Greetings, In RFC 4858 "Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF)", section 4.2, it states:
The answer is binding for the media session, and both offerer and answerer MUST only use feedback mechanisms negotiated in this way. The text "binding for the media session" seems to imply, once the SDP answer is received, there is no room for future negotiation for feedback mechanisms within the SDP session. However, RFC 6337, section 5.1 "General Principle for Constructing Offers and Answers", guides SIP implementers to "send an offer that indicates what [the UA], and its user, are interested in using/doing at that time, without regard for what the other party in the call may have indicated previously." If it is true that the feedback negotiation is "binding for the media session", once the answer is received, it seems that systems that utilize B2BUAs/SBCs would have the inability to negotiate feedback mechanisms as the call was transferred from one UA to another behind the B2BUA/SBC. Can the feedback mechanisms be renegotiated within an SDP session with new SDP offer/answer exchanges? Should there have been text added, such as "until the next offer", to the text in RFC 4858? Thanks, Richard _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
