Session Initiation Protocol

Document Charter Session Initiation Protocol WG (sip)
Title Session Initiation Protocol
Last updated 2009-05-01
State Approved
WG State Concluded
IESG Responsible AD (None)
Charter Edit AD (None)
Send notices to (None)


The Session Initiation Protocol (SIP) working group is chartered to
maintain and continue the development of SIP, currently specified as
proposed standard RFC 3261, and its family of extensions.

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 tasks of the group involve bringing SIP
from proposed to draft standard and 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. The process and
requirements for such extensions are documented in RFC 3427, "Change
Process for the Session Initiation Protocol".

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. Standards-track 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 Internet protocols and architectures and 
with other Internet applications is crucial.

The primary source of change requirements to be considered by the SIP
Working Group is the SIPPING working group, which
analyzes the requirements for application of SIP to several different
tasks, including the tasks of standards-development organizations
that are developing systems based on SIP and that may require changes
or extensions thereto. Additional requirements are produced by the
other IETF working groups that are using SIP, including the SIMPLE WG
(which is using SIP for messaging and presence) and the XCON working
group (which is using SIP for centralized conferencing).

In addition to extending SIP as required to address these externally-
derived requirements, the deliverables of the group include assuring
capable security and privacy mechanisms within SIP and increasing
the stability of the SIP specification.

Specific deliverables toward these goals include:

1. Mechanisms for secure expression of identity in requests and

2. Mechanism to securely request services delivery by non-terminal
elements ("end-to-middle").

3. Guidelines for use of existing security mechanisms such as TLS,
IPsec, and certificates.

4. Guidelines for the use of descriptive techniques such as SAML
(Security Association Markup Language) with SIP.

5. Draft standard versions of SIP and critical supporting

Other deliverables may be agreed upon as extensions are understood
to be necessary. Prospective deliverables will be discussed
with the Area Director before inclusion on agendas, and new
proposed work must be approved via a charter update.