4.15.11 Exposure of Events from UPF

23.5023GPPProcedures for the 5G System (5GS)Release 18TS

4.15.11.1 General

This clause contains the detailed description and the procedures for UPF event exposure service.

The NWDAF can subscribe to the UPF data via the SMF, and the UPF will directly send the collected UPF data to NWDAF. Or, the NWDAF can subscribe directly to UPF.

The Subscription to UPF events via SMF is the rule though there are some exceptions listed below; Subscription via SMF means the final consumer of UPF event notifications sends the subscription request to the SMF and then the SMF is doing a third-party subscription onto UPF on behalf of this final consumer. Conversely the notifications are directly sent by the UPF to the final consumer of UPF notifications.

Exceptions to subscriptions via SMF are subscriptions for data collection where UPF is the source as defined in TS 23.288 [5] in the following cases:

– Data collected by NWDAF is for UPF load analytics described in Table 6.5.2-2 of TS 23.288 [5].

– Data Collected by NWDAF is targeting "any UE" (possibly for specific DNN and or slices) and not related with an AoI or BSSID/SSID or application.

4.15.11.2 Information flow for UPF event exposure service to NWDAF for certain UE(s)

Figure 4.15.11.2-1: UPF Information Exposure to NWDAF

In the case of a group of UEs, the NWDAF issues an Nnrf_NFDiscovery_Request service operation to find the UDM providing the NF type and Group ID and gets the NF profile of the UDM that currently meets the NWDAF discovery request. Then, NWDAF obtains the list of SUPIs that correspond to the Group ID from UDM using Nudm_SDM_Get

NOTE 1: It is assumed that all members of a Group ID belong to the same UDM.

Then, for each SUPI,

1. The NWDAF invokes Nudm_UECM_Get service operation to retrieve the appropriate SMF by providing UE ID and NF type, to request UPF information Exposure for a certain UE.

2. The UDM provides a Nudm_UECM_Get response to the NWDAF with the corresponding SMF.

3. The NWDAF sends the request to the SMF to subscribe UPF data, including the following information:

– Notification Target Address (NWDAF address).

– Indication of UPF Event Exposure Service.

– Event Filter Information: S-NSSAI, Application Id, Area of Interest, SSID/BSSID.

– Target of Event Reporting: a UE.

– Subscription event and Information requested.

4. The SMF sends the request to the UPF including the NWDAF address, Event Filter Information, Target of Event Reporting, and Target Subscription Information. Target of Event Reporting is the certain UE or the group of UEs same as step 1.

NOTE 2: It is up to the conclusion of UPEAS SID on whether SBI and/or PFCP (TS 29.244 [8]) is used for interaction between the SMF and UPF.

5. The UPF responds with the locally collected UPF data by invoking Nupf_EventExposure_Notify service operation to the NWDAF.

4.15.11.3 Information flow for UPF event exposure service to NWDAF for anyUE

When the NWDAF subscription request does not meets the criteria for direct subscription to UPF as described in 4.15.11.1, NWDAF shall subscribe via the SMF. NWDAF send a Nnrf_NFDiscovery_Request to NRF including the related discovery parameters and the NRF returns the SMF(s) which meet(s) the discovery request. NWDAF executes then steps 4-5 in figure 4.15.11.2-1 where the target of the event reporting is in this case anyUE.

When the NWDAF subscription request meets the criteria for direct subscription to UPF as described in 4.15.11.1, NWDAF queries the NRF including the related discovery parameter. The NRF returns the UPF(s) which meet(s) the discovery request, and NWDAF sends the Nupf_EventExposure_Subscription directly to UPF.