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Session Initiation Protocol Core (sipcore)

WG Name Session Initiation Protocol Core
Acronym sipcore
Area Applications and Real-Time Area (art)
State Active
Charter charter-ietf-sipcore-04 Approved
Document dependencies
Additional resources GitHub
Wiki, Zulip Stream
Personnel Chairs Brian Rosen, Jean Mahoney
Area Director Murray Kucherawy
Liaison Contacts Adam Roach, Paul Kyzivat
Mailing list Address
To subscribe
Chat Room address

Charter for Working Group

The Session Initiation Protocol Core (SIPCore) working group is
chartered to maintain and continue the development of the SIP protocol,
currently defined as proposed standard RFCs 3261, 3262, 3263, 3264, and

The SIPCore working group will concentrate on specifications that update
or replace the core SIP specifications named above as well as
specifications pertaining to small, self-contained SIP protocol
extensions. The process and requirements for new SIP extensions are
documented in RFC5727, "Change Process for the Session Initiation

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. Reuse of existing Internet protocols and architectures and
    integrating with other Internet applications is crucial.

  3. Standards-track extensions and new features must be generally
    applicable, and not applicable only to a specific set of session

  4. Simpler solutions that solve a given problem should be favored
    over more complex solutions.

The primary source of change requirements to the core SIP specifications
(enumerated above) will be a) interoperability problems that stem from
ambiguous, or under-defined specification, and b) requirements from
other working groups in the ART Area. The primary source of new protocol
extensions is the DISPATCH working group, which will generally make the
determination regarding whether new SIP-related work warrants a new
working group or belongs in an existing one.


Date Milestone Associated documents
Jun 2023 Multiple Reasons values per protocol (PS) to the IESG draft-sparks-sipcore-multiple-reasons
Dec 2017 Request publication of mechanisms for rapid dual-stack protocol selection in SIP

Done milestones

Date Milestone Associated documents
Done Request publication of a clarification of the use of the "name-addr" production in SIP header fields
Done Request publication of a clarification of the use of Content-ID as a SIP header field
Done Request publication of a mechanism for labeling the nature of SIP calls
Done Request publication of a SIP response code for unwanted communications
Done Request publication of DNS look-up procedures for dual-stack client and server handling of SIP URIs
Done WebSockets transport definition for SIP to the IESG (proposed standard)
Done Mechanism to indicate proxy capabilities to both endpoints and other intermediaries in the path of a REGISTER transaction or dialog-forming transaction to IESG (PS)
Done Delivering request-URI and parameters to UAS via proxy to IESG (PS)
Done Error corrections and clarifications to RFC3265 to IESG (PS)
Done Location Conveyance with SIP to IESG (PS)
Done Example security flows to IESG (Informational)
Done Mechanism for indicating support for keep-alives (PS)
Done Presence Scaling Requirements to IESG as Info
Done SIP Events throttling mechanism to IESG (PS)
Done Invite Transaction Handling Correction to IESG (PS)
Done Extension for use in etags in conditional notification to IESG (PS)
Done Termination of early dialog prior to final response to IESG (PS)
Done INFO package framework to IESG (PS)

Dropped milestones

Date Milestone Associated documents
Dropped WGLC on requirements for a mechanism to indicate proxy capabilities to both endpoints and other proxies in the path of a REGISTER transaction or a dialog-forming transaction.