[5MBUSA] User Service Announcement parameters alignment and clarifications
Source: BBC | WI: 5MBUSA | Affected spec: TS 26.502 (stage 2); mirrors changes in TS 26.580/26.581
During 5G-MAG reference implementation of MBS User Services, multiple gaps and ambiguities were found between stage 2 (TS 26.502) and stage 3 (TS 26.517) definitions for User Service Announcement parameters.
Conformance profiles (table 4.5.6-1 & 4.5.8-1): Added as a new parameter (0..*) assigned by the MBS Application Provider, referencing clause 12 profiles. Impacts Nmb10/Nmb5 (CT3).
Transport security protection (table 4.5.6-1): Clarified that this flag is set by the MBS Application Provider or the MBSF (in the special case of the User Service Announcement Channel). Impacts Nmb10/Nmb5 and Nmb2.
Object acquisition identifiers (table 4.5.6-2): Added optional MIME content type per identifier; made mandatory when the identifier is an Application Service Entry Point locator. Impacts Nmb10/Nmb5 and Nmb2.
Object repair back-off parameters (tables 4.5.6-2 & 4.5.8-2): Defined new parameters (0..2) for in-session and post-session repair scheduling (offset time + random time period). Clarified that Object Repair is enabled by the MBSF, not provisioned by the MBS Application Provider (clause 4.2.6 updated accordingly). No CT impact.
New reference point MBS-1 (clauses 4.3.2, 4.4.1, 5.2, 5.4): Formally defined as the interface by which the MBS Application Provider retrieves User Service Announcement bundles from the MBSF for private re-advertisement via MBS-8. Impacts Nmb10/Nmb5.
User Service advertisement notification (clause 4.6.2, table 4.6.2-1 & clause 5.4): Clarified that the full User Service Announcement exposed in the "User Service advertisement" event notification is the User Service Announcement bundle, and that the notification includes a URL for the MBS Application Provider to retrieve it via MBS-1. Terminology updated from "composite" to "full" where appropriate.
Stage 2/stage 3 misalignment for MBS User Services remains, blocking correct implementation.