	<section anchor='iana-settings'>
	<name>Settings Parameters</name>	<name>Settings Parameters</name>
	<t>This document establishes a registry for HTTP/3 settings. The "HTT P/3 Settings"	<t>This document establishes a registry for HTTP/3 settings. The "HTT P/3 Settings"
	registry governs a 62-bit space. This registry follows the QUIC registry	registry governs a 62-bit space. This registry follows the QUIC registry

	policy; see <xref target="iana-policy" format="default"/>. Permanent registrati	policy; see <xref target='iana-policy'/>. Permanent registrations in this regis
	ons in this registry are	try are
	assigned using the Specification Required policy (<xref target="RFC8126" format=	assigned using the Specification Required policy (<xref target='RFC8126'/>), exc
	"default"/>), except for	ept for
	values between 0x00 and 0x3f (in hexadecimal; inclusive), which are assigned	values between 0x00 and 0x3f (in hexadecimal; inclusive), which are assigned
	using Standards Action or IESG Approval as defined in	using Standards Action or IESG Approval as defined in

	Sections <xref target="RFC8126" section="4.9" sectionFormat="bare" format="defau lt"/> and <xref target="RFC8126" section="4.10" sectionFormat="bare" format="def ault"/> of <xref target="RFC8126" format="default"/>.</t>	Sections <xref section='4.9' sectionFormat='bare' target='RFC8126'/> and <xref s ection='4.10' sectionFormat='bare' target='RFC8126'/> of <xref target='RFC8126'/ >.</t>
	<t>While this registry is separate from the "HTTP/2 Settings" registry defined in	<t>While this registry is separate from the "HTTP/2 Settings" registry defined in

	<xref target="RFC7540" format="default"/>, it is preferable that the assignments	<xref target='RFC9113'/>, it is preferable that the assignments parallel each ot
	parallel each other. If an	her. If an
	entry is present in only one registry, every effort <bcp14>SHOULD</bcp14> be mad	entry is present in only one registry, every effort <bcp14>SHOULD</bc
	e to avoid	p14>
	assigning the corresponding value to an unrelated operation. Expert reviewers	be made to avoid
	<bcp14>MAY</bcp14> reject unrelated registrations which would conflict with the	assigning the corresponding value to an unrelated operation. Expert reviewers
	same value in	<bcp14>MAY</bcp14>
		reject unrelated registrations that would conflict with the same value in
	the corresponding registry.</t>	the corresponding registry.</t>

	<t>In addition to common fields as described in <xref target="iana-pol	<t>In addition to common fields as described in <xref target='iana-pol
	icy" format="default"/>, permanent	icy'/>, permanent
	registrations in this registry <bcp14>MUST</bcp14> include the following fields:	registrations in this registry <bcp14>MUST</bcp14>
	</t>	include the following fields:</t>
	<dl>	<dl>

	<dt>	<dt>Setting Name:</dt>
	Setting Name: </dt>
	<dd>	<dd>
	<t>A symbolic name for the setting. Specifying a setting name is optional.</t>	<t>A symbolic name for the setting. Specifying a setting name is optional.</t>
	</dd>	</dd>

	<dt>	<dt>Default:</dt>
	Default: </dt>
	<dd>	<dd>

	<t>The value of the setting unless otherwise indicated. A default	<t>The value of the setting unless otherwise indicated. A default
	<bcp14>SHOULD</bcp14> be the	<bcp14>SHOULD</bcp14>
		be the
	most restrictive possible value.</t>	most restrictive possible value.</t>
	</dd>	</dd>
	</dl>	</dl>

	<t>The entries in <xref target="iana-setting-table" format="default"/>	<t>The entries in <xref target='iana-setting-table'/> are registered b
	are registered by this document.</t>	y this document.</t>
	<table anchor="iana-setting-table" align="center">	<table anchor='iana-setting-table'>
	<name>Initial HTTP/3 Settings</name>	<name>Initial HTTP/3 Settings</name>
	<thead>	<thead>
	<tr>	<tr>

	<th align="left">Setting Name</th>	<th align='left'>Setting Name</th>
	<th align="center">Value</th>	<th align='center'>Value</th>
	<th align="left">Specification</th>	<th align='left'>Specification</th>
	<th align="left">Default</th>	<th align='left'>Default</th>
	</tr>	</tr>
	</thead>	</thead>
	<tbody>	<tbody>
	<tr>	<tr>

	<td align="left">Reserved</td>	<td align='left'>Reserved</td>
	<td align="center">0x0</td>	<td align='center'>0x00</td>
	<td align="left">N/A</td>	<td align='left'>This document</td>
	<td align="left">N/A</td>	<td align='left'>N/A</td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">Reserved</td>	<td align='left'>Reserved</td>
	<td align="center">0x2</td>	<td align='center'>0x02</td>
	<td align="left">N/A</td>	<td align='left'>This document</td>
	<td align="left">N/A</td>	<td align='left'>N/A</td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">Reserved</td>	<td align='left'>Reserved</td>
	<td align="center">0x3</td>	<td align='center'>0x03</td>
	<td align="left">N/A</td>	<td align='left'>This document</td>
	<td align="left">N/A</td>	<td align='left'>N/A</td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">Reserved</td>	<td align='left'>Reserved</td>
	<td align="center">0x4</td>	<td align='center'>0x04</td>
	<td align="left">N/A</td>	<td align='left'>This document</td>
	<td align="left">N/A</td>	<td align='left'>N/A</td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">Reserved</td>	<td align='left'>Reserved</td>
	<td align="center">0x5</td>	<td align='center'>0x05</td>
	<td align="left">N/A</td>	<td align='left'>This document</td>
	<td align="left">N/A</td>	<td align='left'>N/A</td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">MAX_FIELD_SECTION_SIZE</td>	<td align='left'>MAX_FIELD_SECTION_SIZE</td>
	<td align="center">0x6</td>	<td align='center'>0x06</td>
	<td align="left">	<td align='left'><xref target='settings-parameters'/></td>
	<xref target="settings-parameters" format="default"/></td>	<td align='left'>Unlimited</td>
	<td align="left">Unlimited</td>
	</tr>	</tr>
	</tbody>	</tbody>
	</table>	</table>

	<t>Each code of the format <tt>0x1f * N + 0x21</tt> for non-negative i	<t>For formatting reasons, setting names can be abbreviated by removin
	nteger values of N	g the
	(that is, 0x21, 0x40, ..., through 0x3ffffffffffffffe) <bcp14>MUST NOT</bcp14> b	'SETTINGS_' prefix.</t>
	e assigned by	<t>Each code of the format <tt>0x1f * N + 0x21</tt> for non-negative i
	IANA and <bcp14>MUST NOT</bcp14> appear in the listing of assigned values.</t>	nteger values of <tt>N</tt>
		(that is, 0x21, 0x40, ..., through 0x3ffffffffffffffe) <bcp14>MUST NO
		T</bcp14>
		be assigned by
		IANA and <bcp14>MUST NOT</bcp14>
		appear in the listing of assigned values.</t>
	</section>	</section>

	<section anchor="iana-error-codes" numbered="true" toc="default">	<section anchor='iana-error-codes'>
	<name>Error Codes</name>	<name>Error Codes</name>
	<t>This document establishes a registry for HTTP/3 error codes. The "H TTP/3 Error	<t>This document establishes a registry for HTTP/3 error codes. The "H TTP/3 Error

	Code" registry manages a 62-bit space. This registry follows the QUIC registry	Codes" registry manages a 62-bit space. This registry follows the QUIC registry
	policy; see <xref target="iana-policy" format="default"/>. Permanent registrati	policy; see <xref target='iana-policy'/>. Permanent registrations in this regis
	ons in this registry are	try are
	assigned using the Specification Required policy (<xref target="RFC8126" format=	assigned using the Specification Required policy (<xref target='RFC8126'/>), exc
	"default"/>), except for	ept for
	values between 0x00 and 0x3f (in hexadecimal; inclusive), which are assigned	values between 0x00 and 0x3f (in hexadecimal; inclusive), which are assigned
	using Standards Action or IESG Approval as defined in	using Standards Action or IESG Approval as defined in

	Sections <xref target="RFC8126" section="4.9" sectionFormat="bare" format="defau lt"/> and <xref target="RFC8126" section="4.10" sectionFormat="bare" format="def ault"/> of <xref target="RFC8126" format="default"/>.</t>	Sections <xref section='4.9' sectionFormat='bare' target='RFC8126'/> and <xref s ection='4.10' sectionFormat='bare' target='RFC8126'/> of <xref target='RFC8126'/ >.</t>
	<t>Registrations for error codes are required to include a description of the error	<t>Registrations for error codes are required to include a description of the error
	code. An expert reviewer is advised to examine new registrations for possible	code. An expert reviewer is advised to examine new registrations for possible
	duplication with existing error codes. Use of existing registrations is to be	duplication with existing error codes. Use of existing registrations is to be
	encouraged, but not mandated. Use of values that are registered in the "HTTP/2	encouraged, but not mandated. Use of values that are registered in the "HTTP/2

	Error Code" registry is discouraged, and expert reviewers <bcp14>MAY</bcp14> rej	Error Code" registry is discouraged, and expert reviewers <bcp14>MAY<
	ect such	/bcp14>
		reject such
	registrations.</t>	registrations.</t>

	<t>In addition to common fields as described in <xref target="iana-pol	<t>In addition to common fields as described in <xref target='iana-pol
	icy" format="default"/>, this registry	icy'/>, this registry
	includes two additional fields. Permanent registrations in this registry <bcp14	includes two additional fields. Permanent registrations in this registry
	>MUST</bcp14>	<bcp14>MUST</bcp14>

	include the following field:</t>	include the following field:</t>
	<dl>	<dl>

	<dt>	<dt>Name:</dt>
	Name: </dt>
	<dd>	<dd>
	<t>A name for the error code.</t>	<t>A name for the error code.</t>
	</dd>	</dd>

	<dt>	<dt>Description:</dt>
	Description: </dt>
	<dd>	<dd>
	<t>A brief description of the error code semantics.</t>	<t>A brief description of the error code semantics.</t>
	</dd>	</dd>
	</dl>	</dl>

	<t>The entries in <xref target="iana-error-table" format="default"/> a re registered by this document. These	<t>The entries in <xref target='iana-error-table'/> are registered by this document. These
	error codes were selected from the range that operates on a Specification	error codes were selected from the range that operates on a Specification
	Required policy to avoid collisions with HTTP/2 error codes.</t>	Required policy to avoid collisions with HTTP/2 error codes.</t>

	<table anchor="iana-error-table" align="center">	<table anchor='iana-error-table'>
	<name>Initial HTTP/3 Error Codes</name>	<name>Initial HTTP/3 Error Codes</name>
	<thead>	<thead>
	<tr>	<tr>

	<th align="left">Name</th>	<th align='left'>Name</th>
	<th align="left">Value</th>	<th align='left'>Value</th>
	<th align="left">Description</th>	<th align='left'>Description</th>
	<th align="left">Specification</th>	<th align='left'>Specification</th>
	</tr>	</tr>
	</thead>	</thead>
	<tbody>	<tbody>
	<tr>	<tr>

	<td align="left">H3_NO_ERROR</td>	<td align='left'><xref format='none' target='H3_NO_ERROR'>H3_NO_
	<td align="left">0x100</td>	ERROR</xref><iref item='H3_NO_ERROR'/></td>
	<td align="left">No error</td>	<td align='left'>0x0100</td>
	<td align="left">	<td align='left'>No error</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_GENERAL_PROTOCOL_ERROR</td>	<td align='left'><xref format='none' target='H3_GENERAL_PROTOCOL
	<td align="left">0x101</td>	_ERROR'>H3_GENERAL_PROTOCOL_ERROR</xref><iref item='H3_GENERAL_PROTOCOL_ERROR'/>
	<td align="left">General protocol error</td>	</td>
	<td align="left">	<td align='left'>0x0101</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'>General protocol error</td>
		<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_INTERNAL_ERROR</td>	<td align='left'><xref format='none' target='H3_INTERNAL_ERROR'>
	<td align="left">0x102</td>	H3_INTERNAL_ERROR</xref><iref item='H3_INTERNAL_ERROR'/></td>
	<td align="left">Internal error</td>	<td align='left'>0x0102</td>
	<td align="left">	<td align='left'>Internal error</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_STREAM_CREATION_ERROR</td>	<td align='left'><xref format='none' target='H3_STREAM_CREATION_
	<td align="left">0x103</td>	ERROR'>H3_STREAM_CREATION_ERROR</xref><iref item='H3_STREAM_CREATION_ERROR'/></t
	<td align="left">Stream creation error</td>	d>
	<td align="left">	<td align='left'>0x0103</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'>Stream creation error</td>
		<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_CLOSED_CRITICAL_STREAM</td>	<td align='left'><xref format='none' target='H3_CLOSED_CRITICAL_
	<td align="left">0x104</td>	STREAM'>H3_CLOSED_CRITICAL_STREAM</xref><iref item='H3_CLOSED_CRITICAL_STREAM'/>
	<td align="left">Critical stream was closed</td>	</td>
	<td align="left">	<td align='left'>0x0104</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'>Critical stream was closed</td>
		<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_FRAME_UNEXPECTED</td>	<td align='left'><xref format='none' target='H3_FRAME_UNEXPECTED
	<td align="left">0x105</td>	'>H3_FRAME_UNEXPECTED</xref><iref item='H3_FRAME_UNEXPECTED'/></td>
	<td align="left">Frame not permitted in the current state</td>	<td align='left'>0x0105</td>
	<td align="left">	<td align='left'>Frame not permitted in the current state</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_FRAME_ERROR</td>	<td align='left'><xref format='none' target='H3_FRAME_ERROR'>H3_
	<td align="left">0x106</td>	FRAME_ERROR</xref><iref item='H3_FRAME_ERROR'/></td>
	<td align="left">Frame violated layout or size rules</td>	<td align='left'>0x0106</td>
	<td align="left">	<td align='left'>Frame violated layout or size rules</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_EXCESSIVE_LOAD</td>	<td align='left'><xref format='none' target='H3_EXCESSIVE_LOAD'>
	<td align="left">0x107</td>	H3_EXCESSIVE_LOAD</xref><iref item='H3_EXCESSIVE_LOAD'/></td>
	<td align="left">Peer generating excessive load</td>	<td align='left'>0x0107</td>
	<td align="left">	<td align='left'>Peer generating excessive load</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_ID_ERROR</td>	<td align='left'><xref format='none' target='H3_ID_ERROR'>H3_ID_
	<td align="left">0x108</td>	ERROR</xref><iref item='H3_ID_ERROR'/></td>
	<td align="left">An identifier was used incorrectly</td>	<td align='left'>0x0108</td>
	<td align="left">	<td align='left'>An identifier was used incorrectly</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_SETTINGS_ERROR</td>	<td align='left'><xref format='none' target='H3_SETTINGS_ERROR'>
	<td align="left">0x109</td>	H3_SETTINGS_ERROR</xref><iref item='H3_SETTINGS_ERROR'/></td>
	<td align="left">SETTINGS frame contained invalid values</td>	<td align='left'>0x0109</td>
	<td align="left">	<td align='left'><xref format='none' target='frame-settings'>SET
	<xref target="http-error-codes" format="default"/></td>	TINGS</xref><iref item='SETTINGS'/> frame contained invalid values</td>
		<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_MISSING_SETTINGS</td>	<td align='left'><xref format='none' target='H3_MISSING_SETTINGS
	<td align="left">0x10a</td>	'>H3_MISSING_SETTINGS</xref><iref item='H3_MISSING_SETTINGS'/></td>
	<td align="left">No SETTINGS frame received</td>	<td align='left'>0x010a</td>
	<td align="left">	<td align='left'>No <xref format='none' target='frame-settings'>
	<xref target="http-error-codes" format="default"/></td>	SETTINGS</xref><iref item='SETTINGS'/> frame received</td>
		<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_REQUEST_REJECTED</td>	<td align='left'><xref format='none' target='H3_REQUEST_REJECTED
	<td align="left">0x10b</td>	'>H3_REQUEST_REJECTED</xref><iref item='H3_REQUEST_REJECTED'/></td>
	<td align="left">Request not processed</td>	<td align='left'>0x010b</td>
	<td align="left">	<td align='left'>Request not processed</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_REQUEST_CANCELLED</td>	<td align='left'><xref format='none' target='H3_REQUEST_CANCELLE
	<td align="left">0x10c</td>	D'>H3_REQUEST_CANCELLED</xref><iref item='H3_REQUEST_CANCELLED'/></td>
	<td align="left">Data no longer needed</td>	<td align='left'>0x010c</td>
	<td align="left">	<td align='left'>Data no longer needed</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_REQUEST_INCOMPLETE</td>	<td align='left'><xref format='none' target='H3_REQUEST_INCOMPLE
	<td align="left">0x10d</td>	TE'>H3_REQUEST_INCOMPLETE</xref><iref item='H3_REQUEST_INCOMPLETE'/></td>
	<td align="left">Stream terminated early</td>	<td align='left'>0x010d</td>
	<td align="left">	<td align='left'>Stream terminated early</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_MESSAGE_ERROR</td>	<td align='left'><xref format='none' target='H3_MESSAGE_ERROR'>H
	<td align="left">0x10e</td>	3_MESSAGE_ERROR</xref><iref item='H3_MESSAGE_ERROR'/></td>
	<td align="left">Malformed message</td>	<td align='left'>0x010e</td>
	<td align="left">	<td align='left'>Malformed message</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_CONNECT_ERROR</td>	<td align='left'><xref format='none' target='H3_CONNECT_ERROR'>H
	<td align="left">0x10f</td>	3_CONNECT_ERROR</xref><iref item='H3_CONNECT_ERROR'/></td>
	<td align="left">TCP reset or error on CONNECT request</td>	<td align='left'>0x010f</td>
	<td align="left">	<td align='left'>TCP reset or error on CONNECT request</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">H3_VERSION_FALLBACK</td>	<td align='left'><xref format='none' target='H3_VERSION_FALLBACK
	<td align="left">0x110</td>	'>H3_VERSION_FALLBACK</xref><iref item='H3_VERSION_FALLBACK'/></td>
	<td align="left">Retry over HTTP/1.1</td>	<td align='left'>0x0110</td>
	<td align="left">	<td align='left'>Retry over HTTP/1.1</td>
	<xref target="http-error-codes" format="default"/></td>	<td align='left'><xref target='http-error-codes'/></td>
	</tr>	</tr>
	</tbody>	</tbody>
	</table>	</table>

	<t>Each code of the format <tt>0x1f * N + 0x21</tt> for non-negative i	<t>Each code of the format <tt>0x1f * N + 0x21</tt> for non-negative i
	nteger values of N	nteger values of <tt>N</tt>
	(that is, 0x21, 0x40, ..., through 0x3ffffffffffffffe) <bcp14>MUST NOT</bcp14> b	(that is, 0x21, 0x40, ..., through 0x3ffffffffffffffe) <bcp14>MUST NO
	e assigned by	T</bcp14>
	IANA and <bcp14>MUST NOT</bcp14> appear in the listing of assigned values.</t>	be assigned by
		IANA and <bcp14>MUST NOT</bcp14>
		appear in the listing of assigned values.</t>
	</section>	</section>

	<section anchor="iana-stream-types" numbered="true" toc="default">	<section anchor='iana-stream-types'>
	<name>Stream Types</name>	<name>Stream Types</name>
	<t>This document establishes a registry for HTTP/3 unidirectional stre am types. The	<t>This document establishes a registry for HTTP/3 unidirectional stre am types. The

	"HTTP/3 Stream Type" registry governs a 62-bit space. This registry follows the	"HTTP/3 Stream Types" registry governs a 62-bit space. This registry follows
	QUIC registry policy; see <xref target="iana-policy" format="default"/>. Perman	the QUIC registry policy; see <xref target='iana-policy'/>. Permanent registrat
	ent registrations in this	ions in this
	registry are assigned using the Specification Required policy (<xref target="RFC	registry are assigned using the Specification Required policy (<xref target='RFC
	8126" format="default"/>),	8126'/>),
	except for values between 0x00 and 0x3f (in hexadecimal; inclusive), which are	except for values between 0x00 and 0x3f (in hexadecimal; inclusive), which are

	assigned using Standards Action or IESG Approval as defined in Sections <xref ta	assigned using Standards Action or IESG Approval as defined in Sections <xref se
	rget="RFC8126" section="4.9" sectionFormat="bare" format="default"/> and <xref t	ction='4.9' sectionFormat='bare' target='RFC8126'/> and <xref section='4.10' sec
	arget="RFC8126" section="4.10" sectionFormat="bare" format="default"/> of <xref	tionFormat='bare' target='RFC8126'/> of <xref target='RFC8126'/>.</t>
	target="RFC8126" format="default"/>.</t>	<t>In addition to common fields as described in <xref target='iana-pol
	<t>In addition to common fields as described in <xref target="iana-pol	icy'/>, permanent
	icy" format="default"/>, permanent	registrations in this registry <bcp14>MUST</bcp14>
	registrations in this registry <bcp14>MUST</bcp14> include the following fields:	include the following fields:</t>
	</t>
	<dl>	<dl>

	<dt>	<dt>Stream Type:</dt>
	Stream Type: </dt>
	<dd>	<dd>
	<t>A name or label for the stream type.</t>	<t>A name or label for the stream type.</t>
	</dd>	</dd>

	<dt>	<dt>Sender:</dt>
	Sender: </dt>
	<dd>	<dd>
	<t>Which endpoint on an HTTP/3 connection may initiate a stream of this type.	<t>Which endpoint on an HTTP/3 connection may initiate a stream of this type.
	Values are "Client", "Server", or "Both".</t>	Values are "Client", "Server", or "Both".</t>
	</dd>	</dd>
	</dl>	</dl>

	<t>Specifications for permanent registrations <bcp14>MUST</bcp14> incl	<t>Specifications for permanent registrations <bcp14>MUST</
	ude a description of the	bcp14>
		include a description of the
	stream type, including the layout and semantics of the stream contents.</t>	stream type, including the layout and semantics of the stream contents.</t>

	<t>The entries in the following table are registered by this document.	<t>The entries in <xref target='iana-stream-type-table'/> are register
	</t>	ed by this document.</t>
	<table align="center">	<table anchor='iana-stream-type-table'>
		<name>Initial Stream Types</name>
	<thead>	<thead>
	<tr>	<tr>

	<th align="left">Stream Type</th>	<th align='left'>Stream Type</th>
	<th align="center">Value</th>	<th align='center'>Value</th>
	<th align="left">Specification</th>	<th align='left'>Specification</th>
	<th align="left">Sender</th>	<th align='left'>Sender</th>
	</tr>	</tr>
	</thead>	</thead>
	<tbody>	<tbody>
	<tr>	<tr>

	<td align="left">Control Stream</td>	<td align='left'>Control Stream</td>
	<td align="center">0x00</td>	<td align='center'>0x00</td>
	<td align="left">	<td align='left'><xref target='control-streams'/></td>
	<xref target="control-streams" format="default"/></td>	<td align='left'>Both</td>
	<td align="left">Both</td>
	</tr>	</tr>
	<tr>	<tr>

	<td align="left">Push Stream</td>	<td align='left'>Push Stream</td>
	<td align="center">0x01</td>	<td align='center'>0x01</td>
	<td align="left">	<td align='left'><xref target='server-push'/></td>
	<xref target="server-push" format="default"/></td>	<td align='left'>Server</td>
	<td align="left">Server</td>
	</tr>	</tr>
	</tbody>	</tbody>
	</table>	</table>

	<t>Each code of the format <tt>0x1f * N + 0x21</tt> for non-negative i	<t>Each code of the format <tt>0x1f * N + 0x21</tt> for non-negative i
	nteger values of N	nteger values of <tt>N</tt>
	(that is, 0x21, 0x40, ..., through 0x3ffffffffffffffe) <bcp14>MUST NOT</bcp14> b	(that is, 0x21, 0x40, ..., through 0x3ffffffffffffffe) <bcp14>MUST NO
	e assigned by	T</bcp14>
	IANA and <bcp14>MUST NOT</bcp14> appear in the listing of assigned values.</t>	be assigned by
		IANA and <bcp14>MUST NOT</bcp14>
		appear in the listing of assigned values.</t>
	</section>	</section>
	</section>	</section>
	</section>	</section>
	</middle>	</middle>
	<back>	<back>

		<displayreference target='RFC9204' to='QPACK'/>
	<displayreference target="RFCYYY1" to="QUIC-TRANSPORT"/>	<displayreference target='RFC9110' to='HTTP'/>
	<displayreference target="RFCYYY2" to="QPACK"/>	<displayreference target='RFC9111' to='HTTP-CACHING'/>
	<displayreference target="RFC3986" to="URI"/>	<displayreference target='RFC9112' to='HTTP/1.1'/>
	<displayreference target="RFCYYY3" to="CACHING"/>	<displayreference target='RFC9113' to='HTTP/2'/>
	<displayreference target="RFCYYY4" to="SEMANTICS"/>
	<displayreference target="RFC7838" to="ALTSVC"/>
	<displayreference target="RFC8470" to="HTTP-REPLAY"/>
	<displayreference target="I-D.ietf-httpbis-messaging" to="HTTP11"/>
	<displayreference target="RFC7540" to="HTTP2"/>
	<displayreference target="RFC8446" to="TLS13"/>
	<displayreference target="RFC7413" to="TFO"/>
	<displayreference target="RFC7541" to="HPACK"/>
	<displayreference target="RFC8499" to="DNS-TERMS"/>

	<references>	<references>
	<name>References</name>	<name>References</name>
	<references>	<references>
	<name>Normative References</name>	<name>Normative References</name>

		<reference anchor='RFC9204' target='https://www.rfc-editor.org/info/rfc9
	<!-- [rfced] [QUIC-TRANSPORT] [I-D.ietf-quic-transport] in RFC-EDITOR state as o	204'>
	f 03/25/21; companion document RFC YYY1 -->	<front>
		<title>QPACK: Field Compression for HTTP/3</title>
	<reference anchor='RFCYYY1'>	<author fullname='Charles 'Buck' Krasic' initials='C.' sur
	<front>	name='Krasic'>
	<title>QUIC: A UDP-Based Multiplexed and Secure Transport</title>	<organization>Google, Inc</organization>
		</author>
	<author initials='J' surname='Iyengar' fullname='Jana Iyengar'>	<author fullname='Mike Bishop' initials='M.' surname='Bishop'>
	<organization />	<organization>Akamai Technologies</organization>
	</author>	</author>
		<author fullname='Alan Frindell' initials='A.' role='editor' surname
	<author initials='M' surname='Thomson' fullname='Martin Thomson'>	='Frindell'>
	<organization />	<organization>Facebook</organization>
	</author>	</author>
		<date month='May' year='2022'/>
	<date month='January' day='14' year='2021' />	</front>
		<seriesInfo name='RFC' value='9204'/>
	<abstract><t>This document defines the core of the QUIC transport protocol. QUI	<seriesInfo name='DOI' value='10.17487/RFC9204'/>
	C provides applications with flow-controlled streams for structured communicatio	</reference>
	n, low-latency connection establishment, and network path migration. QUIC inclu	<reference anchor='RFC9110' target='https://www.rfc-editor.org/info/rfc9
	des security measures that ensure confidentiality, integrity, and availability i	110'>
	n a range of deployment circumstances. Accompanying documents describe the inte	<front>
	gration of TLS for key negotiation, loss detection, and an exemplary congestion	<title>HTTP Semantics</title>
	control algorithm. DO NOT DEPLOY THIS VERSION OF QUIC DO NOT DEPLOY THIS VERSI	<author fullname='Roy T. Fielding' initials='R.' role='editor' surna
	ON OF QUIC UNTIL IT IS IN AN RFC. This version is still a work in progress. Fo	me='Fielding'>
	r trial deployments, please use earlier versions. Note to Readers Discussion o	<organization>Adobe</organization>
	f this draft takes place on the QUIC working group mailing list (quic@ietf.org (	</author>
	mailto:quic@ietf.org)), which is archived at https://mailarchive.ietf.org/arch/s	<author fullname='Mark Nottingham' initials='M.' role='editor' surna
	earch/?email_list=quic Working Group information can be found at https://github	me='Nottingham'>
	.com/quicwg; source code and issues list for this draft can be found at https://	<organization>Fastly</organization>
	github.com/quicwg/base-drafts/labels/-transport.</t></abstract>	</author>
		<author fullname='Julian Reschke' initials='J.' role='editor' surnam
	</front>	e='Reschke'>
	<seriesInfo name="RFC" value="YYY1"/>	<organization>greenbytes</organization>
	<seriesInfo name="DOI" value="10.17487/RFCYYY1"/>	</author>
	</reference>	<date month='May' year='2022'/>
		</front>
	<!-- [rfced] [QPACK] [I-D.ietf-quic-qpack] in MISSREF state as of 03/25/21; comp	<seriesInfo name='STD' value='97'/>
	anion document RFC YYY2 -->	<seriesInfo name='RFC' value='9110'/>
		<seriesInfo name='DOI' value='10.17487/RFC9110'/>
	<reference anchor='RFCYYY2'>	</reference>
	<front>	<reference anchor='RFC9111' target='https://www.rfc-editor.org/info/rfc9
	<title>QPACK: Header Compression for HTTP/3</title>	111'>
		<front>
	<author initials='C' surname='Krasic' fullname='Charles Krasic'>	<title>HTTP Caching</title>
	<organization />	<author fullname='Roy T. Fielding' initials='R.' role='editor' surna
	</author>	me='Fielding'>
		<organization>Adobe</organization>
	<author initials='M' surname='Bishop' fullname='Mike Bishop'>	</author>
	<organization />	<author fullname='Mark Nottingham' initials='M.' role='editor' surna
	</author>	me='Nottingham'>
		<organization>Fastly</organization>
	<author initials='A' surname='Frindell' fullname='Alan Frindell'>	</author>
	<organization />	<author fullname='Julian Reschke' initials='J.' role='editor' surnam
	</author>	e='Reschke'>
		<organization>greenbytes</organization>
	<date month='December' day='15' year='2020' />	</author>
		<date month='May' year='2022'/>
	<abstract><t>This specification defines QPACK, a compression format for efficien	</front>
	tly representing HTTP fields, to be used in HTTP/3. This is a variation of HPAC	<seriesInfo name='STD' value='98'/>
	K compression that seeks to reduce head-of-line blocking.</t></abstract>	<seriesInfo name='RFC' value='9111'/>
		<seriesInfo name='DOI' value='10.17487/RFC9111'/>
	</front>	</reference>
	<seriesInfo name="RFC" value="YYY2"/>	<reference anchor='URI' target='https://www.rfc-editor.org/info/rfc3986'
	<seriesInfo name="DOI" value="10.17487/RFCYYY2"/>	>
	</reference>	<front>
		<title>Uniform Resource Identifier (URI): Generic Syntax</title>
	<!-- [rfced] [CACHING] [I-D.ietf-httpbis-cache] IESG state I-D Exists; companion	<author fullname='T. Berners-Lee' initials='T.' surname='Berners-Lee
	document RFC YYY3 -->	'>
		<organization/>
	<reference anchor='RFCYYY3'>	</author>
	<front>	<author fullname='R. Fielding' initials='R.' surname='Fielding'>
	<title>HTTP Caching</title>	<organization/>
		</author>
	<author initials='R' surname='Fielding' fullname='Roy Fielding'>	<author fullname='L. Masinter' initials='L.' surname='Masinter'>
	<organization />	<organization/>
	</author>	</author>
		<date month='January' year='2005'/>
	<author initials='M' surname='Nottingham' fullname='Mark Nottingham'>	<abstract>
	<organization />	<t>A Uniform Resource Identifier (URI) is a compact sequence of ch
	</author>	aracters that identifies an abstract or physical resource. This specification d
		efines the generic URI syntax and a process for resolving URI references that mi
	<author initials='J' surname='Reschke' fullname='Julian Reschke'>	ght be in relative form, along with guidelines and security considerations for t
	<organization />	he use of URIs on the Internet. The URI syntax defines a grammar that is a supe
	</author>	rset of all valid URIs, allowing an implementation to parse the common component
		s of a URI reference without knowing the scheme-specific requirements of every p
	<date month='January' day='12' year='2021' />	ossible identifier. This specification does not define a generative grammar for
		URIs; that task is performed by the individual specifications of each URI schem
	<abstract><t>The Hypertext Transfer Protocol (HTTP) is a stateless application-	e. [STANDARDS-TRACK]</t>
	level protocol for distributed, collaborative, hypertext information systems. T	</abstract>
	his document defines HTTP caches and the associated header fields that control c	</front>
	ache behavior or indicate cacheable response messages. This document obsoletes	<seriesInfo name='STD' value='66'/>
	RFC 7234.</t></abstract>	<seriesInfo name='RFC' value='3986'/>
		<seriesInfo name='DOI' value='10.17487/RFC3986'/>
	</front>	</reference>
	<seriesInfo name="RFC" value="YYY3"/>	<reference anchor='QUIC-TRANSPORT' target='https://www.rfc-editor.org/in
	<seriesInfo name="DOI" value="10.17487/RFCYYY3"/>	fo/rfc9000'>
	</reference>	<front>
		<title>QUIC: A UDP-Based Multiplexed and Secure Transport</title>
	<!-- [rfced] [SEMANTICS] [I-D.ietf-httpbis-semantics] IESG state I-D Exists; com	<author fullname='J. Iyengar' initials='J.' role='editor' surname='I
	panion document RFC YYY4 -->	yengar'>
		<organization/>
	<reference anchor='RFCYYY4'>	</author>
	<front>	<author fullname='M. Thomson' initials='M.' role='editor' surname='T
	<title>HTTP Semantics</title>	homson'>
		<organization/>
	<author initials='R' surname='Fielding' fullname='Roy Fielding'>	</author>
	<organization />	<date month='May' year='2021'/>
	</author>	<abstract>
		<t>This document defines the core of the QUIC transport protocol.
	<author initials='M' surname='Nottingham' fullname='Mark Nottingham'>	QUIC provides applications with flow-controlled streams for structured communic
	<organization />	ation, low-latency connection establishment, and network path migration. QUIC in
	</author>	cludes security measures that ensure confidentiality, integrity, and availabilit
		y in a range of deployment circumstances. Accompanying documents describe the i
	<author initials='J' surname='Reschke' fullname='Julian Reschke'>	ntegration of TLS for key negotiation, loss detection, and an exemplary congesti
	<organization />	on control algorithm.</t>
	</author>	</abstract>
		</front>
	<date month='January' day='12' year='2021' />	<seriesInfo name='RFC' value='9000'/>
		<seriesInfo name='DOI' value='10.17487/RFC9000'/>
	<abstract><t>The Hypertext Transfer Protocol (HTTP) is a stateless application-	</reference>
	level protocol for distributed, collaborative, hypertext information systems. T	<reference anchor='RFC2119' target='https://www.rfc-editor.org/info/rfc2
	his document describes the overall architecture of HTTP, establishes common term	119'>
	inology, and defines aspects of the protocol that are shared by all versions. I	<front>
	n this definition are core protocol elements, extensibility mechanisms, and the	<title>Key words for use in RFCs to Indicate Requirement Levels</tit
	"http" and "https" Uniform Resource Identifier (URI) schemes. This document obs	le>
	oletes RFC 2818, RFC 7231, RFC 7232, RFC 7233, RFC 7235, RFC 7538, RFC 7615, RFC	<author fullname='S. Bradner' initials='S.' surname='Bradner'>
	7694, and portions of RFC 7230.</t></abstract>	<organization/>
		</author>
	</front>	<date month='March' year='1997'/>
	<seriesInfo name="RFC" value="YYY4"/>	<abstract>
	<seriesInfo name="DOI" value="10.17487/RFCYYY4"/>	<t>In many standards track documents several words are used to sig
	</reference>	nify the requirements in the specification. These words are often capitalized.
		This document defines these words as they should be interpreted in IETF document
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3986.	s. This document specifies an Internet Best Current Practices for the Internet
	xml"/>	Community, and requests discussion and suggestions for improvements.</t>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.	</abstract>
	xml"/>	</front>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.	<seriesInfo name='BCP' value='14'/>
	xml"/>	<seriesInfo name='RFC' value='2119'/>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7301.	<seriesInfo name='DOI' value='10.17487/RFC2119'/>
	xml"/>	</reference>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7838.	<reference anchor='RFC8174' target='https://www.rfc-editor.org/info/rfc8
	xml"/>	174'>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6066.	<front>
	xml"/>	<title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</ti
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6265.	tle>
	xml"/>	<author fullname='B. Leiba' initials='B.' surname='Leiba'>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.0793.	<organization/>
	xml"/>	</author>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8470.	<date month='May' year='2017'/>
	xml"/>	<abstract>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8126.	<t>RFC 2119 specifies common key words that may be used in protoco
	xml"/>	l specifications. This document aims to reduce the ambiguity by clarifying tha
		t only UPPERCASE usage of the key words have the defined special meanings.</t>
		</abstract>
		</front>
		<seriesInfo name='BCP' value='14'/>
		<seriesInfo name='RFC' value='8174'/>
		<seriesInfo name='DOI' value='10.17487/RFC8174'/>
		</reference>
		<reference anchor='RFC7301' target='https://www.rfc-editor.org/info/rfc7
		301'>
		<front>
		<title>Transport Layer Security (TLS) Application-Layer Protocol Neg
		otiation Extension</title>
		<author fullname='S. Friedl' initials='S.' surname='Friedl'>
		<organization/>
		</author>
		<author fullname='A. Popov' initials='A.' surname='Popov'>
		<organization/>
		</author>
		<author fullname='A. Langley' initials='A.' surname='Langley'>
		<organization/>
		</author>
		<author fullname='E. Stephan' initials='E.' surname='Stephan'>
		<organization/>
		</author>
		<date month='July' year='2014'/>
		<abstract>
		<t>This document describes a Transport Layer Security (TLS) extens
		ion for application-layer protocol negotiation within the TLS handshake. For ins
		tances in which multiple application protocols are supported on the same TCP or
		UDP port, this extension allows the application layer to negotiate which protoco
		l will be used within the TLS connection.</t>
		</abstract>
		</front>
		<seriesInfo name='RFC' value='7301'/>
		<seriesInfo name='DOI' value='10.17487/RFC7301'/>
		</reference>
		<reference anchor='ALTSVC' target='https://www.rfc-editor.org/info/rfc78
		38'>
		<front>
		<title>HTTP Alternative Services</title>
		<author fullname='M. Nottingham' initials='M.' surname='Nottingham'>
		<organization/>
		</author>
		<author fullname='P. McManus' initials='P.' surname='McManus'>
		<organization/>
		</author>
		<author fullname='J. Reschke' initials='J.' surname='Reschke'>
		<organization/>
		</author>
		<date month='April' year='2016'/>
		<abstract>
		<t>This document specifies "Alternative Services" for HTTP, which
		allow an origin's resources to be authoritatively available at a separate networ
		k location, possibly accessed with a different protocol configuration.</t>
		</abstract>
		</front>
		<seriesInfo name='RFC' value='7838'/>
		<seriesInfo name='DOI' value='10.17487/RFC7838'/>
		</reference>
		<reference anchor='RFC6066' target='https://www.rfc-editor.org/info/rfc6
		066'>
		<front>
		<title>Transport Layer Security (TLS) Extensions: Extension Definiti
		ons</title>
		<author fullname='D. Eastlake 3rd' initials='D.' surname='Eastlake 3
		rd'>
		<organization/>
		</author>
		<date month='January' year='2011'/>
		<abstract>
		<t>This document provides specifications for existing TLS extensio
		ns. It is a companion document for RFC 5246, "The Transport Layer Security (TLS
		) Protocol Version 1.2". The extensions specified are server_name, max_fragment
		_length, client_certificate_url, trusted_ca_keys, truncated_hmac, and status_req
		uest. [STANDARDS-TRACK]</t>
		</abstract>
		</front>
		<seriesInfo name='RFC' value='6066'/>
		<seriesInfo name='DOI' value='10.17487/RFC6066'/>
		</reference>
		<reference anchor='COOKIES' target='https://www.rfc-editor.org/info/rfc6
		265'>
		<front>
		<title>HTTP State Management Mechanism</title>
		<author fullname='A. Barth' initials='A.' surname='Barth'>
		<organization/>
		</author>
		<date month='April' year='2011'/>
		<abstract>
		<t>This document defines the HTTP Cookie and Set-Cookie header fie
		lds. These header fields can be used by HTTP servers to store state (called cook
		ies) at HTTP user agents, letting the servers maintain a stateful session over t
		he mostly stateless HTTP protocol. Although cookies have many historical infeli
		cities that degrade their security and privacy, the Cookie and Set-Cookie header
		fields are widely used on the Internet. This document obsoletes RFC 2965. [ST
		ANDARDS-TRACK]</t>
		</abstract>
		</front>
		<seriesInfo name='RFC' value='6265'/>
		<seriesInfo name='DOI' value='10.17487/RFC6265'/>
		</reference>
		<reference anchor='RFC0793' target='https://www.rfc-editor.org/info/rfc7
		93'>
		<front>
		<title>Transmission Control Protocol</title>
		<author fullname='J. Postel' initials='J.' surname='Postel'>
		<organization/>
		</author>
		<date month='September' year='1981'/>
		</front>
		<seriesInfo name='STD' value='7'/>
		<seriesInfo name='RFC' value='793'/>
		<seriesInfo name='DOI' value='10.17487/RFC0793'/>
		</reference>
		<reference anchor='HTTP-REPLAY' target='https://www.rfc-editor.org/info/
		rfc8470'>
		<front>
		<title>Using Early Data in HTTP</title>
		<author fullname='M. Thomson' initials='M.' surname='Thomson'>
		<organization/>
		</author>
		<author fullname='M. Nottingham' initials='M.' surname='Nottingham'>
		<organization/>
		</author>
		<author fullname='W. Tarreau' initials='W.' surname='Tarreau'>
		<organization/>
		</author>
		<date month='September' year='2018'/>
		<abstract>
		<t>Using TLS early data creates an exposure to the possibility of
		a replay attack. This document defines mechanisms that allow clients to communi
		cate with servers about HTTP requests that are sent in early data. Techniques a
		re described that use these mechanisms to mitigate the risk of replay.</t>
		</abstract>
		</front>
		<seriesInfo name='RFC' value='8470'/>
		<seriesInfo name='DOI' value='10.17487/RFC8470'/>
		</reference>
		<reference anchor='RFC8126' target='https://www.rfc-editor.org/info/rfc8
		126'>
		<front>
		<title>Guidelines for Writing an IANA Considerations Section in RFCs
		</title>
		<author fullname='M. Cotton' initials='M.' surname='Cotton'>
		<organization/>
		</author>
		<author fullname='B. Leiba' initials='B.' surname='Leiba'>
		<organization/>
		</author>
		<author fullname='T. Narten' initials='T.' surname='Narten'>
		<organization/>
		</author>
		<date month='June' year='2017'/>
		<abstract>
		<t>Many protocols make use of points of extensibility that use con
		stants to identify various protocol parameters. To ensure that the values in th
		ese fields do not have conflicting uses and to promote interoperability, their a
		llocations are often coordinated by a central record keeper. For IETF protocols
		, that role is filled by the Internet Assigned Numbers Authority (IANA).</t>
		<t>To make assignments in a given registry prudently, guidance des
		cribing the conditions under which new values should be assigned, as well as whe
		n and how modifications to existing values can be made, is needed. This documen
		t defines a framework for the documentation of these guidelines by specification
		authors, in order to assure that the provided guidance for the IANA Considerati
		ons is clear and addresses the various issues that are likely in the operation o
		f a registry.</t>
		<t>This is the third edition of this document; it obsoletes RFC 52
		26.</t>
		</abstract>
		</front>
		<seriesInfo name='BCP' value='26'/>
		<seriesInfo name='RFC' value='8126'/>
		<seriesInfo name='DOI' value='10.17487/RFC8126'/>
		</reference>
	</references>	</references>
	<references>	<references>
	<name>Informative References</name>	<name>Informative References</name>

		<reference anchor='RFC9112' target='https://www.rfc-editor.org/info/rfc9
	<!-- [rfced] [BREACH] The URL below is correct -->	112'>
		<front>
	<reference anchor="BREACH" target="http://breachattack.com/resources/BRE	<title>HTTP/1.1</title>
	ACH%20-%20SSL,%20gone%20in%2030%20seconds.pdf">	<author fullname='Roy T. Fielding' initials='R.' role='editor' surna
		me='Fielding'>
		<organization>Adobe</organization>
		</author>
		<author fullname='Mark Nottingham' initials='M.' role='editor' surna
		me='Nottingham'>
		<organization>Fastly</organization>
		</author>
		<author fullname='Julian Reschke' initials='J.' role='editor' surnam
		e='Reschke'>
		<organization>greenbytes</organization>
		</author>
		<date month='May' year='2022'/>
		</front>
		<seriesInfo name='STD' value='99'/>
		<seriesInfo name='RFC' value='9112'/>
		<seriesInfo name='DOI' value='10.17487/RFC9112'/>
		</reference>
		<reference anchor='RFC9113' target='https://www.rfc-editor.org/info/rfc9
		113'>
		<front>
		<title>HTTP/2</title>
		<author fullname='Martin Thomson' initials='M.' role='editor' surnam
		e='Thomson'>
		<organization>Mozilla</organization>
		</author>
		<author fullname='Cory Benfield' initials='C.' role='editor' surname
		='Benfield'>
		<organization>Apple Inc.</organization>
		</author>
		<date month='May' year='2022'/>
		</front>
		<seriesInfo name='RFC' value='9113'/>
		<seriesInfo name='DOI' value='10.17487/RFC9113'/>
		</reference>
		<reference anchor='BREACH' target='http://breachattack.com/resources/BRE
		ACH%20-%20SSL,%20gone%20in%2030%20seconds.pdf'>
	<front>	<front>
	<title>BREACH: Reviving the CRIME Attack</title>	<title>BREACH: Reviving the CRIME Attack</title>

	<author initials="Y." surname="Gluck">	<author initials='Y.' surname='Gluck'>
	<organization/>	<organization/>
	</author>	</author>

	<author initials="N." surname="Harris">	<author initials='N.' surname='Harris'>
	<organization/>	<organization/>
	</author>	</author>

	<author initials="A." surname="Prado">	<author initials='A.' surname='Prado'>
	<organization/>	<organization/>
	</author>	</author>

	<date year="2013" month="July"/>	<date month='July' year='2013'/>
	</front>	</front>
	</reference>	</reference>

		<reference anchor='TLS' target='https://www.rfc-editor.org/info/rfc8446'
	<!-- [rfced] [HTTP11] [I-D.ietf-httpbis-messaging] IESG state I-D Exists -->	>
		<front>
	<xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D.ietf-ht	<title>The Transport Layer Security (TLS) Protocol Version 1.3</titl
	tpbis-messaging.xml"/>	e>
		<author fullname='E. Rescorla' initials='E.' surname='Rescorla'>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7540.	<organization/>
	xml"/>	</author>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8446.	<date month='August' year='2018'/>
	xml"/>	<abstract>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7413.	<t>This document specifies version 1.3 of the Transport Layer Secu
	xml"/>	rity (TLS) protocol. TLS allows client/server applications to communicate over
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7541.	the Internet in a way that is designed to prevent eavesdropping, tampering, and
	xml"/>	message forgery.</t>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8164.	<t>This document updates RFCs 5705 and 6066, and obsoletes RFCs 50
	xml"/>	77, 5246, and 6961. This document also specifies new requirements for TLS 1.2 i
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8499.	mplementations.</t>
	xml"/>	</abstract>
	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6585.	</front>
	xml"/>	<seriesInfo name='RFC' value='8446'/>
		<seriesInfo name='DOI' value='10.17487/RFC8446'/>
		</reference>
		<reference anchor='TFO' target='https://www.rfc-editor.org/info/rfc7413'
		>
		<front>
		<title>TCP Fast Open</title>
		<author fullname='Y. Cheng' initials='Y.' surname='Cheng'>
		<organization/>
		</author>
		<author fullname='J. Chu' initials='J.' surname='Chu'>
		<organization/>
		</author>
		<author fullname='S. Radhakrishnan' initials='S.' surname='Radhakris
		hnan'>
		<organization/>
		</author>
		<author fullname='A. Jain' initials='A.' surname='Jain'>
		<organization/>
		</author>
		<date month='December' year='2014'/>
		<abstract>
		<t>This document describes an experimental TCP mechanism called TC
		P Fast Open (TFO). TFO allows data to be carried in the SYN and SYN-ACK packets
		and consumed by the receiving end during the initial connection handshake, and
		saves up to one full round-trip time (RTT) compared to the standard TCP, which r
		equires a three-way handshake (3WHS) to complete before data can be exchanged.
		However, TFO deviates from the standard TCP semantics, since the data in the SYN
		could be replayed to an application in some rare circumstances. Applications s
		hould not use TFO unless they can tolerate this issue, as detailed in the Applic
		ability section.</t>
		</abstract>
		</front>
		<seriesInfo name='RFC' value='7413'/>
		<seriesInfo name='DOI' value='10.17487/RFC7413'/>
		</reference>
		<reference anchor='HPACK' target='https://www.rfc-editor.org/info/rfc754
		1'>
		<front>
		<title>HPACK: Header Compression for HTTP/2</title>
		<author fullname='R. Peon' initials='R.' surname='Peon'>
		<organization/>
		</author>
		<author fullname='H. Ruellan' initials='H.' surname='Ruellan'>
		<organization/>
		</author>
		<date month='May' year='2015'/>
		<abstract>
		<t>This specification defines HPACK, a compression format for effi
		ciently representing HTTP header fields, to be used in HTTP/2.</t>
		</abstract>
		</front>
		<seriesInfo name='RFC' value='7541'/>
		<seriesInfo name='DOI' value='10.17487/RFC7541'/>
		</reference>
		<reference anchor='RFC8164' target='https://www.rfc-editor.org/info/rfc8
		164'>
		<front>
		<title>Opportunistic Security for HTTP/2</title>
		<author fullname='M. Nottingham' initials='M.' surname='Nottingham'>
		<organization/>
		</author>
		<author fullname='M. Thomson' initials='M.' surname='Thomson'>
		<organization/>
		</author>
		<date month='May' year='2017'/>
		<abstract>
		<t>This document describes how "http" URIs can be accessed using T
		ransport Layer Security (TLS) and HTTP/2 to mitigate pervasive monitoring attack
		s. This mechanism not a replacement for "https" URIs; it is vulnerable to activ
		e attacks.</t>
		</abstract>
		</front>
		<seriesInfo name='RFC' value='8164'/>
		<seriesInfo name='DOI' value='10.17487/RFC8164'/>
		</reference>
		<reference anchor='DNS-TERMS' target='https://www.rfc-editor.org/info/rf
		c8499'>
		<front>
		<title>DNS Terminology</title>
		<author fullname='P. Hoffman' initials='P.' surname='Hoffman'>
		<organization/>
		</author>
		<author fullname='A. Sullivan' initials='A.' surname='Sullivan'>
		<organization/>
		</author>
		<author fullname='K. Fujiwara' initials='K.' surname='Fujiwara'>
		<organization/>
		</author>
		<date month='January' year='2019'/>
		<abstract>
		<t>The Domain Name System (DNS) is defined in literally dozens of
		different RFCs. The terminology used by implementers and developers of DNS prot
		ocols, and by operators of DNS systems, has sometimes changed in the decades sin
		ce the DNS was first defined. This document gives current definitions for many
		of the terms used in the DNS in a single document.</t>
		<t>This document obsoletes RFC 7719 and updates RFC 2308.</t>
		</abstract>
		</front>
		<seriesInfo name='BCP' value='219'/>
		<seriesInfo name='RFC' value='8499'/>
		<seriesInfo name='DOI' value='10.17487/RFC8499'/>
		</reference>
		<reference anchor='RFC6585' target='https://www.rfc-editor.org/info/rfc6
		585'>
		<front>
		<title>Additional HTTP Status Codes</title>
		<author fullname='M. Nottingham' initials='M.' surname='Nottingham'>
		<organization/>
		</author>
		<author fullname='R. Fielding' initials='R.' surname='Fielding'>
		<organization/>
		</author>
		<date month='April' year='2012'/>
		<abstract>
		<t>This document specifies additional HyperText Transfer Protocol
		(HTTP) status codes for a variety of common situations. [STANDARDS-TRACK]</t>
		</abstract>
		</front>
		<seriesInfo name='RFC' value='6585'/>
		<seriesInfo name='DOI' value='10.17487/RFC6585'/>
		</reference>
	</references>	</references>
	</references>	</references>

	<section anchor="h2-considerations" numbered="true" toc="default">	<section anchor='h2-considerations'>
	<name>Considerations for Transitioning from HTTP/2</name>	<name>Considerations for Transitioning from HTTP/2</name>

	<t>HTTP/3 is strongly informed by HTTP/2, and bears many similarities. Th is	<t>HTTP/3 is strongly informed by HTTP/2, and it bears many similarities. This
	section describes the approach taken to design HTTP/3, points out important	section describes the approach taken to design HTTP/3, points out important
	differences from HTTP/2, and describes how to map HTTP/2 extensions into HTTP/3. </t>	differences from HTTP/2, and describes how to map HTTP/2 extensions into HTTP/3. </t>
	<t>HTTP/3 begins from the premise that similarity to HTTP/2 is preferable, but not	<t>HTTP/3 begins from the premise that similarity to HTTP/2 is preferable, but not
	a hard requirement. HTTP/3 departs from HTTP/2 where QUIC differs from TCP,	a hard requirement. HTTP/3 departs from HTTP/2 where QUIC differs from TCP,
	either to take advantage of QUIC features (like streams) or to accommodate	either to take advantage of QUIC features (like streams) or to accommodate

	important shortcomings (such as a lack of total ordering). These differences	important shortcomings (such as a lack of total ordering). While HTTP/3 is
	make HTTP/3 similar to HTTP/2 in key aspects, such as the relationship of	similar to HTTP/2 in key aspects, such as the relationship of requests and
	requests and responses to streams. However, the details of the HTTP/3 design are	responses to streams, the details of the HTTP/3 design are substantially
	substantially different from HTTP/2.</t>	different from HTTP/2.</t>
	<t>Some important departures are noted in this section.</t>	<t>Some important departures are noted in this section.</t>

	<section anchor="h2-streams" numbered="true" toc="default">	<section anchor='h2-streams'>
	<name>Streams</name>	<name>Streams</name>
	<t>HTTP/3 permits use of a larger number of streams (2<sup>62</sup>-1) t han HTTP/2.	<t>HTTP/3 permits use of a larger number of streams (2<sup>62</sup>-1) t han HTTP/2.
	The same considerations about exhaustion of stream identifier space apply,	The same considerations about exhaustion of stream identifier space apply,
	though the space is significantly larger such that it is likely that other	though the space is significantly larger such that it is likely that other

	limits in QUIC are reached first, such as the limit on the connection flow	limits in QUIC are reached first, such as the limit on the connection
	control window.</t>	flow-control window.</t>
	<t>In contrast to HTTP/2, stream concurrency in HTTP/3 is managed by QUI C. QUIC	<t>In contrast to HTTP/2, stream concurrency in HTTP/3 is managed by QUI C. QUIC
	considers a stream closed when all data has been received and sent data has been	considers a stream closed when all data has been received and sent data has been
	acknowledged by the peer. HTTP/2 considers a stream closed when the frame	acknowledged by the peer. HTTP/2 considers a stream closed when the frame
	containing the END_STREAM bit has been committed to the transport. As a result,	containing the END_STREAM bit has been committed to the transport. As a result,
	the stream for an equivalent exchange could remain "active" for a longer period	the stream for an equivalent exchange could remain "active" for a longer period
	of time. HTTP/3 servers might choose to permit a larger number of concurrent	of time. HTTP/3 servers might choose to permit a larger number of concurrent
	client-initiated bidirectional streams to achieve equivalent concurrency to	client-initiated bidirectional streams to achieve equivalent concurrency to
	HTTP/2, depending on the expected usage patterns.</t>	HTTP/2, depending on the expected usage patterns.</t>

	<t>In HTTP/2, only request and response bodies (the frame payload of DAT A frames)	<t>In HTTP/2, only request and response bodies (the frame payload of <xr ef format='none' target='frame-data'>DATA</xref><iref item='DATA'/> frames)
	are subject to flow control. All HTTP/3 frames are sent on QUIC streams, so all	are subject to flow control. All HTTP/3 frames are sent on QUIC streams, so all

	frames on all streams are flow-controlled in HTTP/3.</t>	frames on all streams are flow controlled in HTTP/3.</t>
	<t>Due to the presence of other unidirectional stream types, HTTP/3 does not rely	<t>Due to the presence of other unidirectional stream types, HTTP/3 does not rely
	exclusively on the number of concurrent unidirectional streams to control the	exclusively on the number of concurrent unidirectional streams to control the
	number of concurrent in-flight pushes. Instead, HTTP/3 clients use the	number of concurrent in-flight pushes. Instead, HTTP/3 clients use the

	MAX_PUSH_ID frame to control the number of pushes received from an HTTP/3	<xref format='none' target='frame-max-push-id'>MAX_PUSH_ID</xref><iref item='MAX _PUSH_ID'/> frame to control the number of pushes received from an HTTP/3
	server.</t>	server.</t>
	</section>	</section>

	<section anchor="h2-frames" numbered="true" toc="default">	<section anchor='h2-frames'>
	<name>HTTP Frame Types</name>	<name>HTTP Frame Types</name>
	<t>Many framing concepts from HTTP/2 can be elided on QUIC, because the transport	<t>Many framing concepts from HTTP/2 can be elided on QUIC, because the transport
	deals with them. Because frames are already on a stream, they can omit the	deals with them. Because frames are already on a stream, they can omit the
	stream number. Because frames do not block multiplexing (QUIC's multiplexing	stream number. Because frames do not block multiplexing (QUIC's multiplexing
	occurs below this layer), the support for variable-maximum-length packets can be	occurs below this layer), the support for variable-maximum-length packets can be
	removed. Because stream termination is handled by QUIC, an END_STREAM flag is	removed. Because stream termination is handled by QUIC, an END_STREAM flag is
	not required. This permits the removal of the Flags field from the generic	not required. This permits the removal of the Flags field from the generic
	frame layout.</t>	frame layout.</t>

	<t>Frame payloads are largely drawn from <xref target="RFC7540" format=" default"/>. However, QUIC includes many	<t>Frame payloads are largely drawn from <xref target='RFC9113'/>. Howev er, QUIC includes many
	features (e.g., flow control) that are also present in HTTP/2. In these cases,	features (e.g., flow control) that are also present in HTTP/2. In these cases,
	the HTTP mapping does not re-implement them. As a result, several HTTP/2 frame	the HTTP mapping does not re-implement them. As a result, several HTTP/2 frame
	types are not required in HTTP/3. Where an HTTP/2-defined frame is no longer	types are not required in HTTP/3. Where an HTTP/2-defined frame is no longer
	used, the frame ID has been reserved in order to maximize portability between	used, the frame ID has been reserved in order to maximize portability between
	HTTP/2 and HTTP/3 implementations. However, even frame types that appear in	HTTP/2 and HTTP/3 implementations. However, even frame types that appear in
	both mappings do not have identical semantics.</t>	both mappings do not have identical semantics.</t>
	<t>Many of the differences arise from the fact that HTTP/2 provides an a bsolute	<t>Many of the differences arise from the fact that HTTP/2 provides an a bsolute
	ordering between frames across all streams, while QUIC provides this guarantee	ordering between frames across all streams, while QUIC provides this guarantee
	on each stream only. As a result, if a frame type makes assumptions that frames	on each stream only. As a result, if a frame type makes assumptions that frames
	from different streams will still be received in the order sent, HTTP/3 will	from different streams will still be received in the order sent, HTTP/3 will
	break them.</t>	break them.</t>
	<t>Some examples of feature adaptations are described below, as well as general	<t>Some examples of feature adaptations are described below, as well as general
	guidance to extension frame implementors converting an HTTP/2 extension to	guidance to extension frame implementors converting an HTTP/2 extension to
	HTTP/3.</t>	HTTP/3.</t>

	<section anchor="h2-diff-priority" numbered="true" toc="default">	<section anchor='h2-diff-priority'>
	<name>Prioritization Differences</name>	<name>Prioritization Differences</name>
	<t>HTTP/2 specifies priority assignments in PRIORITY frames and (optio nally) in	<t>HTTP/2 specifies priority assignments in PRIORITY frames and (optio nally) in

	HEADERS frames. HTTP/3 does not provide a means of signaling priority.</t>	<xref format='none' target='frame-headers'>HEADERS</xref><iref item='HEADERS'/>
	<t>Note that while there is no explicit signaling for priority, this d	frames. HTTP/3 does not provide a means of signaling priority.</t>
	oes not mean	<t>Note that, while there is no explicit signaling for priority, this
		does not mean
	that prioritization is not important for achieving good performance.</t>	that prioritization is not important for achieving good performance.</t>
	</section>	</section>

	<section anchor="field-compression-differences" numbered="true" toc="def ault">	<section anchor='field-compression-differences'>
	<name>Field Compression Differences</name>	<name>Field Compression Differences</name>
	<t>HPACK was designed with the assumption of in-order delivery. A sequ ence of	<t>HPACK was designed with the assumption of in-order delivery. A sequ ence of
	encoded field sections must arrive (and be decoded) at an endpoint in the same	encoded field sections must arrive (and be decoded) at an endpoint in the same
	order in which they were encoded. This ensures that the dynamic state at the two	order in which they were encoded. This ensures that the dynamic state at the two
	endpoints remains in sync.</t>	endpoints remains in sync.</t>
	<t>Because this total ordering is not provided by QUIC, HTTP/3 uses a modified	<t>Because this total ordering is not provided by QUIC, HTTP/3 uses a modified
	version of HPACK, called QPACK. QPACK uses a single unidirectional stream to	version of HPACK, called QPACK. QPACK uses a single unidirectional stream to
	make all modifications to the dynamic table, ensuring a total order of updates.	make all modifications to the dynamic table, ensuring a total order of updates.
	All frames that contain encoded fields merely reference the table state at a	All frames that contain encoded fields merely reference the table state at a
	given time without modifying it.</t>	given time without modifying it.</t>

	<t><xref target="RFCYYY2" format="default"/> provides additional detai ls.</t>	<t><xref target='RFC9204'/> provides additional details.</t>
	</section>	</section>

	<section anchor="flow-control-differences" numbered="true" toc="default"	<section anchor='flow-control-differences'>
	>	<name>Flow-Control Differences</name>
	<name>Flow Control Differences</name>	<t>HTTP/2 specifies a stream flow-control mechanism. Although all HTTP
	<t>HTTP/2 specifies a stream flow control mechanism. Although all HTTP	/2 frames are
	/2 frames are	delivered on streams, only the <xref format='none' target='frame-data'>DATA</xre
	delivered on streams, only the DATA frame payload is subject to flow control.	f><iref item='DATA'/> frame payload is subject to flow control.
	QUIC provides flow control for stream data and all HTTP/3 frame types defined in	QUIC provides flow control for stream data and all HTTP/3 frame types defined in
	this document are sent on streams. Therefore, all frame headers and payload are	this document are sent on streams. Therefore, all frame headers and payload are
	subject to flow control.</t>	subject to flow control.</t>
	</section>	</section>

	<section anchor="guidance-for-new-frame-type-definitions" numbered="true " toc="default">	<section anchor='guidance-for-new-frame-type-definitions'>
	<name>Guidance for New Frame Type Definitions</name>	<name>Guidance for New Frame Type Definitions</name>
	<t>Frame type definitions in HTTP/3 often use the QUIC variable-length integer	<t>Frame type definitions in HTTP/3 often use the QUIC variable-length integer

	encoding. In particular, Stream IDs use this encoding, which allows for a	encoding. In particular, stream IDs use this encoding, which allows for a
	larger range of possible values than the encoding used in HTTP/2. Some frames	larger range of possible values than the encoding used in HTTP/2. Some frames

	in HTTP/3 use an identifier other than a Stream ID (e.g., Push	in HTTP/3 use an identifier other than a stream ID (e.g., push IDs).
	IDs). Redefinition of the encoding of extension frame types might be necessary	Redefinition of the encoding of extension frame types might be necessary if the
	if the encoding includes a Stream ID.</t>	encoding includes a stream ID.</t>
	<t>Because the Flags field is not present in generic HTTP/3 frames, th ose frames	<t>Because the Flags field is not present in generic HTTP/3 frames, th ose frames
	that depend on the presence of flags need to allocate space for flags as part	that depend on the presence of flags need to allocate space for flags as part
	of their frame payload.</t>	of their frame payload.</t>
	<t>Other than these issues, frame type HTTP/2 extensions are typically portable to	<t>Other than these issues, frame type HTTP/2 extensions are typically portable to

	QUIC simply by replacing Stream 0 in HTTP/2 with a control stream in HTTP/3.	QUIC simply by replacing stream 0 in HTTP/2 with a <xref format='none' target='c ontrol-streams'>control stream</xref><iref item='control stream'/> in HTTP/3.
	HTTP/3 extensions will not assume ordering, but would not be harmed by ordering,	HTTP/3 extensions will not assume ordering, but would not be harmed by ordering,
	and are expected to be portable to HTTP/2.</t>	and are expected to be portable to HTTP/2.</t>
	</section>	</section>

	<section anchor="comparison-between-http2-and-http3-frame-types" numbere	<section anchor='comparison-of-http2-and-http3-frame-types'>
	d="true" toc="default">	<name>Comparison of HTTP/2 and HTTP/3 Frame Types</name>
	<name>Comparison Between HTTP/2 and HTTP/3 Frame Types</name>
	<dl>	<dl>

	<dt>	<dt><xref format='none' target='frame-data'>DATA</xref> (0x00)<iref
	DATA (0x0): </dt>	item='DATA'/>:</dt>
	<dd>	<dd>

	<t>Padding is not defined in HTTP/3 frames. See <xref target="fra me-data" format="default"/>.</t>	<t>Padding is not defined in HTTP/3 frames. See <xref target='fra me-data'/>.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='frame-headers'>HEADERS</xref> (0x01)
	HEADERS (0x1): </dt>	<iref item='HEADERS'/>:</dt>
	<dd>	<dd>

	<t>The PRIORITY region of HEADERS is not defined in HTTP/3 frames.	<t>The PRIORITY region of <xref format='none' target='frame-header
	Padding is not	s'>HEADERS</xref><iref item='HEADERS'/> is not defined in HTTP/3 frames. Padding
	defined in HTTP/3 frames. See <xref target="frame-headers" format="default"/>.<	is not
	/t>	defined in HTTP/3 frames. See <xref target='frame-headers'/>.</t>
	</dd>	</dd>

	<dt>	<dt>PRIORITY (0x02):</dt>
	PRIORITY (0x2): </dt>
	<dd>	<dd>

	<t>As described in <xref target="h2-diff-priority" format="default "/>, HTTP/3 does not provide a means of	<t>As described in <xref target='h2-diff-priority'/>, HTTP/3 does not provide a means of
	signaling priority.</t>	signaling priority.</t>
	</dd>	</dd>

	<dt>	<dt>RST_STREAM (0x03):</dt>
	RST_STREAM (0x3): </dt>
	<dd>	<dd>
	<t>RST_STREAM frames do not exist in HTTP/3, since QUIC provides s tream lifecycle	<t>RST_STREAM frames do not exist in HTTP/3, since QUIC provides s tream lifecycle

	management. The same code point is used for the CANCEL_PUSH frame	management. The same code point is used for the <xref format='none' target='fra
	(<xref target="frame-cancel-push" format="default"/>).</t>	me-cancel-push'>CANCEL_PUSH</xref><iref item='CANCEL_PUSH'/> frame
		(<xref target='frame-cancel-push'/>).</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='frame-settings'>SETTINGS</xref> (0x0
	SETTINGS (0x4): </dt>	4)<iref item='SETTINGS'/>:</dt>
	<dd>	<dd>

	<t>SETTINGS frames are sent only at the beginning of the connectio	<t><xref format='none' target='frame-settings'>SETTINGS</xref><ire
	n. See	f item='SETTINGS'/> frames are sent only at the beginning of the connection. Se
	<xref target="frame-settings" format="default"/> and <xref target="h2-settings"	e
	format="default"/>.</t>	<xref target='frame-settings'/> and <xref target='h2-settings'/>.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='frame-push-promise'>PUSH_PROMISE</xr
	PUSH_PROMISE (0x5): </dt>	ef> (0x05)<iref item='PUSH_PROMISE'/>:</dt>
	<dd>	<dd>

	<t>The PUSH_PROMISE frame does not reference a stream; instead the	<t>The <xref format='none' target='frame-push-promise'>PUSH_PROMIS
	push stream	E</xref><iref item='PUSH_PROMISE'/> frame does not reference a stream; instead,
	references the PUSH_PROMISE frame using a Push ID. See	the <xref format='none' target='push-streams'>push stream</xref><iref item='push
	<xref target="frame-push-promise" format="default"/>.</t>	stream'/>
		references the <xref format='none' target='frame-push-promise'>PUSH_PROMISE</xre
		f><iref item='PUSH_PROMISE'/> frame using a <xref format='none' target='server-p
		ush'>push ID</xref><iref item='push ID'/>. See
		<xref target='frame-push-promise'/>.</t>
	</dd>	</dd>

	<dt>	<dt>PING (0x06):</dt>
	PING (0x6): </dt>
	<dd>	<dd>
	<t>PING frames do not exist in HTTP/3, as QUIC provides equivalent	<t>PING frames do not exist in HTTP/3, as QUIC provides equivalent
	functionality.</t>	functionality.</t>
	</dd>	</dd>

	<dt>	<dt><xref format='none' target='frame-goaway'>GOAWAY</xref> (0x07)<i
	GOAWAY (0x7): </dt>	ref item='GOAWAY'/>:</dt>
	<dd>	<dd>

	<t>GOAWAY does not contain an error code. In the client to server	<t><xref format='none' target='frame-goaway'>GOAWAY</xref><iref it
	direction,	em='GOAWAY'/> does not contain an error code. In the client-to-server direction
	it carries a Push ID instead of a server initiated stream ID.	,
	See <xref target="frame-goaway" format="default"/>.</t>	it carries a <xref format='none' target='server-push'>push ID</xref><iref item='
		push ID'/> instead of a server-initiated stream ID.
		See <xref target='frame-goaway'/>.</t>
	</dd>	</dd>

	<dt>	<dt>WINDOW_UPDATE (0x08):</dt>
	WINDOW_UPDATE (0x8): </dt>
	<dd>	<dd>
	<t>WINDOW_UPDATE frames do not exist in HTTP/3, since QUIC provide s flow control.</t>	<t>WINDOW_UPDATE frames do not exist in HTTP/3, since QUIC provide s flow control.</t>
	</dd>	</dd>

	<dt>	<dt>CONTINUATION (0x09):</dt>
	CONTINUATION (0x9): </dt>
	<dd>	<dd>
	<t>CONTINUATION frames do not exist in HTTP/3; instead, larger	<t>CONTINUATION frames do not exist in HTTP/3; instead, larger

	HEADERS/PUSH_PROMISE frames than HTTP/2 are permitted.</t>	<xref format='none' target='frame-headers'>HEADERS</xref><iref item='HEADERS'/>/ <xref format='none' target='frame-push-promise'>PUSH_PROMISE</xref><iref item='P USH_PROMISE'/> frames than HTTP/2 are permitted.</t>
	</dd>	</dd>
	</dl>	</dl>
	<t>Frame types defined by extensions to HTTP/2 need to be separately r egistered for	<t>Frame types defined by extensions to HTTP/2 need to be separately r egistered for

	HTTP/3 if still applicable. The IDs of frames defined in <xref target="RFC7540" format="default"/> have been	HTTP/3 if still applicable. The IDs of frames defined in <xref target='RFC9113' /> have been
	reserved for simplicity. Note that the frame type space in HTTP/3 is	reserved for simplicity. Note that the frame type space in HTTP/3 is
	substantially larger (62 bits versus 8 bits), so many HTTP/3 frame types have no	substantially larger (62 bits versus 8 bits), so many HTTP/3 frame types have no

	equivalent HTTP/2 code points. See <xref target="iana-frames" format="default"/ >.</t>	equivalent HTTP/2 code points. See <xref target='iana-frames'/>.</t>
	</section>	</section>
	</section>	</section>

	<section anchor="h2-settings" numbered="true" toc="default">	<section anchor='h2-settings'>
	<name>HTTP/2 SETTINGS Parameters</name>	<name>HTTP/2 SETTINGS Parameters</name>
	<t>An important difference from HTTP/2 is that settings are sent once, a s the first	<t>An important difference from HTTP/2 is that settings are sent once, a s the first

	frame of the control stream, and thereafter cannot change. This eliminates many	frame of the <xref format='none' target='control-streams'>control stream</xref>< iref item='control stream'/>, and thereafter cannot change. This eliminates man y
	corner cases around synchronization of changes.</t>	corner cases around synchronization of changes.</t>

	<t>Some transport-level options that HTTP/2 specifies via the SETTINGS f rame are	<t>Some transport-level options that HTTP/2 specifies via the <xref form at='none' target='frame-settings'>SETTINGS</xref><iref item='SETTINGS'/> frame a re
	superseded by QUIC transport parameters in HTTP/3. The HTTP-level setting that	superseded by QUIC transport parameters in HTTP/3. The HTTP-level setting that
	is retained in HTTP/3 has the same value as in HTTP/2. The superseded	is retained in HTTP/3 has the same value as in HTTP/2. The superseded
	settings are reserved, and their receipt is an error. See	settings are reserved, and their receipt is an error. See

	<xref target="settings-parameters" format="default"/> for discussion of both the	<xref target='settings-parameters'/> for discussion of both the retained and res
	retained and reserved values.</t>	erved values.</t>
	<t>Below is a listing of how each HTTP/2 SETTINGS parameter is mapped:</	<t>Below is a listing of how each HTTP/2 <xref format='none' target='fra
	t>	me-settings'>SETTINGS</xref><iref item='SETTINGS'/> parameter is mapped:</t>
	<dl>	<dl>

	<dt>	<dt>SETTINGS_HEADER_TABLE_SIZE (0x01):</dt>
	SETTINGS_HEADER_TABLE_SIZE (0x1): </dt>
	<dd>	<dd>

	<t>See <xref target="RFCYYY2" format="default"/>.</t>	<t>See <xref target='RFC9204'/>.</t>
	</dd>	</dd>

	<dt>	<dt>SETTINGS_ENABLE_PUSH (0x02):</dt>
	SETTINGS_ENABLE_PUSH (0x2): </dt>
	<dd>	<dd>

	<t>This is removed in favor of the MAX_PUSH_ID frame, which provides a more	<t>This is removed in favor of the <xref format='none' target='frame -max-push-id'>MAX_PUSH_ID</xref><iref item='MAX_PUSH_ID'/> frame, which provides a more
	granular control over server push. Specifying a setting with the identifier	granular control over server push. Specifying a setting with the identifier

	0x2 (corresponding to the SETTINGS_ENABLE_PUSH parameter) in the HTTP/3	0x02 (corresponding to the SETTINGS_ENABLE_PUSH parameter) in the HTTP/3
	SETTINGS frame is an error.</t>	<xref format='none' target='frame-settings'>SETTINGS</xref><iref item='SETTINGS'
		/> frame is an error.</t>
	</dd>	</dd>

	<dt>	<dt>SETTINGS_MAX_CONCURRENT_STREAMS (0x03):</dt>
	SETTINGS_MAX_CONCURRENT_STREAMS (0x3): </dt>
	<dd>	<dd>

	<t>QUIC controls the largest open Stream ID as part of its flow cont	<t>QUIC controls the largest open stream ID as part of its flow-cont
	rol logic.	rol logic.
	Specifying a setting with the identifier 0x3 (corresponding to the	Specifying a setting with the identifier 0x03 (corresponding to the
	SETTINGS_MAX_CONCURRENT_STREAMS parameter) in the HTTP/3 SETTINGS frame is an	SETTINGS_MAX_CONCURRENT_STREAMS parameter) in the HTTP/3 <xref format='none' tar
		get='frame-settings'>SETTINGS</xref><iref item='SETTINGS'/> frame is an
	error.</t>	error.</t>
	</dd>	</dd>

	<dt>	<dt>SETTINGS_INITIAL_WINDOW_SIZE (0x04):</dt>
	SETTINGS_INITIAL_WINDOW_SIZE (0x4): </dt>
	<dd>	<dd>

	<t>QUIC requires both stream and connection flow control window size s to be	<t>QUIC requires both stream and connection flow-control window size s to be
	specified in the initial transport handshake. Specifying a setting with the	specified in the initial transport handshake. Specifying a setting with the

	identifier 0x4 (corresponding to the SETTINGS_INITIAL_WINDOW_SIZE parameter)	identifier 0x04 (corresponding to the SETTINGS_INITIAL_WINDOW_SIZE parameter)
	in the HTTP/3 SETTINGS frame is an error.</t>	in the HTTP/3 <xref format='none' target='frame-settings'>SETTINGS</xref><iref i
		tem='SETTINGS'/> frame is an error.</t>
	</dd>	</dd>

	<dt>	<dt>SETTINGS_MAX_FRAME_SIZE (0x05):</dt>
	SETTINGS_MAX_FRAME_SIZE (0x5): </dt>
	<dd>	<dd>
	<t>This setting has no equivalent in HTTP/3. Specifying a setting w ith the	<t>This setting has no equivalent in HTTP/3. Specifying a setting w ith the

	identifier 0x5 (corresponding to the SETTINGS_MAX_FRAME_SIZE parameter) in the	identifier 0x05 (corresponding to the SETTINGS_MAX_FRAME_SIZE parameter) in
	HTTP/3 SETTINGS frame is an error.</t>	the HTTP/3 <xref format='none' target='frame-settings'>SETTINGS</xref><iref item
		='SETTINGS'/> frame is an error.</t>
	</dd>	</dd>

	<dt>	<dt>SETTINGS_MAX_HEADER_LIST_SIZE (0x06):</dt>
	SETTINGS_MAX_HEADER_LIST_SIZE (0x6): </dt>
	<dd>	<dd>

	<t>This setting identifier has been renamed SETTINGS_MAX_FIELD_SECTI ON_SIZE.</t>	<t>This setting identifier has been renamed <xref format='none' targ et='SETTINGS_MAX_FIELD_SECTION_SIZE'>SETTINGS_MAX_FIELD_SECTION_SIZE</xref><iref item='SETTINGS_MAX_FIELD_SECTION_SIZE'/>.</t>
	</dd>	</dd>
	</dl>	</dl>
	<t>In HTTP/3, setting values are variable-length integers (6, 14, 30, or 62 bits	<t>In HTTP/3, setting values are variable-length integers (6, 14, 30, or 62 bits
	long) rather than fixed-length 32-bit fields as in HTTP/2. This will often	long) rather than fixed-length 32-bit fields as in HTTP/2. This will often
	produce a shorter encoding, but can produce a longer encoding for settings that	produce a shorter encoding, but can produce a longer encoding for settings that
	use the full 32-bit space. Settings ported from HTTP/2 might choose to redefine	use the full 32-bit space. Settings ported from HTTP/2 might choose to redefine

	their value to limit it to 30 bits for more efficient encoding, or to make use	their value to limit it to 30 bits for more efficient encoding or to make use
	of the 62-bit space if more than 30 bits are required.</t>	of the 62-bit space if more than 30 bits are required.</t>
	<t>Settings need to be defined separately for HTTP/2 and HTTP/3. The IDs of	<t>Settings need to be defined separately for HTTP/2 and HTTP/3. The IDs of

	settings defined in <xref target="RFC7540" format="default"/> have been reserved for simplicity. Note that	settings defined in <xref target='RFC9113'/> have been reserved for simplicity. Note that
	the settings identifier space in HTTP/3 is substantially larger (62 bits versus	the settings identifier space in HTTP/3 is substantially larger (62 bits versus
	16 bits), so many HTTP/3 settings have no equivalent HTTP/2 code point. See	16 bits), so many HTTP/3 settings have no equivalent HTTP/2 code point. See

	<xref target="iana-settings" format="default"/>.</t>	<xref target='iana-settings'/>.</t>
	<t>As QUIC streams might arrive out of order, endpoints are advised not to wait for	<t>As QUIC streams might arrive out of order, endpoints are advised not to wait for
	the peers' settings to arrive before responding to other streams. See	the peers' settings to arrive before responding to other streams. See

	<xref target="settings-initialization" format="default"/>.</t>	<xref target='settings-initialization'/>.</t>
	</section>	</section>

	<section anchor="http2-error-codes" numbered="true" toc="default">	<section anchor='http2-error-codes'>
	<name>HTTP/2 Error Codes</name>	<name>HTTP/2 Error Codes</name>
	<t>QUIC has the same concepts of "stream" and "connection" errors that H TTP/2	<t>QUIC has the same concepts of "stream" and "connection" errors that H TTP/2
	provides. However, the differences between HTTP/2 and HTTP/3 mean that error	provides. However, the differences between HTTP/2 and HTTP/3 mean that error
	codes are not directly portable between versions.</t>	codes are not directly portable between versions.</t>

	<t>The HTTP/2 error codes defined in <xref section="7" sectionFormat="of " target="RFC7540" format="default"/> logically map to	<t>The HTTP/2 error codes defined in <xref section='7' sectionFormat='of ' target='RFC9113'/> logically map to
	the HTTP/3 error codes as follows:</t>	the HTTP/3 error codes as follows:</t>
	<dl>	<dl>

	<dt>	<dt>NO_ERROR (0x00):</dt>
	NO_ERROR (0x0): </dt>
	<dd>	<dd>

	<t>H3_NO_ERROR in <xref target="http-error-codes" format="default"/> .</t>	<t><xref format='none' target='H3_NO_ERROR'>H3_NO_ERROR</xref><iref item='H3_NO_ERROR'/> in <xref target='http-error-codes'/>.</t>
	</dd>	</dd>

	<dt>	<dt>PROTOCOL_ERROR (0x01):</dt>
	PROTOCOL_ERROR (0x1): </dt>
	<dd>	<dd>

	<t>This is mapped to H3_GENERAL_PROTOCOL_ERROR except in cases where more	<t>This is mapped to <xref format='none' target='H3_GENERAL_PROTOCOL _ERROR'>H3_GENERAL_PROTOCOL_ERROR</xref><iref item='H3_GENERAL_PROTOCOL_ERROR'/> except in cases where more
	specific error codes have been defined. Such cases include	specific error codes have been defined. Such cases include

	H3_FRAME_UNEXPECTED, H3_MESSAGE_ERROR, and H3_CLOSED_CRITICAL_STREAM defined	<xref format='none' target='H3_FRAME_UNEXPECTED'>H3_FRAME_UNEXPECTED</xref><iref
	in <xref target="http-error-codes" format="default"/>.</t>	item='H3_FRAME_UNEXPECTED'/>, <xref format='none' target='H3_MESSAGE_ERROR'>H3_
		MESSAGE_ERROR</xref><iref item='H3_MESSAGE_ERROR'/>, and <xref format='none' tar
		get='H3_CLOSED_CRITICAL_STREAM'>H3_CLOSED_CRITICAL_STREAM</xref><iref item='H3_C
		LOSED_CRITICAL_STREAM'/> defined
		in <xref target='http-error-codes'/>.</t>
	</dd>	</dd>

	<dt>	<dt>INTERNAL_ERROR (0x02):</dt>
	INTERNAL_ERROR (0x2): </dt>
	<dd>	<dd>

	<t>H3_INTERNAL_ERROR in <xref target="http-error-codes" format="defa ult"/>.</t>	<t><xref format='none' target='H3_INTERNAL_ERROR'>H3_INTERNAL_ERROR< /xref><iref item='H3_INTERNAL_ERROR'/> in <xref target='http-error-codes'/>.</t>
	</dd>	</dd>

	<dt>	<dt>FLOW_CONTROL_ERROR (0x03):</dt>
	FLOW_CONTROL_ERROR (0x3): </dt>
	<dd>	<dd>
	<t>Not applicable, since QUIC handles flow control.</t>	<t>Not applicable, since QUIC handles flow control.</t>
	</dd>	</dd>

	<dt>	<dt>SETTINGS_TIMEOUT (0x04):</dt>
	SETTINGS_TIMEOUT (0x4): </dt>
	<dd>	<dd>

	<t>Not applicable, since no acknowledgment of SETTINGS is defined.</ t>	<t>Not applicable, since no acknowledgment of <xref format='none' ta rget='frame-settings'>SETTINGS</xref><iref item='SETTINGS'/> is defined.</t>
	</dd>	</dd>

	<dt>	<dt>STREAM_CLOSED (0x05):</dt>
	STREAM_CLOSED (0x5): </dt>
	<dd>	<dd>
	<t>Not applicable, since QUIC handles stream management.</t>	<t>Not applicable, since QUIC handles stream management.</t>
	</dd>	</dd>

	<dt>	<dt>FRAME_SIZE_ERROR (0x06):</dt>
	FRAME_SIZE_ERROR (0x6): </dt>
	<dd>	<dd>

	<t>H3_FRAME_ERROR error code defined in <xref target="http-error-cod es" format="default"/>.</t>	<t><xref format='none' target='H3_FRAME_ERROR'>H3_FRAME_ERROR</xref> <iref item='H3_FRAME_ERROR'/> error code defined in <xref target='http-error-cod es'/>.</t>
	</dd>	</dd>

	<dt>	<dt>REFUSED_STREAM (0x07):</dt>
	REFUSED_STREAM (0x7): </dt>
	<dd>	<dd>

	<t>H3_REQUEST_REJECTED (in <xref target="http-error-codes" format="d efault"/>) is used to indicate that a	<t><xref format='none' target='H3_REQUEST_REJECTED'>H3_REQUEST_REJEC TED</xref><iref item='H3_REQUEST_REJECTED'/> (in <xref target='http-error-codes' />) is used to indicate that a
	request was not processed. Otherwise, not applicable because QUIC handles	request was not processed. Otherwise, not applicable because QUIC handles
	stream management.</t>	stream management.</t>
	</dd>	</dd>

	<dt>	<dt>CANCEL (0x08):</dt>
	CANCEL (0x8): </dt>
	<dd>	<dd>

	<t>H3_REQUEST_CANCELLED in <xref target="http-error-codes" format="d efault"/>.</t>	<t><xref format='none' target='H3_REQUEST_CANCELLED'>H3_REQUEST_CANC ELLED</xref><iref item='H3_REQUEST_CANCELLED'/> in <xref target='http-error-code s'/>.</t>
	</dd>	</dd>

	<dt>	<dt>COMPRESSION_ERROR (0x09):</dt>
	COMPRESSION_ERROR (0x9): </dt>
	<dd>	<dd>

	<t>Multiple error codes are defined in <xref target="RFCYYY2" format ="default"/>.</t>	<t>Multiple error codes are defined in <xref target='RFC9204'/>.</t>
	</dd>	</dd>

	<dt>	<dt>CONNECT_ERROR (0x0a):</dt>
	CONNECT_ERROR (0xa): </dt>
	<dd>	<dd>

	<t>H3_CONNECT_ERROR in <xref target="http-error-codes" format="defau lt"/>.</t>	<t><xref format='none' target='H3_CONNECT_ERROR'>H3_CONNECT_ERROR</x ref><iref item='H3_CONNECT_ERROR'/> in <xref target='http-error-codes'/>.</t>
	</dd>	</dd>

	<dt>	<dt>ENHANCE_YOUR_CALM (0x0b):</dt>
	ENHANCE_YOUR_CALM (0xb): </dt>
	<dd>	<dd>

	<t>H3_EXCESSIVE_LOAD in <xref target="http-error-codes" format="defa ult"/>.</t>	<t><xref format='none' target='H3_EXCESSIVE_LOAD'>H3_EXCESSIVE_LOAD< /xref><iref item='H3_EXCESSIVE_LOAD'/> in <xref target='http-error-codes'/>.</t>
	</dd>	</dd>

	<dt>	<dt>INADEQUATE_SECURITY (0x0c):</dt>
	INADEQUATE_SECURITY (0xc): </dt>
	<dd>	<dd>
	<t>Not applicable, since QUIC is assumed to provide sufficient secur ity on all	<t>Not applicable, since QUIC is assumed to provide sufficient secur ity on all
	connections.</t>	connections.</t>
	</dd>	</dd>

	<dt>	<dt>HTTP_1_1_REQUIRED (0x0d):</dt>
	HTTP_1_1_REQUIRED (0xd): </dt>
	<dd>	<dd>

	<t>H3_VERSION_FALLBACK in <xref target="http-error-codes" format="de fault"/>.</t>	<t><xref format='none' target='H3_VERSION_FALLBACK'>H3_VERSION_FALLB ACK</xref><iref item='H3_VERSION_FALLBACK'/> in <xref target='http-error-codes'/ >.</t>
	</dd>	</dd>
	</dl>	</dl>
	<t>Error codes need to be defined for HTTP/2 and HTTP/3 separately. See	<t>Error codes need to be defined for HTTP/2 and HTTP/3 separately. See

	<xref target="iana-error-codes" format="default"/>.</t>	<xref target='iana-error-codes'/>.</t>
	<section anchor="mapping-between-http2-and-http3-errors" numbered="true"	<section anchor='mapping-between-http2-and-http3-errors'>
	toc="default">	<name>Mapping between HTTP/2 and HTTP/3 Errors</name>
	<name>Mapping Between HTTP/2 and HTTP/3 Errors</name>
	<t>An intermediary that converts between HTTP/2 and HTTP/3 may encount er error	<t>An intermediary that converts between HTTP/2 and HTTP/3 may encount er error
	conditions from either upstream. It is useful to communicate the occurrence of	conditions from either upstream. It is useful to communicate the occurrence of

	error to the downstream but error codes largely reflect connection-local	errors to the downstream, but error codes largely reflect connection-local
	problems that generally do not make sense to propagate.</t>	problems that generally do not make sense to propagate.</t>
	<t>An intermediary that encounters an error from an upstream origin ca n indicate	<t>An intermediary that encounters an error from an upstream origin ca n indicate

	this by sending an HTTP status code such as 502, which is suitable for a broad	this by sending an HTTP status code such as 502 (Bad Gateway), which is suitable
	class of errors.</t>	for a broad class of errors.</t>
	<t>There are some rare cases where it is beneficial to propagate the e rror by	<t>There are some rare cases where it is beneficial to propagate the e rror by
	mapping it to the closest matching error type to the receiver. For example, an	mapping it to the closest matching error type to the receiver. For example, an

	intermediary that receives an HTTP/2 stream error of type REFUSED_STREAM from	intermediary that receives an HTTP/2 <xref format='none' target='errors'>stream error</xref><iref item='stream error'/> of type REFUSED_STREAM from
	the origin has a clear signal that the request was not processed and that the	the origin has a clear signal that the request was not processed and that the
	request is safe to retry. Propagating this error condition to the client as an	request is safe to retry. Propagating this error condition to the client as an

	HTTP/3 stream error of type H3_REQUEST_REJECTED allows the client to take the	HTTP/3 <xref format='none' target='errors'>stream error</xref><iref item='stream error'/> of type <xref format='none' target='H3_REQUEST_REJECTED'>H3_REQUEST_RE JECTED</xref><iref item='H3_REQUEST_REJECTED'/> allows the client to take the
	action it deems most appropriate. In the reverse direction, the intermediary	action it deems most appropriate. In the reverse direction, the intermediary
	might deem it beneficial to pass on client request cancellations that are	might deem it beneficial to pass on client request cancellations that are

	indicated by terminating a stream with H3_REQUEST_CANCELLED; see	indicated by terminating a stream with <xref format='none' target='H3_REQUEST_CA
	<xref target="request-cancellation" format="default"/>.</t>	NCELLED'>H3_REQUEST_CANCELLED</xref><iref item='H3_REQUEST_CANCELLED'/>; see
		<xref target='request-cancellation'/>.</t>
	<t>Conversion between errors is described in the logical mapping. The error codes	<t>Conversion between errors is described in the logical mapping. The error codes
	are defined in non-overlapping spaces in order to protect against accidental	are defined in non-overlapping spaces in order to protect against accidental
	conversion that could result in the use of inappropriate or unknown error codes	conversion that could result in the use of inappropriate or unknown error codes

	for the target version. An intermediary is permitted to promote stream errors to	for the target version. An intermediary is permitted to promote <xref format='no
	connection errors but they should be aware of the cost to the HTTP/3 connection	ne' target='errors'>stream errors</xref><iref item='stream error'/> to
		<xref format='none' target='errors'>connection errors</xref><iref item='connecti
		on error'/> but they should be aware of the cost to the HTTP/3 connection
	for what might be a temporary or intermittent error.</t>	for what might be a temporary or intermittent error.</t>
	</section>	</section>
	</section>	</section>
	</section>	</section>

		<section anchor='acknowledgments' numbered='false'>
	<!--[rfced] deleted section per instructions <strong>RFC Editor's Note:
	</strong> Please remove this section prior to publication of a
	final version of this document.</li>-->

	<section numbered="false" anchor="acknowledgments" toc="default">
	<name>Acknowledgments</name>	<name>Acknowledgments</name>

	<t>The original authors of this specification were Robbie Shade and Mike W	<t><contact fullname='Robbie Shade'/> and <contact fullname='Mike Warres'/
	arres.</t>	> were the authors of
		draft-shade-quic-http2-mapping, a precursor of this document.</t>
	<t>The IETF QUIC Working Group received an enormous amount of support from many	<t>The IETF QUIC Working Group received an enormous amount of support from many
	people. Among others, the following people provided substantial contributions to	people. Among others, the following people provided substantial contributions to
	this document:</t>	this document:</t>

		<ul spacing='compact'>
	<t><contact fullname="Bence Beky"/></t>	<li>
	<t><contact fullname="Daan De Meyer"/></t>	<t><contact fullname="Bence Beky"/></t>
	<t><contact fullname="Martin Duke"/></t>	</li>
	<t><contact fullname="Roy Fielding"/></t>	<li>
	<t><contact fullname="Alan Frindell"/></t>	<t><contact fullname="Daan De Meyer"/></t>
	<t><contact fullname="Alessandro Ghedini"/></t>	</li>
	<t><contact fullname="Nick Harper"/></t>	<li>
	<t><contact fullname="Ryan Hamilton"/></t>	<t><contact fullname="Martin Duke"/></t>
	<t><contact fullname="Christian Huitema"/></t>	</li>
	<t><contact fullname="Subodh Iyengar"/></t>	<li>
	<t><contact fullname="Robin Marx"/></t>	<t><contact fullname="Roy Fielding"/></t>
	<t><contact fullname="Patrick McManus"/></t>	</li>
	<t><contact fullname="Luca Niccolini"/></t>	<li>
		<t><contact fullname="Alan Frindell"/></t>
	<t> <contact asciiFullname="Kazuho Oku" fullname="奥一穂"/>	</li>
	</t>	<li>
		<t><contact fullname="Alessandro Ghedini"/></t>
	<t><contact fullname="Lucas Pardue"/></t>	</li>
	<t><contact fullname="Roberto Peon"/></t>	<li>
	<t><contact fullname="Julian Reschke"/></t>	<t><contact fullname="Nick Harper"/></t>
	<t><contact fullname="Eric Rescorla"/></t>	</li>
	<t><contact fullname="Martin Seemann"/></t>	<li>
	<t><contact fullname="Ben Schwartz"/></t>	<t><contact fullname="Ryan Hamilton"/></t>
	<t><contact fullname="Ian Swett"/></t>	</li>
	<t><contact fullname="Willy Taureau"/></t>	<li>
	<t><contact fullname="Martin Thomson"/></t>	<t><contact fullname="Christian Huitema"/></t>
	<t><contact fullname="Dmitri Tikhonov"/></t>	</li>
	<t><contact fullname="Tatsuhiro Tsujikawa"/></t>	<li>
		<t><contact fullname="Subodh Iyengar"/></t>
	<t>A portion of Mike's contribution was supported by Microsoft during his	</li>
	employment there.</t>	<li>
		<t><contact fullname="Robin Marx"/></t>
		</li>
		<li>
		<t><contact fullname="Patrick McManus"/></t>
		</li>
		<li>
		<t><contact fullname="Luca Niccolini"/></t>
		</li>
		<li>
		<t><contact asciiFullname="Kazuho Oku" fullname="奥一穂"/></t>
		</li>
		<li>
		<t><contact fullname="Lucas Pardue"/></t>
		</li>
		<li>
		<t><contact fullname="Roberto Peon"/></t>
		</li>
		<li>
		<t><contact fullname="Julian Reschke"/></t>
		</li>
		<li>
		<t><contact fullname="Eric Rescorla"/></t>
		</li>
		<li>
		<t><contact fullname="Martin Seemann"/></t>
		</li>
		<li>
		<t><contact fullname="Ben Schwartz"/></t>
		</li>
		<li>
		<t><contact fullname="Ian Swett"/></t>
		</li>
		<li>
		<t><contact fullname="Willy Taureau"/></t>
		</li>
		<li>
		<t><contact fullname="Martin Thomson"/></t>
		</li>
		<li>
		<t><contact fullname="Dmitri Tikhonov"/></t>
		</li>
		<li>
		<t><contact fullname="Tatsuhiro Tsujikawa"/></t>
		</li>
		</ul>
		<t>A portion of <contact fullname='Mike Bishop'/>'s contribution was suppo
		rted by Microsoft during
		his employment there.</t>
	</section>	</section>
	</back>	</back>


	</rfc>	</rfc>

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