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Content for  TS 23.548  Word version:  17.3.0

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6.4  Network Exposure to Edge Application Serverp. 37

6.4.1  Generalp. 37

Some real time network information, e.g. user path latency, are useful for application layer. In this release, in order to expose network information timely to local AF, the L-PSA UPF may expose i.e. QoS monitoring results as defined in TS 23.501, clause 5.33.3, to the local AF.
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6.4.2  Network Exposure to Edge Application Serverp. 37

6.4.2.1  Usage of Nupf_EventExposure to Report QoS Monitoringp. 37

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 TS 23.501, clause 6.2.5.0. 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 TS 23.501, clause 6.2.5.0 and clause 6.3.14.
The local AF subscribes the low latency exposure 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 subscribe the Npcf_PolicyAuthorization_Subscribe service via 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 may include an indication of direct event notification (including target local NEF address or target AF address) within the PCC rule that it provides to the SMF.
The SMF sends the QoS monitoring request to the RAN and N4 rules to the L-PSA UPF. N4 rules may indicate the service data flow needs local 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 TS 23.501, clause 5.33.3. When N4 rules indicate the service data flow needs local notification of QoS Monitoring, upon the detection of the QoS monitoring event (e.g. when latency threshold of the QoS flow is reached as defined in TS 23.501, clause 5.33.3), the L-PSA UPF notifies the QoS Monitoring event information to the AF (directly or via Local NEF). The L-PSA UPF may support Nupf_EventExposure_Notify service operation, as defined in TS 23.502, clause 5.2.26. In particular, 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 information 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 service data flow needs local 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.
Copy of original 3GPP image for 3GPP TS 23.548, Fig. 6.4.2.1-1: Network exposure to Edge Application Server
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Step 0.
The UE establishes a PDU Session as defined in clause 4.3.2.2.1 of TS 23.502 A L-PSA UPF is assigned for this PDU Session.
Step 1.
The AF initiates setting up an AF session with required QoS procedure as defined in clause 4.15.6.6 of TS 23.502.
In the request, the AF may subscribe to direct notification of QoS monitoring for the service data flow to PCF possibly via Local NEF or NEF. If so, the AF shall include the corresponding QoS monitoring parameters as defined in clause 5.33.3 of TS 23.501.
The AF may also first initiate an AF Session with PCF and later subscribe to direct notification of QoS monitoring to PCF by invoking Npcf_PolicyAuthorization_Subscribe service operation.
The local AF or NEF may discover a local NEF as specified in TS 23.501, clause 6.2.5.0 and using parameters as specified in clause 6.3.14. Alternatively, if the NEF detects that it is not the most suitable NEF instance to serve the local AF request, the NEF may redirect the AF to a (more) local NEF. The NEF may use information on the L-PSA UPF for this determination.
The indication for AF request network real-time information is also provided. Then the Local NEF may subscribe the direct notification of QoS monitoring to PCF.
Step 2.
The PCF makes the policy decision and initiates the PDU Session modification procedure as defined in clause 4.3.3.2 of TS 23.502, steps 1b, 3b, 4-8b.
If the direct notification of QoS monitoring is subscribed, the PCF includes the indication of direct event notification (including target local NEF or local AF address) for the service data flow within the PCC rule.
If the SMF receives the indication of direct event notification form the PCF and the SMF determines that the L-PSA UPF supports such reporting, the SMF sends QoS monitoring parameters and associate them with the target local NEF or local AF address to the L-PSA UPF via N4 rules. Otherwise the SMF activates N4 reporting. The PCF may determine that the duplicated notification is required, i.e. both direct notification to the AF (i.e. sent from UPF) and notification sent via the PCF/SMF is required and indicate it to the SMF with the PCC information. In this case, the SMF may activate the N4 reporting together with the direct reporting to the local NEF/AF.
Step 3.
The L-PSA UPF obtains QoS monitoring information as defined in TS 23.501, clause 5.33.3.
Step 4.
The L-PSA UPF sends the notification related with QoS monitoring information over Nupf_EventExposure_Notify service operation. The notification is sent to Notification Target Address that may correspond (4a) to the local AF or (4b) to the local NEF.
Step 5.
If Local NEF is used, it reports the real-time network information to local AF by invoking Nnef_EventExposure_Notify service operation.
Step 6.
Due to e.g. UE mobility, the PSA relocation and/or EAS relocation may happen as described in clause 6.3. During the PSA and/or EAS relocation (if the event was subscribed e.g. as in step 1), the SMF notifies the (local) NEF or the AF with the PSA and/or EAS relocation, and the AF may trigger a new L-NEF discovery as in step 1. During this step, the application mechanisms may involve a new AF for this session.
Step 7.
The new AF may initiate a new AF session to (re-)subscribe the local notification of QoS monitoring as described in steps 1-4.
Step 8.
The old AF revokes the AF session.
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6.4.2.2  Local NEF Discoveryp. 39

As specified in TS 23.501, clause 6.2.5.0, 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 TS 23.502, clause 4.17.4 to discover the L-NEF. If the AF only knows the NEF and it initiates a service operation for local QoS monitoring exposure towards this NEF, e.g. a Nnef_AFSessionWithQoS_Create/Update_request procedure with an indication of local 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 itself 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.
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6.5  Support of 3GPP Application Layer Architecture for Enabling Edge Computingp. 39

6.5.1  Generalp. 39

The 3GPP application layer architecture for Enabling Edge Computing that is specified in TS 23.558 includes the following functional entities:
  • Edge Enabler Client (EEC).
  • Edge Configuration Server (ECS).
  • Edge Enabler Server (EES).
A UE may host EEC(s) as defined in TS 23.558 and support the ability to receive ECS address(es) from the 5GC and to transfer the ECS address(es) to the EEC(s). In this case, the ECS address provisioning via 5GC is described in clause 6.5.2.
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6.5.2  ECS Address Provisioningp. 40

6.5.2.1  ECS Address Configuration Informationp. 40

The ECS Address Configuration Information consists of one or more ECS Configuration Information as defined in clause 8.3.2.1 of TS 23.558. The ECS Configuration Information may contain Spatial Validity Conditions, which includes one of the following alternatives:
  • a Geographical Service Area (see TS 23.558);
  • a list of TA(s); or
  • a list of countries (list of MCC).
A UE may receive multiple instances of ECS Address Configuration Information e.g., corresponding to different ECSPs (e.g., the MNO or a 3rd party service provider).
The ECS Address Configuration Information is sent to the UE on a per PDU Session basis. The same PDU session can be used by multiple ECS providers.
The SMF does not need to be aware of the internal structure of the ECS Address Configuration Information.
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6.5.2.2  ECS Address Configuration Information Provisioning to the UEp. 40

If the UE hosts an EEC and supports transferring the ECS address received from the 5GC to the EEC, the UE indicates in the PCO at PDU Session establishment that it supports the ability to receive ECS address(es) via NAS and to transfer the ECS Address(es) to the EEC(s) (see TS 23.502). As described in TS 23.502, if the UE supports the ability to receive ECS Address Configuration Information via NAS and to transfer the ECS address(es) to the EEC(s), the UE may receive ECS Address Configuration Information from the SMF via PCO during PDU Session Establishment and/or during PDU Session Modification procedures. If Spatial Validity Condition of ECS is provided, the UE uses the appropriate ECS as defined in TS 23.558.
The SMF may receive ECS Address Configuration Information and associated spatial validity conditions from the UDM together with SM subscription information. The UDM in the HPLMN may provide the SMF (in HPLMN in HR case, in VPLMN in LBO case) with ECS address configuration information that depends on the serving PLMN of the UE.
The SMF determines the ECS Address Configuration Information to be sent to the UE based on UE subscription information received from UDM (as described in Table 4.15.6.3d-2 of TS 23.502).
The SMF may decide to send updated ECS Address Configuration Information to the UE based on locally configured policy or updated UE subscription information. The PDU Session Modification procedure is used to send updated ECS Address Configuration Information to the UE as described in clause 4.3.3 of TS 23.502.
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6.5.2.3  ECS Address Provisioning by a 3rd Party AFp. 40

As described in TS 23.558, the Edge Configuration Server can be deployed in a 3rd party domain by a service provider. An AF in the MNO domain or, if the Edge Configuration Server is deployed in a 3rd party domain by a service provider, a 3rd party AF can use Nnef_ParameterProvision to provide, update, or delete AF provided ECS Address Configuration Information applying on a DNN and/or S-NSSAI for a group of UE, or any UE (See clause 4.15.6.2 of TS 23.502).
When the AF uses Nnef_ParameterProvision to send a new AF provided ECS Address Configuration Information to the UDM (e.g. because on Application layer activity, etc.), the UDM may notify the impacted SMF(s) of the updated Subscription provided ECS Address Configuration Information and the new ECS Address Configuration Information will be sent to the UE(s) in a PDU Session Modification procedure.
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6.5.2.4  ECS Address Provisioning by MNOp. 41

The ECS Address Configuration Information can be provisioned by the MNO subscription provisioning in UDM.

6.5.2.5  Interworking with EPCp. 41

In interworking scenarios, if the UE hosts an EEC and supports transferring the ECS address received from the 5GC to the EEC, the UE indicates in the PCO at PDN Connection establishment that it supports the ability to receive ECS address(es) via NAS and to transfer the ECS Address(es) to the EEC(s) (see TS 23.502) and the bearer modification procedure without bearer QoS update procedure is used to send updated ECS Address Configuration Information to the UE as described in clause 4.11.0a.5 of TS 23.502.
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6.6  Support of AF Guidance to PCF Determination of Proper URSP Rulesp. 41

This clause describes how an Edge Computing related AF may send guidance to PCF determination of proper URSP rules to send to the UE.
An AF related with Edge computing may need to guide PCF determination of proper URSP rules. The guidance sent by the AF may apply to any UE or to a set of UE(s) e.g. identified by a Group Id. The AF may belong to the operator or to a third party.
An AF may deliver such guidance to the PCF via application guidance for URSP rules determination mechanisms defined in clause 4.15.6.10 of TS 23.502. This mechanism is defined only to deliver the guidance to a PCF of the HPLMN of the UE.
The PCF may use the AF guidance received from different AFs, UE subscription data and local operator policy to determine the URSP rules to send to a UE. If received guidance information is not consistent with UE subscription data, or the local operator policy do not allow the specific S-NSSAI and DNN provided by the AF guidance, the corresponding AF guidance shall not be used to determine URSP rules.
  • Application traffic descriptor from the application guidance is used to set the URSP Traffic Descriptor (e.g. Destination FQDNs or a regular expression in the Domain descriptor), and the PCF determines the URSP rules precedence in the URSP rule (defined in TS 23.503 Table 6.6.2.1-2);
  • Route selection parameter from the application guidance is used to set a Route Selection Descriptor as follows:
    • DNN and S-NSSAI from the Route selection parameter from the application guidance are used to set the DNN selection, Network Slice selection components in the Route Selection Descriptor of the URSP rule, respectively (defined in TS 23.503 Table 6.6.2.1-3) based on the UE subscription data;
    • Route selection precedence from the application guidance is used to set the Route Selection Descriptor Precedence in the Route Selection Descriptor (defined in TS 23.503 Table 6.6.2.1-3);
    • The spatial validity condition for the Route selection precedence from the application guidance if any are used to set the Location Criteria in the Route Selection Descriptor of the URSP rule (defined in TS 23.503 Table 6.6.2.1-3).
URSP rules based on AF guidance should not be set as the URSP rules with the "match all" traffic descriptor.
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