A.3 (Conditional) Zero Rating dynamic policy

26.5123GPP5G Media Streaming (5GMS)ProtocolsRelease 17TS

A.3.1 General

In the case of (Conditional) Zero Rating, the quality of a video streaming service should not exceed a certain bit rate threshold (called the policy threshold). This can be realized by deploying a traffic shaper in the network (e.g. a policing function in the UPF) or by instructing the DASH Player not to exceed a certain policy threshold bit rate. The policy threshold may be network-specific, i.e. depending on the 5G System. The following realization assumes the latter, i.e. the DASH Player is not exceeding the bit rate policy and the UPF is just monitoring the compliance of the application flows (one or more TCP and/or UDP flows). The MPD is annotated using DASH Service Descriptions in such a way that the DASH Player can identify which maximal representation bit rates still comply with the policy threshold.

Figure A.3.1-1 below illustrates the per-title quality and the policy threshold. For Title1 and Title2, the 5GMSd Client can activate the SD and HD representations. For Title3, the 5GMSd Client can activate the 480p and the SD representations. For Title4, the 5GMSd Client can activate all available representations (i.e. SD and HD).

Figure A.3.1‑1: Policy threshold versus quality

When the 5GMSd Client receives the bit rate of the policy threshold from the network, the 5GMSd Client filters the MPD for policy-compliant representations (i.e. those that lie at or below the policy threshold).

A.3.2 Procedure

The procedure for activating a (Conditional) Zero Rating dynamic policy is illustrated in figure A.3.2‑1 below.

Figure A.3.2‑1: Procedure for activating (Conditional) Zero Rating dynamic policy

Steps:

1. The 5GMS Application Provider interacts with the 5GMS AF to set up one or more Policy Templates. Each Policy Template is identified by a Policy Template identifier and contains information about how to activate the corresponding policy within the 5G System (e.g. N5 URLs and parameters).

2. The 5GMS Application Provider interacts with its DASH content generation function (e.g. an MPD provider) to annotate the DASH MPD with Service Descriptions (step 2). The intention of the Service Descriptions here is that the DASH Player can identify those representation combinations which do not exceed the bit rate requirement.

3. The 5GMSAware Application is configured via M8 with information about the available content catalogue (e.g. resolving MPD URLs), the available subscription identifiers (e.g. the user has a 4K content subscription or the user has an SD subscription), device type identifiers.

The 5GMSd-Aware Application is configured via M8 about the available (Conditional) Zero Rating policy. This includes the Network Policy Ids.

4. When a user selects an item via the User Interface (U1), the 5GMS-Aware Application translates the input to the needed 5GMSd API calls.

5. The 5GMS Aware Application provides input (via C1) on the selected presentation entry (i.e. MPD URL) and also on the Network Policy Id (the value in this case indicates a (Conditional) Zero-Rating policy, i.e. make the Media Session Handler request the policy threshold parameter from the network).

NOTE: C1 is an abstract interface and indicates that the 5GMS-Aware Application may either first use M6 or M7 for the interactions with the 5GMS Client.

6. The Media Session Handler uses the Network Policy Identifier to find the procedure and the parameters to activate the Dynamic Policy Instance (here a (Conditional) Zero Rating policy). The Media Session Handler has received one or more Policy Descriptions together with matching Service Access Information (via M5_1). The Media Session Handler uses the Network Policy Identifier as a key to find the correct Policy Description. Here, the Network Policy Identifier indicates a (Conditional) Zero Rating policy. The Media Session Handler should activate a dynamic policy in the 5GMS AF, providing Service Data Flow Template information about the DASH media flows (audio, video, etc.) and retrieving the bit rate threshold, which cannot be exceeded to comply with the policy. The Media Session Handler receives (as result of the Dynamic Policy activation) some information on the policy enforcement (enforcementMethod and/or enforcementBitrate), so that the representation selection logic (bit rate adaptation function) in the DASH Player can consider the effects of the enforcement scheme.

7. The Media Session Handler activates the Dynamic Policy instance on M5, providing a Policy Template identifier. Upon positive response, the Media Session Handler notifies the DASH Player, providing Service Descriptor Filters. The Media Session Handler may receive these Service Descriptor Filters with the response, or it may look up the Service Descriptor Filter values by a response value. Alternatively, the Media Session Handler receives a maximum bit rate with the response and the Media Session Handler derives the Service Descriptor Filter. The Media Session Handler may also receive information about Policy Enforcement, e.g. what type of traffic shaper will throttle the bit rate.

The Media Session Handler may need to update the Dynamic Policy instance, depending on the selected traffic detection method. For example, when the Media Session Handler uses 5-Tuples, the Media Session Handler needs to update the Dynamic Policy instance with every newly opened and every closed TCP connection.

8. The DASH Player fetches the MPD of the selected content.

9.The Service Descriptor Filter is used by the DASH Player to filter policy-compliant Service Descriptions from the MPD. The DASH Access Engine or Selection Logic (see ISO/IEC 23009-1 [32] figure K.1) selects only adaptation sets and representations according to the filter. Here, the DASH Player fetches the MPD after the notification from the Media Session Handler.

A.3.3 Example parameters

Table A.3.3‑1: M5_1 parameters for Policy Descriptions (used by the Media Session Handler)

Parameter	Type	Purpose	Example Values
Policy Description	Object
Network Policy Id	String	Identifies the Policy Description.	"(Conditional) Zero Rating".
Service Access Information URL	URL	References the associated Service Access Information.

Table A.3.3.‑2: M5_1 parameters for Service Access Information

Parameter	Type	Purpose
Service Access Information	Object
Policy Template Id	String	Identifies the Policy Template.	"not exceed bit rate"
5GMS AF URL	URL	Used to invoke the 5GMS AF.
sdfMethods	[String]	Indicates which Service Data Flow Description methods are recommended for use by the Media Session Handler.	"5-Tuple", "domainName", "TOS=xx", etc.
Mandatory M5 Request information	List		Policy Template identifier, Service Data Flow Template.
M5 Response information	List	Information to the Media Session Handler on the response parameters.	Bit rate Policy Threshold (upper bit rate bound, which should not be exceeded).