Skip to main content
Real-time Media Communication (RTC) Architecture

Implementation Detail

For what the specifications define, see the Technical Analysis.

What the Reference Tool implements​

The RTC Reference Tool is the SWAP v1 reference implementation of TS 26.113 clause 13.2.4: a Node.js signalling server and a client library for the signalling reference point RTC-4s. It is audited on the main branch of rt-3gpp-swap (2026-10-21). The RTC AF, the Media Session Handler, the ICE function and the other RTC AS functions are not part of it.

  • Implemented: the SWAP signalling over WebSocket at /3gpp-swap/v1 with the 3gpp.SWAP.v1 subprotocol; connect, accept, reject, update, close and application messages; matching criteria and endpoint selection; optional integrity and encryption of messages.
  • Needs fix:
    • The server defaults to plain ws, where the specification requires wss; the client allows ws when its secure option is false.
    • Errors are sent as a SWAP response whose description joins the Problem Details title and detail, not as a Problem Details object.
    • A message to an endpoint that never registered is acknowledged, not answered with an error.
    • On a received close the client does not send the accept itself.
    • The reference to the request in a reject is optional.
    • The server prefers the endpoint with the most matching criteria and picks at random only among ties.
  • Not implemented: handling of the Service Access Information and swapEndpoints, processing criteria, checking the application message type, and a client that listens for point-to-point connections.
  • Not shown: cases that depend on the WebSocket library's own behaviour, which is not part of the repository.

Implementation status​

Open a feature, then a requirement, to see each case and why. Filter by component, profile and release.

  • Real-time Media Communication (RTC) Architecture.
  • SWAP server (SWAP server (WebRTC Signalling Function of the RTC AS, RTC-4s)): rt-3gpp-swap.
  • SWAP client (SWAP client library (signalling side of an RTC endpoint, RTC-4s)): rt-3gpp-swap.
  • RTC AF (RTC AF (Provisioning, Configuration and Network Support Functions; none exists)): .
  • RTC MSH (RTC Media Session Handler (none exists)): .
  • ICE (ICE Function, STUN and TURN (none exists)): .
  • RTC AS (Other RTC AS functions: Media, Application-supporting Web, Transport Gateway, Interworking (none exists)): .
  • Source: code read against every statement of the specifications on the project page; statements a component cannot meet by construction marked absent by group, 2026-10-21.
  • Not shown: 3 further cases (a specification or code outside the audit that could not be read).
3GPP release
105 of 124 implemented · 11 differ · 8 absentcases, over 41 requirements

✓ Implemented≠ Differs from the specification– Absent? Specification inconsistent: its text and its OpenAPI or tables disagreei Noted: observed, not a verdict against a clause

SWAP signalling79 of 91 implemented · 7 differ · 5 absent
ICE and signalling configuration0 of 2 implemented · 2 absent
General26 of 31 implemented · 4 differ · 1 absent
Full audit for members

The full audit, with the code behind each verdict, is available to 5G-MAG members through Developer Tools.

Become a member · Request access