## CR 26.502 CR0049r2 – [5MBUSA] User Service Announcement Parameters Alignment and Clarifications

**Source:** BBC | **Work Item:** 5MBUSA | **Category:** F (Correction) | **Release:** Rel-17 | **Spec:** TS 26.502 v17.11.0

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### Background / Motivation
During 5G-MAG reference implementation of MBS User Services, multiple gaps and ambiguities were identified between the stage 2 definition (TS 26.502) and the stage 3 specification (TS 26.517). This CR corrects TS 26.502 to align with TS 26.517 and resolve implementation issues.

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### Changes Made (6 items)

1. **Conformance Profiles** – New parameter added to MBS Distribution Session (table 4.5.6-1) and MBS Distribution Session Announcement (table 4.5.8-1), assigned by the MBS Application Provider, referencing profiles defined in clause 12.

2. **Transport Security Protection** – Clarified that the flag is provisioned by the MBS Application Provider *or* (for the User Service Announcement Channel) by the MBSF. Assigner column in table 4.5.6-1 updated accordingly.

3. **Object Acquisition Identifiers – MIME Type** – Each identifier may now be accompanied by a content type; this is **mandatory** when the identifier is an Application Service Entry Point locator. MBSTF shall verify content type on ingest. Impacts tables 4.5.6-2 and 4.5.8-2.

4. **Object Repair Back-off Parameters** – New parameter defined in both MBS Distribution Session (table 4.5.6-2) and MBS Distribution Session Announcement (table 4.5.8-2), assigned by the MBSF. Clarified that Object Repair is enabled at MBSF discretion (not provisioned by MBS Application Provider); wording changed from "provisioned" to "enabled" throughout clauses 4.2.6 and 4.5.6.

5. **New Reference Point MBS-1** – Formally defined in clause 4.4.1: exposure of composite User Service Announcement from MBSF to MBS Application Provider for private advertisement via MBS-8. Referenced in procedures (clauses 5.2 and 5.4).

6. **User Service Advertisement Notification** – Clarified in table 4.6.2-1 and clause 5.4 that the "User Service advertisement" event includes a URL for the MBS Application Provider to retrieve the **full User Service Announcement bundle** (not just partial information) via reference point MBS-1 when external delivery mode is indicated.

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### Affected Clauses
4.2.2, 4.2.6, 4.3.1, 4.3.2, 4.4.1, 4.5.2, 4.5.6, 4.5.8, 4.6.2, 5.2, 5.4, 6.1

### Related Specs
TS 26.580, TS 26.581; potential impact on TS 29.580 (Nmb10/Nmb5, CT3) and TS 29.581 (Nmb2, CT4) for items 1–3 and 5–6.

### Consequence if Not Approved
Stage 2/stage 3 misalignment for MBS User Services, blocking correct reference implementation.