2.8.15 Session Initiation Protocol (sip)

In addition to this official charter maintained by the IETF Secretariat, there is additional information about this working group on the Web at:

       http://www.softarmor.com/sipwg/ -- Additional SIP Page
NOTE: This charter is a snapshot of the 58th IETF Meeting in Minneapolis, Minnesota USA. It may now be out-of-date.

Last Modified: 2003-11-04

Dean Willis <dean.willis@softarmor.com>
Rohan Mahy <rohan@cisco.com>
Transport Area Director(s):
Allison Mankin <mankin@psg.com>
Jon Peterson <jon.peterson@neustar.biz>
Transport Area Advisor:
Allison Mankin <mankin@psg.com>
Technical Advisor(s):
Dan Romascanu <dromasca@avaya.com>
Mailing Lists:
General Discussion: sip@ietf.org
To Subscribe: sip-request@ietf.org
In Body: subscribe
Archive: www.ietf.org/mail-archive/working-groups/sip/current/maillist.html
Description of Working Group:
Note: There is another SIP email list for general information and implementations:

Discussion of existing sip: sip-implementors@cs.columbia.edu To Subscribe: sip-implementors-request@cs.columbia.edu In Body: subscribe Archive: http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors =======================================================================

The Session Initiation Protocol (SIP) working group is chartered to continue the development of SIP, currently specified as proposed standard RFC 2543. SIP is a text-based protocol, similar to HTTP and SMTP, for initiating interactive communication sessions between users. Such sessions include voice, video, chat, interactive games, and virtual reality. The main work of the group involves bringing SIP from proposed to draft standard, in addition to specifying and developing proposed extensions that arise out of strong requirements. The SIP working group will concentrate on the specification of SIP and its extensions, and will not explore the use of SIP for specific environments or applications. It will, however respond to general-purpose requirements for changes to SIP provided by other working groups, including the SIPPING working group, when those requirements are within the scope and charter of SIP.

Throughout its work, the group will strive to maintain the basic model and architecture defined by SIP. In particular:

1. Services and features are provided end-to-end whenever possible.

2. Extensions and new features must be generally applicable, and not applicable only to a specific set of session types.

3. Simplicity is key.

4. Reuse of existing IP protocols and architectures, and integrating with other IP applications, is crucial.

SIP was first developed within the Multiparty Multimedia Session Control (MMUSIC) working group, and the SIP working group will continue to maintain active communications with MMUSIC. This is particularly important since the main MIME type carried in SIP messages, the Session Description Protocol (SDP), specified in RFC 2327, is developed by MMUSIC and because MMUSIC is developing a successor to SDP which SIP will also use.

The group will work very closely with the (proposed) SIPPING WG, which is expected to analyze the requirements for application of SIP to several different tasks, and with the SIMPLE WG, which is using SIP for messaging and presence.

The group will also maintain open dialogues with the IP telephony (IPTEL) WG, whose Call Processing Language (CPL) relates to many features of SIP; will continue to consider the requirements and specifications previously established by the PSTN and Internet Internetworking (PINT) working group;: and will consider input from the Distributed Call Signaling (DCS) Group of the PacketCable Consortium for distributed telephony services, and from 3GPP, 3GPP2, and MWIF for third-generation wireless network requirements.

The specific deliverables of the group are:

1. bis: A draft standard version of SIP.

2. callcontrol: Completion of the SIP call control specifications, which enables multiparty services, such as transfer and bridged sessions.

3. callerpref: Completion of the SIP caller preferences extensions, which enables intelligent call routing services.

4. mib: Define a MIB for SIP nodes.

5. precon: Completion of the SIP extensions needed to assure satisfaction of external preconditions such as QoS establishment.

6. state: Completion of the SIP extensions needed to manage state within signaling, aka SIP "cookies".

7. priv: Completion of SIP extensions for security and privacy.

8. security: Assuring generally adequate security and privacy mechanisms within SIP.

9. provrel: Completion of the SIP extensions needed for reliability of provisional messages.

10. servfeat: Completion of the SIP extensions needed for negotiation ofserver features.

11. sesstimer: Completion of the SIP Session Timer extension.

12. events: Completion of the SIP Events extensions (Subscribe/Notify).

13. security: Requirements for Privacy and Security.

14. compression: SIP mechanisms for negotiating and guidelines for using signaling compression as defined in ROHC.

15. content indirection: a Proposed Standard Mechanism to reference SIP content indirectly (by reference, for example using an external URI).

Other deliverables may be agreed upon as extensions are proposed. New deliverables must be approved by the Transport Area Directors before inclusion on the agenda.

NOTE: milestones within the same month are shown in order of planned completion.

Goals and Milestones:
Done  Server Features Negotiation submitted to IESG
Done  Complete IESG requested fixes to provrel and servfeat
Done  Revised proposed standard version of SIP (2543bis) submitted to IESG
Done  SIP Events specification to IESG
Done  The UPDATE Method submitted for Proposed Standard
Done  SIP extensions for media authorization (call-auth) submitted as Informational
Done  Preconditions extensions (manyfolks) spec to IESG
Done  SIP Privacy specification to IESG
Done  SIP Privacy and Security Requirements to IESG
Done  The MESSAGE Method submitted for Proposed Standard
Done  The Replaces Header submitted for Proposed Standard
Done  Refer spec to IESG
Done  SIP NAT extension submitted to IESG
Done  SIP over SCTP specification and applicability statement
Jan 03  Guidelines for Authors of SIP extensions submitted as Informational
Done  Mechanism for Content Indirection in SIP submitted to IESG for Proposed Standard
Done  The SIP Referred-By Header submitted to IESG for Proposed Standard
Done  Session Timer spec, revised to IESG
Done  Caller preferences specification submitted to IESG
Apr 03  The SIP Join Header submitted to IESG for Proposed Standard
Apr 03  Submit SIP Identity documents to IESG for Proposed Standard
Jul 03  MIB spec to IESG
Jul 03  Review WG status (consider closing) and/or submit a future milestones plan to IESG
  • - draft-ietf-sip-session-timer-12.txt
  • - draft-ietf-sip-callerprefs-10.txt
  • - draft-ietf-sip-mib-07.txt
  • - draft-ietf-sip-guidelines-07.txt
  • - draft-ietf-sip-sctp-03.txt
  • - draft-sparks-sip-mimetypes-03.txt
  • - draft-ietf-sip-replaces-04.txt
  • - draft-ietf-sip-referredby-03.txt
  • - draft-ietf-sip-compression-02.txt
  • - draft-ietf-sip-congestsafe-02.txt
  • - draft-ietf-sip-content-indirect-mech-03.txt
  • - draft-ietf-sip-join-02.txt
  • - draft-ietf-sip-identity-01.txt
  • - draft-ietf-sip-authid-body-02.txt
  • - draft-ietf-sip-smime-aes-01.txt
  • - draft-ietf-sip-history-info-01.txt
  • - draft-ietf-sip-resource-priority-01.txt
  • - draft-ietf-sip-callee-caps-01.txt
  • - draft-ietf-sip-connect-reuse-00.txt
  • - draft-ietf-sip-uri-parameter-reg-00.txt
  • - draft-ietf-sip-parameter-registry-00.txt
  • - draft-ietf-sip-publish-01.txt
  • Request For Comments:
    RFC2976 PS The SIP INFO Method
    RFC3204 PS MIME media types for ISUP and QSIG Objects
    RFC3261 PS SIP: Session Initiation Protocol
    RFC3262 PS Reliability of Provisional Responses in SIP
    RFC3263 PS SIP: Locating SIP Servers
    RFC3265 PS SIP-Specific Event Notification
    RFC3361 PS DHCP Option for SIP Servers
    RFC3310 I Hypertext Transfer Protocol (HTTP) Digest Authentication Using Authentication and Key Agreement (AKA)
    RFC3311 PS The Session Initiation Protocol UPDATE Method
    RFC3312 PS Integration of Resource Management and SIP
    RFC3420 PS Internet Media Type message/sipfrag
    RFC3323 PS A Privacy Mechanism for the Session Initiation Protocol (SIP)
    RFC3325 I Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks
    RFC3428 PS Session Initiation Protocol Extension for Instant Messaging
    RFC3326 PS The Reason Header Field for the Session Initiation Protocol (SIP)
    RFC3327 PS Session Initiation Protocol Extension for Registering Non-Adjacent Contacts
    RFC3329 PS Security Mechanism Agreement for the Session Initiation Protocol (SIP) Sessions
    RFC3313 I Private Session Initiation Protocol (SIP)Extensions for Media Authorization
    RFC3515 PS The Session Initiation Protocol (SIP) Refer Method
    RFC3319 PS Dynamic Host Configuration Protocol (DHCPv6)Options for Session Initiation Protocol (SIP) Servers
    RFC3581 PS An Extension to the Session Initiation Protocol (SIP) for Symmetric Response Routing
    RFC3608StandardSession Initiation Protocol Extension Header Field for Service Route Discovery During Registration

    Current Meeting Report


    Minutes, SIP WG, IETF 58

    Official Scribe, Ben Campbell
    Supplementary Scribe, Vijay Gurbani
    Minutes Edited by Dean Willis

    Topic: Call to Order and Agenda Bash

    No issues raised.

    Topic: Status, Chairs

    Slides presented.

    New milestones proposed. No schedule objections raised, but it was proposed that the app-interaction framework be published as a proposed standard instead of BCP. Concerns about MIB status raised. Noted that SIP should certainly plan to operate at least through the current work-elevation plan from SIPPING, which extends through December 2004.
    Topic: Congestion Safety,  Dean Willis
    Reading list:
    There appears to be little interest in implementing this draft.  Some suggestions for simplifying it were made. It was also suggested that we need to change RFC 3263to prefer TCP over UDP, explain congestion issues and avoidance in a BCP, and complete the connection reuse work in order to encourage TCP deployment. Many endpoints now implement only UDP. We also need to differentiate fragmentation and congestion. It was noted that this problem does not just apply to MESSAGE, but can be frequently expected with NOTIFY, and with INVITES using S/MIME protection. DCCP is only a partial solution. Several people volunteered to work on this proposed BCP.

    It was also suggested that the current draft could be simplified to eliminate new response codes 515 and 516, providing a minimal "NO UDP" assurance.

    Topic: RFC 3312 Updates, Gonzalo Camarillo
    Reading list:

    Slides presented.

    Suggested that we adopt as WG item. No objections were raised.

    Conclusion: adopt draft as wg item, negotiate milestone.

    Topic: Publish, Aki Niemi
    Reading List:

    Slides presented.

    Issue: Should etags be updated on every publish? Consensus: Usage should be made consistent with HTTP. If it cannot be, we should call these something else.

    Issue: Publication rate. Proposed that rate from event package be used. Noted that this is probably an irrelevant and meaningless number, as there may be multiple publishers with no knowledge of each other. Much debate ensued, with no resolution  Further discussion deferred to the mailing list.

    Topic:  Request History, Mary Barnes
    Reading List:
        RFC 3087

    Slides presented.

    Issue: r-uri captured anytime request is forwarded. Proposal: Only add reason for history entries added due to retargeting.

    Issue: Privacy. Proposal: information not included when there are privacy considerations. (when uas sets session or header level privacy) .

    Next steps: complete flow detail. Do we want to fold reqs into doc as front matter? Request more mailing list feedback. Dependency on mid-end security draft.
    Presentation of applicability to voicemail.

    Issue: Optionality. Suggested that we apply stronger language to suggest applications gracefully degrade in absence of history.

    Issue: Implementability: Concerns raised by Robert Sparks, who will detail on mailing list.

    Issue: Security. Note that this in-general seems to depend on the middle-to-end and end-to-middle security work.

    Conclusion: Work should continue, but more thinking about optionality is needed. RJS and Mary to talk offline.

    1400 Non-Invite Transactions,   Robert Sparks
    Reading list:

    Slides presented.

    Noted that this problem is not related to the transport protocol, but is specific to the SIP-layer transaction reliability mechanism for all transactions other than INVITE.

    Several alternatives were presented:

    A) a series of tweaks
    B) Eliminate Timer F, allowing non-invite transactions to pend.
    C) USe path-timing estimation techniques to improve UAs knowledge of timing.
    D) Revise 3263 caching language to reduce severity of impact.
    E) Ignore the problem

    Suggested that SIP be revised to use 3-way handshake like INVITE on all transactions. This might be made backward-compatible through use of an option tag.

    Polls indicated  no consensus on any action, and that the working group didn't understand the nature of problem or disagreed as to its severity. Despite the objections of Morton Thiokol engineers, the shuttle was launched in cold-weather conditions under which it had never been tested, and the O-rings in the boosters failed.

    Conclusion: None. Further discussion deferred to the mailing list.

    Topic: GRUU, Jonathan Rosenberg
    Reading list:

    Slides presented.

    Issue: GRUU generation for stateless proxy behavior. Consensus that we need a sample algorithm for understanding.

    Issues: Liftime of a GRUU. Can a gruu change during a registration? Conclusion: No, gruu is good for lifetime of registrations, refreshes get same gruu.
    Do we need a guarantee of difference between registrations? Probably no, discuss on list.

    Issue: Dialog reuse—no longer a need with gruu. Should gruu spec deprecate dialog resuse if both peers support gruu? (Impacts refer, other subscribe usage).
    Conclusion: Do not address in gruu spec, address in other drafts, put pressure on future work to avoid dialog resuse.

    Issue: Does Gruu interferes with e2e signaling. UA can try to generate a local gruu, could use ice-like mechaninsm to decide if it is reachable. Propose to add to draft, but never try to put local address in contact header without using the mechanism.  Chair suggestion: Put statement about not using local gruu in gruu draft, put “iceing” in separate draft. Author agreed.

    Issue:  MUST NOT use locally generated gruu is too strong. Clarified that definition of local gruu is one with a different domain part than AoR, MUST does not apply to the examples given.

    Topic: Join,  Rohan Mahy
    Reading List:

    Slides presented.

    Noted that no comments in wglc. Room shows interest, but no one has implemented.
    We want more list discussion before sending to IESG.

    Topic: REFER Semantics, Rohan Mahy  
    Reading List:

    Slides presented.

    Basic premise is that the semantics of  the various uses of REFER are under-specified. Much discussion ensued.

    Issue: Is this equivalent to specifying fixed services? If we have to specify all the services/features, then the refer approach has failed.

    Issue: How do you put refer requests in a context? Dialog reuse? Separate GRUUs? Explicit refer-to header parameters?  Noted that it may require per-scheme semantics in addition to context.

    Issue: Need more than context—how do you know what an endpoint will do with a particular URI scheme?

    Issue: Not useful for authorization, because referee cannot decide if issuing the request could be bad. Another motivation that is relevant is to determine how to render the UI for the action.

    Sugested: this does not mean fixing refer, it means adding something new to it.

    Discussion on proceeding: How do we proceed? Refer for other than transfer unlikely to work on today’s UAs. Rohan suggests defining semantics for baskets of functionality. Use option tags to make sure they are supported. Propose explicit dialog parameters for refer-to. Provide guidance for remote call control vs. remote UI invocation.

    No conclusion, further discussion deferred to list. Interested parties are to contact Rohan and work on it.

    Final To-Do:

    App Interaction Framework -- change from BCP to PS.
    Add milestone for RFC 3312 update as PS.
    Discuss publication rate on mailing list.


    Interactions of Preconditions with Session Mobility in SIP
    GRUU Mechanism
    Request History - Solution
    draft-ietf-sip-join and Semantics of REFER