Section: 4.15.4.5 Exposure of Events from UPF for UPF Data Collection 4.15.4.5.1 General
Content: This clause contains the detailed description and the procedures for how the UPF event exposure service (see clause 5.2.26.2) is used for UPF data collection. The list of NF consumer which may receive UPF event notifications is defined in clause 5.8.2.17 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]. To get exposure data from UPF, NF consumer may subscribe to the UPF directly or indirectly via SMF. This is further defined in clause 5.8.2.17 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]. The UPF event exposure events are described in clause 5.2.26.2. In this Release of the specification, the following events are used for UPF Data collection: - QoS Monitoring. This event provides QoS Flow performance information. - UserDataUsageMeasures. This event provides information of user data usage of the User PDU Session. - UserDataUsageTrends. This event provides statistics related to user data usage of the User PDU Session. A consumer of UPF event exposure can subscribe to QoS monitoring event via SMF only and UPF sends the QoS Flow Performance information directly to this consumer. For this event, the interaction between SMF and UPF is over PFCP (TS 29.244[ Interface between the Control Plane and the User Plane nodes ]  [69]). TS 23.501[ System architecture for the 5G System (5GS) ]  [2] describes the QoS parameters that can be measured by means of QoS monitoring and how to enable the measurements for QoS flows. When the Subscription request for QoS monitoring event indicates that it is for the QoS Flow associated with the default QoS rule, based on local configuration the subscription request may trigger SMF to enable QoS monitoring. NOTE 1: Packets from multiple applications may share the QoS Flow associated with the default QoS Rule which may diminish the relevance of some measurements like data rate. The subscription to QoS monitoring event can target the QoS flows bound to an application by including an Application Identifier. In this case, at subscription request and/or when the PCC rules change, SMF identifies the active PCC Rule that includes a DataCollection_ApplicationIdentifier matching that Application Identifier. SMF enables this consumer (e.g. NWDAF) to receive the QoS Monitoring reports enabled by that PCC Rule. The consumer may indicate that it can receive QoS Flow Performance information for the QoS Flow associated with the default QoS rule if there are no measurements available for the Application Identifier (that is, if no PCC rule is identified). In this case the SMF may instruct the UPF to perform QoS monitoring for the QoS Flow associated with the default QoS rule and include the Indication of QoS Flow associated with the default QoS Rule (see clause 5.8.2.18 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]). The UPF will then include the Indication of QoS Flow associated with the default QoS Rule in the Nupf_EventExposure_Notify service operation when sending reports. Otherwise, the SMF may accept the request and indicate in the response that reporting will be activated when the measurements are enabled by a PCC rule or the SMF may reject the subscription request for that Application Identifier. NOTE 2: Extensive usage of QoS Monitoring has significant impact on load and signalling. A consumer of UPF event exposure such as NWDAF can subscribe to User Data Usage events directly to UPF or via SMF and UPF sends the event notifications directly to this consumer. For this event, the interaction between SMF and UPF is over SBI. For User Data Usage events, the subscription request may target specific service data flows (e.g. a specific application traffic) by including a traffic description (e.g. an Application Id). Else, the scope of the subscription is all the traffic in the PDU Session. The subscription request may indicate the granularity requested, that is whether the measurement reports should be provided per service data flow, application, or the whole PDU Session. If the event notification can be delayed, i.e. delay tolerant, Reporting suggestion information is included. The Reporting suggestion information includes Report urgency and Reporting time information. Reporting urgency information indicates whether this event report can be delay tolerant, i.e. the event report can be delayed. If the Reporting urgency information indicates "delay tolerant", the Reporting time is also provided, which defines the last valid reporting time and UPF shall report the detected event before the last valid time. Table 4.15.4.5.1-1: Input parameters in subscription to UPF event Exposure events