A.2 Premium QoS dynamic policy

26.5123GPP5G Media Streaming (5GMS)ProtocolsRelease 17TS

A.2.1 General

To realise a Premium QoS service offering, the 5GMS Client should activate a QoS Flow with characteristics matching the service needs. It is assumed that the DASH content is prepared for different subscription levels, e.g. 4K, HDR or SD, and for different target device types, e.g. SmartPhone or SmartTV. When commencing playback of a DASH presentation according to a particular subscription level (e.g. 4K), the 5GMS Client needs to activate a QoS Flow with a matching bit rate setting.

NOTE: The 5GMS Client may choose to activate a QoS Flow with a lower bit rate than the maximum supported by the 5G System, e.g. a small screen SmartPhone may select different QoS settings from a large screen device.

The per-title quality and the subscription levels of an example on-demand catalogue are illustrated in the figure below. The subscription levels in this example are 4K, FullHD, HD, SD and 480p. Only devices entitled to activate a 4K quality should actually select the according representations from the MPDs. In this example, all titles are available in SD and HD quality. Often, not all titles are available in 4K quality. Thus, a device with a 4K subscription can only activate reception of the HD or SD representations.

Figure A.2.1‑1: Subscription Levels for Premium QoS

The bit rate required to sustain a certain quality varies from title to title. In the figure, the bit rate needed for Title4 in HD is in the same range as SD quality of Title3.

The various consumer-facing Network Subscription Levels define a set of bounded Operation Ranges, as illustrated on the right side of the figure. Each such Operation Range is conveniently modelled in the 5GMS architecture as a Policy Template. The Policy Template for SD subscription level (SD Operation Range) is authorized to activate a maximal bit rate of btr#1. The Policy Template for 4K subscription level is authorized to activate between any low bit rate and a maximal bit rate of btr#3.

When activating a Dynamic Policy instance, the 5GMSd Client provides a desired bit rate for the selected title. The desired bit rate can be smaller than the maximal bit rate allowed by the Policy Template. The 5GMSd Client always activates a Dynamic Policy instance from its assigned Network Subscription Level, even when the desired bit rate justifies a different Policy Template.

When activating a QoS Flow for a certain subscription level and title, the 5GMSd Client should preferably select a desired bit rate matching the quality needed. For example, a device with an HD Operation Range subscription needs a higher desired bit rate when consuming Title3 in HD quality and a lower desired bit rate when consuming Title4 in HD quality.

In some cases, the system rejects a requested QoS Flow or drops an established QoS Flow due to insufficient available network resource. The 5GMSd Client can then try to activate a different QoS Flow with a lower desired bit rate.

A.2.2 Procedure

The procedure for activating a Premium Qos dynamic policy is illustrated in figure A.2.2‑1 below.

Figure A.2.2-1: Procedure for activating Premium QoS dynamic policy

Steps:

1. The 5GMS Application Provider interacts with the 5GMS AF to set up one or more Policy Templates (using M1). 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 (using P1). The Service Descriptions define the Operational Ranges within the Media Player should operate. The DASH MPD and the DASH Media Segments are then ingested by the 5GMS AS.

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

The subscription identifiers and the device type identifiers are collectively referred to as Service Description Filters in the following.

NOTE 1: It is for further study whether network policy identifiers are embedded in the MPD Service Descriptions or derived from the Service Descriptions.

NOTE 2: The network policy identifier can be equal to a Policy Template identifier when the 5GMS-Aware Application is aware about its usage (e.g. for QoS streaming or background download). It is assumed here, that a unique Network Policy identifier is assigned to each subscription level.

4. When the 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) together with a Network Policy Identifier (the value indicates here a "HD Premium QoS" policy (alternative Network Policy Identifiers can refer to e.g. 4K quality), i.e. make the Media Session Handler request a QoS Flow) and Service Description Filters. The Service Description Filter is used by the Media Player to identify the usable Service Descriptions from the MPD. The Network Policy Identifier is used by the Media Session Handler to find the according Policy Description containing information on the Dynamic Policy instantiation method (i.e. procedure and parameters such as Policy Template identifier).

6. The DASH player fetches the MPD.

7. The Media Player selects the Service Description and applies the Service Description Filter.

8. The DASH player indicates to the Media Session Handler (M6) that a "HD Premium QoS" network service should be activated (value of the Network Policy Identifier). The DASH player provides input on bit rate ranges (which may depend on the device type and the title quality). The Media Session Handler has received one or more Policy Descriptions together with matching Service Access Information (via M5_1). When the Media Session Handler has received the policy indication, the Media Session Handler uses the Network Policy Identifier to find the procedure and the parameters to activate the Dynamic Policy instance (i.e. find the matching Policy Description). The Media Session Handler activates a Dynamic Policy instance in the 5GMS AF, providing Service Data Flow Templates identifying the DASH media flows (audio, video, etc) and to provide the desired bit rate of the video.

9. The Media Session Handler activates a Dynamic Policy instance with the 5GMS AF. The 5GMS AF uses the Policy Template identifier to look up the matching Policy Template in order to create the PCF or NEF API invocation. As result, the Media Session Handler receives the enforcement bit rate in the 5GMS AF response. The 5GMS Client should not exceed this bit rate threshold.

The Service Access Information (via M5_1) includes a list of recommended traffic detection methods. The Media Session Handler selects a Service Data Flow description method (e.g. 5-Tuples). When the Media Session Handler selects:

– 5-Tuples: For each new TCP connection, the Media Session Handler updates the Dynamic Policy instances and adds a new 5-Tuple. For each closed TCP connection, the Media Session Handler updates the Dynamic Policy instances and removes the 5-Tuple of the closed TCP connection.

– TOS or Traffic Class: The Media Session Handler sets the TOS or Traffic Class for each new TCP connection.

– Domain name: The Media Session Handler provides the domain name with the Dynamic Policy Instance.

A.2.3 Example parameters

Table A.2.3‑1: M5_1 parameters for Policy Descriptions (used by the Media Session Handler)

Parameter	Type	Purpose	Example Values
Policy Description	Object
Network Policy Identifier	String	Identifies the Policy Description.	"4K Premium QoS", "HD Premium QoS".
Service Access Information URL	URL	References the associated Service Access Information.

Table A.2.3‑2: M5_1 parameters for Service Access Information

Parameter	Type	Purpose
Service Access Information	Object
Policy Template identifier	String	Identifies the Policy Template.	"HD QoS".
5GMS AF URL	URL	Used to invoke the 5GMS AF.
Mandatory Request M5 information	List	Desired bit rate, which should be provided by the network for the application.	Policy Template identifier, Desired Bit Rate, Packet Detection Filters.
M5 Response information	List	Information to the Media Session Handler on the response parameters.	OK (requested bit rate is accepted), Proposed Lower Bit rate (requested bit rate cannot be provided).
sdfMethod	[String]	Indicates which Service Data Flow Description methods are recommended to be used by the Media Session Handler.	"5-Tuple", "domainName", "TOS=xx", etc.