Simple definition
RTCP exchanges reception statistics and synchronization data for real-time RTP media streams.
Purpose and use
RTCP, Real-time Transport Control Protocol, accompanies RTP with reception, quality and media-synchronization information.
How does it work?
Reports can include loss, jitter and timestamps useful for analysis. Port selection or multiplexing with RTP depends on the profile and negotiation.
Example and verification
For degraded audio, correlate RTCP statistics with network losses and the periods when the fault was actually experienced.
Points to watch
RTCP does not normally carry speech and does not guarantee quality of service. Missing reports can also result from filtering or implementation choices.
In short
Reports provide measurement evidence to interpret alongside RTP traffic and network context.