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Versions: (RFC 3427) 00 01 02 03 04 RFC 5727

Network Working Group                                        J. Peterson
Internet-Draft                                             NeuStar, Inc.
Intended status: Standards Track                             C. Jennings
Expires: August 30, 2009                                   Cisco Systems
                                                       February 26, 2009

        Change Process for the Session Initiation Protocol (SIP)

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.  This document may contain material
   from IETF Documents or IETF Contributions published or made publicly
   available before November 10, 2008.  The person(s) controlling the
   copyright in some of this material may not have granted the IETF
   Trust the right to allow modifications of such material outside the
   IETF Standards Process.  Without obtaining an adequate license from
   the person(s) controlling the copyright in such materials, this
   document may not be modified outside the IETF Standards Process, and
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on August 30, 2009.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

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   This memo documents a process intended to organize the future
   development of the Session Initiation Protocol (SIP).  As the
   environments in which SIP is deployed grow more numerous and diverse,
   modifying or extending SIP in certain ways may threaten the
   interoperability and security of the protocol; however, the IETF
   process must also cater to the realities of existing deployments and
   serve the needs of the implementers working with SIP.  This document
   therefore defines the functions of two long-lived working groups in
   the RAI Area which are, respectively, responsible for the maintenance
   of the core SIP specifications and development of new efforts to
   extend and apply SIP.  This document obsoletes RFC3427.

Table of Contents

   1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  History and Development  . . . . . . . . . . . . . . . . . . .  5
     2.1.  The IETF SIPCORE Working Group . . . . . . . . . . . . . .  5
     2.2.  The IETF DISPATCH Working Group  . . . . . . . . . . . . .  6
   3.  Introducing New Work to RAI  . . . . . . . . . . . . . . . . .  8
   4.  Extensibility and Architecture . . . . . . . . . . . . . . . . 10
     4.1.  SIP Event Packages . . . . . . . . . . . . . . . . . . . . 11
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
     6.1.  Clarification of RFC3969 . . . . . . . . . . . . . . . . . 15
   7.  Changelog  . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     7.1.  Changes from RFC3427bis-00 . . . . . . . . . . . . . . . . 16
     7.2.  Changes from RFC3427 . . . . . . . . . . . . . . . . . . . 16
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 17
   9.  Normative References . . . . . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19

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1.  Terminology

   In this document, the key words "MAY", "MUST, "MUST NOT", "SHOULD",
   and "SHOULD NOT", are to be interpreted as described in [RFC2119].
   This document additionally uses [RFC5226] language to describe IANA

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2.  History and Development

   The Session Initiation Protocol (SIP) [RFC3261] has grown well beyond
   its origins in Internet-based multimedia sessions, and now enjoys
   widespread popularity in Voice over IP or IP telephony applications,
   both inside IETF and within other standards groups.  One result of
   this popularity has been a continual flood of proposals for SIP
   modifications and extensions.  The challenge for IETF management of
   SIP has to preserve baseline interoperability across its many

   In order to defend SIP against changes that might reduce
   interoperability, the working group chairs and Area Directors
   responsible for its management authored the SIP change process
   [RFC3427].  SIP change defined the role of the SIP and SIPPING
   working groups in shepherding ongoing work on the SIP standard.  It
   also defined ways that external working groups or bodies could define
   extensions intended for limited usage, especially through the "P-"
   header mechanism.

   Over time, however, the management structure of RFC3427 has
   demonstrated some limitations.  The first and most significant of
   these lies in the "P-" headers.  While "P-" headers require expert
   review and IESG shepherding, in practice IETF oversight of these
   headers is quite limited, and the value added by the IETF supervising
   their development remains unclear.  More importantly, the presence of
   a "P-" in front of a header name does nothing to prevent a popular
   header from seeing deployment outside of the original "limited usage"
   it envisioned; a prominent example of this today is the P-Asserted-
   Identity (PAID) header, described in RFC3325 [RFC3325].

   Consequently, this document obsoletes RFC3427 and describes a new
   structure for the management of IETF deliverables.

2.1.  The IETF SIPCORE Working Group

   Historically, the IETF SIP Working Group (sip) was chartered to be
   the "owner" of the SIP protocol [RFC3261] for the duration of the
   life of the working group exists.  All changes or extensions to SIP
   must first exist as SIP Working Group documents.  The SIP working
   group was charged with being the guardian of the SIP protocol for the
   Internet, and therefore was therefore mandated only to extend or
   change the SIP protocol when there are compelling reasons to do so.

   The SIPCORE working group replaces the function of the SIP working
   group in the original RFC3427 account.  Documents that must be
   handled by the SIPCORE working group include all updates or obsoletes
   of RFC3261 through RFC3265.  All SIP extensions considered in SIPCORE

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   must be standards track.  They may be based upon requirements
   developed externally in other IETF working groups.

   Typical IETF working groups do not live forever; SIPCORE's charter is
   however open-ended in order to allow it to remain the place where
   core SIP development will continue.  In the event that the SIPCORE
   working group has closed and no suitable replacement or follow-on
   working group is active (and this specification also has not been
   superseded), then when modifications to the core SIP protocol are
   proposed the RAI Area directors will the use the non-working group
   standards track document process (described in Section 6.1.2 of RFC
   2026 [RFC2026]) using the SIPCORE mailing list and designated experts
   from the SIP community for review.  The IETF will remain the home of
   extensions of SIP and the rest of this document.  The rate of growth
   of extensions of any protocol in the IETF is hoped to be low.

   It is appropriate for any working group to develop SIP event packages
   [RFC3265], but the working group must have charter approval to do so.
   The IETF will also require RFC5226 IETF Review for the registration
   of event packages developed outside the scope of an IETF working
   group.  Instructions for event package registrations are provided in
   Section 4.1.

2.2.  The IETF DISPATCH Working Group

   Historically, the IETF Session Initiation Protocol Proposal
   Investigation (sipping) Working Group was chartered to be a filter in
   front of the SIP Working Group.  This working group investigated
   requirements for applications of SIP, some of which led to requests
   for extensions to SIP.  These requirements may come from the
   community at large, or from individuals who are reporting the
   requirements as determined by another standards body.

   The DISPATCH working group replaces the function of the SIPPING WG,
   although with several important changes to its functionality.  Like
   SIPPING, DISPATCH considers new proposals for work in the RAI Area,
   but rather than taking on specification deliverables as charter items
   itself, DISPATCH identifies the proper venue for work.  If no such
   venue yet exists in the RAI Area, DISPATCH will develop charters and
   consensus for a BoF, working group, or exploratory group [RFC5111] as
   appropriate.  Unlike the previous change structure, a DISPATCH review
   of any proposed change to core SIP is not required before it
   progresses to SIPCORE; however, any new proposed work which does not
   clearly fall within the charter of an existing RAI Area effort should
   be examined by DISPATCH.

   In reaction to a proposal, the DISPATCH Working Group may determine:
   that these requirements justify a change to the core SIP

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   specifications (RFC3261 through RFC3265) and thus any resulting work
   must transpire in SIPCORE, that the requirements do not change the
   SIP core specifications but require a new effort in the RAI area (be
   that a working group, a BoF, or what have you), that the requirements
   fall within the scope of existing chartered work in the RAI Area, or
   that the proposal should not be acted upon at this time.  Because the
   SIP protocol gets so much attention, some application designers may
   want to use it just because it is there, such as for controlling
   household appliances.  DISPATCH should act as a filter, accepting
   only proposals which play to the strengths of SIP, not those that
   confuse its applicability or ultimately reduce its usefulness as a
   means for immediate personal communications on the Internet.

   In practice, it is expected that the DISPATCH WG behaves as a RAI
   "Open Area" working group, similar to those employed in other areas
   of the IETF.  While it does not have the traditional deliverables of
   a working group, DISPATCH may at the discretion of its chairs adopt
   milestones such as the production of charter text for a BoF or
   working group, a "-00" problem statement document that explicates a
   proposed work effort, or a document explaining why a particular
   direction for standards development was not pursued.

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3.  Introducing New Work to RAI

   When proposals arise for modifications or extensions to SIP outside
   the scope of existing chartered RAI Area work, they must be written
   up as an Internet-Draft explaining the problem they are trying to
   solve, why SIP is the applicable protocol, and why the existing SIP
   protocol will not work.  The Internet-Draft must include a detailed
   set of requirements (distinct from solutions) that SIP would need to
   meet to solve the particular problem.  The Internet-Draft must also
   describe in detail any security issues that arise from meeting those
   requirements.  After the Internet-Draft is published, the authors
   should send a note to the DISPATCH Working Group mailing list to
   start discussion on the Internet-Draft.

   The DISPATCH working group chairs, in conjunction with the RAI Area
   Directors, will determine if the particular problems raised in the
   requirements Internet-Draft is indeed outside the charter of existing
   efforts, and if so, if it warrants a DISPATCH milestone for the
   definition of a new effort.  The DISPATCH working group should
   consider whether the requirements can be merged with other
   requirements from other applications, and refine the ID accordingly.

   Once a new effort has been defined in DISPATCH and there is consensus
   that it should go forward, if the new effort will take the form of a
   working group or BoF, then the ADs will present the proposed new
   effort charter to the IESG and IAB, in accordance with the usual
   process for chartering efforts.  If the new effort involves the
   rechartering of an existing working group, then similarly the
   existing working group rechartering functions will be performed by
   the appropriate WG chairs and ADs.  If the IESG (with IAB advice)
   approves of the new charter or Bof, the DISPATCH working group has
   completed its deliverable and the new effort becomes autonomous.

   Anyone proposing requirements for new work is welcome to jointly
   develop, in a separate Internet-Draft, a mechanism that would meet
   the requirements.  No working group is required to adopt the proposed
   solution from this additional Internet-Draft.

   The SIPCORE Working Group is required to protect the architectural
   integrity of SIP and must not add features that do not have general
   use beyond the specific case.  Also, SIPCORE must not add features
   just to make a particular function more efficient at the expense of
   simplicity or robustness.

   With respect to standardization, this process means that SIP
   extensions come only from the IETF, the body that created SIP.  The
   IETF will not publish a SIP extension RFC outside of the processes
   described here.  The DISPATCH working group may also evaluate and

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   approve proposals for extensions if the requirements are judged to be
   appropriate to SIP, but are not sufficiently general for standards
   track activity.

   Some working groups generate requirements for SIP solutions and/or
   extensions.  At the time this document was written, some groups with
   such chartered deliverables include SIP for Instant Messaging and
   Presence Leveraging Extensions (simple), Basic Level of
   Interoperability for SIP Services (bliss) and Session Peering for
   Multimedia Interconnect (speermint).

   The RAI ADs may, on a case by case basis, support a process in which
   the requirements analysis is implicit and the SIP working group
   requests the addition of a charter item for an extension without a
   full DISPATCH process as described.  This will be the exception.

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4.  Extensibility and Architecture

   In an idealized protocol model, extensible design would be self-
   contained, and it would be inherent that new extensions and new
   headers would naturally have an architectural coherence with the
   original protocol.

   However, this idealized vision has not been attained in the world of
   standards track protocols.  While, interoperability implications can
   be addressed by capabilities negotiation rules, the effects of adding
   features that overlap, or that deal with a point solution and are
   not, are much harder to control with rules.  Therefore, the RAI Area
   calls for architectural guardianship and application of Occam's Razor
   by the SIPCORE and DISPATCH Working Groups.

   In keeping with the IETF tradition of "running code and rough
   consensus", it is valid to allow for the development of SIP
   extensions that are either not ready for standards track, but might
   be understood for that role after some running code, or are private
   or proprietary in nature, because a characteristic motivating them is
   usage that is known not to fit the Internet architecture for SIP.  In
   the past, headers associated with those extensions were called "P-"
   headers, for "preliminary", "private", or "proprietary".

   However, the "P-" header process has not served the purpose for which
   it was designed - namely, to restrict to closed environments the
   usage of mechanisms the IETF would not (yet) endorse for general
   usage.  In fact, some "P-" headers have enjoyed widespread
   implementation; because of the "P-" prefix, however, there seems to
   be no plausible migration path to designate these as general-usage
   headers without trying to force implausible changes on large bases of

   Accordingly, this specification deprecates the previous RFC3427
   guidance on the creation of "P-" headers.  Existing "P-" headers are
   to be handled by user agents and proxy servers as the "P-" header
   specifications describe; the deprecation of the change process
   mechanism entails no change in protocol behavior.  New proposals to
   document SIP headers of an experimental or private nature, however,
   shall not use the "P-" prefix.

   Instead, the registration of SIP headers in Informational IETF
   specifications, or in documents outside the IETF, is now permitted
   under the Designated Expert (per RFC5226) criteria.  The use of any
   header field name prefix ("P-" or "X-" or what have you) to designate
   headers of limited applicability is discouraged.  Experts are advised
   to review documents for overlap with existing chartered work in RAI,
   and are furthermore instructed to ensure the following two criteria

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   are met:

   1.  The proposed header MUST be of a purely informational nature, and
       MUST NOT significantly change the behavior of SIP entities which
       support it.  Headers which merely provide additional information
       pertinent to a request or a response are acceptable; these
       headers are thus expected to have few if any implications for
       interoperability and backwards compatibility.  Similarly, headers
       which provide data consumed by applications at the ends of SIP's
       rendez-vous function, rather than changing the behavior of the
       rendez-vous function, are likely to be information in this sense.
       If the headers redefine or contradict normative behavior defined
       in standards track SIP specifications, that is what is meant by
       significantly different behavior.  Ultimately, the significance
       of differences in behavior is a judgment call that must be made
       by the expert reviewer.

   2.  The proposed header MUST NOT undermine SIP security in any sense.
       The Internet Draft proposing the new header MUST address security
       issues in detail as if it were a Standards Track document.  Note
       that, if the intended application scenario makes certain
       assumptions regarding security, the security considerations only
       need to meet the intended application scenario rather than the
       general Internet case.  In any case, security issues need to be
       discussed for arbitrary usage scenarios (including the general
       Internet case).

   Note that the deprecation of the "P-" header process does not alter
   processes for the registration of SIP methods, URI parameters,
   response codes, or option tags.

4.1.  SIP Event Packages

   SIP events [6] defines two different types of event packages: normal
   event packages, and event template-packages.  Event template-packages
   can only be created and registered by the publication of a Standards
   Track RFC (from an IETF Working Group).  Normal event packages can be
   created and registered by the publication of any Working Group RFC
   (Informational, Standards Track, Experimental), provided that the RFC
   is a chartered working group item.  Note that the guidance in RFC3265
   states that the IANA registration policy for normal event packages is
   "First Come First Serve"; this document replaces that policy with the

   Individuals may wish to publish SIP Event packages that they believe
   fall outside the scope of any chartered work currently in RAI.
   Individual proposals for registration of a SIP event package MUST
   first be published as Internet-drafts for review by the DISPATCH

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   Working Group, or the working group, mailing list, or expert
   designated by the RAI Area Directors if the DISPATCH Working Group
   has closed.  Proposals should include a strong motivational section,
   a thorough description of the proposed syntax and semantics, event
   package considerations, security considerations, and examples of
   usage.  The author should submit his or her proposal as an individual
   Internet- Draft, and post an announcement to the working group
   mailing list to begin discussion.  The DISPATCH Working Group will
   determine if the proposed package is a) an appropriate usage of SIP
   which should be spun into a new effort, b) applicable to SIP but not
   sufficiently interesting, general, or in-scope to adopt as a working
   group effort, c) contrary to similar work chartered in an existing
   effort, or d) should be adopted as or merged with chartered work.

   "RFC Required" (as defined in RFC5226) is the procedure for
   registration of event packages developed outside the scope of an IETF
   working group, according to the following guidelines:

   1.  A Designated Expert (as defined in RFC5226) must review the
       proposal for applicability to SIP and conformance with these
       guidelines.  The Designated Expert will send email to the IESG on
       this determination.  The expert reviewer can cite one or more of
       the guidelines that have not been followed in his/her opinion.

   2.  The proposed extension MUST NOT define an event template-package.

   3.  The function of the proposed package MUST NOT overlap with
       current or planned chartered packages.

   4.  The event package MUST NOT redefine or contradict the normative
       behavior of SIP events [6], SIP [3], or related standards track
       extensions.  (See Section 4)

   5.  The proposed package MUST NOT undermine SIP security in any
       sense.  The Internet Draft proposing the new package MUST address
       security issues in detail as if it were a Standards Track
       document.  Security issues need to be discussed for arbitrary
       usage scenarios (including the general Internet case).

   6.  The proposed package MUST be clearly documented in an
       (Individual) Informational RFC, and registered with IANA.  The
       package MUST document all the package considerations required in
       Section 5 of SIP events [6].

   7.  If determined by the Designated Expert or the chairs or ADs of
       the DISPATCH WG, an applicability statement in the Informational
       RFC MUST clearly document the useful scope of the proposal, and
       explain its limitations and why it is not suitable for the

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       general use of SIP in the Internet.

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5.  Security Considerations

   Complexity and indeterminate or hard to define protocol behavior,
   depending on which of many extensions operate, is a fine breeding
   ground for security flaws.

   All Internet-Drafts that present new requirements for SIP must
   include a discussion of the security requirements and implications
   inherent in the proposal.  All RFCs that modify or extend SIP must
   show that they have adequate security and do not worsen SIP's
   existing security considerations.

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6.  IANA Considerations

   RFC 3261 [3] directs the Internet Assigned Numbers Authority (IANA)
   to establish a registry for SIP method names, a registry for SIP
   option tags, and a registry for SIP response codes, and to amend the
   practices used for the existing registry for SIP headers.
   Reiterating the guidance of RFC3261, method names, option tags and
   SIP response codes require a Standards Action for inclusion in the
   IANA registry.  Authors of specifications should also be aware that
   the SIP parameter registry is further elaborated in RFC3968

   Previously in RFC3427, all new SIP header registrations required a
   Standards Action (per RFC5226) with the exception of "P-" headers;
   now, Informational registration of non-"P-" headers is permitted if
   approved by a Designated Expert, as described in Section 4.

   Each RFC shall include an IANA Considerations section which directs
   IANA to create appropriate registrations.  Registration shall be done
   at the time the IESG announces its approval of the draft containing
   the registration requests.

   Standard headers and messages MUST NOT begin with the leading
   characters "P-".  Existing "P-" header registrations are considered
   grandfathered, but new registrations of Informational headers need
   not begin with the leading characters "P-".  Short forms of headers
   MUST only be assigned to standards track headers.

   Similarly, RFC 3265 [6] directs the IANA to establish a registry for
   SIP event packages and SIP event template packages.  For event
   template packages, registrations must follow the RFC5226 processes
   for Standards Action.  For ordinary event packages, as stated
   previously registrations require RFC5226 IETF Review.  In either
   case, the IESG announcement of approval authorizes IANA to make the

6.1.  Clarification of RFC3969

   RFC3969 [4] stipulates that the (original) RFC2434 rule of
   "Specification Required" applies to registrations of new SIP URI
   parameters; however Section 3 of that same document mandates that a
   standards action is required to register new parameters with the
   IANA.  This contradiction arose from a misunderstanding of the nature
   of the RFC2434 categories; the intention was for the IANA
   Considerations to mandate that Standards Action is required.

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7.  Changelog

7.1.  Changes from RFC3427bis-00

      Changed description of the SIP and SIPPING WG functions to the
      SIPCORE and DISPATCH WG functions.

      Deprecated the process for "P-" header registration.

      Updated the document to reflect the publication of RFC5226.

      Numerous informative changes motivating some of the above.

7.2.  Changes from RFC3427

      References to the Transport Areas have been changed to point to
      the RAI ADs.

      Rewrote IANA registry requirements in terms of RFC2434bis.

      Updated list of working groups at the end of Section 3.

      Clarified that the original RFC3427 altered the IANA registration
      policy of RFC3265.

      Clarified the IANA registration policy in 3969.

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8.  Acknowledgments

   The credit for the notion that SIP required careful management
   belongs to the original authors: Allison Mankin, Scott Bradner, Rohan
   Mahy, Dean Willis, Joerg Ott, and Brian Rosen.  The current editors
   have provided only an update to reflect lessons learned from running
   the code, the changing situation of the IETF and the IANA
   registration procedures.  Gonzalo Camarillo was instrumental to the
   development of the concept of SIPCORE and DISPATCH.  Useful comments
   were provided by Jonathan Rosenberg, Mary Barnes, Robert Sparks, and
   Dean Willis.

   The original authors thanked their IESG and IAB colleagues
   (especially Randy Bush, Harald Alvestrand, John Klensin, Leslie
   Daigle, Patrik Faltstrom, and Ned Freed) for valuable discussions of
   extensibility issues in a wide range of protocols, including those
   that our area brings forward and others.  Thanks to the many members
   of the SIP community engaged in interesting dialogue about this
   document as well; including and especially Jonathan Rosenberg,
   Henning Schulzrinne and William Marshall.

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9.  Normative References

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, October 1996.

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

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [RFC3265]  Roach, A., "Session Initiation Protocol (SIP)-Specific
              Event Notification", RFC 3265, June 2002.

   [RFC3325]  Jennings, C., Peterson, J., and M. Watson, "Private
              Extensions to the Session Initiation Protocol (SIP) for
              Asserted Identity within Trusted Networks", RFC 3325,
              November 2002.

   [RFC3427]  Mankin, A., Bradner, S., Mahy, R., Willis, D., Ott, J.,
              and B. Rosen, "Change Process for the Session Initiation
              Protocol (SIP)", BCP 67, RFC 3427, December 2002.

   [RFC3968]  Camarillo, G., "The Internet Assigned Number Authority
              (IANA) Header Field Parameter Registry for the Session
              Initiation Protocol (SIP)", BCP 98, RFC 3968,
              December 2004.

   [RFC5111]  Aboba, B. and L. Dondeti, "Experiment in Exploratory Group
              Formation within the Internet Engineering Task Force
              (IETF)", RFC 5111, January 2008.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

Peterson & Jennings      Expires August 30, 2009               [Page 18]

Internet-Draft                 SIP change                  February 2009

Authors' Addresses

   Jon Peterson
   NeuStar, Inc.

   Email: jon.peterson@neustar.biz

   Cullen Jennings
   Cisco Systems

   Email: fluffy@cisco.com

Peterson & Jennings      Expires August 30, 2009               [Page 19]

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