wdiff ../rfcs-done/rfc8483.txt test8483.v2v3fixed.txt

Independent Submission L. Song, Ed.
Request for Comments: 8483 D. Liu
Category: Informational Beijing Internet Institute
ISSN: 2070-1721 P. Vixie
TISF
A. Kato
Keio/WIDE
S. Kerr
October 2018

Yeti DNS Testbed

Abstract

Yeti DNS is an experimental, non-production root server testbed that
provides an environment where technical and operational experiments
can safely be performed without risk to production root server
infrastructure. This document aims solely to document the technical
and operational experience of deploying a system that is similar to
but different from the Root Server system (on which the Internet's
Domain Name System is designed and built).

Status of This Memo

This document is not an Internet Standards Track specification; it is
published for informational purposes.

This is a contribution to the RFC Series, independently of any other
RFC stream. The RFC Editor has chosen to publish this document at
its discretion and makes no statement about its value for
implementation or deployment. Documents approved for publication by
the RFC Editor are not candidates for any level of Internet Standard;
see Section 2 of RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8483.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info)
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Notation and Conventions . . . . . . . . . . . . 5
3. Areas of Study . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Implementation of a Testbed like the Root Server
System . 5
3.2. Yeti-Root Zone Distribution . . . . . . . . . . . . . . . 5
3.3. Yeti-Root Server Names and Addressing . . . . . . . . . . 5
3.4. IPv6-Only Yeti-Root Servers . . . . . . . . . . . . . . . 6
3.5. DNSSEC in the Yeti-Root Zone . . . . . . . . . . . . . . 6
4. Yeti DNS Testbed Infrastructure . . . . . . . . . . . . . . . 7
4.1. Root Zone Retrieval . . . . . . . . . . . . . . . . . . . 8
4.2. Transformation of Root Zone to Yeti-Root Zone . . . . . . 9
4.2.1. ZSK and KSK Key Sets Shared between DMs . . . . . . . 10
4.2.2. Unique ZSK per DM; No Shared KSK . . . . . . . . . . 10
4.2.3. Preserving Root Zone NSEC Chain and ZSK
RRSIGs . . . 11
4.3. Yeti-Root Zone Distribution . . . . . . . . . . . . . . . 12
4.4. Synchronization of Service Metadata . . . . . . . . . . . 12
4.5. Yeti-Root Server Naming Scheme . . . . . . . . . . . . . 13
4.6. Yeti-Root Servers . . . . . . . . . . . . . . . . . . . . 14
4.7. Experimental Traffic . . . . . . . . . . . . . . . . . . 16
4.8. Traffic Capture and Analysis . . . . . . . . . . . . . . 16
5. Operational Experience with the Yeti DNS Testbed . . . . . . 17
5.1. Viability of IPv6-Only Operation . . . . . . . . . . . . 17
5.1.1. IPv6 Fragmentation . . . . . . . . . . . . . . . . . 18
5.1.2. Serving IPv4-Only End-Users . . . . . . . . . . . . . 19
5.2. Zone Distribution . . . . . . . . . . . . . . . . . . . . 19
5.2.1. Zone Transfers . . . . . . . . . . . . . . . . . . . 19
5.2.2. Delays in Yeti-Root Zone Distribution . . . . . . . . 20
5.2.3. Mixed RRSIGs from Different DM ZSKs . . . . . . . . . 21
5.3. DNSSEC KSK Rollover . . . . . . . . . . . . . . . . . . . 22
5.3.1. Failure-Case KSK Rollover . . . . . . . . . . . . . . 22
5.3.2. KSK Rollover vs. BIND9 Views . . . . . . . . . . . . 22
5.3.3. Large Responses during KSK Rollover . . . . . . . . . 23
5.4. Capture of Large DNS Response . . . . . . . . . . . . . . 24
5.5. Automated Maintenance of the Hints File . . . . . . . . . 24
5.6. Root Label Compression in Knot DNS Server . . . . . . . . 25
6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 26
7. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
9.1. Normative References . . . . . . . . . . . . . . . . . . 29
9.2. Informative References . . . . . . . . . . . . . . . . . 29
Appendix A. Yeti-Root Hints File . . . . . . . . . . . . . . . . 33 IANA Considerations
9. References
9.1. Normative References
9.2. Informative References
Appendix A. Yeti-Root Hints File
Appendix B. Yeti-Root Server Priming Response . . . . . . . . . 34
Appendix C. Active IPv6 Prefixes in Yeti DNS Testbed . . . . . . 36
Appendix D. Tools Developed for Yeti DNS Testbed . . . . . . . . 36
Appendix E. Controversy . . . . . . . . . . . . . . . . . . . . 37
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39

1. Introduction

The Domain Name System (DNS), as originally specified in [RFC1034]
and [RFC1035], has proved to be an enduring and important platform
upon which almost every end-user of the Internet relies. Despite its
longevity, extensions to the protocol, new implementations, and
refinements to DNS operations continue to emerge both inside and
outside the IETF.

The Root Server system in particular has seen technical innovation
and development, for example, in the form of wide-scale anycast
deployment, the mitigation of unwanted traffic on a global scale, the
widespread deployment of Response Rate Limiting [RRL], the
introduction of IPv6 transport, the deployment of DNSSEC, changes in
DNSSEC key sizes, and preparations to roll the root zone's Key
Signing Key (KSK) and corresponding trust anchor. These projects
created tremendous qualitative operational change and required
impressive caution and study prior to implementation. They took
place in parallel with the quantitative expansion or delegations for
new TLDs (see <https://newgtlds.icann.org/>). https://newgtlds.icann.org/).

Aspects of the operational structure of the Root Server system have
been described in such documents as [TNO2009], [ISC-TN-2003-1],
[RSSAC001], and [RFC7720]. Such references, considered together,
provide sufficient insight into the operations of the system as a
whole that it is straightforward to imagine structural changes to the
Root Server system's infrastructure and to wonder what the
operational implications of such changes might be.

The Yeti DNS Project was conceived in May 2015 with the aim of
providing a non-production testbed that would be open for use by
anyone from the technical community to propose or run experiments
designed to answer these kinds of questions. Coordination for the
project was provided by BII, TISF, and the WIDE Project. Thus, Yeti
DNS is an independently coordinated project and is not affiliated
with the IETF, ICANN, IANA, or any Root Server Operator. The
objectives of the Yeti Project were set by the participants in the
project based on experiments that they considered would provide
valuable information.

Many volunteers collaborated to build a distributed testbed that at
the time of writing includes 25 Yeti root servers with 16 operators
and handles experimental traffic from individual volunteers,
universities, DNS vendors, and distributed measurement networks.

By design, the Yeti testbed system serves the root zone published by
the IANA with only those structural modifications necessary to ensure
that it is able to function usefully in the Yeti testbed system
instead of the production Root Server system. In particular, no
delegation for any top-level zone is changed, added, or removed from
the IANA-published root zone to construct the root zone served by the
Yeti testbed system, and changes in the root zone are reflected in
the testbed in near real-time. In this document, for clarity, we
refer to the zone derived from the IANA-published root zone as the
Yeti-Root zone.

The Yeti DNS testbed serves a similar function to the Root Server
system in the sense that they both serve similar zones: the Yeti-Root
zone and the IANA-published root zone. However, the Yeti DNS testbed
only serves clients that are explicitly configured to participate in
the experiment, whereas the Root Server system serves the whole
Internet. Since the dependent end-users and systems of the Yeti DNS
testbed are known and their operations well-coordinated with those of
the Yeti project, it has been possible to deploy structural changes
in the Yeti DNS testbed with effective measurement and analysis,
something that is difficult or simply impractical in the production
Root Server system.

This document describes the motivation for the Yeti project,
describes the Yeti testbed infrastructure, and provides the technical
and operational experiences of some users of the Yeti testbed. This
document neither addresses the relevant policies under which the Root
Server system is operated nor makes any proposal for changing any
aspect of its implementation or operation.

2. Requirements Notation and Conventions

Through the document, any mention of "Root" with an uppercase "R" and
without other prefix, refers to the "IANA Root" systems used in the
production Internet. Proper mentions of the Yeti infrastructure will
be prefixed with "Yeti", like "Yeti-Root zone", "Yeti DNS", and so
on.

3. Areas of Study

This section provides some examples of the topics that the developers
of the Yeti DNS testbed considered important to address. As noted in
Section 1, the Yeti DNS is an independently coordinated project and
is not affiliated with the IETF, ICANN, IANA, or any Root Server
Operator. Thus, the topics and areas for study were selected by (and
for) the proponents of the Yeti project to address their own concerns
and in the hope that the information and tools provided would be of
wider interest.

Each example included below is illustrated with indicative questions.

3.1. Implementation of a Testbed like the Root Server System

* How can a testbed be constructed and deployed on the Internet,
allowing useful public participation without any risk of
disruption of the Root Server system?

* How can representative traffic be introduced into such a testbed
such that insights into the impact of specific differences between
the testbed and the Root Server system can be observed?

3.2. Yeti-Root Zone Distribution

* What are the scaling properties of Yeti-Root zone distribution as
the number of Yeti-Root servers, Yeti-Root server instances, or
intermediate distribution points increases?

3.3. Yeti-Root Server Names and Addressing

* What naming schemes other than those closely analogous to the use
of ROOT-SERVERS.NET in the production root zone are practical, and
what are their respective advantages and disadvantages?

* What are the risks and benefits of signing the zone that contains
the names of the Yeti-Root servers?
o

* What automatic mechanisms might be useful to improve the rate at
which clients of Yeti-Root servers are able to react to a Yeti-
Root server renumbering event?

3.4. IPv6-Only Yeti-Root Servers

* Are there negative operational effects in the use of IPv6-only
Yeti-Root servers, compared to the use of servers that are dual-
stack?

* What effect does the IPv6 fragmentation model have on the
operation of Yeti-Root servers, compared with that of IPv4?

3.5. DNSSEC in the Yeti-Root Zone

* Is it practical to sign the Yeti-Root zone using multiple,
independently operated DNSSEC signers and multiple corresponding
Zone Signing Keys (ZSKs)?

* To what extent is [RFC5011] ("Automated Updates of DNS Security
(DNSSEC) Trust Anchors") supported by resolvers?

* Does the KSK Rollover plan designed and in the process of being
implemented by ICANN work as expected on the Yeti testbed?

* What is the operational impact of using much larger RSA key sizes
in the ZSKs used in a root?

* What are the operational consequences of choosing DNSSEC
algorithms other than RSA to sign a root?

4. Yeti DNS Testbed Infrastructure

The purpose of the testbed is to allow DNS queries from stub
resolvers, mediated by recursive resolvers, to be delivered to Yeti-
Root servers, and for corresponding responses generated on the Yeti-
Root servers to be returned, as illustrated in Figure 1.

Figure 1: High-Level Testbed Components

To use the Yeti DNS testbed, a recursive resolver must be configured
to use the Yeti-Root servers. That configuration consists of a list
of names and addresses for the Yeti-Root servers (often referred to
as a "hints file") that replaces the corresponding hints used for the
production Root Server system (Appendix A). (Section appendix.a). If resolvers are
configured to validate DNSSEC, then they also need to be configured
with a DNSSEC trust anchor that corresponds to a KSK used in the Yeti
DNS Project, in place of the normal trust anchor set used for the
Root Zone.

Since the Yeti root(s) are signed with Yeti keys, rather than those
used by the IANA Root, corresponding changes are needed in the
resolver trust anchors. Corresponding changes are required in the
Yeti-Root hints file Appendix A. Section appendix.a. Those changes would be
properly rejected as bogus by any validator using the production Root
Server system's root zone trust anchor set.

Stub resolvers become part of the Yeti DNS testbed by their use of
recursive resolvers that are configured as described above.

The data flow from IANA to stub resolvers through the Yeti testbed is
illustrated in Figure 2 and is described in more detail in the
sections that follow.

,----------------.
,-- / IANA Root Zone / ---.
| `----------------' |
| | |
| | | Root Zone
,--------------. ,---V---. ,---V---. ,---V---.
| Yeti Traffic | | BII | | WIDE | | TISF |
| Collection | | DM | | DM | | DM |
`----+----+----' `---+---' `---+---' `---+---'
| | ,-----' ,-------' `----.
| | | | | Yeti-Root
^ ^ | | | Zone
| | ,---V---. ,---V---. ,---V---.
| `---+ Yeti | | Yeti | . . . . . . . | Yeti |
| | Root | | Root | | Root |
| `---+---' `---+---' `---+---'
| | | | DNS
| | | | Response
| ,--V----------V-------------------------V--.
`---------+ Yeti Resolvers |
`--------------------+---------------------'
| DNS
| Response
,--------------------V---------------------.
| Yeti Stub Resolvers |
`------------------------------------------'

The three coordinators of the Yeti DNS testbed:
BII : Beijing Internet Institute
WIDE: Widely Integrated Distributed Environment Project
TISF: A collaborative engineering and security project by Paul Vixie

Figure 2: Testbed Data Flow

Note that the roots are not bound to Distribution Masters (DMs). DMs
update their zone on a schedule described in Section 4.1. Each DM
that updates the latest zone can notify all roots, so the zone
transfer can happen between any DM and any root.

4.1. Root Zone Retrieval

The Yeti-Root zone is distributed within the Yeti DNS testbed through
a set of internal master servers that are referred to as Distribution
Masters (DMs). These server elements distribute the Yeti-Root zone
to all Yeti-Root servers. The means by which the Yeti DMs construct
the Yeti-Root zone for distribution is described below.

Since Yeti DNS DMs do not receive DNS NOTIFY [RFC1996] messages from
the Root Server system, a polling approach is used to determine when
new revisions of the root zone are available from the production Root
Server system. Each Yeti DM requests the Root Zone SOA record from a
Root server that permits unauthenticated zone transfers of the root
zone, and performs a zone transfer from that server if the retrieved
value of SOA.SERIAL is greater than that of the last retrieved zone.

At the time of writing, unauthenticated zone transfers of the Root
Zone are available directly from B-Root, C-Root, F-Root, G-Root,
K-Root, and L-Root; two servers XFR.CJR.DNS.ICANN.ORG and
XFR.LAX.DNS.ICANN.ORG; and via FTP from sites maintained by the Root
Zone Maintainer and the IANA Functions Operator. The Yeti DNS
testbed retrieves the Root Zone using zone transfers from F-Root.
The schedule on which F-Root is polled by each Yeti DM is as follows:

+-------------+-----------------------+
| DM Operator | Time |
+-------------+-----------------------+
+=============+=======================+
| BII | UTC hour + 00 minutes |
+-------------+-----------------------+
| WIDE | UTC hour + 20 minutes |
+-------------+-----------------------+
| TISF | UTC hour + 40 minutes |
+-------------+-----------------------+

Table 1

The Yeti DNS testbed uses multiple DMs, each of which acts
autonomously and equivalently to its siblings. Any single DM can act
to distribute new revisions of the Yeti-Root zone and is also
responsible for signing the RRsets that are changed as part of the
transformation of the Root Zone into the Yeti-Root zone described in
Section 4.2. This multiple DM model intends to provide a basic
structure to implement the idea of shared zone control as proposed in
[ITI2014].

4.2. Transformation of Root Zone to Yeti-Root Zone

Two distinct approaches have been deployed in the Yeti DNS testbed,
separately, to transform the Root Zone into the Yeti-Root zone. At a
high level, the approaches are equivalent in the sense that they
replace a minimal set of information in the root zone with
corresponding data for the Yeti DNS testbed; the mechanisms by which
the transforms are executed are different, however. The approaches
are discussed in Sections 4.2.1 and 4.2.2.

A third approach has also been proposed, but not yet implemented.
The motivations and changes implied by that approach are described in
Section 4.2.3.

4.2.1. ZSK and KSK Key Sets Shared between DMs

The approach described here was the first to be implemented. It
features entirely autonomous operation of each DM, but also requires
secret key material (the private key in each of the Yeti-Root KSK and
ZSK key pairs) to be distributed and maintained on each DM in a
coordinated way.

The Root Zone is transformed as follows to produce the Yeti-Root
zone. This transformation is carried out autonomously on each Yeti
DNS Project DM. Each DM carries an authentic copy of the current set
of Yeti KSK and ZSK key pairs, synchronized between all DMs (see
Section 4.4).

1. SOA.MNAME is set to www.yeti-dns.org.

2. SOA.RNAME is set to <dm-operator>.yeti-dns.org, where
<dm-operator> is currently one of "wide", "bii", or "tisf".

3. All DNSKEY, RRSIG, and NSEC records are removed.

4. The apex Name Server (NS) RRset is removed, with the
corresponding root server glue (A and AAAA) RRsets.

5. A Yeti DNSKEY RRset is added to the apex, comprising the public
parts of all Yeti KSK and ZSKs.

6. A Yeti NS RRset is added to the apex that includes all Yeti-Root
servers.

7. Glue records (AAAA only, since Yeti-Root servers are v6-only) for
all Yeti-Root servers are added.

8. The Yeti-Root zone is signed: the NSEC chain is regenerated; the
Yeti KSK is used to sign the DNSKEY RRset; and the shared ZSK is
used to sign every other RRset.

Note that the SOA.SERIAL value published in the Yeti-Root zone is
identical to that found in the root zone.

4.2.2. Unique ZSK per DM; No Shared KSK

The approach described here was the second to be implemented and
maintained as stable state. Each DM is provisioned with its own,
dedicated ZSK key pairs that are not shared with other DMs. A Yeti-
Root DNSKEY RRset is constructed and signed upstream of all DMs as
the union of the set of active Yeti-Root KSKs and the set of active
ZSKs for every individual DM. Each DM now only requires the secret
part of its own dedicated ZSK key pairs to be available locally, and
no other secret key material is shared. The high-level approach is
illustrated in Figure 3.

Figure 3: Unique ZSK per DM

The process of retrieving the Root Zone from the Root Server system
and replacing and signing the apex DNSKEY RRset no longer takes place
on the DMs; instead, it takes place on a central Hidden Master. The
production of signed DNSKEY RRsets is analogous to the use of Signed
Key Responses (SKRs) produced during ICANN KSK key ceremonies
[ICANN2010].

Each DM now retrieves source data (with a premodified and Yeti-signed
DNSKEY RRset, but otherwise unchanged) from the Yeti DNS Hidden
Master instead of from the Root Server system.

Each DM carries out a similar transformation to that described in
Section 4.2.1, except that DMs no longer need to modify or sign the
DNSKEY RRset, and the DM's unique local ZSK is used to sign every
other RRset.

4.2.3. Preserving Root Zone NSEC Chain and ZSK RRSIGs

A change to the transformation described in Section 4.2.2 has been
proposed as a Yeti experiment called PINZ [PINZ], which would
preserve the NSEC chain from the Root Zone and all RRSIG RRs
generated using the Root Zone's ZSKs. The DNSKEY RRset would
continue to be modified to replace the Root Zone KSKs, but Root Zone
ZSKs would be kept intact, and the Yeti KSK would be used to generate
replacement signatures over the apex DNSKEY and NS RRsets. Source
data would continue to flow from the Root Server system through the
Hidden Master to the set of DMs, but no DNSSEC operations would be
required on the DMs, and the source NSEC and most RRSIGs would remain
intact.

This approach has been suggested in order to keep minimal changes
from the IANA Root zone and provide cryptographically verifiable
confidence that no owner name in the root zone had been changed in
the process of producing the Yeti-Root zone from the Root Zone,
thereby addressing one of the concerns described in Appendix E
Section appendix.e in a way that can be verified automatically.

4.3. Yeti-Root Zone Distribution

Each Yeti DM is configured with a full list of Yeti-Root server
addresses to send NOTIFY [RFC1996] messages to. This also forms the
basis for an address-based access-control list for zone transfers.
Authentication by address could be replaced with more rigorous
mechanisms (e.g., using Transaction Signatures (TSIGs) [RFC2845]).
This has not been done at the time of writing since the use of
address-based controls avoids the need for the distribution of shared
secrets amongst the Yeti-Root server operators.

Individual Yeti-Root servers are configured with a full set of Yeti
DM addresses to which SOA and AXFR queries may be sent in the
conventional manner.

4.4. Synchronization of Service Metadata

Changes in the Yeti DNS testbed infrastructure such as the addition
or removal of Yeti-Root servers, renumbering Yeti-Root servers, or
DNSSEC key rollovers require coordinated changes to take place on all
DMs. The Yeti DNS testbed is subject to more frequent changes than
are observed in the Root Server system and includes substantially
more Yeti-Root servers than there are IANA Root Servers, and hence a
manual change process in the Yeti testbed would be more likely to
suffer from human error. An automated and cooperative process was
consequently implemented.

The theory of this operation is that each DM operator runs a Git
repository locally, containing all service metadata involved in the
operation of each DM. When a change is desired and approved among
all Yeti coordinators, one DM operator (usually BII) updates the
local Git repository. A serial number in the future (in two days) is
chosen for when the changes become active. The DM operator then
pushes the changes to the Git repositories of the other two DM
operators who have a chance to check and edit the changes. When the
serial number of the root zone passes the number chosen, the changes
are pulled automatically to individual DMs and promoted to
production.

The three Git repositories are synchronized by configuring them as
remote servers. For example, at BII we push to all three DMs'
repositories as follows:

$ git remote -v
origin yeticonf@yeti-conf.dns-lab.net:dm (fetch)
origin yeticonf@yeti-conf.dns-lab.net:dm (push)
origin yeticonf@yeti-dns.tisf.net:dm (push)
origin yeticonf@yeti-repository.wide.ad.jp:dm (push)

For more detailed information on DM synchronization, please see this
document in Yeti's GitHub repository: <https://github.com/BII-Lab/
Yeti-Project/blob/master/doc/Yeti-DM-Sync.md>. https://github.com/BII-Lab/
Yeti-Project/blob/master/doc/Yeti-DM-Sync.md.

4.5. Yeti-Root Server Naming Scheme

The current naming scheme for Root Servers was normalized to use
single-character host names ("A" through "M") under the domain ROOT-
SERVERS.NET, as described in [RSSAC023]. The principal benefit of
this naming scheme was that DNS label compression could be used to
produce a priming response that would fit within 512 bytes at the
time it was introduced, where 512 bytes is the maximum DNS message
size using UDP transport without EDNS(0) [RFC6891].

Yeti-Root servers do not use this optimization, but rather use free-
form nameserver names chosen by their respective operators -- in
other words, no attempt is made to minimize the size of the priming
response through the use of label compression. This approach aims to
challenge the need to minimize the priming response in a modern DNS
ecosystem where EDNS(0) is prevalent.

Priming responses from Yeti-Root servers (unlike those from Root
Servers) do not always include server addresses in the additional
section. In particular, Yeti-Root servers running BIND9 return an
empty additional section if the configuration parameter "minimum-
responses" is set, forcing resolvers to complete the priming process
with a set of conventional recursive lookups in order to resolve
addresses for each Yeti-Root server. The Yeti-Root servers running
NSD were observed to return a fully populated additional section
(depending, of course, on the EDNS buffer size in use).

Various approaches to normalize the composition of the priming
response were considered, including:

* Require use of DNS implementations that exhibit a desired behavior
in the priming response.

* Modify nameserver software or configuration as used by Yeti-Root
servers.

* Isolate the names of Yeti-Root servers in one or more zones that
could be slaved on each Yeti-Root server, renaming servers as
necessary, giving each a source of authoritative data with which
the authority section of a priming response could be fully
populated. This is the approach used in the Root Server system
with the ROOT-SERVERS.NET zone.

The potential mitigation of renaming all Yeti-Root servers using a
scheme that would allow their names to exist directly in the root
zone was not considered because that approach implies the invention
of new top-level labels not present in the Root Zone.

Given the relative infrequency of priming queries by individual
resolvers and the additional complexity or other compromises implied
by each of those mitigations, the decision was made to make no effort
to ensure that the composition of priming responses was identical
across servers. Even the empty additional sections generated by
Yeti-Root servers running BIND9 seem to be sufficient for all
resolver software tested; resolvers simply perform a new recursive
lookup for each authoritative server name they need to resolve.

4.6. Yeti-Root Servers

Various volunteers have donated authoritative servers to act as Yeti-
Root servers. At the time of writing, there are 25 Yeti-Root servers
distributed globally, one of which is named using a label as
specified in IDNA2008 [RFC5890] (it is shown in the following list in
punycode).

Table 2

The current list of Yeti-Root servers is made available to a
participating resolver first using a substitute hints file Appendix A
Section appendix.a and subsequently by the usual resolver priming
process [RFC8109]. All Yeti-Root servers are IPv6-only, because of
the IPv6-only Internet of the foreseeable future, and hence the Yeti-Root Yeti-
Root hints file contains no IPv4 addresses and the Yeti-Root zone
contains no IPv4 glue records. Note that the rationale of an
IPv6-only testbed is to test whether an IPv6-only root can survive
any problem or impact when IPv4 is turned off, much like the context
of the IETF SUNSET4 WG [SUNSET4].

At the time of writing, all root servers within the Root Server
system serve the ROOT-SERVERS.NET zone in addition to the root zone,
and all but one also serve the ARPA zone. Yeti-Root servers serve
the Yeti-Root zone only.

Significant software diversity exists across the set of Yeti-Root
servers, as reported by their volunteer operators at the time of
writing:

* Platform: 18 of 25 Yeti-Root servers are implemented on a Virtual
Private Server (VPS) rather than bare metal.

* Operating System: 15 Yeti-Root servers run on Linux (Ubuntu,
Debian, CentOS, Red Hat, and ArchLinux); 4 run on FreeBSD; 1 on
NetBSD; and 1 on Windows Server 2016.

* DNS software: 16 of 25 Yeti-Root servers use BIND9 (versions
varying between 9.9.7 and 9.10.3); 4 use NSD (4.10 and 4.15); 2
use Knot (2.0.1 and 2.1.0); 1 uses Bundy (1.2.0); 1 uses PowerDNS
(4.1.3); and 1 uses MS DNS (10.0.14300.1000).

4.7. Experimental Traffic

For the Yeti DNS testbed to be useful as a platform for
experimentation, it needs to carry statistically representative
traffic. Several approaches have been taken to load the system with
traffic, including both real-world traffic triggered by end-users and
synthetic traffic.

Resolvers that have been explicitly configured to participate in the
testbed, as described in Section 4, are a source of real-world, end-
user traffic. Due to an efficient cache mechanism, the mean query
rate is less than 100 qps in the Yeti testbed, but a variety of
sources were observed as active during 2017, as summarized in
Appendix C.
Section appendix.c.

Synthetic traffic has been introduced to the system from time to time
in order to increase traffic loads. Approaches include the use of
distributed measurement platforms such as RIPE ATLAS to send DNS
queries to Yeti-Root servers and the capture of traffic (sent from
non-Yeti resolvers to the Root Server system) that was subsequently
modified and replayed towards Yeti-Root servers.

4.8. Traffic Capture and Analysis

Traffic capture of queries and responses is available in the testbed
in both Yeti resolvers and Yeti-Root servers in anticipation of
experiments that require packet-level visibility into DNS traffic.

Traffic capture is performed on Yeti-Root servers using either

* dnscap <https://www.dns-oarc.net/tools/dnscap> https://www.dns-oarc.net/tools/dnscap or

* pcapdump, part of the pcaputils Debian package
<https://packages.debian.org/sid/pcaputils>,
https://packages.debian.org/sid/pcaputils, with a patch to
facilitate triggered file upload (see <https://bugs.debian.org/
cgi-bin/bugreport.cgi?bug=545985>). https://bugs.debian.org/cgi-
bin/bugreport.cgi?bug=545985).

PCAP-format files containing packet captures are uploaded using rsync
to central storage.

5. Operational Experience with the Yeti DNS Testbed

The following sections provide commentary on the operation and impact
analyses of the Yeti DNS testbed described in Section 4. More
detailed descriptions of observed phenomena are available in the Yeti
DNS mailing list archives <http://lists.yeti-dns.org/pipermail/
discuss/> http://lists.yeti-dns.org/pipermail/
discuss/ and on the Yeti DNS blog <https://yeti-dns.org/blog.html>. https://yeti-dns.org/blog.html.

5.1. Viability of IPv6-Only Operation

All Yeti-Root servers were deployed with IPv6 connectivity, and no
IPv4 addresses for any Yeti-Root server were made available (e.g., in
the Yeti hints file or in the DNS itself). This implementation
decision constrained the Yeti-Root system to be v6 only.

DNS implementations are generally adept at using both IPv4 and IPv6
when both are available. Servers that cannot be reliably reached
over one protocol might be better queried over the other, to the
benefit of end-users in the common case where DNS resolution is on
the critical path for end-users' perception of performance. However,
this optimization also means that systemic problems with one protocol
can be masked by the other. By forcing all traffic to be carried
over IPv6, the Yeti DNS testbed aimed to expose any such problems and
make them easier to identify and understand. Several examples of
IPv6-specific phenomena observed during the operation of the testbed
are described in the sections that follow.

Although the Yeti-Root servers themselves were only reachable using
IPv6, real-world end-users often have no IPv6 connectivity. The
testbed was also able to explore the degree to which IPv6-only Yeti-
Root servers were able to serve single-stack, IPv4-only end-user
populations through the use of dual-stack Yeti resolvers.

5.1.1. IPv6 Fragmentation

In the Root Server system, structural changes with the potential to
increase response sizes (and hence fragmentation, fallback to TCP
transport, or both) have been exercised with great care, since the
impact on clients has been difficult to predict or measure. The Yeti
DNS testbed is experimental and has the luxury of a known client
base, making it far easier to make such changes and measure their
impact.

Many of the experimental design choices described in this document
were expected to trigger larger responses. For example, the choice
of naming scheme for Yeti-Root servers described in Section 4.5
defeats label compression. It makes a large priming response (up to
1754 octets with 25 NS records and their corresponding glue records);
the Yeti-Root zone transformation approach described in Section 4.2.2
greatly enlarges the apex DNSKEY RRset especially during the KSK
rollover (up to 1975 octets with 3 ZSKs and 2 KSKs). Therefore, an
increased incidence of fragmentation was expected.

The Yeti DNS testbed provides service on IPv6 only. However,
middleboxes (such as firewalls and some routers) are not friendly on
IPv6 fragments. There are reports of a notable packet drop rate due
to the mistreatment of middleboxes on IPv6 fragments [FRAGDROP]
[RFC7872]. One APNIC study [IPv6-frag-DNS] reported that 37% of
endpoints using IPv6-capable DNS resolvers cannot receive a
fragmented IPv6 response over UDP.

To study the impact, RIPE Atlas probes were used. For each Yeti-Root
server, an Atlas measurement was set up using 100 IPv6-enabled probes
from five regions, sending a DNS query for "./IN/DNSKEY" using UDP
transport with DO=1. This measurement, when carried out concurrently
with a Yeti KSK rollover, further exacerbating the potential for
fragmentation, identified a 7% failure rate compared with a non-
fragmented control. A failure rate of 2% was observed with response
sizes of 1414 octets, which was surprising given the expected
prevalence of 1500-octet (Ethernet-framed) MTUs.

The consequences of fragmentation were not limited to failures in
delivering DNS responses over UDP transport. There were two cases
where a Yeti-Root server failed when using TCP to transfer the Yeti-
Root zone from a DM. DM log files revealed "socket is not connected"
errors corresponding to zone transfer requests. Further
experimentation revealed that combinations of NetBSD 6.1, NetBSD
7.0RC1, FreeBSD 10.0, Debian 3.2, and VMWare ESXI 5.5 resulted in a
high TCP Maximum Segment Size (MSS) value of 1440 octets being
negotiated between client and server despite the presence of the
IPV6_USE_MIN_MTU socket option, as described in [USE_MIN_MTU]. The
mismatch appears to cause outbound segments of a size greater than
1280 octets to be dropped before sending. Setting the local TCP MSS
to 1220 octets (chosen as 1280 - 60, the size of the IPv6 TCP header
with no other extension headers) was observed to be a pragmatic
mitigation.

5.1.2. Serving IPv4-Only End-Users

Yeti resolvers have been successfully used by real-world end-users
for general name resolution within a number of participant
organizations, including resolution of names to IPv4 addresses and
resolution by IPv4-only end-user devices.

Some participants, recognizing the operational importance of
reliability in resolver infrastructure and concerned about the
stability of their IPv6 connectivity, chose to deploy Yeti resolvers
in parallel to conventional resolvers, making both available to end-
users. While the viability of this approach provides a useful data
point, end-users using Yeti resolvers exclusively provided a better
opportunity to identify and understand any failures in the Yeti DNS
testbed infrastructure.

Resolvers deployed in IPv4-only environments were able to join the
Yeti DNS testbed by way of upstream, dual-stack Yeti resolvers. In
one case (CERNET2), this was done by assigning IPv4 addresses to
Yeti-Root servers and mapping them in dual-stack IVI translation
devices [RFC6219].

5.2. Zone Distribution

The Yeti DNS testbed makes use of multiple DMs to distribute the
Yeti-Root zone, an approach that would allow the number of Yeti-Root
servers to scale to a higher number than could be supported by a
single distribution source and that provided redundancy. The use of
multiple DMs introduced some operational challenges, however, which
are described in the following sections.

5.2.1. Zone Transfers

Yeti-Root servers were configured to serve the Yeti-Root zone as
slaves. Each slave had all DMs configured as masters, providing
redundancy in zone synchronization.

Each DM in the Yeti testbed served a Yeti-Root zone that was
functionally equivalent but not congruent to that served by every
other DM (see Section 4.3). The differences included variations in
the SOA.MNAME field and, more critically, in the RRSIGs for
everything other than the apex DNSKEY RRset, since signatures for all
other RRsets are generated using a private key that is only available
to the DM serving its particular variant of the zone (see Sections
4.2.1 and 4.2.2).

Incremental Zone Transfer (IXFR), as described in [RFC1995], is a
viable mechanism to use for zone synchronization between any Yeti-
Root server and a consistent, single DM. However, if that Yeti-Root
server ever selected a different DM, IXFR would no longer be a safe
mechanism; structural changes between the incongruent zones on
different DMs would not be included in any transferred delta, and the
result would be a zone that was not internally self-consistent. For
this reason, the first transfer after a change of DM would require
AXFR not IXFR.

None of the DNS software in use on Yeti-Root servers supports this
mixture of IXFR/AXFR according to the master server in use. This is
unsurprising, given that the environment described above in the Yeti-
Root system is idiosyncratic; conventional zone transfer graphs
involve zones that are congruent between all nodes. For this reason,
all Yeti-Root servers are configured to use AXFR at all times, and
never IXFR, to ensure that zones being served are internally self-
consistent.

5.2.2. Delays in Yeti-Root Zone Distribution

Each Yeti DM polled the Root Server system for a new revision of the
root zone on an interleaved schedule, as described in Section 4.1.
Consequently, different DMs were expected to retrieve each revision
of the root zone, and make a corresponding revision of the Yeti-Root
zone available, at different times. The availability of a new
revision of the Yeti-Root zone on the first DM would typically
precede that of the last by 40 minutes.

Given this distribution mechanism, it might be expected that the
maximum latency between the publication of a new revision of the root
zone and the availability of the corresponding Yeti-Root zone on any
Yeti-Root server would be 20 minutes, since in normal operation at
least one DM should serve that Yeti-Zone within 20 minutes of root
zone publication. In practice, this was not observed.

In one case, a Yeti-Root server running Bundy 1.2.0 on FreeBSD
10.2-RELEASE was found to lag root zone publication by as much as ten
hours. Upon investigation, this was found to be due to software
defects that were subsequently corrected.

More generally, Yeti-Root servers were observed routinely to lag root
zone publication by more than 20 minutes, and relatively often by
more than 40 minutes. Whilst in some cases this might be assumed to
be a result of connectivity problems, perhaps suppressing the
delivery of NOTIFY messages, it was also observed that Yeti-Root
servers receiving a NOTIFY from one DM would often send SOA queries
and AXFR requests to a different DM. If that DM were not yet serving
the new revision of the Yeti-Root zone, a delay in updating the Yeti-
Root server would naturally result.

5.2.3. Mixed RRSIGs from Different DM ZSKs

The second approach for doing the transformation of Root Zone to
Yeti-Root zone (Section 4.2.2) introduces a situation where mixed
RRSIGs from different DM ZSKs are cached in one resolver.

It is observed that the Yeti-Root zone served by any particular Yeti-
Root server will include signatures generated using the ZSK from the
DM that served the Yeti-Root zone to that Yeti-Root server.
Signatures cached at resolvers might be retrieved from any Yeti-Root
server, and hence are expected to be a mixture of signatures
generated by different ZSKs. Since all ZSKs can be trusted through
the signature by the Yeti KSK over the DNSKEY RRset, which includes
all ZSKs, the mixture of signatures was predicted not to be a threat
to reliable validation.

It was first tested in BII's lab environment as a proof of concept.
It was observed in the resolver's DNSSEC log that the process of
verifying an RDATA set shows "success" with a key (keyid) in the
DNSKEY RRset. It was implemented later in three DMs that were
carefully coordinated and made public to all Yeti resolver operators
and participants in Yeti's mailing list. At least 45 Yeti resolvers
(deployed by Yeti operators) were being monitored and had set a
reporting trigger if anything was wrong. In addition, the Yeti
mailing list is open for error reports from other participants. So
far, the Yeti testbed has been operated in this configuration (with
multiple ZSKs) for 2 years. This configuration has proven workable
and reliable, even when rollovers of individual ZSKs are on different
schedules.

Another consequence of this approach is that the apex DNSKEY RRset in
the Yeti-Root zone is much larger than the corresponding DNSKEY RRset
in the Root Zone. This requires more space and produces a larger
response to the query for the DNSKEY RRset especially during the KSK
rollover.

5.3. DNSSEC KSK Rollover

At the time of writing, the Root Zone KSK is expected to undergo a
carefully orchestrated rollover as described in [ICANN2016]. ICANN
has commissioned various tests and has published an external test
plan [ICANN2017].

Three related DNSSEC KSK rollover exercises were carried out on the
Yeti DNS testbed, somewhat concurrent with the planning and execution
of the rollover in the root zone. Brief descriptions of these
exercises are included below.

5.3.1. Failure-Case KSK Rollover

The first KSK rollover that was executed on the Yeti DNS testbed
deliberately ignored the 30-day hold-down timer specified in
[RFC5011] before retiring the outgoing KSK.

It was confirmed that clients of some (but not all) validating Yeti
resolvers experienced resolution failures (received SERVFAIL
responses) following this change. Those resolvers required
administrator intervention to install a functional trust anchor
before resolution was restored.

5.3.2. KSK Rollover vs. BIND9 Views

The second Yeti KSK rollover was designed with similar phases to the
ICANN's KSK rollover, although with modified timings to reduce the
time required to complete the process. The "slot" used in this
rollover was ten days long, as follows:

+-----------------+----------------+----------+
| | Old Key: 19444 | New Key |
+-----------------+----------------+----------+
+=================+================+==========+
| slot 1 | pub+sign | |
+-----------------+----------------+----------+
| slot 2, 3, 4, 5 | pub+sign | pub |
+-----------------+----------------+----------+
| slot 6, 7 | pub | pub+sign |
+-----------------+----------------+----------+
| slot 8 | revoke | pub+sign |
+-----------------+----------------+----------+
| slot 9 | | pub+sign |
+-----------------+----------------+----------+

Table 3

During this rollover exercise, a problem was observed on one Yeti
resolver that was running BIND 9.10.4-p2 [KROLL-ISSUE]. That
resolver was configured with multiple views serving clients in
different subnets at the time that the KSK rollover began. DNSSEC
validation failures were observed following the completion of the KSK
rollover, triggered by the addition of a new view that was intended
to serve clients from a new subnet.

BIND 9.10 requires "managed-keys" configuration to be specified in
every view, a detail that was apparently not obvious to the operator
in this case and that was subsequently highlighted by the Internet
Systems Consortium (ISC) in their general advice relating to KSK
rollover in the root zone to users of BIND 9 [ISC-BIND]. When the
"managed-keys" configuration is present in every view that is
configured to perform validation, trust anchors for all views are
updated during a KSK rollover.

5.3.3. Large Responses during KSK Rollover

Since a KSK rollover necessarily involves the publication of outgoing
and incoming public keys simultaneously, an increase in the size of
DNSKEY responses is expected. The third KSK rollover carried out on
the Yeti DNS testbed was accompanied by a concerted effort to observe
response sizes and their impact on end-users.

As described in Section 4.2.2, in the Yeti DNS testbed each DM can
maintain control of its own set of ZSKs, which can undergo rollover
independently. During a KSK rollover where concurrent ZSK rollovers
are executed by each of three DMs, the maximum number of apex DNSKEY
RRs present is eight (incoming and outgoing KSK, plus incoming and
outgoing of each of three ZSKs). In practice, however, such
concurrency did not occur; only the BII ZSK was rolled during the KSK
rollover, and hence only three DNSKEY RRset configurations were
observed:

* 3 ZSKs and 2 KSKs, DNSKEY response of 1975 octets;

* 3 ZSKs and 1 KSK, DNSKEY response of 1414 octets; and

* 2 ZSKs and 1 KSK, DNSKEY response of 1139 octets.

RIPE Atlas probes were used as described in Section 5.1.1 to send
DNSKEY queries directly to Yeti-Root servers. The numbers of queries
and failures were recorded and categorized according to the response
sizes at the time the queries were sent. A summary of the results
([YetiLR]) is as follows:

+---------------+----------+---------------+--------------+
| Response Size | Failures | Total Queries | Failure Rate |
+---------------+----------+---------------+--------------+
+===============+==========+===============+==============+
| 1139 | 274 | 64252 | 0.0042 |
+---------------+----------+---------------+--------------+
| 1414 | 3141 | 126951 | 0.0247 |
+---------------+----------+---------------+--------------+
| 1975 | 2920 | 42529 | 0.0687 |
+---------------+----------+---------------+--------------+

Table 4

The general approach illustrated briefly here provides a useful
example of how the design of the Yeti DNS testbed, separate from the
Root Server system but constructed as a live testbed on the Internet,
facilitates the use of general-purpose active measurement facilities
(such as RIPE Atlas probes) as well as internal passive measurement
(such as packet capture).

5.4. Capture of Large DNS Response

Packet capture is a common approach in production DNS systems where
operators require fine-grained insight into traffic in order to
understand production traffic. For authoritative servers, capture of
inbound query traffic is often sufficient, since responses can be
synthesized with knowledge of the zones being served at the time the
query was received. Queries are generally small enough not to be
fragmented, and even with TCP transport are generally packed within a
single segment.

The Yeti DNS testbed has different requirements; in particular, there
is a desire to compare responses obtained from the Yeti
infrastructure with those received from the Root Server system in
response to a single query stream (e.g., using the "Yeti Many Mirror
Verifier" (YmmV) as described in Appendix D). Section appendix.d). Some Yeti-Root
servers were capable of recovering complete DNS messages from within
nameservers, e.g., using dnstap; however, not all servers provided
that functionality, and a consistent approach was desirable.

The requirement to perform passive capture of responses from the wire
together with experiments that were expected (and in some cases
designed) to trigger fragmentation and use of TCP transport led to
the development of a new tool, PcapParser, to perform fragment and
TCP stream reassembly from raw packet capture data. A brief
description of PcapParser is included in Appendix D. Section appendix.d.

5.5. Automated Maintenance of the Hints File

Renumbering events in the Root Server system are relatively rare.
Although each such event is accompanied by the publication of an
updated hints file in standard locations, the task of updating local
copies of that file used by DNS resolvers is manual, and the process
has an observably long tail. For example, in 2015 J-Root was still
receiving traffic at its old address some thirteen years after
renumbering [Wessels2015].

The observed impact of these old, deployed hints files is minimal,
likely due to the very low frequency of such renumbering events.
Even the oldest of hints files would still contain some accurate root
server addresses from which priming responses could be obtained.

By contrast, due to the experimental nature of the system and the
fact that it is operated mainly by volunteers, Yeti-Root servers are
added, removed, and renumbered with much greater frequency. A tool
to facilitate automatic maintenance of hints files was therefore
created: [hintUpdate].

The automated procedure followed by the hintUpdate tool is as
follows.

1. Use the local resolver to obtain a response to the query
"./IN/NS". "./IN/
NS".

2. Use the local resolver to obtain a set of IPv4 and IPv6 addresses
for each name server.

3. Validate all signatures obtained from the local resolvers and
confirm that all data is signed.

4. Compare the data obtained to that contained within the currently
active hints file; if there are differences, rotate the old one
away and replace it with a new one.

This tool would not function unmodified when used in the Root Server
system, since the names of individual Root Servers (e.g., A.ROOT-
SERVERS.NET) are not DNSSEC signed. All Yeti-Root server names are
DNSSEC signed, however, and hence this tool functions as expected in
that environment.

5.6. Root Label Compression in Knot DNS Server

[RFC1035] specifies that domain names can be compressed when encoded
in DNS messages, and can be represented as one of

1. a sequence of labels ending in a zero octet;

2. a pointer; or

3. a sequence of labels ending with a pointer.

The purpose of this flexibility is to reduce the size of domain names
encoded in DNS messages.

It was observed that Yeti-Root servers running Knot 2.0 would
compress the zero-length label (the root domain, often represented as
".") using a pointer to an earlier example. Although legal, this
encoding increases the encoded size of the root label from one octet
to two; it was also found to break some client software -- in
particular, the Go DNS library. Bug reports were filed against both
Knot and the Go DNS library, and both were resolved in subsequent
releases.

6. Conclusions

Yeti DNS was designed and implemented as a live DNS root system
testbed. It serves a root zone ("Yeti-Root" in this document)
derived from the root zone published by the IANA with only those
structural modifications necessary to ensure its function in the
testbed system. The Yeti DNS testbed has proven to be a useful
platform to address many questions that would be challenging to
answer using the production Root Server system, such as those
included in Section 3.

Indicative findings following from the construction and operation of
the Yeti DNS testbed include:

* Operation in a pure IPv6-only environment; confirmation of a
significant failure rate in the transmission of large responses
(~7%), but no other persistent failures observed. Two cases in
which Yeti-Root servers failed to retrieve the Yeti-Root zone due
to fragmentation of TCP segments; mitigated by setting a TCP MSS
of 1220 octets (see Section 5.1.1).

* Successful operation with three autonomous Yeti-Root zone signers
and 25 Yeti-Root servers, and confirmation that IXFR is not an
appropriate transfer mechanism of zones that are structurally
incongruent across different transfer paths (see Section 5.2).

* ZSK size increased to 2048 bits and multiple KSK rollovers
executed to exercise support of RFC 5011 in validating resolvers;
identification of pitfalls relating to views in BIND9 when
configured with "managed-keys" (see Section 5.3).

* Use of natural (non-normalized) names for Yeti-Root servers
exposed some differences between implementations in the inclusion
of additional-section glue in responses to priming queries;
however, despite this inefficiency, Yeti resolvers were observed
to function adequately (see Section 4.5).

* It was observed that Knot 2.0 performed label compression on the
root (empty) label. This resulted in an increased encoding size
for references to the root label, since a pointer is encoded as
two octets whilst the root label itself only requires one (see
Section 5.6).

* Some tools were developed in response to the operational
experience of running and using the Yeti DNS testbed: DNS fragment
and DNS Additional Truncated Response (ATR) for large DNS
responses, a BIND9 patch for additional-section glue, YmmV, and
IPv6 defrag for capturing and mirroring traffic. In addition, a
tool to facilitate automatic maintenance of hints files was
created (see Appendix D). Section appendix.d).

The Yeti DNS testbed was used only by end-users whose local
infrastructure providers had made the conscious decision to do so, as
is appropriate for an experimental, non-production system. So far,
no serious user complaints have reached Yeti's mailing list during
Yeti normal operation. Adding more instances into the Yeti root
system may help to enhance the quality of service, but it is
generally accepted that Yeti DNS performance is good enough to serve
the purpose of DNS Root testbed.

The experience gained during the operation of the Yeti DNS testbed
suggested several topics worthy of further study:

* Priming truncation and TCP-only Yeti-Root servers: observe and
measure the worst-possible case for priming truncation by
responding with TC=1 to all priming queries received over UDP
transport, forcing clients to retry using TCP. This should also
give some insight into the usefulness of TCP-only DNS in general.

* KSK ECDSA Rollover: one possible way to reduce DNSKEY response
sizes is to change to an elliptic curve signing algorithm. While
in principle this can be done separately for the KSK and the ZSK,
the RIPE NCC has done research recently and discovered that some
resolvers require that both KSK and ZSK use the same algorithm.
This means that an algorithm roll also involves a KSK roll.
Performing an algorithm roll at the root would be an interesting
challenge.

* Sticky Notify for zone transfer: the non-applicability of IXFR as
a zone transfer mechanism in the Yeti DNS testbed could be
mitigated by the implementation of a sticky preference for master
server for each slave. This would be so that an initial AXFR
response could be followed up with IXFR requests without
compromising zone integrity in the case (as with Yeti) that
equivalent but incongruent versions of a zone are served by
different masters.

* Key distribution for zone transfer credentials: the use of a
shared secret between slave and master requires key distribution
and management whose scaling properties are not ideally suited to
systems with large numbers of transfer clients. Other approaches
for key distribution and authentication could be considered.

* DNS is a tree-based hierarchical database. Mathematically, it has
a root node and dependency between parent and child nodes. So,
any failures and instability of parent nodes (Root in Yeti's case)
may impact their child nodes if there is a human mistake, a
malicious attack, or even an earthquake. It is proposed to define
technology and practices to allow any organization, from the
smallest company to nations, to be self-sufficient in their DNS.

* In Section 3.12 of [RFC8324], a "Centrally Controlled Root" is
viewed as an issue of DNS. In future work, it would be
interesting to test some technical tools like blockchain [BC] to
either remove the technical requirement for a central authority
over the root or enhance the security and stability of the
existing Root.

7. Security Considerations

As introduced in Section 4.4, service metadata is synchronized among
3 DMs using Git tool. Any security issue around Git may affect Yeti
DM operation. For example, a hacker may compromise one DM's Git
repository and push unwanted changes to the Yeti DM system; this may
introduce a bad root server or bad key for a period of time.

The Yeti resolver needs the bootstrapping files to join the testbed,
like the hints file and trust anchor of Yeti. All required
information is published on <yeti-dns.org> yeti-dns.org and <github.com>. github.com. If a hacker
tampers with those websites by creating a fake page, a new resolver
may lose its way and be configured with a bad root.

DNSSEC is an important research goal in the Yeti DNS testbed. To
reduce the central function of DNSSEC for Root zone, we sign the
Yeti-Root zone using multiple, independently operated DNSSEC signers
and multiple corresponding ZSKs (see Section 4.2). To verify ICANN's
KSK rollover, we rolled the Yeti KSK three times according to RFC
5011, and we do have some observations (see Section 5.3). In
addition, larger RSA key sizes were used in the testbed before
2048-bit keys were used in the ZSK signing process of the IANA Root
zone.

8. IANA Considerations

This document has no IANA actions.

9. References

9.1. Normative References

[RFC1034] Mockapetris, P., P.V., "Domain names - concepts and
facilities", STD 13, RFC 1034, DOI 10.17487/RFC1034,
November 1987, <https://www.rfc-editor.org/info/rfc1034>.

[RFC1035] Mockapetris, P., P.V., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.

[RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995,
DOI 10.17487/RFC1995, August 1996,
<https://www.rfc-editor.org/info/rfc1995>.

[RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone
Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996,
August 1996, <https://www.rfc-editor.org/info/rfc1996>.

[RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC)
Trust Anchors", STD 74, RFC 5011, DOI 10.17487/RFC5011,
September 2007, <https://www.rfc-editor.org/info/rfc5011>.

[RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework",
RFC 5890, DOI 10.17487/RFC5890, August 2010,
<https://www.rfc-editor.org/info/rfc5890>.

9.2. Informative References

[ATR] Song, L., "ATR: Additional Truncation Response for Large
DNS Response", Work in Progress, draft-song-atr-large-
resp-02, 2 August 2018.

[BC] Wikipedia, "Blockchain", September 2018,
<https://en.wikipedia.org/w/
index.php?title=Blockchain&oldid=861681529>.

[FRAGDROP] Jaeggli, J., Colitti, L., Kumari, W., Vyncke, E., Kaeo,
M., and T. Taylor, "Why Operators Filter Fragments and
What It Implies", Work in Progress, draft-taylor-v6ops-
fragdrop-02, 3 December 2013.

[FRAGMENTS]
Sivaraman,

[FRAGMENTS]Sivaraman, M., Kerr, S., and D. Song, "DNS message
fragments", Work in Progress, draft-muks-dns-message-
fragments-00, 20 July 2015.

[hintUpdate]
"Hintfile Auto Update", commit de428c0, October 2015,
<https://github.com/BII-Lab/Hintfile-Auto-Update>.

[HOW_ATR_WORKS]
Huston, G., "How well does ATR actually work?",
APNIC blog, 16 April 2018,
<https://blog.apnic.net/2018/04/16/
how-well-does-atr-actually-work/>.

[ICANN2010]
Schlyter,
<https://blog.apnic.net/2018/04/16/how-well-does-atr-
actually-work/>.

[ICANN2010]Schlyter, J., Lamb, R., and R. Balasubramanian, "DNSSEC
Key Management Implementation for the Root Zone (DRAFT)",
11 May 2010, <http://www.root-dnssec.org/wp-content/
uploads/2010/05/draft-icann-dnssec-keymgmt-01.txt>.

[ICANN2016]
Design
<http://www.root-dnssec.org/wp-content/uploads/2010/05/
draft-icann-dnssec-keymgmt-01.txt>.

[ICANN2016]Design Team, "Root Zone KSK Rollover Plan", March 2016,
<https://www.iana.org/reports/2016/
root-ksk-rollover-design-20160307.pdf>.

[ICANN2017]
ICANN,
<https://www.iana.org/reports/2016/root-ksk-rollover-
design-20160307.pdf>.

[ICANN2017]ICANN, "2017 KSK Rollover External Test Plan", 22 July
2016,
<https://www.icann.org/en/system/files/files/
ksk-rollover-external-test-plan-22jul16-en.pdf>.
<https://www.icann.org/en/system/files/files/ksk-rollover-
external-test-plan-22jul16-en.pdf>.

[IPv6-frag-DNS]
Huston, G., "Dealing with IPv6 fragmentation in the DNS",
APNIC blog, 22 August 2017,
<https://blog.apnic.net/2017/08/22/
dealing-ipv6-fragmentation-dns>.
<https://blog.apnic.net/2017/08/22/dealing-ipv6-
fragmentation-dns>.

[ISC-BIND] Risk, V., "2017 Root Key Rollover - What Does it Mean for
BIND Users?", Internet Systems Consortium, December 2016,
<https://www.isc.org/blogs/2017-root-key-rollover-what-
does-it-mean-for-bind-users/>.

[ISC-TN-2003-1]
Abley, J., "Hierarchical Anycast for Global Service
Distribution", March 2003,
<http://ftp.isc.org/isc/pubs/tn/isc-tn-2003-1.txt>.

[ITI2014] ICANN, "Identifier Technology Innovation Report", 15 May
2014, <https://www.icann.org/en/system/files/files/
iti-report-15may14-en.pdf>.
<https://www.icann.org/en/system/files/files/iti-report-
15may14-en.pdf>.

[KROLL-ISSUE]
Song, D., "A DNSSEC issue during Yeti KSK rollover", Yeti
DNS blog, October 2016, <http://yeti-dns.org/yeti/blog/
2016/10/26/A-DNSSEC-issue-during-Yeti-KSK-rollover.html>.
<http://yeti-dns.org/yeti/blog/2016/10/26/A-DNSSEC-issue-
during-Yeti-KSK-rollover.html>.

[PINZ] Song, D., "Yeti experiment plan for PINZ", Yeti DNS blog,
May 2018, <http://yeti-dns.org/yeti/blog/2018/05/01/
Experiment-plan-for-PINZ.html>.
<http://yeti-dns.org/yeti/blog/2018/05/01/Experiment-plan-
for-PINZ.html>.

[RFC2826] Internet Architecture Board, "IAB Technical Comment on the
Unique DNS Root", RFC 2826, DOI 10.17487/RFC2826, May
2000, <https://www.rfc-editor.org/info/rfc2826>.

[RFC2845] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
Wellington, "Secret Key Transaction Authentication for DNS
(TSIG)", RFC 2845, DOI 10.17487/RFC2845, May 2000,
<https://www.rfc-editor.org/info/rfc2845>.

[RFC6219] Li, X., Bao, C., Chen, M., Zhang, H., and J. Wu, "The
China Education and Research Network (CERNET) IVI
Translation Design and Deployment for the IPv4/IPv6
Coexistence and Transition", RFC 6219,
DOI 10.17487/RFC6219, May 2011,
<https://www.rfc-editor.org/info/rfc6219>.

[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891,
DOI 10.17487/RFC6891, April 2013,
<https://www.rfc-editor.org/info/rfc6891>.

[RFC7720] Blanchet, M. and L-J. Liman, "DNS Root Name Service
Protocol and Deployment Requirements", BCP 40, RFC 7720,
DOI 10.17487/RFC7720, December 2015,
<https://www.rfc-editor.org/info/rfc7720>.

[RFC7872] Gont, F., Linkova, J., Chown, T., and W. Liu,
"Observations on the Dropping of Packets with IPv6
Extension Headers in the Real World", RFC 7872,
DOI 10.17487/RFC7872, June 2016,
<https://www.rfc-editor.org/info/rfc7872>.

[RFC8109] Koch, P., Larson, M., and P. Hoffman, "Initializing a DNS
Resolver with Priming Queries", BCP 209, RFC 8109,
DOI 10.17487/RFC8109, March 2017,
<https://www.rfc-editor.org/info/rfc8109>.

[RFC8324] Klensin, J., "DNS Privacy, Authorization, Special Uses,
Encoding, Characters, Matching, and Root Structure: Time
for Another Look?", RFC 8324, DOI 10.17487/RFC8324,
February 2018, <https://www.rfc-editor.org/info/rfc8324>.

[RRL] Vixie, P. and V. Schryver, "Response Rate Limiting in the
Domain Name System (DNS RRL)", 10 June 2012,
<http://www.redbarn.org/dns/ratelimits>.

[RSSAC001] Root Server System Advisory Committee (RSSAC), "Service
Expectations of Root Servers", RSSAC001 Version 1, 4
December 2015,
<https://www.icann.org/en/system/files/files/
rssac-001-root-service-expectations-04dec15-en.pdf>.
<https://www.icann.org/en/system/files/files/rssac-001-
root-service-expectations-04dec15-en.pdf>.

[RSSAC023] Root Server System Advisory Committee (RSSAC), "History of
the Root Server System", 4 November 2016,
<https://www.icann.org/en/system/files/files/
rssac-023-04nov16-en.pdf>.
<https://www.icann.org/en/system/files/files/rssac-
023-04nov16-en.pdf>.

[SUNSET4] IETF, "Sunsetting IPv4 (sunset4) Concluded WG", January
2019, <https://datatracker.ietf.org/wg/sunset4/about/>.

[TNO2009] Gijsen, B., Jamakovic, A., and F. Roijers, "Root Scaling
Study: Description of the DNS Root Scaling Model",
TNO report, 29 September 2009,
<https://www.icann.org/en/system/files/files/
root-scaling-model-description-29sep09-en.pdf>.
<https://www.icann.org/en/system/files/files/root-scaling-
model-description-29sep09-en.pdf>.

[USE_MIN_MTU]
Andrews, M., "TCP Fails To Respect IPV6_USE_MIN_MTU", Work
in Progress, draft-andrews-tcp-and-ipv6-use-minmtu-04, 18
October 2015.

[Wessels2015]
Wessels, D., Castonguay, J., and P. Barber, "Thirteen
Years of 'Old J-Root'", DNS-OARC Fall 2015 Workshop,
October 2015, <https://indico.dns-oarc.net/event/24/
session/10/contribution/10/material/slides/0.pdf>. <https://indico.dns-
oarc.net/event/24/session/10/contribution/10/material/
slides/0.pdf>.

[YetiLR] "Observation on Large response issue during Yeti KSK
rollover", Yeti DNS blog, 2 August 2017,
<https://yeti-dns.org/yeti/blog/2017/08/02/
large-packet-impact-during-yeti-ksk-rollover.html>.
<https://yeti-dns.org/yeti/blog/2017/08/02/large-packet-
impact-during-yeti-ksk-rollover.html>.

Appendix A. Yeti-Root Hints File

The following hints file (complete and accurate at the time of
writing) causes a DNS resolver to use the Yeti DNS testbed in place
of the production Root Server system and hence participate in
experiments running on the testbed.

Note that some lines have been wrapped in the text that follows in
order to fit within the production constraints of this document.
Wrapped lines are indicated with a blackslash character ("\"),
following common convention.

. 3600000 IN NS bii.dns-lab.net
bii.dns-lab.net 3600000 IN AAAA 240c:f:1:22::6
. 3600000 IN NS yeti-ns.tisf.net
yeti-ns.tisf.net 3600000 IN AAAA 2001:559:8000::6
. 3600000 IN NS yeti-ns.wide.ad.jp
yeti-ns.wide.ad.jp 3600000 IN AAAA 2001:200:1d9::35
. 3600000 IN NS yeti-ns.as59715.net
yeti-ns.as59715.net 3600000 IN AAAA \
2a02:cdc5:9715:0:185:5:203:53
. 3600000 IN NS dahu1.yeti.eu.org
dahu1.yeti.eu.org 3600000 IN AAAA \
2001:4b98:dc2:45:216:3eff:fe4b:8c5b
. 3600000 IN NS ns-yeti.bondis.org
ns-yeti.bondis.org 3600000 IN AAAA 2a02:2810:0:405::250
. 3600000 IN NS yeti-ns.ix.ru
yeti-ns.ix.ru 3600000 IN AAAA 2001:6d0:6d06::53
. 3600000 IN NS yeti.bofh.priv.at
yeti.bofh.priv.at 3600000 IN AAAA 2a01:4f8:161:6106:1::10
. 3600000 IN NS yeti.ipv6.ernet.in
yeti.ipv6.ernet.in 3600000 IN AAAA 2001:e30:1c1e:1::333
. 3600000 IN NS yeti-dns01.dnsworkshop.org
yeti-dns01.dnsworkshop.org \
3600000 IN AAAA 2001:1608:10:167:32e::53
. 3600000 IN NS yeti-ns.conit.co
yeti-ns.conit.co 3600000 IN AAAA \
2604:6600:2000:11::4854:a010
. 3600000 IN NS dahu2.yeti.eu.org
dahu2.yeti.eu.org 3600000 IN AAAA 2001:67c:217c:6::2
. 3600000 IN NS yeti.aquaray.com
yeti.aquaray.com 3600000 IN AAAA 2a02:ec0:200::1
. 3600000 IN NS yeti-ns.switch.ch
yeti-ns.switch.ch 3600000 IN AAAA 2001:620:0:ff::29
. 3600000 IN NS yeti-ns.lab.nic.cl
yeti-ns.lab.nic.cl 3600000 IN AAAA 2001:1398:1:21::8001
. 3600000 IN NS yeti-ns1.dns-lab.net
yeti-ns1.dns-lab.net 3600000 IN AAAA 2001:da8:a3:a027::6
. 3600000 IN NS yeti-ns2.dns-lab.net
yeti-ns2.dns-lab.net 3600000 IN AAAA 2001:da8:268:4200::6
. 3600000 IN NS yeti-ns3.dns-lab.net
yeti-ns3.dns-lab.net 3600000 IN AAAA 2400:a980:30ff::6
. 3600000 IN NS \
ca978112ca1bbdcafac231b39a23dc.yeti-dns.net
ca978112ca1bbdcafac231b39a23dc.yeti-dns.net \
3600000 IN AAAA 2c0f:f530::6
. 3600000 IN NS \
3e23e8160039594a33894f6564e1b1.yeti-dns.net
3e23e8160039594a33894f6564e1b1.yeti-dns.net \
3600000 IN AAAA 2803:80:1004:63::1
. 3600000 IN NS \
3f79bb7b435b05321651daefd374cd.yeti-dns.net
3f79bb7b435b05321651daefd374cd.yeti-dns.net \
3600000 IN AAAA 2401:c900:1401:3b:c::6
. 3600000 IN NS \
xn--r2bi1c.xn--h2bv6c0a.xn--h2brj9c
xn--r2bi1c.xn--h2bv6c0a.xn--h2brj9c \
3600000 IN AAAA 2001:e30:1c1e:10::333
. 3600000 IN NS yeti1.ipv6.ernet.in
yeti1.ipv6.ernet.in 3600000 IN AAAA 2001:e30:187d::333
. 3600000 IN NS yeti-dns02.dnsworkshop.org
yeti-dns02.dnsworkshop.org \
3600000 IN AAAA 2001:19f0:0:1133::53
. 3600000 IN NS yeti.mind-dns.nl
yeti.mind-dns.nl 3600000 IN AAAA 2a02:990:100:b01::53:0

Appendix B. Yeti-Root Server Priming Response

Here is the reply of a Yeti root name server to a priming request.
The authoritative server runs NSD.

...
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 62391
;; flags: qr aa rd; QUERY: 1, ANSWER: 26, AUTHORITY: 0, ADDITIONAL: 7
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags: do; udp: 1460
;; QUESTION SECTION:
;. IN NS

;; ANSWER SECTION:
. 86400 IN NS bii.dns-lab.net.
. 86400 IN NS yeti.bofh.priv.at.
. 86400 IN NS yeti.ipv6.ernet.in.
. 86400 IN NS yeti.aquaray.com.
. 86400 IN NS yeti.jhcloos.net.
. 86400 IN NS yeti.mind-dns.nl.
. 86400 IN NS dahu1.yeti.eu.org.
. 86400 IN NS dahu2.yeti.eu.org.
. 86400 IN NS yeti1.ipv6.ernet.in.
. 86400 IN NS ns-yeti.bondis.org.
. 86400 IN NS yeti-ns.ix.ru.
. 86400 IN NS yeti-ns.lab.nic.cl.
. 86400 IN NS yeti-ns.tisf.net.
. 86400 IN NS yeti-ns.wide.ad.jp.
. 86400 IN NS yeti-ns.datev.net.
. 86400 IN NS yeti-ns.switch.ch.
. 86400 IN NS yeti-ns.as59715.net.
. 86400 IN NS yeti-ns1.dns-lab.net.
. 86400 IN NS yeti-ns2.dns-lab.net.
. 86400 IN NS yeti-ns3.dns-lab.net.
. 86400 IN NS xn--r2bi1c.xn--h2bv6c0a.xn--h2brj9c.
. 86400 IN NS yeti-dns01.dnsworkshop.org.
. 86400 IN NS yeti-dns02.dnsworkshop.org.
. 86400 IN NS 3f79bb7b435b05321651daefd374cd.yeti-dns.net.
. 86400 IN NS ca978112ca1bbdcafac231b39a23dc.yeti-dns.net.
. 86400 IN RRSIG NS 8 0 86400 (
20171121050105 20171114050105 26253 .
FUvezvZgKtlLzQx2WKyg+D6dw/pITcbuZhzStZfg+LNa
DjLJ9oGIBTU1BuqTujKHdxQn0DcdFh9QE68EPs+93bZr
VlplkmObj8f0B7zTQgGWBkI/K4Tn6bZ1I7QJ0Zwnk1mS
BmEPkWmvo0kkaTQbcID+tMTodL6wPAgW1AdwQUInfy21
p+31GGm3+SU6SJsgeHOzPUQW+dUVWmdj6uvWCnUkzW9p
+5en4+85jBfEOf+qiyvaQwUUe98xZ1TOiSwYvk5s/qiv
AMjG6nY+xndwJUwhcJAXBVmGgrtbiR8GiGZfGqt748VX
4esLNtD8vdypucffem6n0T0eV1c+7j/eIA== )

;; ADDITIONAL SECTION:
bii.dns-lab.net. 86400 IN AAAA 240c:f:1:22::6
yeti.bofh.priv.at. 86400 IN AAAA 2a01:4f8:161:6106:1::10
yeti.ipv6.ernet.in. 86400 IN AAAA 2001:e30:1c1e:1::333
yeti.aquaray.com. 86400 IN AAAA 2a02:ec0:200::1
yeti.jhcloos.net. 86400 IN AAAA 2001:19f0:5401:1c3::53
yeti.mind-dns.nl. 86400 IN AAAA 2a02:990:100:b01::53:0

;; Query time: 163 msec
;; SERVER: 2001:4b98:dc2:45:216:3eff:fe4b:8c5b#53
;; WHEN: Tue Nov 14 16:45:37 +08 2017
;; MSG SIZE rcvd: 1222

Appendix C. Active IPv6 Prefixes in Yeti DNS Testbed

The following table shows the prefixes that were active during 2017.

+----------------------+---------------------------------+----------+

+----------------------+--------------------------+----------+
| Prefix | Originator | Location |
+----------------------+---------------------------------+----------+
+======================+==========================+==========+
| 240c::/28 | BII | CN |
+----------------------+--------------------------+----------+
| 2001:6d0:6d06::/48 | MSK-IX | RU |
+----------------------+--------------------------+----------+
| 2001:1488::/32 | CZ.NIC | CZ |
+----------------------+--------------------------+----------+
| 2001:620::/32 | SWITCH | CH |
+----------------------+--------------------------+----------+
| 2001:470::/32 | Hurricane Electric, Inc. | US |
+----------------------+--------------------------+----------+
| 2001:0DA8:0202::/48 | BUPT6-CERNET2 | CN |
+----------------------+--------------------------+----------+
| 2001:19f0:6c00::/38 | Choopa, LLC | US |
+----------------------+--------------------------+----------+
| 2001:da8:205::/48 | BJTU6-CERNET2 | CN |
+----------------------+--------------------------+----------+
| 2001:62a::/31 | Vienna University Computer | AT |
| | Computer Center | |
+----------------------+--------------------------+----------+
| 2001:67c:217c::/48 | AFNIC | FR |
+----------------------+--------------------------+----------+
| 2a02:2478::/32 | Profitbricks GmbH | DE |
+----------------------+--------------------------+----------+
| 2001:1398:1::/48 | NIC Chile | CL |
+----------------------+--------------------------+----------+
| 2001:4490:dc4c::/46 | NIB (National Internet | IN |
| | Backbone) | |
+----------------------+--------------------------+----------+
| 2001:4b98::/32 | Gandi | FR |
+----------------------+--------------------------+----------+
| 2a02:aa8:0:2000::/52 | T-Systems-Eltec | ES |
+----------------------+--------------------------+----------+
| 2a03:b240::/32 | Netskin GmbH | CH |
+----------------------+--------------------------+----------+
| 2801:1a0::/42 | Universidad de Ibague | CO |
+----------------------+--------------------------+----------+
| 2a00:1cc8::/40 | ICT Valle Umbra s.r.l. | IT |
+----------------------+--------------------------+----------+
| 2a02:cdc0::/29 | ORG-CdSB1-RIPE | IT |
+----------------------+---------------------------------+----------+
+----------------------+--------------------------+----------+

Table 5

Appendix D. Tools Developed for Yeti DNS Testbed

Various tools were developed to support the Yeti DNS testbed, a
selection of which are described briefly below.

YmmV ("Yeti Many Mirror Verifier") is designed to make it easy and
safe for a DNS administrator to capture traffic sent from a resolver
to the Root Server system and to replay it towards Yeti-Root servers.
Responses from both systems are recorded and compared, and
differences are logged. See <https://github.com/BII-Lab/ymmv>. https://github.com/BII-Lab/ymmv.

PcapParser is a module used by YmmV which reassembles fragmented IPv6
datagrams and TCP segments from a PCAP archive and extracts DNS
messages contained within them. See <https://github.com/RunxiaWan/
PcapParser>. https://github.com/RunxiaWan/
PcapParser.

DNS-layer-fragmentation implements DNS proxies that perform
application-level fragmentation of DNS messages, based on
[FRAGMENTS]. The idea with these proxies is to explore splitting DNS
messages in the protocol itself, so they will not by fragmented by
the IP layer. See <https://github.com/BII-Lab/DNS-layer-
Fragmentation>. https://github.com/BII-Lab/DNS-layer-
Fragmentation.

DNS_ATR is an implementation of DNS Additional Truncated Response
(ATR), as described in [ATR] and [HOW_ATR_WORKS]. DNS_ATR acts as a
proxy between resolver and authoritative servers, forwarding queries
and responses as a silent and transparent listener. Responses that
are larger than a nominated threshold (1280 octets by default)
trigger additional truncated responses to be sent immediately
following the large response. See <https://github.com/songlinjian/
DNS_ATR>. https://github.com/songlinjian/
DNS_ATR.

Appendix E. Controversy

The Yeti DNS Project, its infrastructure and the various experiments
that have been carried out using that infrastructure, have been
described by people involved in the project in many public meetings
at technical venues since its inception. The mailing lists using
which the operation of the infrastructure has been coordinated are
open to join, and their archives are public. The project as a whole
has been the subject of robust public discussion.

Some commentators have expressed concern that the Yeti DNS Project
is, in effect, operating an alternate root, challenging the IAB's
comments published in [RFC2826]. Other such alternate roots are
considered to have caused end-user confusion and instability in the
namespace of the DNS by the introduction of new top-level labels or
the different use of top-level labels present in the Root Server
system. The coordinators of the Yeti DNS Project do not consider the
Yeti DNS Project to be an alternate root in this sense, since by
design the namespace enabled by the Yeti-Root zone is identical to
that of the Root Zone.

Some commentators have expressed concern that the Yeti DNS Project
seeks to influence or subvert administrative policy relating to the
Root Server system, in particular in the use of DNSSEC trust anchors
not published by the IANA and the use of Yeti-Root servers in regions
where governments or other organizations have expressed interest in
operating a Root Server. The coordinators of the Yeti-Root project
observe that their mandate is entirely technical and has no ambition
to influence policy directly; they do hope, however, that technical
findings from the Yeti DNS Project might act as a useful resource for
the wider technical community.

Acknowledgments

Firstly, the authors would like to acknowledge the contributions from
the people who were involved in the implementation and operation of
the Yeti DNS by donating their time and resources. They are:

Tomohiro Ishihara, Antonio Prado, Stephane Bortzmeyer, Mickael
Jouanne, Pierre Beyssac, Joao Damas, Pavel Khramtsov, Dmitry
Burkov, Dima Burkov, Kovalenko Dmitry, Otmar Lendl, Praveen Misra,
Carsten Strotmann, Edwin Gomez, Daniel Stirnimann, Andreas
Schulze, Remi Gacogne, Guillaume de Lafond, Yves Bovard, Hugo
Salgado, Kees Monshouwer, Li Zhen, Daobiao Gong, Andreas Schulze,
James Cloos, and Runxia Wan.

Thanks to all people who gave important advice and comments to Yeti,
either in face-to-face meetings or virtually via phone or mailing
list. Some of the individuals are as follows:

Wu Hequan, Zhou Hongren, Cheng Yunqing, Xia Chongfeng, Tang
Xiongyan, Li Yuxiao, Feng Ming, Zhang Tongxu, Duan Xiaodong, Wang
Yang, Wang JiYe, Wang Lei, Zhao Zhifeng, Chen Wei, Wang Wei, Wang
Jilong, Du Yuejing, Tan XiaoSheng, Chen Shangyi, Huang Chenqing,
Ma Yan, Li Xing, Cui Yong, Bi Jun, Duan Haixing, Marc Blanchet,
Andrew Sullivan, Suzanne Wolf, Terry Manderson, Geoff Huston, Jaap
Akkerhuis, Kaveh Ranjbar, Jun Murai, Paul Wilson, and Kilnam
Chonm.

The authors also acknowledge the assistance of the Independent
Submissions Editorial Board, and of the following reviewers whose
opinions helped improve the clarity of this document:

Joe Abley, Paul Mockapetris, and Subramanian Moonesamy.

Authors' Addresses

Linjian Song (editor)

China
100176
Beijing Internet Institute
2nd Floor, Building 5, No.58 Jing Hai Wu Lu, BDA
Beijing 100176
China Internet Institute
Linjian Song (editor)

Email: songlinjian@gmail.com
URI: http://www.biigroup.com/

Dong Liu

China
100176
Beijing Internet Institute
2nd Floor, Building 5, No.58 Jing Hai Wu Lu, BDA
Beijing 100176
China Internet Institute
Dong Liu

Email: dliu@biigroup.com
URI: http://www.biigroup.com/

Paul Vixie
TISF
11400 La Honda Road
Woodside, California 94062
United States of America

Email: vixie@tisf.net
URI: http://www.redbarn.org/

Akira Kato
Keio University/WIDE Project

Japan
〒223-8526
Graduate School of Media Design, 4-1-1 Hiyoshi, Kohoku
Yokohama 223-8526
Japan
Keio University/WIDE Project
Akira Kato

Email: kato@wide.ad.jp
URI: http://www.kmd.keio.ac.jp/

Shane Kerr
Antoon Coolenlaan 41
Uithoorn 1422 GN
The Netherlands

Email: shane@time-travellers.org