Subject: Protocol Action: SIP: Session Initiation Protocol to Proposed Standard

From: The IESG <[email-masked]>
Date: Tue, 02 Feb 1999 14:30:17 -0500

The IESG has approved the Internet-Draft 'SIP: Session Initiation
Protocol' <draft-ietf-mmusic-sip-12.txt> as a Proposed Standard.  This
document is the product of the Multiparty Multimedia Session Control
Working Group. The IESG contact persons are Scott Bradner and Vern
Paxson.

Technical Summary
 
 SIP is a control protocol for creating, modifying and terminating sessions
 with one or more participants. These sessions include Internet multimedia
 conferences, Internet telephone calls and multimedia distribution. Members
 in a session can communicate via multicast or via a mesh of unicast
 relations, or a combination of these.  SIP supports session descriptions
 that allow participants to agree on a set of compatible media types. It
 also supports user mobility by proxying and redirecting requests to the
 user's current location.  SIP is not tied to any particular conference
 control protocol.  There is widespread interest in the protocol, especially
 for telephony-related applications.

Working Group Summary

 The current SIP protocol spec was the result of a merger of two
 alternative proposals presented to the WG in early 1996.  Since then, the
 protocol specification has undergone many refinements, including the
 addition of comprehensive security considerations.  Many small problems
 were found with the specification during this process and corrected, but
 nothing major was found.  In general working group consensus was good.
 Feature creep has been a problem during SIP development.  To reduce this
 problem somewhat, SIP call control functionality (which is not a core SIP
 functionality) was removed from the SIP spec and moved to a separate
 specification.

 The relationship between SIP and H.323 was a point of discussion during
 the development of SIP.  There is some overlap, but the two protocols come
 from different problem domains, and do not attempt to tackle precisely the
 same set of problems.

 The final specification is the result of much WG discussion, and
 represents near-unanimous consensus on the details and rough consensus on
 the proposal as a whole.  All of the issues raised during last call have
 been addressed in the revised specification.  The only significant last
 call change was making the SIP UDP retransmission timers back off
 exponentially to address congestion concerns.

Protocol Quality

 Vern Paxson reviewed the spec for the IESG.  There are a number of
 implementations.

Note to RFC Editor:

The IESG requests the following be added as an IESG Note:

	The IESG intends to charter, in the near future, one or more working
	groups to produce standards for "name lookup", where such names would
    	include electronic mail addresses and telephone numbers, and the result
	of such a lookup would be a list of attributes and characteristics
	of the user or terminal associated with the name.  Groups which are
	in need of a "name lookup" protocol should follow the development
	of these new working groups rather than using SIP for this function.
	In addition it is anticipated that SIP will migrate towards using
	such protocols, and SIP implementors are advised to monitor
	these efforts.