[Docs] [txt|pdf|xml] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-johansson-sip-dual-stack) 00 01 02 03 04 05 06 07 08 RFC 7984

SIPCORE                                                     O. Johansson
Internet-Draft                                                 Edvina AB
Updates: RFC 3263 (if approved)                             G. Salgueiro
Intended status: Standards Track                           Cisco Systems
Expires: August 26, 2016                                      V. Gurbani
                                               Bell Labs, Alcatel-Lucent
                                                          D. Worley, Ed.
                                                                 Ariadne
                                                       February 23, 2016


 Locating Session Initiation Protocol (SIP) Servers in a Dual-Stack IP
                                Network
                  draft-ietf-sipcore-dns-dual-stack-04

Abstract

   RFC 3263 defines how a Session Initiation Protocol (SIP)
   implementation, given a SIP Uniform Resource Identifier (URI), should
   locate the next hop SIP server using Domain Name System (DNS)
   procedures.  As SIP networks increasingly transition from IPv4-only
   to dual-stack, a quality user experience must be ensured for dual-
   stack SIP implementations.  This document updates the DNS procedures
   described in RFC 3263 for dual-stack SIP implementations in
   preparation for forthcoming specifications for applying Happy
   Eyeballs to SIP.

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 August 26, 2016.








Johansson, et al.        Expires August 26, 2016                [Page 1]


Internet-Draft      Locating SIP Servers in IPv4/IPv6      February 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
   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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  DNS Procedures in a Dual-Stack Network  . . . . . . . . . . .   4
     4.1.  Dual-Stack SIP UA DNS Record Lookup Procedure . . . . . .   4
     4.2.  Indicating Address Family Preference in DNS SRV Records .   5
   5.  Clarification of RFC 6157 . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Revision History  . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Changes from draft-ietf-sipcore-dns-dual-stack-03 to
           draft-ietf-sipcore-dns-dual-stack-04  . . . . . . . . . .   6
     9.2.  Changes from draft-ietf-sipcore-dns-dual-stack-02 to
           draft-ietf-sipcore-dns-dual-stack-03  . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The Session Initiation Protocol (SIP, [RFC3261]) and the additional
   documents that extended it provide support for both IPv4 and IPv6.
   However, this support does not fully extend to the highly hybridized
   environments that are characteristic of the transitional migratory
   phase from IPv4 to IPv6 networks.  During this phase, many server and
   client implementations run on dual-stack hosts.  In such
   environments, a dual-stack host will likely suffer greater connection
   delay, and by extension an inferior user experience, than an
   IPv4-only host.  The need to remedy this diminished performance of



Johansson, et al.        Expires August 26, 2016                [Page 2]


Internet-Draft      Locating SIP Servers in IPv4/IPv6      February 2016


   dual-stack hosts led to the development of the Happy Eyeballs
   [RFC6555] algorithm, which has since been implemented in many
   protocols and applications.

   This document updates the DNS lookup procedures of RFC 3263[RFC3263]
   in preparation for the specification of the application of Happy
   Eyeballs to SIP to provide enhanced performance, and consequently
   user experience, in highly hybridized dual-stack SIP networks.  The
   procedures described herein are such that a dual-stack client should
   look up both A and AAAA records in DNS and then select the best way
   to set up a network flow.  The details of how the latter is done is
   considered out of scope for this document.  See the Happy Eyeballs
   algorithm and implementation and design considerations in RFC 6555
   [RFC6555] for more information about issues with setting up dual-
   stack network flows.

   This document clarifies the interaction of [RFC3263] with [RFC6157]
   as described in Section 5.

2.  Notational Conventions

   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 RFC 2119 [RFC2119].

3.  Terminology

   RFC 3261 [RFC3261] defines additional terms used in this document
   that are specific to the SIP domain such as "proxy"; "registrar";
   "redirect server"; "user agent server" or "UAS"; "user agent client"
   or "UAC"; "back-to-back user agent" or "B2BUA"; "dialog";
   "transaction"; "server transaction".

   This document uses the term "SIP Server" that is defined to include
   the following SIP entities: user agent server, registrar, redirect
   server, a SIP proxy in the role of user agent server, and a B2BUA in
   the role of a user agent server.

   This document also uses the following terminology to make clear
   distinction between SIP entities supporting only IPv4, only IPv6 or
   supporting both IPv4 and IPv6.

   IPv4-only UA/UAC/UAS:  An IPv4-only UA/UAC/UAS supports SIP signaling
      and media only on the IPv4 network.  It does not understand IPv6
      addresses.






Johansson, et al.        Expires August 26, 2016                [Page 3]


Internet-Draft      Locating SIP Servers in IPv4/IPv6      February 2016


   IPv6-only UA/UAC/UAS:  An IPv6-only UA/UAC/UAS supports SIP signaling
      and media only on the IPv6 network.  It does not understand IPv4
      addresses.

   IPv4/IPv6 UA/UAC/UAS:  A UA/UAC/UAS that supports SIP signaling and
      media on both IPv4 and IPv6 networks; such a UA/UAC/UAS is known
      (and will be referred to in this document) as a "dual-stack"
      [RFC4213] UA/UAC/UAS.

   address records:  The DNS records which translate a domain name into
      addresses within the address family(ies) that the UA supports, as
      A RR's provide IPv4 addresses and AAAA RR's provide IPv6
      addresses.

4.  DNS Procedures in a Dual-Stack Network

   This specification introduces two normative DNS lookup procedures.
   These are designed to improve the performance of dual-stack clients
   in IPv4/IPv6 networks.

4.1.  Dual-Stack SIP UA DNS Record Lookup Procedure

   Once the transport protocol has been determined, the procedure for
   discovering an IP address if the TARGET is not a numeric IP address
   but the port is explicitly stated in the URI, is detailed in
   Section 4.2 of RFC 3263[RFC3263].  The piece relevant to to this
   discussion is:

      If the TARGET was not a numeric IP address, but a port is present
      in the URI, the client performs an A or AAAA record lookup of the
      domain name.  The result will be a list of IP addresses, each of
      which can be contacted at the specific port from the URI and
      transport protocol determined previously.

   Section 4.2 of RFC 3263 [RFC3263] also goes on to describe the
   procedure for discovering an IP address if the TARGET is not a
   numeric IP address, and no port is present in the URI.  The piece
   relevant to to this discussion is:

      If no SRV records were found, the client performs an A or AAAA
      record lookup of the domain name.  The result will be a list of IP
      addresses, each of which can be contacted using the transport
      protocol determined previously, at the default port for that
      transport.  Processing then proceeds as described above for an
      explicit port once the A or AAAA records have been looked up.

   Happy Eyeballs [RFC6555] documents that looking up the "A or AAAA
   record" is not an effective practice for dual-stack clients and that



Johansson, et al.        Expires August 26, 2016                [Page 4]


Internet-Draft      Locating SIP Servers in IPv4/IPv6      February 2016


   it can add significant connection delay and greatly degrade user
   experience.  Therefore, this document makes the following normative
   addendum to the DNS lookup procedures of Section 4.2 of RFC 3263
   [RFC3263] for IPv4/IPv6 hybrid SIP networks and recommends it as a
   best practice for such dual-stack networks:

      The dual-stack client SHOULD look up all address records (i.e.,
      for all address family(ies) that it supports) for the domain name
      and add the resulting addresses to the list of IP addresses to be
      contacted.  A client MUST be prepared for DNS lookups to return
      addresses in families that it does not support; such addresses
      MUST be ignored as unusable and the supported addresses used as
      specified herein.

4.2.  Indicating Address Family Preference in DNS SRV Records

   The Happy Eyeballs algorithm [RFC6555] is particularly effective when
   dual-stack client applications have significant performance
   differences in their IPv4 or IPv6 network paths.  In this common
   scenario it is often necessary for a dual-stack client to indicate a
   preference for either IPv4 or IPv6.  A service may use DNS SRV
   records to indicate such a preference for an address family.  This
   way, a server with a high-latency and/or low-capacity IPv4 tunnel may
   indicate a preference for being contacted using IPv6.  A server that
   wishes to do this can use the lowest SRV priority to publish
   hostnames that only resolve in IPv6 and the next priority with host
   names that resolve in both address families.

5.  Clarification of RFC 6157

   [RFC6157] defers to the Source and Destination Address Selection
   algorithms defined in [RFC6724] (the successor of [RFC3484]) when
   allowing a client to choose a specific server (c.f.  Section 5 in
   [RFC6157]).

   This document clarifies the process: If SRV lookup is successful, the
   major ordering of the list of destination addresses is determined by
   the priority and weight fields of the SRV records as specified in
   [RFC2782].  The (minor) ordering among the destinations derived from
   the "target" field of a single SRV record is determined by [RFC6724].

6.  Security Considerations

   This document introduces two new normative procedures to the existing
   DNS procedures used to locate SIP servers.  While both of these
   procedures are optimizations designed to improve the performance of
   dual-stack clients, neither introduces any new security
   considerations.



Johansson, et al.        Expires August 26, 2016                [Page 5]


Internet-Draft      Locating SIP Servers in IPv4/IPv6      February 2016


   The specific security vulnerabilities, attacks and threat models of
   the various protocols discussed in this document (SIP, DNS, SRV
   records, Happy Eyeballs requirements and algorithm, etc.) are well
   documented in their respective specifications.

7.  IANA Considerations

   This document does not require any actions by IANA.

8.  Acknowledgments

   The authors would like to acknowledge the support and contribution of
   the SIP Forum IPv6 Working Group.  This document is based on a lot of
   tests and discussions at SIPit events, organized by the SIP Forum.

   This document has benefited from the expertise and review feedback of
   many participants of the IETF DISPATCH and SIPCORE WG mailing lists
   as well as those on the SIP Forum IPv6 Task Group mailing list.  The
   authors wish to specifically call out the efforts and express their
   gratitude for the detailed and thoughtful comments and corrections of
   Dan Wing, Brett Tate, Rifaat Shekh-Yusef, Carl Klatsky, Mary Barnes,
   Keith Drage, Cullen Jennings and Simon Perreault.

   The authors also thank the SIPCORE WG chairs, Paul Kyzivat and Adam
   Roach, and assigned Area Director, Richard Barnes, for their support
   and thorough evaluation of this work.

9.  Revision History

   [Note to RFC Editor: Please remove this entire section upon
   publication as an RFC.]

9.1.  Changes from draft-ietf-sipcore-dns-dual-stack-03 to draft-ietf-
      sipcore-dns-dual-stack-04

   Changed the "updates" specification to add RFC 3263 and remove RFC
   6157.

   Added Simon Perreault to the acknowledgments.

   Minor wording changes.

9.2.  Changes from draft-ietf-sipcore-dns-dual-stack-02 to draft-ietf-
      sipcore-dns-dual-stack-03

   Described the relationship to RFC 3263 as "update", since the
   existing wording in 3263 is not what we want.  Arguably, the new




Johansson, et al.        Expires August 26, 2016                [Page 6]


Internet-Draft      Locating SIP Servers in IPv4/IPv6      February 2016


   wording is what was intended in 3263, but the existing wording either
   does not say that or says it in a way that is easily misunderstood.

   Described the relationship to RFC 6157 as "clarification", since the
   described interaction between 3263 and 6157 appears to be the only
   reasonable interpretation.

   Revised wording, punctuation, and capitalization in various places.

   Clarified that this draft does not document Happy Eyeballs for SIP,
   but is preparatory for it.

   Attempted to use "update" for text that is definitively a change to
   the preexisting text and "clarify" for text that is a more clear
   statement of the (presumed) intention of the preexisting text.

   Removed normative words from section 1, the introduction.

   Copied definition of "address records" from RFC 2782 (SRV records) to
   allow the specifications to expand automatically to include any new
   address families.

   Relocated the text requiring a client to ignore addresses that it
   discovers in address families it does not support from section 4.2
   (which describes why the situation arises) to section 4.1 (which
   describes how clients look up RRs).

   Clarified the interaction with RFC 6157 (source and destination
   address selection in IPv6) to specify what must have been intended:
   The major sort of the destinations is the ordering determined by
   priority/weight in the SRV records; the addresses derived from a
   single SRV record's target are minorly sorted based on RFC 6157.

   Removed editor's name from the acknowledgments list.

10.  References

10.1.  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,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2782]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
              specifying the location of services (DNS SRV)", RFC 2782,
              DOI 10.17487/RFC2782, February 2000,
              <http://www.rfc-editor.org/info/rfc2782>.



Johansson, et al.        Expires August 26, 2016                [Page 7]


Internet-Draft      Locating SIP Servers in IPv4/IPv6      February 2016


   [RFC3263]  Rosenberg, J. and H. Schulzrinne, "Session Initiation
              Protocol (SIP): Locating SIP Servers", RFC 3263,
              DOI 10.17487/RFC3263, June 2002,
              <http://www.rfc-editor.org/info/rfc3263>.

   [RFC6157]  Camarillo, G., El Malki, K., and V. Gurbani, "IPv6
              Transition in the Session Initiation Protocol (SIP)",
              RFC 6157, DOI 10.17487/RFC6157, April 2011,
              <http://www.rfc-editor.org/info/rfc6157>.

10.2.  Informative References

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <http://www.rfc-editor.org/info/rfc3261>.

   [RFC3484]  Draves, R., "Default Address Selection for Internet
              Protocol version 6 (IPv6)", RFC 3484,
              DOI 10.17487/RFC3484, February 2003,
              <http://www.rfc-editor.org/info/rfc3484>.

   [RFC4213]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
              for IPv6 Hosts and Routers", RFC 4213,
              DOI 10.17487/RFC4213, October 2005,
              <http://www.rfc-editor.org/info/rfc4213>.

   [RFC6555]  Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
              Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April
              2012, <http://www.rfc-editor.org/info/rfc6555>.

   [RFC6724]  Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
              "Default Address Selection for Internet Protocol Version 6
              (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,
              <http://www.rfc-editor.org/info/rfc6724>.

Authors' Addresses

   Olle E. Johansson
   Edvina AB
   Runbovaegen 10
   Sollentuna  SE-192 48
   SE

   Email: oej@edvina.net





Johansson, et al.        Expires August 26, 2016                [Page 8]


Internet-Draft      Locating SIP Servers in IPv4/IPv6      February 2016


   Gonzalo Salgueiro
   Cisco Systems
   7200-12 Kit Creek Road
   Research Triangle Park, NC  27709
   US

   Email: gsalguei@cisco.com


   Vijay Gurbani
   Bell Labs, Alcatel-Lucent
   1960 Lucent Lane
   Rm 9C-533
   Naperville, IL  60563
   US

   Email: vkg@bell-labs.com


   Dale R. Worley (editor)
   Ariadne Internet Services
   738 Main St.
   Waltham, MA  02451
   US

   Email: worley@ariadne.com

























Johansson, et al.        Expires August 26, 2016                [Page 9]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/