RRTR stands for Receiver Reference Time Report.
RRTR is an RTCP extended report (XR) block that allows the receiver to communicate its local clock time to the sender. Combined with Delay Since Last Receiver Report (DLRR), this enables RTT (Round Trip Time) measurement from the sender’s perspective without requiring the receiver to send Sender Reports.
Why RRTR matters in WebRTC
In a typical WebRTC session, a PeerConnection needs to know the RTT to the remote peer for:
- BWE (Bandwidth Estimation) calculations
- NACK retransmission decisions (is there enough time to retransmit before the playout deadline?)
- Jitter buffer sizing
RRTR is defined in IETF RFC 3611 and is part of the RTCP extended reports mechanism. It is commonly used alongside Transport-CC for comprehensive network quality monitoring.
