Glossary

Running every m= section of a session over a single ICE transport, so one port, one DTLS handshake and one TURN allocation carry all the media.

How WebRTC keys its media: a DTLS handshake over the ICE-selected path, whose exported keys feed SRTP. There is no unencrypted mode.

An ICE agent that only ever answers checks. It gathers one host candidate on a public address, sends nothing of its own, and is always the controlled agent.

Throwing away the current ICE session and starting gathering and connectivity checks from scratch under a new ufrag and password.

The short username fragment each side generates for an ICE session. Changing it is what makes a restart a restart.

A receiver telling the sender which RTP sequence numbers never arrived, so it can retransmit them.

A receiver saying it can no longer decode and needs a fresh keyframe. Cheap to send, expensive to answer.

A short label that names one RTP stream inside a media section, so simulcast layers can be told apart and constrained individually.

Sending retransmissions as their own stream, with their own SSRC and payload type, instead of repeating the original packet.

Editing the SDP string by hand between createOffer and setLocalDescription. Almost every reason to do it now has a real API.

A server that terminates each participant transport and forwards selected RTP streams onward without decoding them.

Encoding one camera at several resolutions at once and sending all of them, so a forwarding server can hand each viewer a layer without transcoding.

One message with two jobs: asking a server for your public address, and probing whether a candidate pair actually carries traffic.

The feedback scheme where the receiver reports the arrival time of every packet and the sender does the bandwidth estimation. Never an RFC, implemented everywhere.

Sending the offer or answer before gathering has finished, then delivering candidates over signalling as they turn up.

The relayed transport address a TURN server reserves for one client, and the two round trips it takes to get one.