16 Usage of 5GC interfaces and APIs

26.5123GPP5G Media Streaming (5GMS)ProtocolsRelease 17TS

16.1 General

While the core functionality of 5GMS is specified in terms of the dedicated system interfaces and APIs specified in clauses 7 to 14 (for M1 to M8 respectively), certain features of 5GMS rely on interfaces and APIs defined within the scope of the 5GC.

Each such case of usage of a 5GC interface and API is documented in subsequent sub-clauses of the present clause.

NOTE: The 5GMS architecture may be applied to an EPS although such an application is not specified in the present document and is left to the discretion of deployments and implementations.

16.2 Usage of N5/N33 for AF-based Network Assistance

The feature of AF-based Network Assistance operates within interface M5 between the UE and an AF that provides Network Assistance capabilities, as defined in clause 11.6. The Network Assistance protocol and API within M5 is defined in a generic way so that the associated Network Assistance functionality in the 5GC may be realised by various means.

In the present specification the 5GMS AF converts the Network Assistance API calls and responses carried in interface M5 into API calls to the Session Management Policy Control Service, as specified in TS 29.514 [34].

If the Network Assistance feature is supported, then the 5GMS AF shall offer the bitrate recommendation and delivery boost request API based on existing policy templates that match the filtering criteria for a media streaming session, through the usage of either the Npcf_PolicyAuthorization API over N5, or the Nnef_AFSessionWithQoS over N33 interface to the PCF.

When serving a media streaming session that belongs to the AF application session context, the AF shall subscribe to the following PCF notifications with the PCF:

– Service Data Flow QoS notification control;

– Service Data Flow Deactivation;

– Resources allocation outcome.

If no corresponding AF application session context already exists, the AF shall use the Npcf_PolicyAuthorization_Create method with the appropriate service information to create and provision an application session context. The information in the AppSessionContextReqData shall be derived from the policy template.

When requesting QoS provisioning for a media streaming session, the 5GMS AF shall use the configured policy templates of the Provisioning Session to determine the list of the QoS references within the "altSerReqs". The lowest priority index shall be assigned to the policy template with the lowest QoS requirement and the highest priority shall be assigned to the requested operation point by the UE (if the UE is allowed to use that operation point).

Media streaming sessions shall use exactly one component per session. It is assumed that a single sub-component is used, unless otherwise indicated.

NOTE: This clause is not limiting the possible set of 5G System exposure functionalities for obtaining Network Assistance information.