3GPP TR 26.942 CR 0021 rev 2 - Media Application Service Model

Overview

This Change Request introduces a comprehensive Media Application Service model to TR 26.942 for the FS_Energy_Ph2_MED study item. The CR establishes a common baseline understanding of how Application Services interact with the 5G System to exchange media over the User Plane, providing conceptual models for different media service types.

Main Technical Contributions

1. Generalised Media Application Service Model (Clause 4.2.2.6.2)

The CR defines a foundational model describing media delivery sessions over the 5G System User Plane:

Key Characteristics:

• Service Data Flows: Media delivery sessions comprise one or more Service Data Flows traversing the User Plane between Media Client and Media AS at reference point M4
• Directionality: Media content may flow in downlink and/or uplink directions
• Flow Multiplexing: Multiple Application Data Flows may be multiplexed onto a single Service Data Flow (IP 5-tuple) or mapped to unique Service Data Flows

Examples Provided:

• MPEG-DASH: Independent HTTP/1.1 sessions per Adaptation Set to avoid head-of-line blocking, each on separate TCP connections (distinct Service Data Flows)
• CMMF-based DASH: Coded object requests raced over independent HTTP connections to multiple diverse service locations
• Split-rendered RTC: Multiple SRTP sessions for different media types, with Application Data Flows potentially multiplexed or separated

Complex Session Scenarios:

• Multiparty RTC sessions via RTC AS or peer-to-peer (when 5G System policy allows)
• Multiple Media Clients communicating as peers or via intermediate Media AS
• Note: Peer-to-peer Service Data Flow energy consumption not visible in Media AS application logs

Dynamic Behavior Characteristics:

1. Service Location Diversity: Different Service Data Flows may target different service location endpoints during a session
2. Concurrent Service Locations: Multiple service locations may be used in parallel (e.g., CMMF)
3. Server Deployment Variability: Each service location endpoint may be provided by different deployed servers with different energy consumption profiles
4. PDU Session Mapping: Service Data Flows may map to one or several parallel PDU Sessions depending on active service locations and UE Route Selection Policy (URSP)
5. Network Slice Diversity: PDU Sessions may traverse different logical network slices and/or Data Networks based on URSP
6. Multi-Access Support: PDU Sessions may be Multi-Access PDU Sessions, transparently traversing different Access Networks
7. Flow Migration: Service Data Flows may migrate between PDU Sessions due to UE mobility and/or gNodeB mobility (e.g., NTN)

Energy Consumption Implications:

• Dynamic Nature: Energy consumption may change dynamically during media delivery sessions, especially with edge computing, UE mobility, and service location switching
• Incomplete EIF Picture: User Plane network energy information from EIF (clause 4.2.2.3) doesn't account for:
• Energy consumed north of UPF (especially Media Application Server)
• Energy consumed south of gNodeB (especially UE)

2. 5GMS Application Service Model (Clause 4.2.2.6.3)

Based on TS 26.501 reference architecture, the CR defines separate conceptual models for downlink and uplink media streaming.

5GMSd (Downlink) Conceptual Model:

| Concept | Description |
|---------|-------------|
| 5GMSd AS instance | (Edge) 5GMSd AS instance in deployment |
| Content Hosting Configuration | Corresponds to single Provisioning Session in 5GMSd AF; may be present in multiple (Edge) 5GMSd AS instances |
| Distribution Configuration | Models a service location exposed by (Edge) 5GMSd AS instance |
| Downlink media streaming session | Models session spanning one or more content items |
| Service Data Flow | HTTP connection at reference point M4d described by IP 5-tuple |
| Application Data Flow | Series of media segment download requests at M4d; multiple HTTP requests may be multiplexed onto same HTTP connection (serial or parallel) |

5GMSu (Uplink) Conceptual Model:

| Concept | Description |
|---------|-------------|
| 5GMSu AS instance | (Edge) 5GMSu AS instance in deployment |
| Content Publishing Configuration | Corresponds to single Provisioning Session in 5GMSu AF; may be present in multiple (Edge) 5GMSu AS instances |
| Contribution Configuration | Models a service location exposed by (Edge) 5GMSu AS instance |
| Uplink media streaming session | Models session spanning one or more content items |
| Service Data Flow | HTTP connection at reference point M4u described by IP 5-tuple |
| Application Data Flow | Series of media segment upload requests at M4u; multiple HTTP requests may be multiplexed onto same HTTP connection |

Visibility and Association:

• Finest Granularity: Service Data Flow (HTTP connection at M4) is finest level visible to 5GMS AS
• Individual Application Data Flows: Not easily distinguishable when multiplexed on same Service Data Flow using HTTP
• Session Association: Service Data Flows associated with media streaming session via media delivery session identifier conveyed as HTTP request header (per TS 26.512 clause 6.2.3.6)
• Configuration Association: Service location (HTTP authority and leading URL path elements) enables HTTP request association with Distribution Configuration

3. RTC Application Service Model (Clause 4.2.2.6.4)

Based on TS 26.506 reference architecture, the RTC model has a simpler structure than 5GMS.

RTC Conceptual Model:

| Concept | Description |
|---------|-------------|
| RTC AS instance | (Edge) RTC AS instance in deployment |
| Media Function Configuration | Corresponds to single Provisioning Session in RTC AF; may be present in multiple (Edge) RTC AS instances |
| RTC session | Models set of RTP sessions comprising a WebRTC session |
| Service Data Flow | UDP association at reference point RTC-4 described by IP 5-tuple; one or more Application Data Flows may be multiplexed |
| Application Data Flow | SRTP packets sharing same Synchronisation Source (SSRC) value in packet headers |

Visibility and Association:

• Finest Granularity: Application Data Flow is finest level visible to RTC AS
• SSRC Visibility: When multiple SRTP streams are multiplexed on same Service Data Flow, SSRC field remains visible in unencrypted RTP header
• Session Association Limitation: In Release 19, no media delivery session identifier conveyed in RTP header, so individual Service Data Flows cannot be associated with an RTC session by RTC AS
• Configuration Association: Service Data Flows could be associated with Media Function Configuration if different service location (IP 3-tuple) is exposed per configuration
• Note: Different service location endpoints may be desirable to avoid service level pollution between RTC sessions from different RTC AF Provisioning Sessions

References Added

• [26512]: 3GPP TS 26.512: "5G Media Streaming (5GMS); Protocols"

Scope and Application

The introduction (clause 4.2.2.6.1) clarifies that these models establish a common baseline understanding for how Application Services interact with the 5G System. Candidate Solutions in the Technical Report may reference one or more of these models as applicable.