Negotiating Media Multiplexing Using the Session Description Protocol (SDP)
Ericsson
Google
Cisco
This specification defines a new Session Description Protocol (SDP) Grouping Framework extension, 'BUNDLE'. The extension can be used with the SDP Offer/Answer mechanism to negotiate the usage of a single transport (5-tuple) for sending and receiving media described by multiple SDP media descriptions ("m=" sections). Such transport is referred to as a BUNDLE transport, and the media is referred to as bundled media. The "m=" sections that use the BUNDLE transport form a BUNDLE group. To assist endpoints in negotiating the use of bundle this specification defines a new SDP attribute, 'bundle-only', which can be used to request that specific media is only used if bundled. The specification also updates RFC 3264, to allow assigning a zero port value to a "m=" section without meaning that the media described by the "m=" section is disabled or rejected. When Real-time Transport Protocol (RTP)-based media is used, there are multiple ways to correlate bundled RTP packets with the appropriate "m=" section. This specification defines a new RTP Control Protocol (RTCP) source description (SDES) item and a new RTP header extension that provides an additional way to do this correlation by using them to carry a value that associates the RTP/ RTCP packets with a specific "m=" section.