Correcting the DC call constraint
Source: Huawei
Meeting:
TSGS4_135_India
Agenda Item:
10.4
| Agenda item description | Release 19 and earlier matters |
|---|---|
| Doc type | CR |
| Secretary remarks | Source modified on 2/2/2026. Original source : HuaWei Technologies Co., Ltd |
| Release | Rel-19 |
| Specification | 26.114 |
| Version | 19.2.0 |
| Related WIs | 5G_MEDIA_MTSI_ext |
| CR number | 604.0 |
| CR revision | 1.0 |
| CR category | F |
| Clauses affected | 6.2.10.1 |
| download_url | Download Original |
| CN | True |
| CR | 604.0 |
| Spec | 26.114 |
| Type | CR |
| Contact | Shuxin Ouyang |
| Uploaded | 2026-02-02T09:33:19.480000 |
| Contact ID | 103366 |
| Revised to | S4-260438 |
| TDoc Status | revised |
| Is revision of | S4-260081 |
| Clauses Affected | 6.2.10.1 |
| Reservation date | 02/02/2026 09:30:05 |
| Secretary Remarks | Source modified on 2/2/2026. Original source : HuaWei Technologies Co., Ltd |
| Agenda item sort order | 51 |
Review Comments
[Technical] Removing “A data channel SDP media description shall not be placed before the first SDP speech media description” is directionally correct for standalone data channel sessions, but the CR does not add any replacement normative text clarifying that an SDP offer/answer with only data channel m-lines (no speech/video/text) is valid and how it interacts with the rest of clause 6.2.10.1 requirements.
[Technical] The change claims alignment with “R19 SA2 standalone data channel sessions” but provides no explicit reference to the SA2 stage-2 specification/clause that introduces this capability; TS 26.114 should normatively cite the relevant TS 24.229/TS 23.xxx/TS 24.xxx clause to justify the behavioral change.
[Technical] If ordering constraints are removed, the CR should verify and, if needed, update any dependent procedures elsewhere in TS 26.114 (e.g., offer/answer handling, media stream identification, media feature tag usage) that may implicitly assume speech m-lines exist or appear first.
[Technical] The updated sentence only addresses “added into the SDP independently” but does not explicitly state that data channel m-lines may appear in any position; if ordering freedom is the intent, it should be stated normatively (e.g., “may appear before or after any other m-line”) to avoid ambiguous interpretation.
[Technical] Standalone data channel sessions may affect session-level attributes (e.g., BUNDLE usage, a=group, a=msid semantics, DTLS role negotiation) and the CR does not assess whether clause 6.2.10.1 or related clauses need additional constraints when no RTP-based media is present.
[Editorial] The modified wording “may be added into the SDP independently, or to be added alongside” is grammatically incorrect and redundant; it should be simplified (e.g., “may be included in the SDP either alone or alongside other SDP media descriptions…”).
[Editorial] The phrase “added into the SDP” is non-standard SDP/spec wording; TS 26.114 typically uses “included/contained in the SDP offer/answer” and should keep consistent terminology.
[Technical] The CR summary says “flexible SDP ordering … in any position,” but the actual proposed text does not explicitly remove all ordering constraints beyond the deleted sentence; confirm there are no other ordering rules in the clause (or elsewhere) that still effectively block standalone/early placement.
[Technical] The “Unchanged Requirements” list includes media feature tags (+sip.app-subtype, g.3gpp.dc-mux) but the CR does not confirm whether these tags are still applicable/required in standalone data channel sessions (i.e., without MMTel context) or whether additional tags are needed to indicate standalone usage.
[Editorial] The summary references “MMTel media (e.g., audio, video, messaging)” but “messaging” is not an SDP media type in the same sense as audio/video/text; consider tightening the wording to avoid confusion (e.g., “audio/video/text m-lines”).
[Technical] If standalone data channel sessions are allowed, TS 26.114 should ensure interoperability guidance exists for endpoints that do not support data channels (optional support): e.g., expected behavior when receiving an offer with only a data channel m-line (reject session vs. reject m-line), which is not addressed by this CR.
[Editorial] The change description says “formatted according to IETF RFC 8864 [172]” but does not check whether the reference number [172] and RFC are correct for the data channel SDP format in this TS version; ensure the citation matches the spec’s reference list and intended RFC.