Content for  TS 23.548  Word version:  19.0.0

The UPF may be instructed to report information about a PDU Session directly i.e. bypassing the SMF and the PCF. This reporting may target an Edge Application Server (EAS) or a local AF that itself interfaces the EAS. Local NEF deployed at the edge may be used to support network exposure with low latency to local AF. The local NEF may support one or more of the functionalities described in clause 6.2.5.0 of TS 23.501. and may support a subset of the APIs specified for capability exposure based on local policy. In order to support the network exposure locally, the local NEF shall support Nnef_AFSessionWithQoS service operation for the local AF. The local NEF selection by AF is described in clauses 6.2.5.0 and 6.3.14 of TS 23.501. The local AF subscribes the direct notification of QoS Monitoring results from the PCF via a local NEF or NEF. If the NEF detects that it is not the most suitable NEF instance to serve the local AF request, it may redirect the AF to a local NEF instance. The local AF may also use the Npcf_PolicyAuthorization_Create or Update service of the PCF directly. In this case, reporting is done directly from the UPF to the local AF. Based on the indication of direct event notification and operator's policy, the PCF includes Direct event notification method and the Target of reporting (including target local NEF address or target AF address) within the PCC rule that it provides to the SMF as described in clause 6.1.3.21 of TS 23.503. The SMF sends the QoS monitoring request to the RAN and N4 rules to the L-PSA UPF. If the L-PSA UPF supports such reporting, N4 rules indicate that the QoS flow needs direct notification of QoS Monitoring. When QoS monitoring of GTP-U Path(s) is used, it is also activated if needed. This is as defined in clause 5.33.3 of TS 23.501. When N4 rules indicate that the QoS flow needs direct notification of QoS Monitoring results, upon the detection of the QoS monitoring event (e.g. when threshold for the packet delay of the QoS flow is reached as defined in clause 5.33.3 of TS 23.501), the L-PSA UPF notifies the QoS Monitoring event information to the AF (directly or via Local NEF). If the L-PSA UPF supports the Nupf_EventExposure_Notify service operation, as defined in clause 5.2.26 of TS 23.502, the L-PSA UPF sends the Nupf_EventExposure_Notify to the Notification Target Address indicated by the Session Reporting Rule received from the SMF. The Notification Target Address may correspond to the AF or to a local NEF. When the Notification Target Address corresponds to a Local NEF, the local NEF reports the QoS Monitoring result to the AF. During UE mobility, the SMF may trigger the L-PSA UPF relocation/reselection and then send the N4 rules to the new L-PSA UPF to indicate the QoS flow needs direct notification of QoS Monitoring. The UE mobility may also trigger AF relocation or local NEF reselection, then the local AF should update the subscription for local exposure with QoS monitoring results possibly via local NEF, towards the PCF. This updated /new subscription is then propagated via SMF (via PCC rule updates) and then to the L-PSA UPF via N4 rules.

As specified in clause 6.2.5.0 of TS 23.501, the NRF may be used by the AF to discover the L-NEF. To become discoverable, the L-NEF registers with an NRF deployed within the operator's domain where the AF resides. The AF uses existing procedures as described in clause 4.17.4 of TS 23.502 to discover the L-NEF. If the AF only knows the NEF and it initiates a Nnef_AFSessionWithQoS_Create/Update_request procedure with an indication of direct event notification as described in clause 6.4.2.1 and clause 6.1.3.21 of TS 23.503, the NEF may decide that it is not suitable for local exposure, and re-direct the request to an L-NEF as described in TS 29.500. NEF may use NRF to find a suitable L-NEF for the re-direction.