3GPP 23.501 v20.2.0 — the document's own text
5.37.5.1 General
Taught in 23. Very fast, very reliable, very picky (The 5G system architecture, in depth).
The PDU Set based Handling comprises the treatment of PDU Sets with or without PDU Set QoS Parameters. The PDU Set based QoS Handling refers to the PDU Set based Handling with PDU Set QoS Parameters.
A PDU Set is comprised of one or more PDUs carrying an application layer payload such as a video frame or video slice. The PDU Set based QoS Handling by the 5G-AN is determined by PDU Set QoS Parameters in the QoS profile of the QoS Flow (specified in clause 5.7.7) and PDU Set Information provided by the PSA UPF via N3/N9 interface as described in clause 5.37.5.2. The PDU Set based Handling can be applied for GBR and non-GBR QoS Flows. The AF should provide PDU Set related assistance information for dynamic PCC control. One or more of the following PDU Set related assistance information may be provided to the NEF/PCF using the AF session with required QoS procedures in clauses 4.15.6.6 and 4.15.6.6a of TS 23.502 [3].
- PDU Set QoS Parameters as described in clause 5.7.7
- Protocol Description: Indicates the transport protocol used by the service data flow (e.g. RTP, SRTP) and information, e.g. the following:
- RTP [185] or SRTP [186];
- RTP or SRTP with RTP Header Extensions, including:
- RTP Header Extensions for PDU Set Marking as defined in TS 26.522 [179];
- Other RTP Header Extensions as defined RFC 8285 [189], RFC 9143 [207];
- RTP or SRTP without RTP Header Extensions, but together with RTP Payload Format (e.g. H.264 [187] or H.265 [188]);
- RTP or SRTP with RTP Header Extensions for PDU Set Marking as defined in TS 26.522 [179] and together with RTP Payload Format (e.g. H.264 [187] or H.265 [188]);
- RTP or SRTP with other RTP Header Extensions following RFC 8285 [189] and together with RTP Payload Format (e.g. H.264 [187] or H.265 [188]).
NOTE 1: With the Protocol Description options combining SRTP together with RTP Payload Format the UPF can still obtain some of the PDU Set information from the RTP Header (refer to Annex A of TS 26.522 [179]).
When RTP Header Extensions for PDU Set Marking (as defined in TS 26.522 [179] or other RTP header extensions as defined in RFC 8285 [189] is included, the differentiation between different RTP Header Extension Types should be supported.
When RTP Payload Format is included, the differentiation between different RTP Payload Formats should be supported.
NOTE 2: Multiplexing of different transport protocols and different media traffic for differentiated PDU Set based Handling is not supported in the current Release.
The Protocol Description can be UL only, DL only or UL and DL. The Protocol Description for UL and DL traffic may be different.
For end-to-end encrypted traffic, PDU Set Information is received as media related information from the Application Server, see clause 5.37.9.
NOTE 3: Identification of PDU Set information for end-to-end encrypted traffic is supported in the DL direction only.
AF provided PDU Set QoS Parameters and UL and/or DL Protocol Description may be used in determining the PCC Rule by the PCF as defined in clause 6.1.3.27.4 of TS 23.503 [45] and the DL Protocol Description may be used for identifying the PDU Set Information and PDU Set Information marking by the PSA UPF.
When the SMF receives the PCC rule, the SMF performs binding of the PCC rule to one QoS Flow as described in clause 6.1.3.2.4 of TS 23.503 [45]. At least one of the following shall be included in the PCC rule to enable PDU Set based QoS Handling: 1) a PSIHI and/or 2) both PSDB and PSER. Based on the PCC rule, the SMF adds the PDU Set QoS Parameters to the QoS Profile of the QoS Flow as described in clause 6.2.2.4 of TS 23.503 [45]. Alternatively, the SMF may be configured to support PDU Set based Handling without receiving PCC rules from a PCF.
If no DL PDU Set QoS parameters are included in the PCC rule, but a DL Protocol Description is included in the PCC rule received by the SMF and the PSA UPF supports PDU Set based Handling (i.e. supports to perform PDU Set Information marking), the SMF may, based on the local operator policy, send to the NG-RAN, a DL PDU Set Information Marking Support Indication indicating that the DL PDU Set Information marking is supported.
For the downlink direction, the PSA UPF identifies PDUs that belong to PDU Sets and marks them accordingly as described in clause 5.37.5.2. If the PSA UPF receives a PDU that does not belong to a PDU Set based on Protocol Description for PDU Set identification, then the PSA UPF still maps it to a PDU Set and determines the PDU Set Information as described in clause 5.37.5.2 and sets its PDU Set Importance to the value indicated by the parameter PDU Set Importance for N6-unmarked PDUs, if this parameter is received from the SMF in the QER.
NOTE 4: If the PSA UPF receives a PDU that does not belong to a PDU Set and has not received the parameter PDU Set Importance for N6-unmarked PDUs PDUs, then it is assumed that the UPF determines the PDU Set Importance value based on pre-configuration.
For the uplink direction, the UE may identify PDU Sets and how this is done is left up to UE implementation. The SMF may send the UL Protocol Description associated with the QoS rule to UE.
NOTE 5: Using the Protocol Description or not is left to UE implementation. The use of Protocol Description does not impact QoS Flow Mapping in the UE.
In this Release, the PDU Set based Handling is supported in 5GS for a UE registered in 3GPP access for single access PDU Session with IP PDU Session Type, for a UE registered in untrusted or trusted non-3GPP accesses for single access PDU Session with IP PDU Session Type, and for a 5G-RG registered in W-5GAN for single access PDU Session with IP PDU Session Type. The support of PDU Set based Handling in 5G-RG is specified in TS 23.316 [84].