Related specifications
RFC 3605, Real Time Control Protocol (RTCP) attribute in Session Description Protocol (SDP), available at http://www.ietf.org/
RFC 3960, Early Media and Ringing Tone Generation in the Session Initiation Protocol (SIP), available at http://www.ietf.org/
Implementation notes
Only separated RTP and RTCP ports are supported.
Support is provided for different IP addresses for RTCP and RTP as follows:
Local ports for RTP and RTCP can be mapped (by a NAT) to different external IP addresses. These are obtained from STUN Binding Responses.
Remote IP addresses for RTP and RTCP can be different. These are obtained from a remote SDP.