Correcting the DC call constraint
This CR addresses an outdated constraint in TS 26.114 clause 6.2.10.1 regarding data channel SDP media descriptions. The constraint was introduced when data channels were only supported alongside MMTel media (audio, video, messaging). However, 3GPP R19 SA2 has now specified standalone data channel sessions that can establish data channels without requiring MMTel media.
The CR removes the following restriction:
"A data channel SDP media description shall not be placed before the first SDP speech media description."
This constraint is no longer applicable given the support for standalone data channel sessions.
The clause describing data channel SDP media description placement has been updated from:
Before:
"One or more data channel SDP media descriptions formatted according to IETF RFC 8864 [172] may be contained alongside other SDP media descriptions such as e.g. speech, video, and text."
After:
"One or more data channel SDP media descriptions formatted according to IETF RFC 8864 [172] may be added into the SDP independently, or to be added alongside other SDP media descriptions such as e.g. speech, video, and text."
This correction:
- Aligns TS 26.114 with SA2 specifications for standalone data channel sessions
- Removes an unnecessary ordering constraint on SDP media descriptions
- Enables more flexible data channel deployment scenarios without mandatory MMTel media
The CR maintains all other aspects of clause 6.2.10.1, including:
- Media feature tag requirements (+sip.app-subtype with "webrtc-datachannel" value)
- Support indication for bootstrap and application data channel multiplexing (g.3gpp.dc-mux)
- Protocol identifier and media format specifications (UDP/DTLS/SCTP and webrtc-datachannel)
- Bandwidth limit determination requirements