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Versions: 00                                                            
Network Working Group                                           J. Abley
Internet-Draft                                                 Dyn, Inc.
Updates: 1034, 1035 (if approved)                        October 9, 2015
Intended status: Standards Track
Expires: April 11, 2016


                   Ordering of RRSets in DNS Messages
                 draft-jabley-dnsop-ordered-answers-00

Abstract

   The existing Domain Name System (DNS) specifications lack some
   clarity in their description of the process by which individual
   sections of a DNS message are constructed.

   This document updates RFC 1034 and RFC 1035 to provide a clearer
   specification, consistent with deployed implementations.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 11, 2016.

Copyright Notice

   Copyright (c) 2015 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
   Provisions Relating to IETF Documents
   (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.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Updates to RFC 1034  . . . . . . . . . . . . . . . . . . . . .  5
   4.  Updates to RFC 1035  . . . . . . . . . . . . . . . . . . . . .  6
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Appendix A.  Editorial Notes . . . . . . . . . . . . . . . . . . . 11
     A.1.  Venue  . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     A.2.  Change History . . . . . . . . . . . . . . . . . . . . . . 11
       A.2.1.  draft-jabley-dnsop-ordered-answers-00  . . . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12






























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1.  Terminology

   This document uses terminology specific to the Domain Name System
   (DNS), descriptions of which can be found in
   [I-D.ietf-dnsop-dns-terminology].

   In an exchange of DNS messages between two hosts, this document
   refers to the host sending a DNS request as the initiator, and the
   host sending a DNS response as the responder.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].






































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2.  Introduction

   [RFC1034] specifies an algorithm for use by responders when
   constructing response to a DNS QUERY.  This algorithm in some cases
   can result in multiple RRSets being included in a single section of a
   DNS message, e.g. when handling CNAME resource records.

   Many responder implementations have interpreted the direction to copy
   or store particular RRSets in the answer section of a DNS response to
   mean "append", treating each section as an ordered list of RRSets.
   Many initiators, in particular stub resolvers, are known to rely upon
   that interpretation when processing DNS responses received from
   responders.

   Some DNS implementations employ algorithms in other sections that aim
   to optimise processing of responses received by initiators, e.g.
   NAPTR before SRV before A/AAAA in the additional section of a
   response.  This behaviour has not been observed to cause any
   interoperability problems, and is explicitly permitted by this
   document.

   This document updates [RFC1035] to specify that the answer section in
   a DNS message is an ordered list of RRSets, but that other sections
   may be constructed differently, and clarifies the directions provided
   in [RFC1034] to match the observed behaviour and expectations of
   deployed software.

























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3.  Updates to RFC 1034

   [RFC1034] specifies the algorithms by which sections of a DNS
   response are constructed by a responder.  For example, step 3 of the
   algorithm described in [RFC1034] section 4.3.2 contains the direction
   "copy all RRs which match QTYPE into answer section".

   In this case, and in all other cases where [RFC1034] specifies that
   particular RRSets be included in the answer section of a DNS message,
   the section MUST be treated as an ordered list of RRSets.  When it is
   necessary to include new RRSets in a section of a DNS message that is
   under construction, those RRSets MUST be appended.  The receiver of a
   DNS message MAY refuse to process DNS messages that have been
   constructed differently.

   When constructing other sections of a DNS message, each section MAY
   be treated as a non-ordered list, and a receiver of a DNS message
   MUST NOT reject a DNS message on the basis of the order of RRSets in
   those sections.
































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4.  Updates to RFC 1035

   In a DNS message, the answer section MUST be considered to be an
   ordered set of RRSets; all other sections MUST be considered to be a
   non-ordered set.

   DNS implementations MUST construct each section in a DNS response
   according to the algorithms specified in [RFC1034], as clarified in
   Section 3 of this document.










































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5.  Security Considerations

   The recommendations contained in this document have no known security
   implications.















































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6.  IANA Considerations

   This document has no IANA actions.
















































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7.  Acknowledgements

   The contributions of Mark Andrews and Paul Vixie to this document are
   acknowledged.















































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8.  References

8.1.  Normative References

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

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

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
              RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

8.2.  Informative References

   [I-D.ietf-dnsop-dns-terminology]
              Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
              Terminology", draft-ietf-dnsop-dns-terminology-05 (work in
              progress), September 2015.




























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Appendix A.  Editorial Notes

   This section (and sub-sections) to be removed prior to publication.

A.1.  Venue

   An appropriate forum for discussion of this draft is the dnsop
   working group.

A.2.  Change History

A.2.1.  draft-jabley-dnsop-ordered-answers-00

   Initial draft circulated for comment.





































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Author's Address

   Joe Abley
   Dyn, Inc.
   103-186 Albert Street
   London, ON  N6A 1M1
   Canada

   Phone: +1 519 670 9327
   Email: jabley@dyn.com









































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