Content for &nbsp; TS 23.502 &nbsp; Word version:&nbsp; 19.1.0

A consumer of event exposure for events detected in AMF or SMF (e.g. NWDAF) sends an Nudm_EventExposure Subscribe/Unsubscribe request to the UDM for a UE or group of UEs, including the subscription details (Event ID, Event filters, etc.).

UDM examines the event type and subscription details to determine whether one or more events are to be detected by the AMF. In this case, for those applicable events that are detected by the AMF, if an AMF is registered in UDM for the UE (or for a UE that is member of the group of UEs), UDM creates an Namf_EventExposure Subscribe/Unsubscribe request and sends it to the AMF of the UE, including the subscription details.

AMF answers with an Namf_EventExposure Subscribe/Unsubscribe response.

UDM examines the event type and subscription details to determine whether one or more events are to be detected by the SMF. In this case, for those applicable events that are detected by the SMF, if one or more SMFs are registered in UDM for the UE (or for a UE that is member of the group of UEs), UDM creates an Nsmf_EventExposure Subscribe/Unsubscribe request and sends it to each applicable SMF of the UE, including the subscription details.

SMF answers with an Nsmf_EventExposure Subscribe/Unsubscribe response.

Table 4.15.4.5.1-1: Input parameters in subscription to UPF event Exposure events

UDM sends an Nudm_EventExposure Subscribe/Unsubscribe response to the consumer of event exposure.

4.15.4.5 Exposure of Events from UPF for UPF Data Collection |R18| p. 424

4.15.4.5.1 General p. 424

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.

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.

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.
User DataUsage Measures: This event provides information of user data usage of the User PDU Session.
User DataUsage Trends: 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). TS 23.501 describes the QoS monitoring 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.

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). 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.

A consumer of UPF event exposure such as NWDAF/AF/NEF may subscribe to User Data Usage events (i.e. User Data Usage Measures and User Data Usage Trends) directly to UPF (under the conditions defined in clause 5.8.2.17 of TS 23.501) or via SMF, and UPF sends the event notifications directly to this consumer. For these events, the interaction between SMF and UPF is over SBI. For User Data Usage events, the subscription request targets the traffic matching Event Filter Information (details are described in clause 5.2.26.2.1) for a user's PDU Session or for each PDU Session served by the UPF. The subscription request may indicate the granularity requested, that is whether the measurement reports should be provided per data flow, per application, or per 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.

If a consumer subscribes to an UPF event via the SMF including an AoI ("Area of Interest"), the SMF starts the subscription to the UPF only when the UE is located in the requested AoI. When the UE leaves the AoI, the SMF stops the subscription on the UPF. The SMF may subscribe to AMF about UE moving in or out of an AoI for this purpose. Clause 4.15.4.5.4 describes an alternative procedure for subscription via SMF to UPF event exposure service related with AOI.

Information	To SMF	To UPF (NOTE 4)
UE identification (NOTE 5)	Y	Y
GroupID	Y	N
Any UE	Y	Y
DNN	Y	Y (NOTE 6)
S-NSSAI	Y	Y (NOTE 6)
AOI	Y	N
BSSID/SSID	Y	N
DNAI (NOTE 3)	Y	N
UPF Id (NOTE 3)	Y	not applicable
Type of Measurement	Y	Y
Granularity of Measurement (NOTE 2)	Y	Y
Application ID (NOTE 1)	Y	Y
Traffic Filtering Information (NOTE 1), (NOTE 2)	Y	Y
Reporting suggestion information	Y	Y
NOTE 1: Application ID and Traffic Filtering Information are exclusive. NOTE 2: This parameter does not apply to QoS monitoring event. NOTE 3: This parameter is used to indicate a UP Path as defined in Table 6.4.1-1 of TS 23.288. NOTE 4: This column is not applicable to events where SMF-UPF interactions are using PFCP (e.g. QoS Monitoring event). That interaction is described in clause 5.8.5 of TS 23.501. NOTE 5: Input parameter when the target is a UE. When the target is a UE, the SUPI is the the UE identification input to SMF. For IP PDU session type, the UE identification input to the UPF shall be the UE IP address associated with the PDU session. For non-IP PDU session types, when the UPF is allowed by local SMF configuration to receive the SUPI associated with a N4 session, the UE identification input to the UPF is the SUPI. UPF event Exposure targeting a UE is not supported for non-IP PDU session types, when the UPF is not allowed by local SMF configuration to receive the SUPI associated with a N4 session. NOTE 6: In a deployment where UPF reporting filtered per DNN and /or S-NSSAI is expected, the SMF should provide UPF with the necessary information over N4. If the SMF is not configured to provide UPF with this information then such UPF reporting filtering is not possible.

4.15.4.5.2 Information flow for subscription to UPF event exposure service for certain UE(s) via SMF p. 426

Reproduction of 3GPP TS 23.502, Fig. 4.15.4.5.2-1: Subscription to UPF event exposure service for certain UE(s) via SMF

Figure 4.15.4.5.2-1: Subscription to UPF event exposure service for certain UE(s) via SMF

In the case of a group of UEs, the UPF event consumer (e.g. NWDAF) first issues an Nnrf_NFDiscovery_Request service operation to find the UDM providing the target Group ID and gets the NF profile of the UDM serves this group. Then, NWDAF obtains the list of SUPIs that correspond to the Group ID from UDM using Nudm_SDM_Get

Then, for each SUPI:

The UPF event consumer (e.g. NWDAF) invokes Nudm_UECM_Get service operation to retrieve the appropriate SMF by providing UE ID, DNN, S-NSSAI and NF type = SMF.

The UDM provides a Nudm_UECM_Get response with the corresponding SMF.

The UPF event consumer sends the Nsmf_EventExposure Subscription request to the SMF to subscribe to UPF data, including the following information:

Notification Target Address (UPF event consumer address), Notification Correlation Information.
UPF Event Id.
Event Filter Information, i.e. one or more of the following parameters: S-NSSAI, DNN, DNAI, UPF Id, either Application Id(s) or Traffic Filtering Information, Area of Interest, SSID/BSSID.
Target of Event Reporting: a UE.
Reporting suggestion information.
Type of Measurement and Granularity of Measurement.

If the consumer is NWDAF and the analytic filter information includes application server IP address/FQDN, the NWDAF may need to first obtain the DNAI from NEF as described in steps 2 and 3 in Figure 4.15.4.5.3-1.

The SMF selects the PDU session(s) and the UPFs it has to send the request to. The SMF sends the request to the UPF including the UPF event consumer address, UPF Event Id, Notification Correlation Information, Event Filter Information (but only Application Id(s) or Traffic Filtering Information, if received in step 3), Reporting suggestion information, Target of Event Reporting, Type of Measurement and Granularity of Measurement as required. Target of Event Reporting indicates the PDU Session of the UE. The interaction mechanism used between SMF and UPF depends on UPF exposure event and which mechanism applies for each event as described in clause 5.2.26.2.1. For some events, the SMF shall contact UPF (4a) with N4 Session Modification with PFCP (TS 29.244), for other events (4b) with Nupf_event exposure subscribe request (as defined in clause 5.2.26.2.3).

In case 4b, if an I-SMF is used for this PDU session, for UPF events (except the QoS monitoring) involving UPFs controlled by the I-SMF, the SMF sends the Nsmf_EventExposure_Subscribe including the UPF event subscription related information to I-SMF if relaying of UPF event subscription is supported by the I-SMF and I-SMF forwards the subscription to the local UPF.

Figure 4.15.4.5.3-1: UPF Information Exposure to the UPF event consumer (e.g. NWDAF) of any UE scenario

Per Reporting suggestion information (if available), the UPF sends the locally collected UPF data by invoking Nupf_EventExposure_Notify service operation to the UPF event consumer.

4.15.4.5.3 Information flow for UPF event exposure service for any UE p. 427

Reproduction of 3GPP TS 23.502, Fig. 4.15.4.5.3-1: UPF Information Exposure to the UPF event consumer (e.g. NWDAF) of any UE scenario

(For the case when the UPF event consumer is NWDAF) The analytics consumer sends a request to the NWDAF for analytics on any UE. The analytics consumer provides the value "any UE" in the Target of Analytics Reporting. Analytics Filter Information optionally contains DNN, S-NSSAI, Area of Interest, Application server IP address/FQDN, Application ID, DNAI, etc.

(Optional and only when the UPF event consumer is NWDAF) If the Analytic Filter Information does not contain DNN/S-NSSAI, but only includes application server IP address/FQDN, the NWDAF should first obtain the DNAI from NEF. The NWDAF invokes Nnef_DNAIMapping_Subscribe service to request the DNAI information. The request includes EAS IP/IP range and/or FQDN.

(Conditional, if step 2 took place) The NEF determines the suitable DNAI(s) and provides them to NWDAF.

The UPF event consumer triggers the SMF(s)/UPF(s) discovery to NRF by Nnrf_NFDiscovery_Request providing the DNN, S-NSSAI, DNAI etc. This procedure is to discover the related SMF(s)/UPF(s) associated with any UE and support the indicated DNAI. Either SMF(s) or UPF(s) are discovered depending on whether the subscription request to UPF events meets the criteria for direct subscription to UPF as defined in clause 5.8.2.17 of TS 23.501).

The NRF provides Nnrf_NFDiscovery_Response that may refer to several SMFs/UPFs.

Figure 4.15.4.5.4-1: Subscription to UPF event exposure service for AOI via SMF

(Option 1) If the subscribed UPF events needs the SMF(s) to do a third-party subscription onto UPF (as defined in clause 5.8.2.17 of TS 23.501), the same procedure as Indirect subscription via several SMFs (steps 3 - 5 in Figure 4.15.4.5.2-1(for single UE)) takes place via each discovered SMF.

Step 7.

(Option 2) If the subscribed UPF events allows to directly subscribe to UPF (as defined in clause 5.8.2.17 of TS 23.501), the UPF event consumer (e.g. NWDAF) triggers the Nupf_EventExposure_Subscribe to all discovered UPFs. The information included in the subscription is:

Notification Target Address (UPF event consumer address), Notification Correlation Information.
UPF Event Id.
Event Filter Information, i.e. one or more of the following parameters: S-NSSAI, DNN, either Application Id(s) or Traffic Filtering Information.
Target of Event Reporting: any UE.
Reporting suggestion information.
Type of Measurement and Granularity of Measurement.

Step 8.

Each of the UPFs invokes Nupf_EventExposure_Notify service operation directly to the UPF event consumer (e.g. NWDAF).

4.15.4.5.4 Information flow for subscription via SMF to UPF event exposure service related with AOI p. 428

Reproduction of 3GPP TS 23.502, Fig. 4.15.4.5.4-1: Subscription to UPF event exposure service for AOI via SMF

If the subscription is related to AOI, the UPF event consumer (e.g. NWDAF) firstly get the UE list which includes the UE(s) located in the AOI from the AMF(s), then subscribe to UPF via SMF as described in clause 4.15.4.5.2. If the UPF event consumer (e.g. NWDAF) further needs to filter certain UE(s) out from the UE list get from the AMF(s), the UPF event consumer (e.g. NWDAF) locally decides the final UE list.

The UPF event consumer (e.g. NWDAF) determines the AMF(s) based on the AOI, i.e. TAIs and possibly on the target S-NSSAI and obtains the UE list which includes the UE(s) located in the AoI from AMF(s) by invoking Namf_EventExposure_Subscribe service operation to get the presence of UE(s) and moving in or out status in Area of Interest as described in clause 5.2.2.3 and in clause 5.3.4.4 of TS 23.501. The target of Namf_EventExposure_Subscribe depends on whether the UPF event consumer (e.g. NWDAF) targets one UE a group of UE or Any UE.

The UPF event consumer (e.g. NWDAF) locally computes the final UE list by comparing the UE list from AMF(s) and its own target UE list if it exists.

Figure 4.15.4.5.5-1: Subscription to UPF event exposure service for certain UE(s) directly

For each UE in the final UE list, the UPF event consumer (e.g. NWDAF) issues a subscription to UPF event exposure service via the SMF serving the UE (Nsmf_EventExposure Subscription) to get UPF data as described in clause 4.15.4.5.2. When an AMF reports a change of the list of UE(s) in the AoI (Namf_EventExposure_Notify), the UPF event consumer (e.g. NWDAF) may need to cancel the Nsmf_EventExposure Subscription or to issue a new Nsmf_EventExposure Subscription.

4.15.4.5.5 Information flow for direct subscription to UPF event exposure service for certain UE using UE's IP address |R19| p. 429

Reproduction of 3GPP TS 23.502, Fig. 4.15.4.5.5-1: Subscription to UPF event exposure service for certain UE(s) directly

In the case, UPF event consumer (e.g. AF (when in trusted domain) or NEF) is aware of the UE IP address and the UPF Event ID(s) that are to be subscribed meets the criteria for direct subscription to UPF as defined in clause 5.8.2.17 of TS 23.501), then UPF Event consumer can subscribe to UPF directly for Event Exposure using the following procedure:

The UPF event consumer triggers the UPF discovery to NRF by Nnrf_NFDiscovery_Request providing the UE IP address and optionally the DNN, S-NSSAI, IP domain. UE IP address provided to NRF maybe the IP address as seen by the DN (e.g. a Public IP address)

The NRF responds with Nnrf_NFDiscovery response message including the information of UPF for the provided UE IP address.

The UPF event consumer sends the Nupf_EventExposure Subscription request for the UPF Event(s) including the following information:

Notification Target Address (UPF event consumer address), Notification Correlation Information.
UPF Event Id.
Event Filter Information, i.e. one or more of the following parameters: S-NSSAI, DNN, either Application Id(s) or Traffic Filtering Information.
Target of Event Reporting: UE IP address.
Reporting suggestion information.
Type of Measurement and Granularity of Measurement.

Figure 4.15.4.5.6-1: Subscription to UPF event exposure service via SMF during UPF relocation

As per the information provided in the previous step, UPF reports the collected data to the UPF event consumer by invoking Nupf_EventExposure Notify.

4.15.4.5.6 Information flow for subscription to UPF event exposure service via SMF during UPF relocation |R19| p. 430

Reproduction of 3GPP TS 23.502, Fig. 4.15.4.5.6-1: Subscription to UPF event exposure service via SMF during UPF relocation

This information flow is used in the scenario of UPF relocation, e.g. the source UPF is I-UPF which is relocated in SSC mode 1, or the source UPF is PSA UPF which is relocated in SSC mode 3, or the source UPF is local PSA UPF which is relocated due to UE mobility.

The UPF event consumer (e.g. NWDAF) subscribes to the UPF data via SMF by invoking Nsmf_EventExposure_Subscribe service operation, and the Target of Event Reporting indicates a specific UE. The consumer may include a relocation reporting indication, which indicates how to handle the data collected by the source UPF when UPF relocation occurs, e.g. discard the collected data or send the collected data to the consumer.

The SMF selects the source UPF and subscribes to the source UPF by invoking Nupf_EventExposure_Subscribe service operation.

The source UPF sends the locally collected UPF data by invoking Nupf_EventExposure_Notify service operation to the UPF event consumer.

The SMF determines that the UPF needs to be relocated.

The SMF unsubscribes to the source UPF by invoking Nupf_EventExposure_Unsubscribe service operation. The SMF may include the relocation reporting indication from the UPF event consumer.

Figure 4.15.4.5.7-1: Subscription directly to UPF event exposure service during UPF relocation

The source UPF sends the collected data to the UPF event consumer if the relocation reporting indication from SMF indicates that the source UPF should send the collected data to the UPF event consumer. For example, for periodic reporting type of the UPF event exposure service when the UPF changes, the source UPF may report to the consumer any data collected between the time instance of the last notification to the consumer and the time instance of the UPF change. Or for event triggered reporting with Reporting suggestion information, when the UPF changes, the source UPF may report to the consumer any data that has been collected but not sent to the consumer yet based on the relocation reporting indication.

Step 7-8.

To continue the subscription of the UPF event consumer, the SMF may select a target UPF, and re-subscribe to the target UPF based on the subscription from UPF event consumer in step 1. The target UPF will send the locally collected UPF data by invoking Nupf_EventExposure_Notify service operation to the UPF event consumer.

4.15.4.5.7 Information flow for subscription directly to UPF event exposure service during UPF relocation |R19| p. 431

Reproduction of 3GPP TS 23.502, Fig. 4.15.4.5.7-1: Subscription directly to UPF event exposure service during UPF relocation

(For the case when the UPF event consumer is NWDAF) The analytics consumer (e.g. AF/NEF) sends a request to the NWDAF for analytics, and indicates a single UE (e.g. UE IP address) in the Target of Analytics Reporting. Analytics Filter Information optionally contains DNN, S-NSSAI, Area of Interest, Application server IP address/FQDN, Application ID, DNAI, etc.

The UPF event consumer triggers the UPF discovery to NRF by Nnrf_NFDiscovery_Request providing the UE IP address, and optional DNN, S-NSSAI, DNAI, etc.

The NRF provides Nnrf_NFDiscovery_Response that may refer to an UPF.

If the subscribed UPF events allows to directly subscribe to UPF (as defined in clause 5.8.2.17 of TS 23.501), the UPF event consumer (e.g. NWDAF) triggers the Nupf_EventExposure_Subscribe to the discovered UPF, and the Target of Event Reporting contains a single UE. The consumer may include a relocation reporting indication, which indicates how to handle the data collected by the source UPF when UPF changes. The consumer may include an indication to receive subscription termination indication.

The UPF invokes Nupf_EventExposure_Notify service operation directly to the UPF event consumer (e.g. NWDAF).