Implement "SCTP Negotiation Acceleration Protocol" when ready

Context

• Draft: "SNAP: SCTP Negotiation Acceleration Protocol" https://datatracker.ietf.org/doc/html/draft-hancke-tsvwg-snap

Abstract WebRTC Data Channels use the Stream Control Transmission Protocol (SCTP) over a Datagram Transport Layer Security (DTLS) association. The standard SCTP connection establishment requires a handshake that introduces latency. This document specifies a method to accelerate the datachannel establishment by embedding the SCTP initialization parameters within the Session Description Protocol (SDP) offer/answer exchange. This reduces the time required to open a data channel by up to two network round-trip times.

• Ticket in libwebrtc: https://issues.webrtc.org/issues/426480601
• Code already available in libwebrtc under WebRTC-Sctp-Snap field trial (see webrtc/pc/peer_connection.cc).

Notes

• Notice that there is no need to exchange/validate SCTP Cookie since ICE and DTLS mechanism replaces it. So basically, the SDP offer and answer only contain a SCTP INIT chunk (of peer A and peer B). There is no need for INIT_ACK which is the same as a INIT chunk + cookie.
• Run Canary with SNAP enabled in macos:
  bash复制

  /Applications/Google\ Chrome\ Canary.app/Contents/MacOS/Google\ Chrome\ Canary \
    --enable-logging=stderr --v=1 \
    --vmodule='*/webrtc/*=9,*dcsctp*=9,*sctp*=9,*data_channel*=9,*=-2' \
    --autoplay-policy=no-user-gesture-required \
    --force-fieldtrials='WebRTC-Sctp-Snap/Enabled/' \
    --disable-field-trial-config \
    "$@" 2>&1 | tee webrtc.log