rfc8770.original.v2v3.xml   rfc8770.form.xml 
<?xml version='1.0' encoding='utf-8'?> <?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE rfc SYSTEM "rfc2629-xhtml.ent"> <!DOCTYPE rfc SYSTEM "rfc2629-xhtml.ent">
<rfc xmlns:xi="http://www.w3.org/2001/XInclude" submissionType="IETF" docName="d <rfc xmlns:xi="http://www.w3.org/2001/XInclude" submissionType="IETF"
raft-ietf-ospf-ospfv2-hbit-12" category="std" updates="6987" ipr="trust200902" o consensus="true" docName="draft-ietf-ospf-ospfv2-hbit-12" number="0000" cat
bsoletes="" xml:lang="en" sortRefs="true" symRefs="true" tocInclude="true" versi egory="std" updates="6987" ipr="trust200902" obsoletes="" xml:lang="en" sortRefs
on="3"> ="true" symRefs="true" tocInclude="true" version="3">
<!-- xml2rfc v2v3 conversion 2.39.0 --> <!-- xml2rfc v2v3 conversion 2.39.0 -->
<!-- Generated by id2xml 1.5.0 on 2020-02-12T16:52:09Z --> <!-- Generated by id2xml 1.5.0 on 2020-02-12T16:52:09Z -->
<front> <front>
<title>Host Router Support for OSPFv2</title> <title>Host Router Support for OSPFv2</title>
<seriesInfo name="Internet-Draft" value="draft-ietf-ospf-ospfv2-hbit-12"/> <seriesInfo name="RFC" value="0000"/>
<author fullname="Keyur Patel" initials="K." surname="Patel"> <author fullname="Keyur Patel" initials="K." surname="Patel">
<organization>Arrcus</organization> <organization>Arrcus</organization>
<address> <address>
<email>keyur@arrcus.com</email> <email>keyur@arrcus.com</email>
</address> </address>
</author> </author>
<author fullname="Padma Pillay-Esnault" initials="P." surname="Pillay-Esnaul t"> <author fullname="Padma Pillay-Esnault" initials="P." surname="Pillay-Esnaul t">
<organization>PPE Consulting</organization> <organization>PPE Consulting</organization>
<address> <address>
<email>padma.ietf@gmail.com</email> <email>padma.ietf@gmail.com</email>
</address> </address>
</author> </author>
<author fullname="Manish Bhardwaj" initials="M." surname="Bhardwaj"> <author fullname="Manish Bhardwaj" initials="M." surname="Bhardwaj">
<organization>Cisco Systems</organization> <organization>Cisco Systems</organization>
<address> <address>
<postal> <postal>
<street>170 W. Tasman Drive</street> <street>170 W. Tasman Drive</street>
<street>San Jose, CA 95134</street> <city>San Jose</city>
<street>USA</street> <region>CA</region>
<code>95134</code>
<country>United States of America</country>
</postal> </postal>
<email>manbhard@cisco.com</email> <email>manbhard@cisco.com</email>
</address> </address>
</author> </author>
<author fullname="Serpil Bayraktar" initials="S." surname="Bayraktar"> <author fullname="Serpil Bayraktar" initials="S." surname="Bayraktar">
<organization>Cisco Systems</organization> <organization>Cisco Systems</organization>
<address> <address>
<postal> <postal>
<street>170 W. Tasman Drive</street> <street>170 W. Tasman Drive</street>
<street>San Jose, CA 95134</street> <city>San Jose</city>
<street>USA</street> <region>CA</region>
<code>95134</code>
<country>United States of America</country>
</postal> </postal>
<email>serpil@cisco.com</email> <email>serpil@cisco.com</email>
</address> </address>
</author> </author>
<date day="18" month="December" year="2019"/> <date month="March" year="2020"/>
<workgroup>OSPF</workgroup> <workgroup>OSPF</workgroup>
<abstract> <abstract>
<t> <t>
The Open Shortest Path First Version 2 (OSPFv2) protocol does not The Open Shortest Path First Version 2 (OSPFv2) protocol does not
have a mechanism for a node to repel transit traffic if it is on the have a mechanism for a node to repel transit traffic if it is on the
shortest path. This document defines a bit (Host-bit) that enables a shortest path. This document defines a bit (Host-bit) that enables a
router to advertise that it is a non-transit router. It also router to advertise that it is a non-transit router. It also
describes the changes needed to support the H-bit in the domain. In describes the changes needed to support the H-bit in the domain. In
addition, this document updates RFC 6987 to advertise type-2 External addition, this document updates RFC 6987 to advertise type-2 External
and Not-So-Stubby-Area (NSSA) Link State Advertisements (LSAs) with a and Not-So-Stubby-Area (NSSA) Link State Advertisements (LSAs) with a
skipping to change at line 85 skipping to change at line 90
to participate in the topology.</li> to participate in the topology.</li>
<li>Overloaded routers could use such a capability to temporarily <li>Overloaded routers could use such a capability to temporarily
repel traffic until they stabilize.</li> repel traffic until they stabilize.</li>
<li>BGP Route reflectors known as virtual Route Reflectors (vRRs), <li>BGP Route reflectors known as virtual Route Reflectors (vRRs),
that are not in the forwarding path but are in central locations that are not in the forwarding path but are in central locations
such as data centers. Such Route Reflectors typically are used such as data centers. Such Route Reflectors typically are used
for route distribution and are not capable of forwarding transit for route distribution and are not capable of forwarding transit
traffic. However, they need to learn the OSPF topology to traffic. However, they need to learn the OSPF topology to
perform SPF computation for optimal routes and reachability perform SPF computation for optimal routes and reachability
resolution for its clients resolution for its clients
<xref target="I-D.ietf-idr-bgp-optimal-route-reflection" format="default" />.</li> <xref target="BGP-ORR" format="default"/>.</li>
</ol> </ol>
<t> <t>
This document describes the Host-bit (H-bit) functionality that This document describes the Host-bit (H-bit) functionality that
prevents other OSPFv2 routers from using the host router by excluding prevents other OSPFv2 routers from using the host router by excluding
it in path calculations for transit traffic in OSPFv2 routing it in path calculations for transit traffic in OSPFv2 routing
domains. If the H-bit is set then the calculation of the shortest- domains. If the H-bit is set then the calculation of the shortest-
path tree for an area, as described in section 16.1 of <xref target="RFC2328" format="default"/>, is path tree for an area, as described in <xref target="RFC2328" sectionFormat=" of" section="16.1"/>, is
modified by including a check to verify that transit vertices DO NOT modified by including a check to verify that transit vertices DO NOT
have the H-bit set (see <xref target="sect-4" format="default"/>). Furthermo re, in order to repel have the H-bit set (see <xref target="sect-4" format="default"/>). Furthermo re, in order to repel
traffic effectively, <xref target="RFC6987" format="default"/> is updated so that type-2 External and traffic effectively, <xref target="RFC6987" format="default"/> is updated so that type-2 External and
NSSA LSAs are advertised with a high cost (see <xref target="sect-6" format=" default"/>). Open NSSA LSAs are advertised with a high cost (see <xref target="sect-6" format=" default"/>). Open
Shortest Path First Version 3 defines an option bit for router-LSAs Shortest Path First Version 3 defines an option bit for router-LSAs
known as the R-bit in <xref target="RFC5340" format="default"/> to support a similar functionality.</t> known as the R-bit in <xref target="RFC5340" format="default"/> to support a similar functionality.</t>
</section> </section>
<section anchor="sect-2" numbered="true" toc="default"> <section anchor="sect-2" numbered="true" toc="default">
<name>Requirements Language</name> <name>Requirements Language</name>
<t> <t>The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>",
"OPTIONAL" in this document are to be interpreted as described in BCP "<bcp14>SHOULD NOT</bcp14>",
14 <xref target="RFC2119" format="default"/> <xref target="RFC8174" format="d "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
efault"/> when, and only when, they appear in all "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document
capitals, as shown here.</t> are to be interpreted as described in BCP&nbsp;14
<xref target="RFC2119"/> <xref target="RFC8174"/> when, and only
when, they appear in all capitals, as shown here.</t>
</section> </section>
<section anchor="sect-3" numbered="true" toc="default"> <section anchor="sect-3" numbered="true" toc="default">
<name>Host-bit Support</name> <name>Host-bit Support</name>
<t> <t>
This document defines a new router-LSA bit known as the Host Bit or This document defines a new router-LSA bit known as the Host Bit or
the H-bit. An OSPFv2 router advertising a router-LSA with the H-bit the H-bit. An OSPFv2 router advertising a router-LSA with the H-bit
set indicates that it MUST NOT be used as a transit router (see set indicates that it <bcp14>MUST NOT</bcp14> be used as a transit router (se e
<xref target="sect-4" format="default"/>) by other OSPFv2 routers in the area supporting the <xref target="sect-4" format="default"/>) by other OSPFv2 routers in the area supporting the
functionality.</t> functionality.</t>
<t> <t>
If the H-bit is not set then backwards compatibility is achieved as If the H-bit is not set then backwards compatibility is achieved as
the behavior will be the same as in <xref target="RFC2328" format="default"/> .</t> the behavior will be the same as in <xref target="RFC2328" format="default"/> .</t>
<figure anchor="ure-ospf-router-lsa"> <figure anchor="ure-ospf-router-lsa">
<name>OSPF Router-LSA</name> <name>OSPF Router-LSA</name>
<artwork name="" type="" align="left" alt=""><![CDATA[ <artwork name="" type="" align="left" alt=""><![CDATA[
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
skipping to change at line 152 skipping to change at line 160
| Type | # TOS | metric | | Type | # TOS | metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TOS | 0 | TOS metric | | TOS | 0 | TOS metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID | | Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data | | Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |]]></artwor
]]></artwork> k>
</figure> </figure>
<dl newline="true" spacing="normal" indent="-1"> <t>Bit H is the high-order bit of the OSPF flags as shown below.</t>
<dt>Bit H is the high-order bit of the OSPF flags as shown below.</dt>
<dd/>
</dl>
<figure anchor="ure-ospf-router-lsa-option-bits"> <figure anchor="ure-ospf-router-lsa-option-bits">
<name>OSPF Router-LSA Option bits</name> <name>OSPF Router-LSA Option bits</name>
<artwork name="" type="" align="left" alt=""><![CDATA[ <artwork name="" type="" align="left" alt=""><![CDATA[
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|H|0|0|N|W|V|E|B| |H|0|0|N|W|V|E|B|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+]]></artwork>
]]></artwork>
</figure> </figure>
<t> <t>
When the H-bit is set, the OSPFv2 router is a Host (non-transit) When the H-bit is set, the OSPFv2 router is a Host (non-transit)
router and is incapable of forwarding transit traffic. In this mode, router and is incapable of forwarding transit traffic. In this mode,
the other OSPFv2 routers in the area MUST NOT use the host router for the other OSPFv2 routers in the area <bcp14>MUST NOT</bcp14> use the host rou ter for
transit traffic, but may send traffic to its local destinations.</t> transit traffic, but may send traffic to its local destinations.</t>
<t> <t>
An OSPFv2 router originating a router-LSA with the H-bit set MUST An OSPFv2 router originating a router-LSA with the H-bit set <bcp14>MUST</bcp 14>
advertise all its non-stub links with a link cost of MaxLinkMetric advertise all its non-stub links with a link cost of MaxLinkMetric
<xref target="RFC6987" format="default"/>.</t> <xref target="RFC6987" format="default"/>.</t>
<t> <t>
When the H-bit is set, an Area Border Router (ABR) MUST advertise the When the H-bit is set, an Area Border Router (ABR) <bcp14>MUST</bcp14> advert ise the
same H-bit setting in its self-originated router-LSAs for all same H-bit setting in its self-originated router-LSAs for all
attached areas. The consistency of the setting will prevent inter- attached areas. The consistency of the setting will prevent inter-
area traffic transiting through the router by suppressing area traffic transiting through the router by suppressing
advertisement of prefixes from other routers in the area in its advertisement of prefixes from other routers in the area in its
summary LSAs. Only IPv4 prefixes associated with its local summary LSAs. Only IPv4 prefixes associated with its local
interfaces MUST be advertised in summary-LSAs to provide reachability interfaces <bcp14>MUST</bcp14> be advertised in summary-LSAs to provide reach ability
to end hosts attached to a router with the H-bit set.</t> to end hosts attached to a router with the H-bit set.</t>
<t> <t>
When the H-bit is set the host router cannot act as an AS Boundary When the H-bit is set the host router cannot act as an AS Boundary
Router (ASBR). Indeed, ASBR are transit routers to prefixes that are Router (ASBR). Indeed, ASBR are transit routers to prefixes that are
typically imported through redistribution of prefixes from other typically imported through redistribution of prefixes from other
routing protocols. Therefore, non-local IPv4 prefixes, e.g., those routing protocols. Therefore, non-local IPv4 prefixes, e.g., those
imported from other routing protocols, SHOULD NOT be advertised in imported from other routing protocols, <bcp14>SHOULD NOT</bcp14> be advertise d in
AS-external-LSAs if the H-bit is set. Some use cases, such as an AS-external-LSAs if the H-bit is set. Some use cases, such as an
overloaded router or a router being gracefully isolated, may benefit overloaded router or a router being gracefully isolated, may benefit
from continued advertisement of non-local prefixes. In these cases, from continued advertisement of non-local prefixes. In these cases,
the type 2-metric in AS-external-LSAs MUST be set to LSInfinity to the type 2-metric in AS-external-LSAs <bcp14>MUST</bcp14> be set to LSInfinit
repel traffic.(see Section 6 of this document).</t> y to
repel traffic.(see <xref target="sect-6"/> of this document).</t>
</section> </section>
<section anchor="sect-4" numbered="true" toc="default"> <section anchor="sect-4" numbered="true" toc="default">
<name>SPF Modifications</name> <name>SPF Modifications</name>
<t> <t>
The SPF calculation described in section 16.1 <xref target="RFC2328" format=" The SPF calculation described in <xref target="RFC2328" sectionFormat="of"
default"/> will be section="16.1"/> will be
modified to ensure that the routers originating router-LSAs with the modified to ensure that the routers originating router-LSAs with the
H-bit set will not be used for transit traffic. The Step 2 is H-bit set will not be used for transit traffic. The Step 2 is
modified to include a check on H-bit as shown below. (Please note modified to include a check on H-bit as shown below. (Please note
all the sub-procedures of Step 2 remain unchanged and not included in all the sub-procedures of Step 2 remain unchanged and not included in
the excerpt below.)</t> the excerpt below.)</t>
<ul empty="true" spacing="normal"> <ul empty="true" spacing="normal">
<li> <li>
<dl newline="true" spacing="normal" indent="3"> <dl newline="false" spacing="normal" indent="4">
<dt>2) Call the vertex just added to the</dt> <dt>2)</dt><dd>Call the vertex just added to the
<dd>
tree vertex V. Examine the LSA tree vertex V. Examine the LSA
associated with vertex V. This is associated with vertex V. This is
a lookup in the Area A's link state a lookup in the Area A's link state
database based on the Vertex ID. If database based on the Vertex ID. If
this is a router-LSA, and the H-bit this is a router-LSA, and the H-bit
of the router-LSA is set, and of the router-LSA is set, and
vertex V is not the root, then the vertex V is not the root, then the
router should not be used for transit router should not be used for transit
and step (3) should be executed and step (3) should be executed
immediately. If this is a router-LSA, immediately. If this is a router-LSA,
and bit V of the router-LSA (see and bit V of the router-LSA (see
Section A.4.2) is set, set Area A's Section A.4.2) is set, set Area A's
TransitCapability to TRUE. In any case, TransitCapability to TRUE. In any case,
each link described by the LSA gives each link described by the LSA gives
the cost to an adjacent vertex. For the cost to an adjacent vertex. For
each described link, (say it joins each described link, (say it joins
vertex V to vertex W): vertex V to vertex W):</dd>
</dd>
</dl> </dl>
</li> </li>
</ul> </ul>
</section> </section>
<section anchor="sect-5" numbered="true" toc="default"> <section anchor="sect-5" numbered="true" toc="default">
<name>Auto Discovery and Backward Compatibility</name> <name>Auto Discovery and Backward Compatibility</name>
<t> <t>
To reduce the possibility of any routing loops due to partial To reduce the possibility of any routing loops due to partial
deployment, this document defines an OSPF Router Information (RI) LSA deployment, this document defines an OSPF Router Information (RI) LSA
<xref target="RFC7770" format="default"/> capability. The RI LSA MUST be are <xref target="RFC7770" format="default"/> capability. The RI LSA <bcp14>MUST
a-scoped. Bit:</t> </bcp14> be area-scoped. Bit:</t>
<ul empty="true" spacing="normal">
<li> <table anchor="tab-1">
<dl newline="false" spacing="normal" indent="-1"> <name>OSPF Router Information LSA Capabilities</name>
<dt>Bit</dt> <thead>
<dd> <tr>
<t> <th>Bit</th>
Capabilities <th align="center">Capabilities</th>
</t> </tr>
<ul empty="true" spacing="normal"> </thead>
<li> 7 Host Router Support capability</li> <tbody>
</ul> <tr>
</dd> <td align="center">7</td>
</dl> <td>Host Router Support capability</td>
</li> </tr>
</ul> </tbody>
<dl newline="false" spacing="normal" indent="7"> </table>
<dt/>
<dd>
Table 1: OSPF Router Information LSA Capabilities</dd>
</dl>
<t> <t>
Auto Discovery via announcement of the Host Router Support Capability Auto Discovery via announcement of the Host Router Support Capability
ensures that the H-bit functionality and its associated SPF changes ensures that the H-bit functionality and its associated SPF changes
MUST only take effect if all the routers in a given OSPF area support <bcp14>MUST</bcp14> only take effect if all the routers in a given OSPF area support
this functionality.</t> this functionality.</t>
<t> <t>
In normal operation, it is possible that the RI LSA will fail to In normal operation, it is possible that the RI LSA will fail to
reach all routers in an area in a timely manner. For example, if a reach all routers in an area in a timely manner. For example, if a
new router without H-bit support joins an area that previously had new router without H-bit support joins an area that previously had
only H-bit capable routers with H-bit set then it may take some time only H-bit capable routers with H-bit set then it may take some time
for the RI to propagate to all routers. While it is propagating, the for the RI to propagate to all routers. While it is propagating, the
routers in the area will gradually detect the presence of a router routers in the area will gradually detect the presence of a router
not supporting the capability and revert back to normal SPF not supporting the capability and revert back to normal SPF
calculation. During the propagation time, the area as a whole is calculation. During the propagation time, the area as a whole is
unsure of the status of the new router, and that can cause temporary unsure of the status of the new router, and that can cause temporary
transient loops.</t> transient loops.</t>
<t> <t>
The following recommendations will mitigate transient routing loops:</t> The following recommendations will mitigate transient routing loops:</t>
<ul spacing="normal"> <ul spacing="normal">
<li>Implementations are RECOMMENDED to provide a configuration <li>Implementations are <bcp14>RECOMMENDED</bcp14> to provide a configur ation
parameter to manually override enforcement of the H-bit parameter to manually override enforcement of the H-bit
functionality in partial deployments where the topology guarantees functionality in partial deployments where the topology guarantees
that OSPFv2 routers not supporting the H-bit do not compute routes that OSPFv2 routers not supporting the H-bit do not compute routes
resulting in routing loops.</li> resulting in routing loops.</li>
<li>All routers with the H-bit set MUST advertise all of the router's <li>All routers with the H-bit set <bcp14>MUST</bcp14> advertise all of the router's
non-stub links with a metric equal to MaxLinkMetric <xref target="RFC6987" format="default"/> in non-stub links with a metric equal to MaxLinkMetric <xref target="RFC6987" format="default"/> in
its LSAs in order to avoid OSPFv2 (unless last resort) routers not its LSAs in order to avoid OSPFv2 (unless last resort) routers not
supporting the H-bit from attempting to use it for transit supporting the H-bit from attempting to use it for transit
traffic.</li> traffic.</li>
<li>All routers supporting the H-Bit MUST check the RI LSAs of all <li>All routers supporting the H-Bit <bcp14>MUST</bcp14> check the RI LS As of all
nodes in the area to verify that all nodes support the H-Bit nodes in the area to verify that all nodes support the H-Bit
before actively using the H-Bit feature. If any router does not before actively using the H-Bit feature. If any router does not
advertise the Host Router Support capability then the SPF advertise the Host Router Support capability then the SPF
Modifications (<xref target="sect-4" format="default"/>) MUST NOT be used in the area.</li> Modifications (<xref target="sect-4" format="default"/>) <bcp14>MUST NOT</ bcp14> be used in the area.</li>
</ul> </ul>
</section> </section>
<section anchor="sect-6" numbered="true" toc="default"> <section anchor="sect-6" numbered="true" toc="default">
<name>OSPF AS-External-LSAs/NSSA LSAs with Type 2 Metrics</name> <name>OSPF AS-External-LSAs/NSSA LSAs with Type 2 Metrics</name>
<t> <t>
When calculating the path to a prefix in an OSPF AS-External-LSA or When calculating the path to a prefix in an OSPF AS-External-LSA or
NSSA-LSA <xref target="RFC3101" format="default"/> with a Type-2 metric, the advertised Type-2 metric NSSA-LSA <xref target="RFC3101" format="default"/> with a Type-2 metric, the advertised Type-2 metric
is taken as more significant than the OSPF intra-area or inter-area is taken as more significant than the OSPF intra-area or inter-area
path. Hence, advertising the links with MaxLinkMetric as specified path. Hence, advertising the links with MaxLinkMetric as specified
in <xref target="RFC6987" format="default"/> does not discourage transit traf fic when calculating AS in <xref target="RFC6987" format="default"/> does not discourage transit traf fic when calculating AS
external or NSSA routes with Type-2 metrics.</t> external or NSSA routes with Type-2 metrics.</t>
<t> <t>
Consequently, <xref target="RFC6987" format="default"/> is updated so that th e Type-2 metric in any Consequently, <xref target="RFC6987" format="default"/> is updated so that th e Type-2 metric in any
self-originated AS-External-LSAs or NSSA-LSAs is advertised as self-originated AS-External-LSAs or NSSA-LSAs is advertised as
LSInfinity-1 <xref target="RFC2328" format="default"/>. If the H-bit is set, then the Type-2 metric LSInfinity-1 <xref target="RFC2328" format="default"/>. If the H-bit is set, then the Type-2 metric
MUST be set to LSInfinity.</t> <bcp14>MUST</bcp14> be set to LSInfinity.</t>
</section> </section>
<section anchor="sect-7" numbered="true" toc="default"> <section anchor="sect-7" numbered="true" toc="default">
<name>IANA Considerations</name> <name>IANA Considerations</name>
<t> <t>
This document requests the IANA to assign the 0x80 value to the Host- This document requests the IANA to assign the 0x80 value to the Host-
Bit (H-bit)in the OSPFv2 Router Properties Registry</t> Bit (H-bit)in the OSPFv2 Router Properties Registry</t>
<ul empty="true" spacing="normal">
<li> <table anchor="tab-2">
<dl newline="false" spacing="normal" indent="-1"> <name>H-Bit</name>
<dt>Value</dt> <thead>
<dd> <tr>
<t> <th>Value</th>
Description Reference <th>Description</th>
</t> <th>Reference</th>
<t/> </tr>
</dd> </thead>
<dt>0x80</dt> <tbody>
<dd> <tr>
<t> <td>0x80</td>
Host (H-bit) This Document <td>Host (H-bit)</td>
</t> <td>This Document</td>
<t/> </tr>
</dd> </tbody>
</dl> </table>
</li>
</ul>
<t> <t>
This document requests the IANA to assign the Bit Number value of 7 This document requests the IANA to assign the Bit Number value of 7
to the Host Router Support Capability in the OSPF Router to the Host Router Support Capability in the OSPF Router
Informational Capability Bits Registry.</t> Informational Capability Bits Registry.</t>
<ul empty="true" spacing="normal">
<li> <table anchor="tab-3">
<dl newline="false" spacing="normal" indent="3"> <name>OSPF Host Router Capability Bit</name>
<dt>Bit Number</dt> <thead>
<dd> <tr>
<t> <th>Bit Number</th>
Capability Name Reference <th>Capability Name</th>
</t> <th>Reference</th>
<t> </tr>
7 OSPF Host Router This Document </thead>
</t> <tbody>
</dd> <tr>
</dl> <td align="center">7</td>
</li> <td>OSPF Host Router</td>
</ul> <td>This Document</td>
</tr>
</tbody>
</table>
</section> </section>
<section anchor="sect-8" numbered="true" toc="default"> <section anchor="sect-8" numbered="true" toc="default">
<name>Security Considerations</name> <name>Security Considerations</name>
<t> <t>
This document introduces the H-bit which is a capability that This document introduces the H-bit which is a capability that
restricts the use of a router for transit, while only its local restricts the use of a router for transit, while only its local
destinations are reachable. This is a subset of the operations of a destinations are reachable. This is a subset of the operations of a
normal router and therefore should not introduce new security normal router and therefore should not introduce new security
considerations beyond those already known in OSPFv2 <xref target="RFC2328" fo rmat="default"/>. The considerations beyond those already known in OSPFv2 <xref target="RFC2328" fo rmat="default"/>. The
feature introduces the advertising of a host router capability feature introduces the advertising of a host router capability
skipping to change at line 397 skipping to change at line 399
effectively partition the network. This case is indistinguishable effectively partition the network. This case is indistinguishable
from the normal case where the operator may consciously decide to from the normal case where the operator may consciously decide to
set the H-bit to perform maintenance on a router that is on the set the H-bit to perform maintenance on a router that is on the
only transit path. The OSPF protocol will continue to function only transit path. The OSPF protocol will continue to function
within the partitioned domains.</li> within the partitioned domains.</li>
</ul> </ul>
</section> </section>
<section anchor="sect-9" numbered="true" toc="default"> <section anchor="sect-9" numbered="true" toc="default">
<name>Acknowledgements</name> <name>Acknowledgements</name>
<t> <t>
The authors would like to acknowledge Hasmit Grover for discovery of The authors would like to acknowledge <contact fullname="Hasmit Grover"/> for
the limitation in <xref target="RFC6987" format="default"/>, Acee Lindem, Abh discovery of
ay Roy, David Ward, the limitation in <xref target="RFC6987" format="default"/>, <contact
Burjiz Pithawala, and Michael Barnes for their comments.</t> fullname="Acee Lindem"/>, <contact fullname="Abhay Roy"/>, <contact
fullname="David Ward"/>, <contact fullname="Burjiz Pithawala"/>, and <contact
fullname="Michael Barnes"/> for their comments.</t>
</section> </section>
</middle> </middle>
<back> <back>
<references> <references>
<name>References</name> <name>References</name>
<references> <references>
<name>Normative References</name> <name>Normative References</name>
<reference anchor="RFC2119" target="https://www.rfc-editor.org/info/rfc2 <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.
119" xml:base="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.21 xml"/>
19.xml"> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2328.
<front> xml"/>
<title>Key words for use in RFCs to Indicate Requirement Levels</tit <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6987.
le> xml"/>
<seriesInfo name="DOI" value="10.17487/RFC2119"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7770.
<seriesInfo name="RFC" value="2119"/> xml"/>
<seriesInfo name="BCP" value="14"/> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.
<author initials="S." surname="Bradner" fullname="S. Bradner"> xml"/>
<organization/>
</author>
<date year="1997" month="March"/>
<abstract>
<t>In many standards track documents several words are used to sig
nify the requirements in the specification. These words are often capitalized.
This document defines these words as they should be interpreted in IETF document
s. This document specifies an Internet Best Current Practices for the Internet
Community, and requests discussion and suggestions for improvements.</t>
</abstract>
</front>
</reference>
<reference anchor="RFC2328" target="https://www.rfc-editor.org/info/rfc2
328" xml:base="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.23
28.xml">
<front>
<title>OSPF Version 2</title>
<seriesInfo name="DOI" value="10.17487/RFC2328"/>
<seriesInfo name="RFC" value="2328"/>
<seriesInfo name="STD" value="54"/>
<author initials="J." surname="Moy" fullname="J. Moy">
<organization/>
</author>
<date year="1998" month="April"/>
<abstract>
<t>This memo documents version 2 of the OSPF protocol. OSPF is a
link- state routing protocol. [STANDARDS-TRACK]</t>
</abstract>
</front>
</reference>
<reference anchor="RFC6987" target="https://www.rfc-editor.org/info/rfc6
987" xml:base="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.69
87.xml">
<front>
<title>OSPF Stub Router Advertisement</title>
<seriesInfo name="DOI" value="10.17487/RFC6987"/>
<seriesInfo name="RFC" value="6987"/>
<author initials="A." surname="Retana" fullname="A. Retana">
<organization/>
</author>
<author initials="L." surname="Nguyen" fullname="L. Nguyen">
<organization/>
</author>
<author initials="A." surname="Zinin" fullname="A. Zinin">
<organization/>
</author>
<author initials="R." surname="White" fullname="R. White">
<organization/>
</author>
<author initials="D." surname="McPherson" fullname="D. McPherson">
<organization/>
</author>
<date year="2013" month="September"/>
<abstract>
<t>This document describes a backward-compatible technique that ma
y be used by OSPF (Open Shortest Path First) implementations to advertise a rout
er's unavailability to forward transit traffic or to lower the preference level
for the paths through such a router.</t>
<t>This document obsoletes RFC 3137.</t>
</abstract>
</front>
</reference>
<reference anchor="RFC7770" target="https://www.rfc-editor.org/info/rfc7
770" xml:base="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.77
70.xml">
<front>
<title>Extensions to OSPF for Advertising Optional Router Capabiliti
es</title>
<seriesInfo name="DOI" value="10.17487/RFC7770"/>
<seriesInfo name="RFC" value="7770"/>
<author initials="A." surname="Lindem" fullname="A. Lindem" role="ed
itor">
<organization/>
</author>
<author initials="N." surname="Shen" fullname="N. Shen">
<organization/>
</author>
<author initials="JP." surname="Vasseur" fullname="JP. Vasseur">
<organization/>
</author>
<author initials="R." surname="Aggarwal" fullname="R. Aggarwal">
<organization/>
</author>
<author initials="S." surname="Shaffer" fullname="S. Shaffer">
<organization/>
</author>
<date year="2016" month="February"/>
<abstract>
<t>It is useful for routers in an OSPFv2 or OSPFv3 routing domain
to know the capabilities of their neighbors and other routers in the routing dom
ain. This document proposes extensions to OSPFv2 and OSPFv3 for advertising opt
ional router capabilities. The Router Information (RI) Link State Advertisement
(LSA) is defined for this purpose. In OSPFv2, the RI LSA will be implemented w
ith an Opaque LSA type ID. In OSPFv3, the RI LSA will be implemented with a uni
que LSA type function code. In both protocols, the RI LSA can be advertised at
any of the defined flooding scopes (link, area, or autonomous system (AS)). Thi
s document obsoletes RFC 4970 by providing a revised specification that includes
support for advertisement of multiple instances of the RI LSA and a TLV for fun
ctional capabilities.</t>
</abstract>
</front>
</reference>
<reference anchor="RFC8174" target="https://www.rfc-editor.org/info/rfc8
174" xml:base="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.81
74.xml">
<front>
<title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</ti
tle>
<seriesInfo name="DOI" value="10.17487/RFC8174"/>
<seriesInfo name="RFC" value="8174"/>
<seriesInfo name="BCP" value="14"/>
<author initials="B." surname="Leiba" fullname="B. Leiba">
<organization/>
</author>
<date year="2017" month="May"/>
<abstract>
<t>RFC 2119 specifies common key words that may be used in protoco
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>
</reference>
</references> </references>
<references> <references>
<name>Informative References</name> <name>Informative References</name>
<reference anchor="I-D.ietf-idr-bgp-optimal-route-reflection" xml:base="
https://xml2rfc.tools.ietf.org/public/rfc/bibxml3/reference.I-D.draft-ietf-idr-b <!-- draft-ietf-idr-bgp-optimal-route-reflection (I-D Exists) -->
gp-optimal-route-reflection-19.xml" target="http://www.ietf.org/internet-drafts/ <!-- Repository file missing "editor" entry, so have to do "long way" -->
draft-ietf-idr-bgp-optimal-route-reflection-19.txt"> <reference anchor="BGP-ORR"
target="https://tools.ietf.org/html/draft-ietf-idr-bgp-optimal-route-reflection-
20">
<front> <front>
<title>BGP Optimal Route Reflection (BGP-ORR)</title> <title>BGP Optimal Route Reflection (BGP-ORR)</title>
<seriesInfo name="Internet-Draft" value="draft-ietf-idr-bgp-optimal- <seriesInfo name="Work in Progress, Internet-Draft," value="draft-ie
route-reflection-19"/> tf-idr-bgp-optimal-route-reflection-20"/>
<author initials="R" surname="Raszuk" fullname="Robert Raszuk"> <author initials="R" surname="Raszuk" fullname="Robert Raszuk" role=
"editor">
<organization/> <organization/>
</author> </author>
<author initials="C" surname="Cassar" fullname="Christian Cassar"> <author initials="C" surname="Cassar" fullname="Christian Cassar">
<organization/> <organization/>
</author> </author>
<author initials="E" surname="Aman" fullname="Erik Aman"> <author initials="E" surname="Aman" fullname="Erik Aman">
<organization/> <organization/>
</author> </author>
<author initials="B" surname="Decraene" fullname="Bruno Decraene"> <author initials="B" surname="Decraene" fullname="Bruno Decraene">
<organization/> <organization/>
</author> </author>
<author initials="K" surname="Wang" fullname="Kevin Wang"> <author initials="K" surname="Wang" fullname="Kevin Wang">
<organization/> <organization/>
</author> </author>
<date month="July" day="8" year="2019"/> <date month="January" day="8" year="2020"/>
<abstract>
<t>This document proposes a solution for BGP route reflectors to a
llow them to choose the best path for their clients that the clients themselves
would have chosen under the same conditions, without requiring further state or
any new features to be placed on the clients. This facilitates, for example, be
st exit point policy (hot potato routing). This solution is primarily applicabl
e in deployments using centralized route reflectors. The solution relies upon a
ll route reflectors learning all paths which are eligible for consideration. Be
st path selection is performed in each route reflector based on a configured vir
tual location in the IGP. The location can be the same for all clients or diffe
rent per peer/update group or per peer. Best path selection can also be perform
ed based on user configured policies in each route reflector.</t>
</abstract>
</front>
</reference>
<reference anchor="RFC3101" target="https://www.rfc-editor.org/info/rfc3
101" xml:base="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.31
01.xml">
<front>
<title>The OSPF Not-So-Stubby Area (NSSA) Option</title>
<seriesInfo name="DOI" value="10.17487/RFC3101"/>
<seriesInfo name="RFC" value="3101"/>
<author initials="P." surname="Murphy" fullname="P. Murphy">
<organization/>
</author>
<date year="2003" month="January"/>
<abstract>
<t>This memo documents an optional type of Open Shortest Path Firs
t (OSPF) area that is somewhat humorously referred to as a "not-so-stubby" area
(or NSSA). NSSAs are similar to the existing OSPF stub area configuration optio
n but have the additional capability of importing AS external routes in a limite
d fashion. The OSPF NSSA Option was originally defined in RFC 1587. The functio
nal differences between this memo and RFC 1587 are explained in Appendix F. All
differences, while expanding capability, are backward-compatible in nature. Imp
lementations of this memo and of RFC 1587 will interoperate. [STANDARDS-TRACK]</
t>
</abstract>
</front>
</reference>
<reference anchor="RFC5340" target="https://www.rfc-editor.org/info/rfc5
340" xml:base="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.53
40.xml">
<front>
<title>OSPF for IPv6</title>
<seriesInfo name="DOI" value="10.17487/RFC5340"/>
<seriesInfo name="RFC" value="5340"/>
<author initials="R." surname="Coltun" fullname="R. Coltun">
<organization/>
</author>
<author initials="D." surname="Ferguson" fullname="D. Ferguson">
<organization/>
</author>
<author initials="J." surname="Moy" fullname="J. Moy">
<organization/>
</author>
<author initials="A." surname="Lindem" fullname="A. Lindem">
<organization/>
</author>
<date year="2008" month="July"/>
<abstract>
<t>This document describes the modifications to OSPF to support ve
rsion 6 of the Internet Protocol (IPv6). The fundamental mechanisms of OSPF (fl
ooding, Designated Router (DR) election, area support, Short Path First (SPF) ca
lculations, etc.) remain unchanged. However, some changes have been necessary,
either due to changes in protocol semantics between IPv4 and IPv6, or simply to
handle the increased address size of IPv6. These modifications will necessitate
incrementing the protocol version from version 2 to version 3. OSPF for IPv6 i
s also referred to as OSPF version 3 (OSPFv3).</t>
<t>Changes between OSPF for IPv4, OSPF Version 2, and OSPF for IPv
6 as described herein include the following. Addressing semantics have been rem
oved from OSPF packets and the basic Link State Advertisements (LSAs). New LSAs
have been created to carry IPv6 addresses and prefixes. OSPF now runs on a per
-link basis rather than on a per-IP-subnet basis. Flooding scope for LSAs has b
een generalized. Authentication has been removed from the OSPF protocol and ins
tead relies on IPv6's Authentication Header and Encapsulating Security Payload (
ESP).</t>
<t>Even with larger IPv6 addresses, most packets in OSPF for IPv6
are almost as compact as those in OSPF for IPv4. Most fields and packet- size l
imitations present in OSPF for IPv4 have been relaxed. In addition, option hand
ling has been made more flexible.</t>
<t>All of OSPF for IPv4's optional capabilities, including demand
circuit support and Not-So-Stubby Areas (NSSAs), are also supported in OSPF for
IPv6. [STANDARDS-TRACK]</t>
</abstract>
</front> </front>
</reference> </reference>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3101.
xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5340.
xml"/>
</references> </references>
</references> </references>
</back> </back>
</rfc> </rfc>
 End of changes. 36 change blocks. 
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