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 widely deployed.
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 for media loopback.
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 families).
- 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