2.5.7 Multiparty Multimedia Session Control (mmusic)

NOTE: This charter is a snapshot of the 70th IETF Meeting in Vancouver, BC Canada. It may now be out-of-date.

Last Modified: 2006-07-05


Joerg Ott <jo@acm.org>
Colin Perkins <csp@csperkins.org>
Jean-Francois Mule <jf.mule@cablelabs.com>

Real-time Applications and Infrastructure Area Director(s):

Jon Peterson <jon.peterson@neustar.biz>
Cullen Jennings <fluffy@cisco.com>

* The Real-time Applications and Infrastructure Area Directors were seated during the IETF 65.

Real-time Applications and Infrastructure Area Advisor:

Cullen Jennings <fluffy@cisco.com>

Mailing Lists:

General Discussion: mmusic@ietf.org
To Subscribe: mmusic-request@ietf.org
In Body: subscribe your_email_address
Archive: http://www.ietf.org/mail-archive/web/mmusic/index.html

Description of Working Group:

The Multiparty MUltimedia SessIon Control (MMUSIC) Working Group 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 to express
media and session descriptions: 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

- 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
(e.g. via the ICE methodology), and exchange of media session
security keys.

With the exception of these specific items, only extensions within
the existing SDP framework will be done (e.g. registering new codecs
and defining parameters for them extending SDP to include new address

To address the more fundamental issues with SDP, a next generation of
SDP, referred to as SDPng, will be needed. An initial proposal is now
available, and will be progressed to Experimental RFC while we gain
experience with implementations. An informational document will be
produced describing how the transition to a new session description
protocol can be managed, to prepare implementors for such a future

MMUSIC will maintain and revise the specification of the Real Time
Streaming Protocol (RTSP), including fixes and clarifications based
on implementation experience. The revised RTSP specification will be
re-issued as a Proposed Standard RFC. We will also document how RTSP
can be used in the presence of NAT boxes.

An Internet Media Guide (IMG) is a collection of multimedia session
descriptions expressed using SDP or some other 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

MMUSIC will investigate delivery mechanisms for IMGs, generalizing
our 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, SIMPLE, XCON, MEGACO and, where appropriate, MIDCOM and NSIS).
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:

Done  Conduct WG Last Call for SAP Internet-Draft
Done  Submit a revised Internet Multimedia Conferencing Architecture I-D.
Done  Submit a revised SIP I-D.
Done  Submit SDP to the IESG for consideration as a Proposed Standard.
Done  Submit SAP Internet-Draft to IESG for publication as an Experimental Protocol.
Done  Conduct WG Last Call for RTSP Internet-Draft.
Done  Submit Internet-Draft on Internet Multimedia Conferencing Architecture.
Done  Submit RTSP to IESG for consideration as a Proposed Standard.
Done  Conduct WG Last Call for SIP Internet-Draft.
Done  Submit SIP Internet-Draft to IESG for consideration as a Proposed Standard.
Done  Conduct WG Last Call for SAP Security Internet-Draft.
Done  Conduct second WG Last Call for SAP.
Done  Submit SAP Internet-Draft to IESG for consideration as a Proposed Standard.
Done  Submit SAP Security Internet-Draft to IESG for consideration as a Proposed Standard.
Done  Submit IPv6 Extensions to SDP for Proposed Standard
Done  Submit SIP's offer/answer use of SDP for Proposed Standard
Done  Submit SDP4NAT for Proposed Standard (Informational?)
Done  Submit SDP source filter extensions for Proposed Standard
Done  Submit draft on SDPng motivations, comparisons with current SDP capabilities. Request charter review on SDPng work from IAB and IESG.
Done  Submit SDP security extension for Proposed Standard
Done  Submit IMG requirements and framework for Informational
Done  Submit revised SDP spec for Proposed (or Draft) Standard
Done  Submit SDP Offer/Answer examples for Informational
Aug 2004  Review work on IMGs and update charter accordingly
Done  Submit SDP connection-oriented media draft for Proposed Standard
Done  Submit SDPng transition scenarios for Informational
Nov 2004  Submit SDPng base specification for Experimental
Nov 2004  Submit ICE draft for Proposed Standard
Feb 2005  Submit revised RTSP spec for Proposed or Draft Standard (as appropriate)
May 2005  Submit RTSP NAT considerations draft
Done  Submit updated SDP Offer/Answer examples draft for Informational


  • draft-ietf-mmusic-rfc2326bis-15.txt
  • draft-ietf-mmusic-rtsp-nat-05.txt
  • draft-ietf-mmusic-ice-17.txt
  • draft-ietf-mmusic-media-loopback-06.txt
  • draft-ietf-mmusic-securityprecondition-04.txt
  • draft-ietf-mmusic-ice-tcp-04.txt
  • draft-ietf-mmusic-sdp-capability-negotiation-reqts-01.txt
  • draft-ietf-mmusic-file-transfer-mech-03.txt
  • draft-ietf-mmusic-sdp-capability-negotiation-06.txt
  • draft-ietf-mmusic-sdp-media-capabilities-01.txt
  • draft-ietf-mmusic-rtsp-nat-evaluation-00.txt

    Request For Comments:

    RFC2326 PS Real Time Streaming Protocol (RTSP)
    RFC2327 PS SDP: Session Description Protocol
    RFC2543 PS SIP: Session Initiation Protocol
    RFC2974 E Session Announcement Protocol
    RFC3108 PS Conventions for the use of the Session Description Protocol (SDP)for ATM Bearer Connections
    RFC3259 I A Message Bus for Local Coordiantion
    RFC3264 PS An Offer/Answer Model with SDP
    RFC3266 PS Support for IPv6 in SDP
    RFC3388 PS Grouping of media lines in Session Description Protocol SDP
    RFC3524 PS Mapping of Media Streams to Resource Reservation Flows
    RFC3605 Standard RTCP attribute in SDP
    RFC3890 Standard A Transport Independent Bandwidth Modifier for the Session Description Protocol (SDP)
    RFC4091 Standard The Alternative Network Address Types (ANAT) Semantics for the Session Description Protocol (SDP) Grouping Framework
    RFC4145 Standard TCP-Based Media Transport in the Session Description Protocol (SDP)
    RFC4317 I Session Description Protocol (SDP) Offer/Answer Examples
    RFC4435 I A Framework for the Usage of Internet Media Guides (IMGs)
    RFC4473 I Requirements for Internet Media Guides (IMGs)
    RFC4566 PS SDP: Session Description Protocol
    RFC4567 PS Key Management Extensions for Session Description Protocol (SDP) and Real Time Streaming Protocol (RTSP)
    RFC4568 PS Session Description Protocol Security Descriptions for Media Streams
    RFC4570 PS Session Description Protocol (SDP) Source Filters
    RFC4572 PS Connection-Oriented Media Transport over the Transport Layer Security (TLS) Protocol in the Session Description Protocol (SDP)
    RFC4574 PS The Session Description Protocol (SDP) Label Attribute
    RFC4583 PS Session Description Protocol (SDP) Format for Binary Floor Control Protocol (BFCP) Streams
    RFC4756 PS Forward Error Correction Grouping Semantics in Session Description Protocol
    RFC4796 PS The Session Description Protocol (SDP) Content Attribute

    Meeting Minutes


    Agenda and Progress Report
    SDP Media Capability Negotiation
    Source-Specific Media Attributes
    Decoding Dependency in SDP
    SDP Elements for FEC Framework
    RTSP Asynchronous Notification
    RTSP 2.0
    Multiple ptime problem
    Analysis of Middlebox Interactions
    Media Description for IKE in SDP