Summary

This chapter has described the RTP control protocol, RTCP, in some detail. There are three components :

1. The RTCP packet formats, and the means by which compound packets are generated

2. The participant database as the main data structure for an RTP-based application, and the information that needs to be stored for correct operation of RTCP

3. The rules governing timing of RTCP packets: periodic transmission, adaptation to the size of the session, and reconsideration

We have also briefly discussed security and privacy issues, which are discussed in depth in Chapter 13, Security Considerations, as well as the correct validation of RTCP packets.

The RTP control protocol is an integral part of RTP, used for reception quality reporting, source description, membership control, and lip synchronization. Correct implementation of RTCP can significantly enhance an RTP session: It permits the receiver to lipsync audio and video, identifies the other members of a session, and allows the sender to make an informed choice of error protection scheme to use to achieve optimum quality.