Huawei Technologies Vidyo Huawei Technologies The RTP fixed header includes the payload type number and the SSRC values of the RTP stream. RTP defines how to de-multiplex streams within an RTP session, but in some use cases applications need further identifiers in order to identify the signaling descriptions associated with particular RTP media streams. This document defines a mechanism to provide the mapping between the SSRCs of RTP streams and the SDP m-line description by defining extensions to RTP and RTCP messages.