1.1.f [iii] RTP/RTCP concepts
Real-time Transport Control Protocol (RTCP) is a sister protocol of the Real -time Transport Protocol (RTP). RTCP provides out-of-band control information for an RTP flow. It partners RTP in the delivery and packaging of multimedia data, but does not transport any data itself. It is used periodically to transmit control packets to participants in a streaming multimedia session. The primary function of RTCP is to provide feedback on the quality of service being provided by RTP.
Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 1179-1180). . Kindle Edition.