Subject: WG Review: Multiparty Multimedia Session Control (mmusic)

From: The IESG <[email-masked]>
Date: Tue, 20 May 2003 10:01:52 -0400

A modified charter has been submitted for Multiparty Multimedia Session Control 
(mmusic) in the Transport Area of the IETF. The IESG has not made 
any determination as yet.

The following description was submitted, and is provided for informational
purposes only.

Multiparty Multimedia Session Control (mmusic)
-------------------------------------

Current Status: Active Working Group

Description of Working Group:

The Multiparty MUltimedia SessIon Control (MMUSIC) Working Group (WG) was
chartered to develop protocols to support Internet teleconferencing and
multimedia communications. These protocols are now reasonably mature, and
many have received widespread deployment. The group is now focussed on the
revisions of these protocols in the light of implementation experience and
additional demands that have arisen from other WGs (such as AVT, SIP,
SIPPING, and MEGACO).

Multimedia communications protocols use a common platform for expressing
media and session descriptions. This is the Session Description Protocol,
SDP. The many uses of SDP have led to (requests for) numerous extensions
and have led to recognition of several flaws in the protocol design. In
spite of these, it is widely deployed.

- To support this current deployment, MMUSIC will revise SDP 
suitable for publication as a Draft Standard RFC. This will involve 
correcting minor bugs and clarifying the current specification.
- Various extensions to SDP will be pursued to remedy the most 
urgent of SDP's shortcomings. These will be limited to use of SDP in 
conjunction with connection-oriented media such as TCP and SCTP, offering 
support to work with NATs and firewalls, exchange of media session security
keys.

Apart from these, which are explicitly agreed to by the Area Directors and
shown in the milestones, only extensions within the existing framework of
SDP will be done (e.g. registering new codecs and defining parameters for
them extending SDP to include new address families).

To address the more fundamental issues with SDP, a next generation of SDP,
referred to as SDPng, has been in progress and will be continued towards a
Proposed Standard RFC. A requirements document will be devised that gathers
the requirements from the areas in which SDP is currently deployed.

MMUSIC will continue to maintain and revise the specification of the Real
Time Streaming Protocol (RTSP) based on implementation experience. The RTSP
specification will be revised to include various fixes and clarifications.
Depending on the changes, the revised RTSP specification will be re-issued
as either a Proposed or Draft Standard RFC. A MIB will be considered.

An Internet Media Guide (IMG) is a collection of multimedia session
descriptions expressed using SDP, SDPng or some similar session description
format. It is used to describe a collection of multimedia sessions (e.g.
television programme schedules). The IMG must be delivered to a
potentially large audience, who use it to join a subset of the sessions
described, and who may need to be notified of changes to the IMG.

MMUSIC will investigate work on delivery mechanisms for IMGs, generalizing
its work on session announcement and discovery protocols (SAP, RTSP, SIP).
We will investigate and document requirements for IMG delivery mechanisms,
and identify the requirements that these delivery mechanisms impose on the
session description formats used by the IMG. We will then work to produce
a framework document outlining the use of (existing) protocols to create an
IMG delivery infrastructure. After successful completion of these initial
milestones for IMG delivery, the MMUSIC working group will decide whether
or not MMUSIC is the proper place to pursue any needed mechanisms for IMGs,
and if so, recharter accordingly

The MMUSIC work items will be pursued in close coordination with other IETF
WGs related to multimedia conferencing and IP telephony (AVT, SIP, SIPPING,
IPTEL, MEGACO). Where appropriate, new separate working groups may be split
off (as has happened with the SIP WG).

The Working Group is also charged with addressing security issues related
to the protocols it develops.

Goals and Milestones:

APR 03 Submit SDP source filter extensions for Proposed Standard
MAY 03 Submit draft on SDPng motivations, comparisons with current SDP
       capabilities. Request charter review on SDPng work from IAB and IESG.
JUL 03 Submit revised SDP spec for Proposed Standard
JUL 03 Submit IMG requirements and framework for Informational
JUL 03 Review work on IMGs and update charter accordingly
AUG 03 Submit SDPng base spec profile for Proposed Standard
OCT 03 Submit revised RTSP spec for Proposed or Draft Standard (as appropriate)
OCT 03 Submit SDP Offer/Answer examples for Informational
NOV 03 Submit SDP security extension for Proposed Standard
NOV 03 Submit SDPng RTP profile spec for Proposed Standard
NOV 03 Submit SDPng audio profile spec for Proposed Standard
NOV 03 Submit SDPng video profile spec for Proposed Standard
DEC 03 Submit RTSP MIB for Proposed Standard