5.7 Establishing a Unicast Downlink Media Streaming Session with 5GMSd AF interactions for dynamic policy updates

26.5013GPP5G Media Streaming (5GMS)General description and architectureRelease 18TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

5.7.1 General

This clause describes the provisioning for dynamic policy invocation and the establishment of a unicast downlink streaming session using the dynamic policy API. The establishment of the unicast downlink media streaming session uses 5GMSd AF interactions, as described in steps 4 to 8 of clause 5.1. The dynamic policy API allows separate handling of Service Data Flows within the same PDU Session. The Media Session Handler provides a Policy Template Id together with Service Data Flow Descriptions when requesting a dynamic policy. An example Policy Template Id value is "background_data".

The Media Session Handler provides needed information to the 5GMSd AF, so that the 5GMSd AF can combine the semi-static parameters from a Policy Template (which is associated with the Policy Template Id) with the API parameters to trigger a dynamic PCC rule update using the NEF or PCF.

The 5GMSd AF may trigger, for example, the "AF session with required QoS procedure" (see TS 23.502 [3] clause 4.15.6.6) for updating QoS related dynamic PCC rules. For changing charging related rules, the 5GMSd AF may trigger the "Change the chargeable party during the session" procedure (see TS 23.502 [3] clause 4.15.6.5).

5.7.2 Provisioning

The provisioning for the dynamic policy procedure follows generally the procedure from clause 5.3. Specifically, the Dynamic Policy feature is activated and, as result, the 5GMSd Application Provider is able to provision one or more Policy Templates.

The domain model of M1d and M5d APIs is depicted in Figure 5.7.2-1. Realization of the dependencies between M1d and M5d data entries are up to implementation.

NOTE: Multiple M5d 5GMSd AF nodes may reference the same M1d resource.

Figure 5.7.2-1: Domain model for dynamic policies

A Policy Template is identified by a Policy Template Id and contains semi-static parameters, including the API entry for the PCF/NEF interactions. The list of provisioned Policy Template Ids is communicated as valid Policy Template Ids to the Media Session Handler. The Media Session Handler uses one of the valid Policy Template Ids when invoking a dynamic policy.

5.7.3 Progressive Download of On-Demand Content

This procedure describes the establishment of a unicast downlink media streaming session with 5GMSd AF interactions for dynamic policy updates. A streaming session may use 3GP File Format (Progressive Download), 3GP Timed Text or other (potentially non-3GPP defined) formats.

Figure 5.7-1: High Level Procedure for progressive download for on-demand media

Prerequisites:

– The 5GMSd Application Provider has provisioned the 5G Media Streaming System and has set up content ingest.

– The 5GMSd-Aware Application has received the Service Announcement from the 5GMSd Application Provider.

– The Service Access Information contains detailed information for the policy related interactions. Specifically, the information includes URL(s) for the 5GMSd AF, an identifier of the 5GMS Provisioning Session and a list of authorized Policy Type indications for that specific application.

– The 5GMSd Application Provider has agreed an SLA with the Network Operator defining the possible QoS levels and their charging rates (see TS 23.503 [4] clause 6.1.3.22). The PCF is configured with the corresponding QoS parameters and charging information.

Steps:

1: The 5GMSd-Aware Application triggers the Service Announcement and Content Discovery procedure. The Service Announcement includes either the whole Service Access Information (i.e. details for Media Session Handling (M5d) and for Media Streaming access (M4d)) or a reference to the Service Access Information. The configuration parameters are listed in Table 5.7.4-1.

NOTE: The Service and Content Discovery procedure only involves the 5GMSd-Aware Application and the external Application Server, and hence is out of scope of the present document.

2: A Media Player Entry is selected.

3: The 5GMSd-Aware Application triggers the Media Session Handler to start media playback. The Media Player Entry is provided to the Media Session Handler.

4: When the 5GMSd-Aware Application has received a reference to the Service Access Information (see step 1), the Media Session Handler interacts with the 5GMSd AF to acquire the whole Service Access Information.

5: The Media Session Handler triggers the Media Player to start the session.

6: The Media Player establishes the transport session, e.g. a TCP connection.

7: The Media Player notifies the Media Session Handler about the Service Data Flow Description(s) of the transport session established in the previous step (see TS 23.502 [3]), as defined in the Service Access Information. This can be for example 5-tuples.

8: The Media Session Handler requests that a dynamic policy be applied to the media session. The request includes at least the Provisioning Session identifier, the Service Data Flow Description(s) and the Policy Template identifier (see Table 5.7.4‑1) to be applied to the described transport session. In some cases, a QoS specification is also provided, containing desired QoS information. The 5GMSd AF uses the Policy Template indication for the related procedure and to identify the related network function.

9: This step applies when the 5GMSd AF resides in the trusted Data Network. Depending on the Policy Template, the step is executed either:

a. When the Policy Template relates to QoS, the 5GMSd AF may either directly interact with the PCF or may use a NEF service:

– when directly interacting with the PCF, the 5GMSd AF uses the Npcf_PolicyAuthorization Service as defined in TS 23.502 [3] clause 5.2.5.3).

– when interacting via the NEF with the PCF, continue at step 10a.

b. When the Policy Template relates to a different charging scheme, the 5GMSd AF may either directly interact with the PCF or may use a NEF service:

– when directly interacting with the PCF, the 5GMSd AF uses the Npcf_PolicyAuthorization Service as defined in TS 23.502 [3] clause 5.2.5.3).

– when interacting via the NEF with the PCF, continue at step 10b.

10: This step applies when the 5GMSd AF resides in the external Data Network. Depending on the Policy Template, the step is executed either:

a. When the Policy Template relates to QoS, the 5GMSd AF may use the Nnef_AFsessionWithQoS service as defined in TS 23.502 [3] clause 5.2.6.9. (The complete call flow is described in TS 23.502 [3] clause 4.15.6.6.)

b. When the Policy Template relates to a different charging scheme, the 5GMSd AF may use the Nnef_ChargeableParty service as defined in TS 23.502 [3] clause 5.2.6.8. (The complete call flow is described in TS 23.502 [3] clause 4.15.6.4 and clause 4.15.6.5.) The Policy Template may contain the Sponsor Information (values, based on SLA negotiation) and Background Data Transfer Reference ID. The Flow description is provided by the Media Session Handler at API invocation.

11: The Media Session Handler queries the status of the dynamic policy invocation. The response contains status information (policy accepted, rejected, etc) and information on policy enforcement such as the enforcement method and enforcement bit rate.

12: The Media Session Handler notifies the Media Player according to the response from the 5GMSd AF (see Table 5.6.4-2).

13: The Media Player sends the request for the progressive download content.

14: The Media Player receives the initialization information of the progressive download content. The initialization information contains configuration parameters for reception of the media, and optionally also DRM information.

15: The Media Player configures the rendering pipeline for media playback.

16: The Media Player notifies the Media Session Handler, providing the transport session information and some media content related information.

17: Optional: Media Player acquires a DRM License from as the 5GMSd Application Provider.

18: The Media Player receives media content and puts it into the rendering pipeline.

19: The Media Player continues to receive and play back the media content.

5.7.4 DASH Streaming

It is assumed here that the key information to initialize the media decoding and rendering pipeline is present in the Media Player Entry (or referenced by the Media Player Entry). The intention is to provide the client with information to setup the media decoding and rendering pipeline in such a way that no pipeline reset is needed during the session. Implementations need to consider that parts of the information are provided with the initialization segments.

It is assumed that the client is enabled to use the same media decoding and rendering pipeline during the session.

Figure 5.7-2: High Level Procedure for DASH content

Prerequisites:

– The 5GMSd Application Provider has provisioned the 5G Media Streaming System and has set up content ingest.

– The 5GMSd-Aware Application has received the service announcement from the 5GMSd Application Provider.

– The Service Announcement Information contains detailed information for the policy related interactions. Specifically, the information includes URLs for the 5GMSd AF, an identifier of the Provisioning Session and a list of authorized Policy Type indications for that specific application.

Steps:

1: The 5GMSd-Aware Application triggers the Service Announcement and Content Discovery procedure. The Content Discovery procedure only involves the App 5GMSd-Aware Application and the 5GMSd Application Provider. The Service Announcement includes either the whole Service Access Information (i.e. details for Media Session Handling (M5d) and for Media Streaming access (M4d)) or a reference to the Service Access Information. The configuration parameters are listed in Table 5.7.4-1.

2: A media content item is selected.

3: The 5GMSd-Aware Application triggers the Media Session Handler to start media playback. The Media Player Entry is provided to the Media Session Handler.

4: When the 5GMS-Aware Application has received only a reference to the Service Access Information (see step 1), the Media Session Handler interacts with the 5GMSd AF to acquire the whole Service Access Information.

5: The Media Session Handler triggers the Media Player to start the session.

6: The Media Player establishes a transport session for acquiring the MPD referenced by the Media Player Entry.

7: The Media Player requests the MPD.

8: The Media Player receives the MPD.

9: The Media Player processes the MPD. It determines, for example, the number of needed transport sessions for media acquisition. The Media Player should be able to use the MPD information to initialize the media pipelines for each media stream. The MPD should also contain information to start the DRM client initialization, when DRM is used.

10: The Media Player notifies the Media Session Handler about the MPD. The notification may contain parameters from the MPD.

11: (Optional) the Media Player acquires the necessary DRM information, for example a DRM License.

12: The Media Player configures the media rendering pipeline.

13: The Media Player establishes the necessary transport session(s) for acquiring the content. For example, the Media Player may establish one transport session for each media component (audio, video, etc) and possibly additional transport sessions for other media representations.

14: The Media Session Handler is notified about the established transport session(s) for the content by providing the Service Data Flow Description of the application flows as defined in the Service Access Information. This can be for example 5-tuples.

15: The Media Session Handler requests that a dynamic policy be applied to the media session. The request includes at least the Provisioning Session identifier, the Service Data Flow Description(s) and the Policy Template identifier (see Table 5.7.4-1), to be applied to the described transport session. In some cases, a QoS specification is also provided, containing desired QoS information. The 5GMSd AF uses the Policy Template for the related procedure and to identify the related network function.

NOTE: The Media Session Handler may add and remove Service Data Flow description(s) from the dynamic policy resource during the lifetime of the Media Streaming Session.

16: This step applies when the 5GMSd AF resides in the trusted Data Network. Depending on the Policy Template, the step is executed either:

a. When the Policy Template relates to QoS, the 5GMSd AF may either directly interact with the PCF or may use a NEF service:

– when directly interacting with the PCF, the 5GMSd AF uses the Npcf_PolicyAuthorization service as defined in TS 23.502 [3] clause 5.2.5.3).

– when interacting via the NEF with the PCF, continue at step 17a.

b. When the Policy Template relates to a different charging scheme, the 5GMSd AF may either directly interact with the PCF or may use a NEF service:

– when directly interacting with the PCF, the 5GMSd AF uses the Npcf_PolicyAuthorization service as defined in TS 23.502 [3] clause 5.2.5.3).

– when interacting via the NEF with the PCF, continue at step 17b.

17: This step applies when the 5GMSd AF resides in the external Data Network. Depending on the Policy Template, the step is executed either:

b. When the Policy Template relates to a different charging scheme, the 5GMSd AF may use the Nnef_ChargeableParty service as defined in TS 23.502 [3] clause 5.2.6.8. (The complete call flow is described in TS 23.502 clause 4.15.6.4 and clause 4.15.6.5.) The Policy Template may contain the Sponsor Information (values, based on SLA negotiation) and Background Data Transfer Reference ID. The Flow Description is provided by the Media Session Handler at API invocation.

18: The Media Session Handler queries the status of the dynamic policy invocation. The response contains status information (policy accepted, rejected, etc) and information on policy enforcement such as the enforcement method and enforcement bit rate.

19: The Media Session Handler updates the configuration of the Media Player according to the response from the 5GMSd AF (See Table 5.6.4-2).

20: The Media Player requests a DASH initialization segment. The Media Player repeats this step for each required initialization segment.

21: The Media Player receives the initialization segments.

22: The Media Player requests DASH media segments according to the MPD.

23: The Media Player receives media segments and feeds them into the appropriate media rendering pipeline.

24: Previous steps are repeated according to the MPD information.

5.7.5 Parameters for dynamic policy invocation configuration

Table 5.7.5-1: Status information dynamic policy

Parameters	Description
Policy Enforcement	Information about the policy enforcement system.