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 deployments. The group has revised
some of these protocols in the light of implementation experience and
additional demands that have arisen from other WGs (such as AVT, SIP,
and SIPPING). It is focused on using and negotiating mechanisms such
STUN and TURN in order to enable media sessions to traverse Network
Address Translators NATs, and on new means to exchange SDP capabilities.
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, some of
which were addressed in the revision of SDP. In spite of these, it is
The current aims of the working group include the following:
- To support the establishment of multi-party multimedia sessions across
NATs, MMUSIC will define an Internet Connectivity Establishment
protocol (ICE). This will define several SDP extensions to work with
NATs for media sessions carried over both UDP and TCP.
- Various extensions to SDP will be pursued to remedy the most urgent of
SDP's shortcomings. These will be limited and include adding support
for limited but generic capability negotiations in SDP, defining the
means to select QoS mechanisms to use for a particular media stream,
enabling file transfer via the SDP Offer/Answer model, and support
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 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.
The MMUSIC work items will be pursued in close coordination with other
IETF WGs including AVT, SIP, SIPPING, SIMPLE, XCON, and BEHAVE, as well
as others where appropriate such as NSIS.
Submit SDP extensions for duplicated streams as Proposed Standard