Correcting the DC call constraint
3GPP R19 SA2 has specified standalone data channel sessions that can establish data channels without MMTel media (e.g., audio, video, messaging). The existing constraint in TS 26.114 clause 6.2.10.1 requiring that a data channel SDP media description shall not be placed before the first SDP speech media description is therefore no longer applicable and needs to be removed to align with the new SA2 specifications.
Modified Text:
The CR updates the paragraph describing data channel SDP media descriptions to remove the ordering constraint. The changes are:
Previous text: "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."
Updated text: "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."
Deleted Constraint:
The following sentence is completely removed:
- "A data channel SDP media description shall not be placed before the first SDP speech media description."
This correction enables:
- Standalone data channel sessions without requiring MMTel media
- Flexibility in SDP media description ordering
- Alignment with SA2 Rel-19 specifications for data channel sessions
The change maintains all other requirements including:
- Protocol identifier ("UDP/DTLS/SCTP") and media format ("webrtc-datachannel") specifications
- Media feature tag requirements (+sip.app-subtype and g.3gpp.dc-mux)
- Bandwidth limit determination procedures