Section: 5.37.4 Network Exposure of 5GS information
Content: 5GS and XR/media services cooperate to provide a better user experience using External Network Exposure. Based on the AF request, the 5GS can expose the following information based on the QoS Monitoring as defined in clause 5.33.3 and/or clause 5.45: - The UL and/or DL congestion information monitoring (see clause 5.45.3). Based on the PCC rule from PCF, the SMF requests the NG-RAN to report the information via GTP-U header to PSA UPF. This NG-RAN reported information is common to support congestion information exposure and to support ECN marking for L4S in PSA UPF as described in clause 5.37.3.3. In the case of congestion information exposure, the PSA UPF exposes the UL and/or DL congestion information via Nupf_EventExposure service or via SMF/PCF/NEF as described in clause 5.8.2.18. It can be applied to a Non-GBR or GBR QoS Flow. - The UL and/or DL Data rate information (see clause 5.45.4). Based on the PCC rule from PCF, the SMF requests the PSA UPF to measure and report the information. They may be exposed to the AF directly by PSA UPF via Nupf_EventExposure service or via SMF/PCF/NEF as described in clause 5.8.2.18. - The round trip delay for two service data flows considering the UL direction of a service data flow and the DL direction of another service data flow. in the same PDU Session. It is determined based on the QoS Monitoring for packet delay of individual QoS Flows as described in clause 5.33.3. The PCF derives the separate QoS monitoring policies for each direction packet delay (see clause 5.33.3) based on AF request and local policy. The PCF provides the two QoS Monitoring policies in the PCC rules for the service data flows. The PSA UPF reports the delay information per QoS Flow to the SMF. The SMF reports to PCF. The PCF derives round trip delay information based on the two direction's packet delay result for the service data flows and exposes the information to the AF directly or via NEF. - The round trip delay for one service data flow. If the service data flow is mapped to two QoS Flows (i.e. the UL traffic and DL traffic of the service data flow are separated into two QoS flows respectively) in the same PDU Session, similarly to the round trip delay for two service data flows over two QoS flows, the PCF triggers QoS Monitoring for each direction packet delay of individual QoS flows respectively and derives round trip delay based on the two direction QoS flows' packet delay monitored result. NOTE: How PCF calculates the requested round trip delay for multiple QoS Flows from delays of individual QoS Flows is not specified in this specification. The AF may provide the Alternative QoS parameter set requirements and Averaging Window to the NEF/PCF for the GBR QoS Flow as specified in clause 4.15.6.6 of TS 23.502[ Procedures for the 5G System (5GS) ]  [3].