The RTP protocol is augmented with a control protocol RTCP to monitor the quality of service and to convey information about the participants in an on-going session.
The RTCP messages are not always present in the Wireshark captures.
The column RTCP Type gives the different types:
|Generic RTP Feedback
|Receiver Summary Information
Between the brackets [ ] the number of occurrences of the specific RTCP type is displayed :
Selecting the link displays the full list of the RTCP messages and the contents :