RTP = Real-time Transport Protocol. RFC 3550 (2003).
RTP is a protocol designed to be used over UDP to transfer media streams (video/audio). Streams are send without container.
RTP packets flow in one direction, and accompanying RTCP protocol is used for Quality of Service feedback and synchronization.
RTP is mandated transport for WebRTC.
- Payload Type (PT)
- some types are predefined, but most apps define new types dynamically (in the 96–127 range)
- the payload type is negotiated out of band (usually using SDP)
- Sequence number
- starts from arbitrary number
- not absolute, only diffs between timestamps are used
- grows monotonically by the speed defined by clock rate
- SSRC (Synchronization Source)
- identifies media track