ABSTRACT
Earlier, we explained that Session Description Protocol (SDP) itself cannot be used for session capability negotiation, because it needs a call control protocol to carry its attributes. The actual application of SDP for capability negotiations between conferencing parties happens when a call control protocol (e.g., Session Initiation Protocol (SIP) or web real-time communication [WebRTC]) initiates the call setup where SDP attributes are carried by the call control protocol in the form of, for example, the offer/answer model. We have chosen SIP and WebRTC call control protocols that will use SDP attributes for capability negotiations for setting up the multimedia conferencing. That is, we provide the use cases for how both call protocols use SDP attributes to meet the common agreed-upon capabilities of the multimedia application/session, transport, and network under a huge variety of conferencing circumstances. For SIP, we have used Request for Comments 4317 that shows the capability negotiations using SDP attributes. Similarly, the Internet Engineering Task Force draft (draft-ietf-rtcweb-sdp-06) provides many scenarios for capability negotiations using SDP under a variety of multimedia conferencing environments.
