Content for  TS 26.502  Word version:  17.3.0

An MBS Distribution Session shall be in the INACTIVE state when it is first provisioned in the MBSF by the MBS Application Provider. The MBSF shall provision a corresponding MBS Distribution Session entity in the MBSTF. This replica of the MBS Distribution Session shall also be in the INACTIVE state. If the provisioned end date-time of the parent MBS User Data Ingest Session is in the past, the MBS Distribution Session shall immediately expire and shall transition to a state in which it is no longer provisioned. It is an error for the end date-time of the parent MBS User Data Ingest Session to be prior to the start date-time. The MBSF shall reject such a configuration at the time of provisioning.

Shortly before the provisioned start date-time of the parent MBS User Data Ingest Session (or immediately if the start date-time is in the past at the point of provisioning) the MBS Distribution Session shall transition into the ESTABLISHED state. At this point:

1. The MBSF shall reserve resources for the MBS Distribution Session in the MBS System by interacting with the MB-SMF at reference point Nmb1 using the procedures defined in clause 7.1.1 of TS 23.247.
2. The MBSF shall establish the MBS Distribution Session in the MBSTF by invoking the MBS Distribution Session establishment procedure on the Nmbstf service at reference point Nmb2 using the procedures defined in clause 5.4 of the present document. As a result, the MBSTF shall attempt to establish an MBS User Data Ingest Session with the upstream data source at reference point Nmb8 and may commence ingesting data (but not distributing it).

If either of these procedures fail, a suitable error shall be returned to the MBSF. Any successfully reserved resources in the MBS System shall be released and the MBS Distribution Session shall return to the INACTIVE state. Otherwise, the MBSF shall advertise the successfully established MBS Distribution Session to MBSF Clients (either directly via MBS-5, or indirectly via MBS-8, depending on the provisioned advertisement mode) by means of an MBS User Service Announcement that it has compiled. An MBS Client in receipt of this advertisement may activate reception of the established MBS Distribution Session at this point (but will not yet receive any MBS data packets).

At the provisioned start date-time of the parent MBS User Data Ingest Session (or immediately if the start date-time is in the past at the point of provisioning) the MBS Distribution Session shall transition into the ACTIVE state. The MBSF shall inform the MBSTF of this state transition by invoking the MBS Distribution Session activation procedure on the Nmbstf service at reference point Nmb2, as specified in clause 5.4 of the present document. As a result, the MBSTF shall commence sending MBS data packets to the MB-UPF at reference point Nmb9, and any MBS Clients that have activated reception of the previously advertised MBS Distribution Session in step 2 above may start to receive MBS data packets at reference point MBS-4-MC.

If the MBSTF encounters any error conditions when the MBS Distribution Session is in the ACTIVE state it shall notify the MBSF by invoking the MBS Distribution Session notification procedure defined by the Nmbstf service at reference point Nmb2 per clause 5.4. If the MBSF determines that the error is of such a severity that the MBS Distribution Session cannot continue, it shall transition to the DEACTIVATING state.

1. The MBSF shall stop advertising the MBS Distribution Session by means of an MBS User Service Announcement.
2. The MBSF shall inform the MBSTF of this state transition by invoking the MBS Distribution Session deactivation procedure on the Nmbstf service at reference point Nmb2 using the procedures defined in clause 5.4 of the present document. As a result, the MBSTF shall cease sending MBS data packets to the MB-UPF at reference point Nmb9.
3. The MBSF shall release the MBS Distribution Session in the MBSTF by invoking the MBS Distribution Session release procedure on the Nmbstf service at reference point Nmb2 using the procedures defined in clause 5.4 of the present document. As a result, the MBSTF shall stop ingesting data at reference point Nmb8 from the upstream data source. As a result of this procedure, the MBSTF shall automatically transition to the INACTIVE state.
4. The MBSF shall release resources in the MBS System associated with the MBS Distribution Session by interacting with the MB-SMF at reference point Nmb1 using the procedures defined in clause 7.1.1 of TS 23.247. As a result of this procedure, the MBSF shall automatically transition to the INACTIVE state.

At the provisioned end date-time of the parent MBS User Data Ingest Session (or immediately if the MBS Distribution Session or its parent MBS User Data Ingest Session are destroyed by the MBS Application Provider earlier than the provisioned end date-time) an MBS Distribution Session in the ACTIVE state shall transition into the DEACTIVATNG state and the deactivation procedure described in steps 4a to 4d inclusive shall be followed. Once the deactivation procedure is complete, the expired MBS Distribution Session shall transition automatically to a state in which it is no longer provisioned.