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Network Working Group                                      S. Bortzmeyer
Internet-Draft                                                     AFNIC
Intended status: Standards Track                          April 29, 2016
Expires: October 31, 2016

    Using DNAME in the DNS root zone for sinking of special-use TLDs


   This documents asks IANA to add DNAME records in the DNS root zone
   for TLDs which are in the Special-Use Domain Names registry, in order
   to ensure they receive an appropriate reply (NXDOMAIN) and that the
   root nameservers are not too bothered by them.

   REMOVE BEFORE PUBLICATION: there is no obvious place to discuss this
   document.  May be the IETF DNSOP (DNS Operations) group, through its
   mailing list (the author reads it).  Or may AS112 operators mailing
   lists?  The source of the document, as well as a list of open issues,
   is currently kept at Github [1].

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on October 31, 2016.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents

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   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction and background . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Terminology  . . . . . . . . . . . . . . . .   2
   2.  Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Benefits  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Possible issues . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
     8.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction and background

   The DNS root nameservers receive a lot of requests for TLDs which do
   not exist.  See for instance [fujiwara-root-traffic] or
   [icann-l-root-stats] or [ssac-045].  In the spirit of [RFC7534], it
   would be good if they could be redirected to a sink such as AS112, to
   save root nameservers's resources.

   Some of these names, and specially one of the biggest offenders,
   .local ([RFC6762]), are registered in the Special-Use Domain Names
   registry [2] of [RFC6761].  They are obvious candidates for a
   "delegation" to the sink.

   It is proposed to use the new AS112, the one described by [RFC7535]
   to implement this sink.

1.1.  Requirements Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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2.  Rules

   Every TLD ([RFC7719], section 2) which is in the Special-Use Domain
   Names registry [3] ([RFC6761]) SHOULD be "delegated" by IANA through
   a DNAME to empty.as112.arpa as described in [RFC7535] if and only if
   the registration of this TLD say that resolvers SHOULD NOT or MUST
   NOT look them up in the DNS.

   It is important to notice that this document does not define a policy
   to decide if a TLD should be "delegated" or not.  Instead, it relies
   on the existing Special-Use Domain Names registry and its rules.

   RFC-EDITOR: remove before publication.  As of today, with these
   rules, .local ([RFC6762]) or .onion ([RFC7686]) would be "delegated"
   but not .example (its registration in [RFC6761] does not define
   special handling for resolvers) or .home ([RFC7788]) or .belkin (this
   last one generates a huge traffic at the root nameservers but is not
   in the Special-Use Domain Names registry).

3.  Benefits

   The main benefit is less load on the root nameservers and a better
   efficiency of the caches, therefore helping the entire DNS ecosystem.

4.  Possible issues

   Of course, the solution described in this document requires a good
   support of DNAME by the resolvers.  Appendix A of [RFC7535] describes
   an experiment which was run in 2013 and which shows that, indeed, we
   can rely on DNAME (quoting the authors: "We conclude that there is no
   evidence of a consistent failure on the part of deployed DNS
   resolvers to correctly resolve a DNAME construct.").  The technical
   tests documented in [damas-dname] have the same conclusion: DNAMEs
   work fine.

   What could be the expected "saving" of resources by this
   "delegation"?  Well-behaved resolvers should cache the NXDOMAIN
   (negative caching duration in the root zone is currently one day) but
   this covers only the requested name, not the whole TLD (until
   [I-D.ietf-dnsop-nxdomain-cut] is widely deployed and it would only
   partially solved the issue).  There is also a concern that the
   requests for these non-existing TLDs are not issued by "proper"
   systems (because they are supposed to never leave the local network).
   If these requests are sent by badly programmed or badly configured
   systems, can we be sure they will honor the "delegation" and the
   caching?  To summarise, it would be interesting to design and conduct
   an experiment to measure the expected effect.  Ideas are welcome (the
   most obvious one, running a "delegation" during a moment then

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   deleting it and comparing the results, is difficult to foresee, for
   political reasons).

   To be sure AS112 could handle the load, AS 112 operators were
   consulted and expressed no objection.

   Regarding DNSSEC, do note the future DNAMEs in the root zone will be
   signed, but the target, empty.as112.arpa, is not.  See George
   Michaelson's message [4].  So, it will not be possible to validate
   the answers.  Not a problem since these requests should never have
   been sent to the root nameservers, anyway.

   RFC-EDITOR: remove before publication.  As of today, it exists
   apparently five nodes in the new AS112.  There is no "official"
   "delegation" to it.  Do note that, as a consequence of the new AS122
   structure, it is not possible to see how many unofficial
   "delegations" exist (to see an example, see junk.bortzmeyer.fr).

5.  IANA Considerations

   IANA is directed to add a DNAME in the root zone for every TLD which
   fits the rules of Section 2.

   RFC-EDITOR: remove before publication.  There is currently no DNAME
   in the root zone.  It is expected that the creation of the first one
   will require a top-down, multi-stakeholder, long and complicated
   process with a lot of meetings, reports by consultants and design
   teams.  We already have one short mention of this possibility in
   [ssac-009], then one decision by ICANN [icann-idn-dname] to study the
   matter and one technical report made after that decision
   [damas-dname] ("This report found no failure in resolution nor in the
   ability to perform DNSSEC validation when DNAME was used in the root

   TODO: if DNAMEs in the "real" root zone are delayed, is it possible/
   realistic for IANA to create an experimental root zone containing the
   new AS112 "delegations", so that roots like Yeti could publish it and
   test it?

   REMOVE BEFORE PUBLICATION: there are today TLDs with a DNAME at their
   apex (not the same thing): xn--kprw13d and xn--mgba3a4f16a.

6.  Security Considerations

   The requests for the TLD in the Special-Use Domain Names registry are
   typically NOT supposed to leak to the authoritative public name
   servers such as the ones of the root zone.  If they do, it means a
   misconfiguration somewhere.  The leak is independant on whether the

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   name is "delegated" to AS112 or not.  See section 8 of [RFC7534] for
   an analysis.

   Nevertheless, privacy considerations have to be taken into account.
   Some people believe there are added risks, because the queries will
   be seen by AS112 servers which, unlike the root nameservers, are
   managed by many "random people".  This means that population of
   people who can see the query streams is increased from the set of
   root nameserver operators and people that they share data with, to
   potentially anybody.  There's no defence against a malefactor
   hijacking AS112 traffic, because in a real sense that traffic is
   intended to be hijacked.

7.  Acknowledgments

   Thanks to Paul Hoffman to say that it may be a good idea, for Patrik
   Faltstrom for documentation and research, for Joe Abley for tough
   proofreading and many suggestions, and for Ted Lemon to give the
   final impulse, with his [I-D.tldr-sutld-ps].

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
              RFC2119, March 1997,

   [RFC6761]  Cheshire, S. and M. Krochmal, "Special-Use Domain Names",
              RFC 6761, DOI 10.17487/RFC6761, February 2013,

   [RFC7534]  Abley, J. and W. Sotomayor, "AS112 Nameserver Operations",
              RFC 7534, DOI 10.17487/RFC7534, May 2015,

   [RFC7535]  Abley, J., Dickson, B., Kumari, W., and G. Michaelson,
              "AS112 Redirection Using DNAME", RFC 7535, DOI 10.17487/
              RFC7535, May 2015,

   [RFC7719]  Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
              Terminology", RFC 7719, DOI 10.17487/RFC7719, December
              2015, <http://www.rfc-editor.org/info/rfc7719>.

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8.2.  Informative References

   [RFC6762]  Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
              DOI 10.17487/RFC6762, February 2013,

   [RFC7686]  Appelbaum, J. and A. Muffett, "The ".onion" Special-Use
              Domain Name", RFC 7686, DOI 10.17487/RFC7686, October
              2015, <http://www.rfc-editor.org/info/rfc7686>.

   [RFC7788]  Stenberg, M., Barth, S., and P. Pfister, "Home Networking
              Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April
              2016, <http://www.rfc-editor.org/info/rfc7788>.

              Lemon, T. and R. Droms, "Special Use TLD Problem
              Statement", draft-tldr-sutld-ps-00 (work in progress),
              April 2016.

              Bortzmeyer, S. and S. Huque, "NXDOMAIN really means there
              is nothing underneath", draft-ietf-dnsop-nxdomain-cut-02
              (work in progress), April 2016.

              Fujiwara, K., "2014 Root DITL Data analysis and TLD
              popularity analysis (OARC workshop)", October 2014,

              "QTYPE values for most popular TLDs (ICANN's L-root server
              public statistics)", April 2016,

              ICANN, , "SAC 009 - Alternative TLD Name Systems and
              Roots: Conflict, Control and Consequences", March 2006,

              ICANN, , "SAC 045 - Invalid Top Level Domain Queries at
              the Root Level of the Domain Name System", November 2010,

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              Damas, J., "Report on the Assessment of Security and
              Stability Implications of the Use of DNAME Resource
              Records in the Root Zone of the DNS", May 2011,

              ICANN, , "Adopted Board Resolutions - IDN Variants", March
              2010, <https://www.icann.org/resources/board-material/

8.3.  URIs

   [1] http://www.iana.org/assignments/special-use-domain-names/special-

   [2] http://www.iana.org/assignments/special-use-domain-names/special-

   [3] https://mailarchive.ietf.org/arch/msg/dnsop/

Author's Address

   Stephane Bortzmeyer
   1, rue Stephenson
   Montigny-le-Bretonneux  78180

   Phone: +33 1 39 30 83 46
   Email: bortzmeyer+ietf@nic.fr
   URI:   http://www.afnic.fr/

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