[Standards] Re: Proposed XMPP Extension: Jingle Synchronized Real-Time Text

On Tue, 2026-06-02 at 19:41 -0500, Stephen Paul Weber wrote: Only if the gateway is a MITM gateway, requiring server resources and increasing latency. Using the T.140 standard via standard RTP (RFC 4103) and WebRTC Data Channels (RFC 8865) seems sensible for better end-to-end real-time interop. XEP-0167 already supports RTP/T.140 out of the box, the only addition in this specification is the rtt-sync metadata element. It's thus important that the specification points out that other implementations may use RTP/T.140 without the rtt-sync element. RFC 8865 uses the dcmap and dcsa attributes from RFC 8864. We don't have a mapping for RFC 8864 at this point. Rather than only specifying the use of RFC 8865, it would be more sensible to add an RFC 8864 mapping, which implies compatibility with RFC 8865 in the same way as XEP-0167 supports RTP/T.140. The sync-group/-reference/-name rtt-sync attributes should use the existing XEP-0338 instead. The lang rtt-sync attribute should be transported using a mapping of RFC 8373 SDP, which we don't have yet, but would potentially also be useful for other Jingle media. As you already explained that SIP gateways are a target usecase, I am interested in seeing an example SDP as it would be on the SIP side, so we can together figure what is the best way to map these. I am not a subject matter expert of RTT over SIP, but I believe the SDP likely is to refer to IANA registered SDP attributes, which typically have RFC or other standard documents referred, which could be very useful to discover both the most reasonable SDP mapping for XMPP and for more specification of the meaning of certain attribute values. If the SDP does include attributes that are not well defined in any existing specification documents at applicable standards organizations (IETF, ITU, 3GPP), it may be useful to specify them with any of them first, so we can build our XMPP/Jingle on top of those. Marvin