Content for TS 26.502 Word version: 18.1.0
4.6 Dynamic model
4.6.0 Introduction
4.6.1 MBS Distribution Session life-cycle
4.6.2 Notification events
4.7 QoS model
4.8 Security
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4.6 Dynamic model p. 33
4.6.0 Introduction p. 33
When provisioning an MBS User Data Ingest Session in the MBSF (directly, or indirectly via the NEF) the MBS Application Provider may specify a set of Active periods that apply to it and to all its subordinate MBS Distribution Sessions. Each Active period is described in terms of a start time and an end time or else a repetition rule that specifies a sequence of scheduled activation times (e.g. a first occurrence and a periodicity). The MBSF shall include the Active periods (if any) in the Service Announcement that it compiles and makes available to the MBS Client.
As described in clause 6.16 of TS 23.247, advance knowledge of the scheduled activation times of an MBS Distribution Session is especially useful in waking up a UE that implements power saving functions, e.g. MICO (Mobile-Initiated Connection Only) mode with Active Time, or extended DRX (Discontinuous Reception) as defined in clause 5.31.7 of TS 23.501.
4.6.1 MBS Distribution Session life-cycle p. 33
The life-cycle model for the MBS Distribution Session is depicted in Figure 4.6.1-1 below. The current state of a provisioned MBS Distribution Session is reflected in the state parameter of the information entities maintained by the MBSF and the MBSTF, and is exposed to the MBS Application Provider via the Nmbsf service.
1)
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.
2)
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:
3)
- 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.
- 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).
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.
4)
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.
5)
- The MBSF shall stop advertising the MBS Distribution Session by means of an MBS User Service Announcement.
- 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.
- 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.
- 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.
4.6.2 Notification events p. 35
During the lifecycle of a MBS User Service Session, a number of notification messages may be sent by different Network Functions. The MBSF may modify event information when passing on notifications from other Network Functions to the MBS Application Provider (AF/AS) at reference point Nmb10 or (via the NEF) at reference point Nmb5.
The events may originate from different sources:
- If the event originates in the MB-SMF at reference point Nmb1 or in the PCF at reference point Nmb12, it is propagated to the MBS Application Provider (AF/AS) at reference point Nmb10 (or via the NEF at reference point Nmb5). The MBSF conditions the event payload for external usage.
- If the event originates in the MBSTF at reference point Nmb2, it is propagated to the MBS Application Provider (AF/AS) at reference point Nmb10 (or via the NEF at reference point Nmb5). The MBSF conditions the event payload for external usage.
- If the event originates in the MBSF itself, it is propagated directly to the MBS Application Provider (AF/AS) at reference point Nmb10 (or via the NEF at reference point Nmb5).
| Event | Description | Applicable reference point(s) |
|---|---|---|
| Session started | The MBS Session is started. | (Nmb1), Nmb10/Nmb5 |
| Session released | The MBS Session is released. | (Nmb1), Nmb10/Nmb5 |
| Distribution Session starting | The MBSF is starting to establish the MBS Distribution session at the MBSTF. | Nmb10/Nmb5 |
| Distribution Session establishment failure | The MBSF failed to successfully establish the MBS Distribution Session at the MBSTF. | Nmb10/Nmb5 |
| Distribution Session established | The MBS Distribution Session is established. | Nmb10/Nmb5 |
| Distribution Session service management failure | The MBS Distribution Session could not be started, for example because the necessary resources could not be allocated by the MBS System. | (Nmb1), (Nmb2), Nmb10/Nmb5 |
| Distribution Session policy control failure | The MBS Distribution Session could not be started because of a policy authorization/control failure or rejection. | (Nmb12), Nmb10/Nmb5 |
| Distribution Session activated | The MBS Distribution Session is activated successfully. | (Nmb2), Nmb10/Nmb5 |
| Distribution Session deactivated | The MBS Distribution Session is deactivated. | (Nmb2), Nmb10/Nmb5 |
| User Data Ingest Session established | The MBSTF has successfully established the User Data Ingest Session. In the case of pull-based content ingest for the Object Distribution Method, the MBSTF has successfully connected at least once to the origin server at reference point Nmb8. In the case of the Packet Distribution Method or push-based content ingest for the Object Distribution Method, the MBSTF has successfully received some data at reference point Nmb8. | (Nmb2), Nmb10/Nmb5 |
| User data ingest failure | The MBSTF is expecting ingest data for an active MBS Distribution session but is not receiving data. | (Nmb2), Nmb10/Nmb5 |
| User Data Ingest Session terminated | The MBSTF has stopped the User Data Ingest Session at the end of the current active period. In the case of pull-based content ingest for the Object Distribution Method, the MBSTF has stopped pulling data. In the case of the Packet Distribution Method or push-based content ingest for the Object Distribution Method, the MBSTF is ignoring data. | (Nmb2), Nmb10/Nmb5 |
| User Service advertisement | The MBSF advertises the User Service Announcement information to the MBS Application Provider. The event shall include the list of external service identifiers provisioned for the User Service Announcement if the Service announcement modes parameter indicates unicast. The event shall include the full User Service Announcement information if the Service announcement modes parameter indicates external delivery. | Nmb10/Nmb5 |
4.7 QoS model p. 36
How MBS User Services make use of the network Quality of Service primitives defined in TS 23.247 is for further study.
4.8 Security p. 36
The security protection of MBS traffic is supported by use of either a control plane procedure or a user plane procedure at the service layer as defined in annex W of TS 33.501. The control plane procedure is only applicable for multicast sessions, while the user plane procedure is applicable for both multicast sessions and broadcast sessions. The MBSSF, as a logical function co-located with either the MBSF or the MBSTF, is responsible for key generation, management and distribution, including both MBS Session Keys and MBS Traffic Keys defined by TS 33.501).
