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Content for  TS 23.502  Word version:  17.3.0

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4.15  Network ExposureWord‑p. 324

4.15.1  GeneralWord‑p. 324

The network capability exposure comprises
  • Exposure of network events externally as well as internally towards core network NFs;
  • Exposure of provisioning capability towards external functions;
  • Exposure of policy and charging capabilities towards external functions;
  • Exposure of core network internal capabilities for analytics.
  • Exposure of analytics to external party.
  • Retrieval of data from external party by NWDAF.
  • Exposure of number of registered UEs and/or established PDU Sessions for a network slice that is subject to Network Slice Admission Control towards core network NFs or external party.
When subscribing to event reporting the NF consumer(s) provide:
  • One or multiple Event ID(s). An Event ID identifies the type of event being subscribed to (e.g. PDU Session Release, UE mobility out of an Area of Interest, etc.).
  • Event Filter Information: Provides Event Parameter Types and Event Parameter Value(s) to be matched against, in order to meet the condition for notifying the subscribed Event ID e.g. the Event Parameter Type could be "Area of interest" and Event Parameter Value list could be list of TAs; The Event Filter depends on the Event ID. The Event Filter Information is provided per Event ID(s) being subscribed to: within a subscription different Event ID(s) may be associated with different Event Filter Information.
  • Event Reporting Information described in the Table 4.15.1-1 below. Within a subscription all Event ID(s) are associated with a unique Event Reporting Information.
  • Target of Event Reporting: this may indicate a specific UE or PDU Session, a group of UE(s) or any UE (i.e. all UEs), Within a subscription all Event ID (s) are associated with the same Target of Event Reporting (possibly corresponding to multiple UE or multiple PDU Sessions).
  • A Notification Target Address (+ Notification Correlation ID) allowing the Event Receiving NF to correlate notifications received from the Event provider with this subscription. A subscription is associated with an unique Notification Target Address (+ Notification Correlation ID). In the case that the NF consumer subscribes to the NF producer on behalf of other NF, the NF consumer includes the Notification Target Address(+Notification Correlation ID) of other NF for the Event ID which is to be notified to other NF directly, and the Notification Target Address(+Notification Correlation ID) of itself for the Subscription change related event notification. Each Notification Target Address(+ Notification Correlation ID) is associated with related (set of) Event ID(s).
  • An Expiry time represents the time upto which the subscription is desired to be kept as active. The NF service consumer may suggest an Expiry time and provide to the NF service producer. Based on the operator's policy, the NF service producer decides whether the subscription can be expired. If the subscription can be expired, the NF service producer determines the Expiry time and provide it in the response to the NF service consumer. If the event subscription is about to expire based on the received Expiry time and the NF service consumer wants to keep receiving notifications, the NF service consumer update the subscription with the NF service producer in order to extend the Expiry time. Once the Expiry time associated with the subscription is reached, the subscription becomes invalid at the NF service producer. If the NF service consumer wants to keep receiving notifications, it shall create a new subscription with the NF service producer.
When the subscription is accepted by the Event provider NF, the consumer NF receives from the event provider NF an identifier (Subscription Correlation ID) allowing to further manage (modify, delete) this subscription.
The consumer NF may use an operation dedicated to subscription modification to add or remove Event ID(s) to this subscription or to modify Event Filter Information.
Events are subscribed by the consumer NF(s) by providing Event Filters. The contents of the Event Reporting Information along with the presence requirement of each information element is described in Table 4.15.1-1.
Event Reporting Information Parameter Description Presence requirement
Event reporting modeMode of reporting - e.g. reporting up to a maximum number of reports, periodic reporting along with periodicity, reporting up to a maximum duration, reporting when threshold is reachedmandatory
Maximum number of reportsMaximum number of reports after which the event subscription ceases to exist(see NOTE 1)
Maximum duration of reportingMaximum duration after which the event subscription ceases to exist(see NOTE 1)
Immediate reporting flagThe Event provider NF notifies the current status of the subscribed event, if available, immediately to the consumer NF.
Sampling ratioPercentage of sampling (1%..100%) among impacted UEs.optional
(see NOTE 2)
Partitioning criteriaCriteria for partitioning UEs before applying sampling ratio.optional
(see NOTE 2)
Group Reporting Guard TimeParameter for group-based monitoring configuration to indicate the time for which the Monitoring Event Reporting(s) related with the UEs in a group can be aggregated before sending them to the consumer NF.optional
Deactivate notification flagIndicates to the Event provider NF that the notification of the available events shall be muted until the Event consumer NF provides the retrieval notification flag to retrieve the events stored.optional
Retrieval notification flagIndicates to the Event provider NF to send the notification to the Event consumer NF with the stored events and mutes again the notification of future events.optional
Granularity of dynamicsThe maximum amount of dynamics in the event which allows to skip an event notification.optional
(see NOTE 3)
Reporting typeEvent provider NF reports only when the events differs from the previously notified event.optional
(see NOTE 4)
Reporting ThresholdThreshold values indicate conditions on the level to be reached for the reportingOptional
(see NOTE 5)
NOTE 1:
The requester shall include 2) Maximum number of reports or 3) Maximum duration of reporting, or both, depending on 1) Event reporting mode.
NOTE 2:
Parameter only applicable to certain event IDs reporting metrics (e.g. Number of UEs present in a geographical area) used and used e.g. by the NWDAF for data collection.
NOTE 3:
The Granularity of dynamics includes 1) the range of scalar value, 2) the list of events identification, or 3) the previous notification. The range of scalar value is only applicable to the event depicted as number (e.g. the number of UE), the others is applicable to the event depicted as identification (e.g. UE location, UE identification).
NOTE 4:
The differences in event includes the events have been newly appeared, disappeared, and changed from the previous notification.
NOTE 5:
This parameter is included only if the Event reporting mode indicates reporting when threshold is reached.
 
Maximum number of reports is applicable to the subscription to one UE or a group of UE(s). When the subscription is applied to a group of UE(s), the initial value of the parameter is applied to each individual member UE. The count of number of reports is per UE and per Event Type granularity also for group member UE.
Maximum duration of reporting is applicable to the subscription to one UE, a group of UE(s) or any UE. When the subscription is applied to a group of UE(s), this parameter applies to each group member UE. When the subscription is applied to any UE, this parameter applies to all the impacted UEs.
If for a given subscription Maximum duration of reporting is included then the subscription is cancelled locally in the NF as soon as Maximum duration of reporting is reached. If the Maximum number of reports is reached for a given subscription, the NEF cancels the subscription in the affected NFs. If both Maximum Number of reports and Maximum duration of reporting are included then the subscription expires or is cancelled as soon as one of the conditions is met.
Sampling ratio is applicable to subscription targeting a group of UEs or any UE. When a sampling ratio is provided, a random subset is selected among the target UEs according to the sampling ratio and only the events related to this subset are reported. A UE remains selected until it is no longer managed by the event provider NF. A UE newly managed by the NF may be selected.
Partitioning criteria are applicable to subscription targeting a group of UEs or any UE, and may be used when sampling ratio is used. These criteria are used to instruct the NF on how to group the UEs before applying the sampling ratio. When partitioning criteria are provided, the NF groups the targeted UEs (i.e., creates sub-populations/strata) based on the partition criteria parameter. Then, from each sub-population/stratum, the NF selects a subset of UEs by sampling randomly from each sub-population according to the sampling ratio. For a given type of partitioning criteria, the UE belongs to a single sub-population/stratum as long as it is served by the NF. The types of Partitioning Criteria are described in Table 4.15.1-2:
Types of Partitioning Criteria
Type Allocation Code
Subscriber PLMN ID
Geographical area, i.e. list(s) of TAI(s)
S-NSSAI
DNN
 
Group Reporting Guard Time is an optional parameter for group-based monitoring configuration to indicate the time for which the Monitoring Event Reporting(s) related with the UEs in a group can be aggregated before sending them to the consumer NF. The value of the Group Reporting Guard time should be set less than the Maximum duration of reporting. For the continuous monitoring reporting, unless the Maximum duration of reporting has been reached, the Group Reporting Guard timer is restarted when it expires. If the time left until the Maximum duration of reporting is less than the Group Reporting Guard Time, then the Group Reporting Guard timer shall be set to expire when the Maximum duration of reporting expires. If the Maximum duration of reporting is expired, the Group Reporting Guard Time, if running, shall be considered to expire and aggregated Monitoring Event Reporting(s) is sent to destination immediately.
Deactivation notification flag and retrieval notification flag enable the mute storage of events for a limited size of events at the Event producer NF, thus reducing the number of notifications and the overall signalling between the Event producer NF and the Event consumer NF. Usage of these parameters is further specified in clause 6.2.7 of TS 23.288.
Granularity of dynamics indicates negligible changes in the target event of the subscription for which notification is not required. The changes in the Granularity of dynamics are depicted as the range of scalar value (x, y) where it means [the previously notified scalar value - x, the previously notified scalar value + y), the list of event identification(s) (e.g. list of SUPI(s)), or the previous notification. If the Granularity of dynamics is provided, the provider NF shall send the notification only when the changes in the target event are not described in the Granularity of dynamics, except for the first notification.
Reporting type is a parameter to reduce the data volume of notification. If the Reporting type is provided, the provider NF shall notify the events that have been newly appeared, disappeared, and changed compared to the previous notification, except for the first notification.
Table 4.15.1-1 indicates the presence requirements for the Event Reporting Information.
Corresponding notifications contain at least the Notification Correlation ID together with the Event ID and the individual target (e.g. UE or PDU Session ID) associated with the notification.
If the NF service consumer decides to terminate the event subscription, it unsubscribes the event subscription by sending unsubscription request to the event provider NF. After receiving unsubscription request from the NF service consumer, the event provider NF terminates the event subscription.
If the NF service consumer has subscribed to group-based monitoring, then the NF service consumer may subsequently unsubscribe to the whole group or one or more identified group member UEs. Such partial cancellation of group-based monitoring does not affect the other group member UEs, but it only cancels the monitoring event subscription for the identified group member UEs. Partial cancellation of group-based monitoring can be caused by the following reasons:
  • UE's subscription is discontinued in the UDM;
  • UE's authorisation to the subscribed event type is revoked;
  • The subscribing NF explicitly unsubscribes to monitoring of selected UE(s); or
  • UE is removed from the monitoring target group that was identified in monitoring subscription.
If the NF service consumer has subscribed to group-based monitoring and later new group member UEs are added to the group, then the NF service consumer may also subsequently add monitoring event subscription for the new group member UEs.
The following clauses describe the external exposure of network capabilities and core network internal event and capability exposure.
When the immediate reporting flag is set, the first corresponding event report is included in the subscription response message, if corresponding information is available at the reception of the subscription request of the event.
During Monitoring Event Subscription as in clause 4.15.3, Parameter Provisioning as in clause 4.15.6, NIDD configuration as in clause 4.25.3 and Enhanced Coverage Restriction Control as in clause 4.27.1, the optional parameter MTC Provider Information is a reference parameter that may be provided by AF or determined by NEF based on which AF it communicates with. The MTC Provider Information identifies the MTC Service Provider and/or MTC Application.
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4.15.2  External Exposure of Network CapabilitiesWord‑p. 327

The Network Exposure Function (NEF) supports external exposure of capabilities of network functions. External exposure can be categorized as Monitoring capability, Provisioning capability, Policy/Charging capability, network status reporting capability and Analytics reporting capability. The Monitoring capability is for monitoring of specific event for UE in 5GS and making such monitoring events information available for external exposure via the NEF. The Provisioning capability is for allowing external party to provision of information which can be used for the UE in 5GS. The Policy/Charging capability is for handling QoS and charging policy for the UE based on the request from external party. The Analytics capability is for allowing external party to acquire analytics information generated by 5G System.
The details for the External Exposure of Analytics capabilities as well as interactions between NEF, external party and NWDAF are described in TS 23.288.
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4.15.2a  Data Collection from an AF |R16|Word‑p. 327

The Network Exposure Function (NEF) supports the capability to collect data from an AF as specified in TS 23.501.

4.15.3  Event Exposure using NEFWord‑p. 327

4.15.3.1  Monitoring EventsWord‑p. 327

The Monitoring Events feature is intended for monitoring of specific events in 3GPP system and making such monitoring events information reported via the NEF. It is comprised of means that allow NFs in 5GS for configuring the specific events, the event detection, and the event reporting to the requested party.
To support monitoring features in roaming scenarios, a roaming agreement needs to be made between the HPLMN and the VPLMN. If the AMF/SMF in the VPLMN determine that normalisation of an event report is required, the AMF/SMF normalises the event report before sending it to the NEF.
The set of capabilities required for monitoring shall be accessible via NEF to NFs in 5GS. Monitoring Events via the UDM, the AMF, the SMF, the NSACF and the GMLC enables NEF to configure a given Monitor Event at UDM, AMF, SMF, NSACF or GMLC, and reporting of the event via UDM and/or AMF, SMF, NSACF or GMLC. Depending on the specific monitoring event or information, it is the AMF, GMLC, NSACF or the UDM that is aware of the monitoring event or information and makes it reported via the NEF.
The following Table enumerates the monitoring events and their detection criteria:
Event Detection criteria Which NF detects the event
Loss of Connectivity Network detects that the UE is no longer reachable for either signalling or user plane communication (see NOTE 4).
The AF may provide a Maximum Detection Time, which indicates the maximum period of time without any communication with the UE after which the AF is to be informed that the UE is considered to be unreachable (see NOTE 7).
AMF
UE reachability Detected when the UE transitions to CM-CONNECTED state or when the UE will become reachable for paging, e.g., Periodic Registration Update timer. It indicates when the UE becomes reachable for sending downlink data to the UE.
The AF may provide the following parameters:
  1. Maximum Latency;
  2. Maximum Response Time;
  3. Suggested number of downlink packets. (see NOTE 5 and NOTE 7).
This event requires the Reachability Filter set to "UE reachable for DL traffic" (see Table 5.2.2.3.1-1). For the usage of this event, see clauses 4.2.5.2 and 4.2.5.3.
When requesting UE reachability monitoring, the AF may in addition request Idle Status Indication to be included in the UE reachability event reporting.
AMF, UDM
Location Reporting This event is detected based on the Event Reporting Information Parameters that were received in the Monitoring Request (one-time reporting, maximum number of reports, maximum duration of reporting, periodicity, etc., as specified in clause 4.15.1).
It reports either the Current Location or the Last Known Location of a UE.
When AMF is the detecting NF:
One-time and Continuous Location Reporting are supported. For Continuous Location Reporting the serving node(s) sends a notification every time it becomes aware of a location change, with the granularity depending on the accepted accuracy of location (see NOTE 1).
For One-time Reporting with immediate reporting flag set, AMF reports the Last Known Location immediately.
When AMF is the detecting NF:
If the immediate reporting flag is not set, the AMF reports the UE Current Location (In case the AMF does not have the UE current location in the granularity as requested by the location report, the AMF retrieves the information via NG-RAN Location reporting procedure as defined in clause 4.10).
When GMLC is the detecting NF:
Immediate and Deferred Location Reporting is supported. For Deferred Location Reporting the event types UE availability, Area, Periodic Location and Motion are supported.
AMF, GMLC
Change of SUPI-PEI association This event is detected when the association between PEI and subscription (SUPI) changes (USIM change). UDM
Roaming status This event is detected based on the UE's current roaming status (the serving PLMN and/or whether the UE is in its HPLMN) and notification is sent when that status changes. (see NOTE 2).
If the UE is registered via both 3GPP and N3GPP Access Type, then both instances of Roaming status are included.
UDM
Communication failure This event is detected when RAN or NAS level failure is detected based on connection release and it identifies RAN/NAS release code. AMF
Availability after Downlink Data Notification failure This event is detected when the UE becomes reachable again after downlink data delivery failure.
When requesting Availability after Downlink Data Notification failure monitoring, the AF may in addition request Idle Status Indication to be included in the UE reachability event reporting.
AMF
PDU Session Status This event is detected when PDU session is established or released. (see NOTE 6) SMF
Number of UEs present in a geographical area This event is detected based on the Event Reporting Information Parameters that were received in the Monitoring Request (Level of aggregation, Sampling ratio, see clause 4.15.1).
It indicates the number of UEs that are in the geographical area described by the AF. The AF may ask for the UEs that the system knows by its normal operation to be within the area (Last Known Location) or the AF may request the system to also actively look for the UEs within the area (Current Location).
AMF
CN Type change The event is detected when the UE moves between EPC and 5GC. It indicates the current CN type for a UE or a group of UEs when detecting that the UE switches between being served by a MME and an AMF or when accepting the event subscription. (see NOTE 3) UDM
Downlink data delivery status It indicates the downlink data delivery status in the core network. Events are reported at the first occurrence of packets being buffered, transmitted or discarded, including:
  • Downlink data in extended buffering, including:
    • First data packet buffered event
    • Estimated buffering time, as per clause 4.2.3.3
  • First downlink data transmitted event
  • First downlink data discarded event
SMF
UE reachability for SMS delivery This event is detected when an SMSF is registered for a UE and the UE is reachable as determined by the AMF and the UDM. This enables the UE to receive an SMS. See clauses 4.2.5.2 and 4.2.5.3. UDM
Number of registered UEs and/or established PDU Sessions It indicates the current number of registered UEs or established PDU Sessions for a network slice that is subject to NSAC.
For One-time Reporting with Immediate Reporting Flag set, NSACF reports the number of registered UEs or established PDU Sessions immediately.
NSACF
Area Of Interest It indicates change of the UE presence in the Area Of Interest. AMF, GMLC
NOTE 1:
Location granularity for event request, or event report, or both could be at cell level (Cell ID) or TA level. The granularity can also be expressed by other formats such as geodetic uncertainty shapes (e.g. polygons, circles, etc.) or civic addresses (e.g. streets, districts, etc.) which can be mapped by NEF to AMF specific granularity levels.
NOTE 2:
Roaming status means whether the UE is in HPLMN or VPLMN based on the most recently received registration state in the UDM.
NOTE 3:
CN type of CN Type change event is defined in clause 5.17.5.1 of TS 23.501.
NOTE 4:
In the case of UDM service operation information flow, the UDM should set the subscribed periodic registration timer to a smaller value than the value of Maximum Detection Time, since the value of the mobile reachable timer is larger than the value of the periodic registration timer.
NOTE 5:
Maximum Latency, Maximum Response Time and Suggested number of downlink packets are defined in clause 4.15.6.3a.
NOTE 6:
The NEF makes a mapping between the 5GS internal event "PDU Session Status" and the T8 API event "PDN Connectivity Status".
NOTE 7:
The preferred method for provisioning Network Configuration Parameters is External Parameter Provisioning specified in clause 4.15.6.3a. Provisioning event specific parameters as part of Monitoring Request is expected to be used only by the AF that does not support Parameter Provisioning procedure specified in clause 4.15.6.3a.
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4.15.3.2  Information flowsWord‑p. 333

4.15.3.2.1  AMF service operations information flowWord‑p. 333
The procedure is used by the NF to subscribe to notifications and to explicitly cancel a previous subscription. Cancelling is done by sending Namf_EventExposure_UnSubscribe request identifying Subscription Correlation ID. The notification steps 3 and 4 are not applicable in cancellation case.
Reproduction of 3GPP TS 23.502, Figure 4.15.3.2.1-1: Namf_EventExposure_Subscribe, Unsubscribe and Notify operations
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Step 1.
A NEF sends a request to subscribe to a (set of) Event ID(s) in AMF in Namf_EventExposure_Subscribe request. The NEF could be the same NF subscribing to receive the event notification reports (i.e. Event Receiving NF) or it could be a different NF. The NEF subscribes to one or several Event(s) (identified by Event ID) and provides the associated notification endpoint of the Event Receiving NF. If the NEF itself is not the Event Receiving NF, the NEF shall additionally provide the notification endpoint of itself besides the notification endpoint of Event Receiving NF. Each notification endpoint is associated with the related (set of) Event ID(s). This is to assure the NEF can receive the notification of subscription change related event (e.g. Subscripiont Correlation ID Change).
Event Reporting information defines the type of reporting requested. If the reporting event subscription is authorized by the AMF, the AMF records the association of the event trigger and the requester identity.
Step 2.
AMF acknowledges the execution of Namf_EventExposure_Subscribe.
Step 3.
[Conditional - depending on the Event] The AMF detects the monitored event occurs and sends the event report by means of Namf_EventExposure_Notify message, to the notification endpoint of the Event Receiving NF.
Step 4.
[Conditional- depending on the Event] The AMF detects the subscription change related event occurs, e.g. Subscription Correlation ID change due to AMF reallocation, it sends the event report by means of Namf_EventExposure_Notify message to the NEF.
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4.15.3.2.2  UDM service operations information flowWord‑p. 334
The procedure is used by the NEF to subscribe to event notifications, to modify group-based subscriptions to event notifications, including removal or addition of certain UEs in a UE group and to explicitly cancel a previous subscription (see clause 4.15.1). Cancelling is done by sending Nudm_EventExposure_Unsubscribe request identifying the subscription to cancel. The notification steps 4 and 5 are not applicable in cancellation case.
Reproduction of 3GPP TS 23.502, Figure 4.15.3.2.2-1: Nudm_EventExposure_Subscribe, Unsubscribe and Notify operations
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Step 1.
The NEF subscribes to one or several monitoring events by sending Nudm_EventExposure_Subscribe request. The NEF subscribes to one or several Event(s) (identified by Event ID) and provides the associated notification endpoint of the NEF.
Event Reporting Information defines the type of reporting requested. If the reporting event subscription is authorized by the UDM, the UDM records the association of the event trigger and the requester identity.
The subscription may include Maximum number of reports and/or Maximum duration of reporting IE and optionally MTC Provider Information.
If subscription to group-based event notifications are removed for certain UEs in a group of UEs for which there is an event notification subscription, the NEF provides impacted UE information (e.g. SUPI, MSISDN or External Identity) and operation indication (cancellation) to UDM via Nudm_EventExposure_Subscribe without cancelling the entire group-based event notification subscription. If the Maximum Number of Reports applies to the event subscription, the NEF sets the stored number of reports of the indicated UE(s) to Maximum Number of Reports.
If subscription to group-based event notifications are added for certain UEs in a group of UEs for which there is an event notification subscription, the NEF provides impacted UE information (e.g. SUPI, MSISDN or External Identity) and operation indication (addition) to UDM via Nudm_EventExposure_Subscribe.
Step 2a.
[Conditional] Some events, require that UDM sends Namf_EventExposure_Subscribe request to the AMF serving that UE. As the UDM itself is not the Event Receiving NF, the UDM shall additionally provide the notification endpoint of itself besides the notification endpoint of NEF. Each notification endpoint is associated with the related (set of) Event ID(s). This is to assure the UDM can receive the notification of subscription change related event.
The UDM sends the Namf_EventExposure_Subscribe request to all serving AMF(s) (if subscription applies to a UE or a group of UE(s)), or to all the AMF(s) in the same PLMN as UDM (if subscription applies to any UE). The UDM stores the subscription even if the target UE or group member UE is not registered at the time of subscription.
If the subscription applies to a group of UE(s), the UDM shall include the same notification endpoint of itself, i.e. Notification Target Address (+ Notification Correlation Id), in the subscriptions to all UE's serving AMF(s).
If Nudm_EventExposure_Subscribe with update is received in step 1 indicating removal of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the UDM provides impacted UE information (e.g. SUPI, MSISDN) and operation indication (cancellation) to AMF via Namf_EventExposure_Subscribe without cancelling the entire group-based event notification subscription, for the event monitored by AMF.
If Nudm_EventExposure_Subscribe with update is received in step 1 indicating addition of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the UDM provides impacted UE information (e.g. SUPI, MSISDN) and operation indication (addition) to AMF via Namf_EventExposure_Subscribe for the event monitored by AMF.
Step 2b.
[Conditional] AMF acknowledges the execution of Namf_EventExposure_Subscribe.
Step 3.
UDM acknowledges the execution of Nudm_EventExposure_Subscribe.
If the subscription is applicable to a group of UE(s) and the Maximum number of reports is included in the Event Report information in step 1, the Number of UEs (including all group member UEs irrespective of their registration state) within this group is included in the acknowledgement. If AMF provides the first event report in step 2b, the UDM includes the event report in the acknowledgement.
Step 4a - 4b.
[Conditional - depending on the Event] The UDM detects the monitored event occurs and sends the event report, by means of Nudm_EventExposure_Notify message, to the associated notification endpoint of the NEF, along with the time stamp. NEF may store the information in the UDR along with the time stamp using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.
If Nudm_EventExposure_Subscribe with update is received in step 1 indicating removal of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the UDM shall stop the event notification for the impacted UEs. If Maximum number of Reports is applied, the UDM shall set the number of reports of the indicated UE(s) to Maximum Number of Reports for the events monitored by UDM.
If Nudm_EventExposure_Subscribe with update is received in step 1 indicating addition of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the UDM shall create subscription to the event notification for the impacted UEs so as to detect the monitored event and send the event report for such impacted UEs.
Step 4c - 4d.
[Conditional - depending on the Event] The AMF detects the monitored event occurs and sends the event report, by means of Namf_EventExposure_Notify message, to the associated notification endpoint of the NEF, along with the time stamp. NEF may store the information in the UDR along with the time stamp using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.
If the AMF has a maximum number of reports stored for the UE, the AMF shall decrease its value by one for the reported event.
If Namf_EventExposure_Subscribe with update is received in step 2a indicating removal of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the AMF shall stop the event notifications for the impacted UEs. If Maximum number of Reports is applied, the AMF shall set the number of reports of the indicated UE(s) to Maximum Number of Reports.
If Namf_EventExposure_Subscribe with update is received in step 2a indicating addition of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the AMF shall create subscription to the event notification for the impacted UEs so as to detect the monitored event and send the event report for such impacted UEs.
For both step 4a and step 4c, when the maximum number of reports is reached and if the subscription is applied to a UE, The NEF unsubscribes the monitoring event(s) to the UDM and the UDM unsubscribes the monitoring event(s) to AMF serving that UE.
For both step 4a and step 4c, when the maximum number of reports is reached for an individual group member UE, the NEF uses the Number of UEs received in step 3 and the Maximum number of reports to determine if reporting for the group is complete. If the NEF determines that reporting for the group is complete, the NEF unsubscribes the monitoring event(s) to the UDM and the UDM unsubscribes the monitoring event(s) to all AMF(s) serving the UEs belonging to that group.
When the Maximum duration of reporting expires in the NEF, the UDM and the AMF, then each of these nodes shall locally unsubscribe the monitoring event.
Step 5.
[Conditional - depending on the Event] The AMF detects the subscription change related event occurs, e.g. Subscription Correlation ID change due to AMF reallocation or addition of new Subscription Correlation ID due to a new group UE registered, it sends the event report by means of Namf_EventExposure_Notify message to the associated notification endpoint of the UDM.
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4.15.3.2.3  NEF service operations information flowWord‑p. 336
The procedure is used by the AF to subscribe to event notifications, to modify group-based subscriptions to event notification and to explicitly cancel a previous subscription (see clause 4.15.1). Cancelling is done by sending Nnef_EventExposure_Unsubscribe request identifying the subscription to cancel with Subscription Correlation ID. The notification steps 6 to 8 are not applicable in cancellation case.
Reproduction of 3GPP TS 23.502, Figure 4.15.3.2.3-1: Nnef_EventExposure_Subscribe, Unsubscribe and Notify operations
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Step 1.
The AF subscribes to one or several Event(s) (identified by Event ID) and provides the associated notification endpoint of the AF by sending Nnef_EventExposure_Subscribe request.
Event Reporting Information defines the type of reporting requested (e.g. one-time reporting, periodic reporting or event based reporting, for Monitoring Events). If the reporting event subscription is authorized by the NEF, the NEF records the association of the event trigger and the requester identity. The subscription may also include Maximum number of reports and/or Maximum duration of reporting IE and optionally MTC Provider Information.
If subscription to group-based event notifications are removed or added for certain UEs in a group of UEs for which there is an event notification subscription, the AF provides impacted UE information (e.g. SUPI, MSISDN or External Identity) with operation indication which is either cancellation or addition to NEF via Nnef_EventExposure_Subscribe without cancelling the entire group-based event notification subscription.
Step 2.
[Conditional - depending on authorization in step 1] The NEF subscribes to received Event(s) (identified by Event ID) and provides the associated notification endpoint of the NEF to UDM by sending Nudm_EventExposure_Subscribe request. The NEF may either receive DNN, S-NSSAI from AF in step 1 or maps the AF-Identifier into DNN and S-NSSAI combination based on local configuration, and include DNN, S-NSSAI in the request.
If the reporting event subscription is authorized by the UDM, the UDM records the association of the event trigger and the requester identity. Otherwise, the UDM continues in step 4 indicating failure.
If Nnef_EventExposure_Subscribe with update is received in step 1 indicating removal of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the NEF provides impacted UE information (e.g. SUPI, MSISDN or External Identity) with operation indication (cancellation) to UDM via Nudm_EventExposure_Subscribe without cancelling the entire group-based event notification subscription. If the Maximum Number of Reports applies to the event subscription, the NEF sets the stored number of reports of the indicated UE(s) to Maximum Number of Reports.
If Nnef_EventExposure_Subscribe with update is received in step 1 indicating addition of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the NEF provides impacted UE information (e.g. SUPI, MSISDN or External Identity) with operation indication (addition) to UDM via Nudm_EventExposure_Subscribe.
Step 3a.
[Conditional] If the requested event (e.g. monitoring of Loss of Connectivity) requires AMF assistance, then the UDM sends the Namf_EventExposure_Subscribe to the AMF serving the requested user. The UDM sends the Namf_EventExposure_Subscribe request to the all serving AMF(s) (if subscription applies to a UE or a group of UE(s)), or all the AMF in the same PLMN as the UDM (if subscription applies to any UE).
As the UDM itself is not the Event Receiving NF, the UDM shall additionally provide the notification endpoint of itself besides the notification endpoint of NEF. Each notification endpoint is associated with the related (set of) Event ID(s). This is to assure the UDM can receive the notification of subscription change related event.
If the subscription applies to a group of UE(s), the UDM shall include the same notification endpoint of itself, i.e. Notification Target Address (+ Notification Correlation Id), in the subscriptions to all UE's serving AMF(s).
If Nudm_EventExposure_Subscribe with update is received in step 2 indicating removal of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the UDM provides impacted UE information (e.g. SUPI, MSISDN) with operation indication (cancellation) to AMF via Namf_EventExposure_Subscribe without cancelling the entire group-based event notification subscription, for the event monitored by AMF.
If Nudm_EventExposure_Subscribe with update is received in step 2 indicating addition of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the UDM provides impacted UE information (e.g. SUPI, MSISDN) with operation indication (addition) to AMF via Namf_EventExposure_Subscribe for the event monitored by AMF.
Step 3b.
[Conditional] AMF acknowledges the execution of Namf_EventExposure_Subscribe.
Step 3c.
[Conditional] If the requested event (e.g. PDU Session Status) requires SMF assistance, then the UDM sends the Nsmf_EventExposure_Subscribe Request message to each SMF where at least one UE identified in step 2 has a PDU session established. The NEF notification endpoint received in step 2 is included in the message.
Step 3d.
[Conditional] The SMF acknowledges the execution of Nsmf_EventExposure_Subscribe.
Step 4.
[Conditional] UDM acknowledges the execution of Nudm_EventExposure_Subscribe.
If the subscription is applicable to a group of UE(s) and the Maximum number of reports is included in the Event Report information in step 1, the Number of UEs (including all group member UEs irrespective of their registration state) is included in the acknowledgement. If AMF or SMF provides the first event report in step 3b or step 3d, the UDM includes the event report in the acknowledgement.
Step 5.
NEF acknowledges the execution of Nnef_EventExposure_Subscribe to the requester that initiated the request. If the NEF has received the first event report already in step 4, the NEF includes the event report in the acknowledgement.
Step 6a - 6b.
[Conditional - depending on the Event] The UDM (depending on the Event) detects the event occurs and sends the event report, by means of Nudm_EventExposure_Notify message to the associated notification endpoint of the NEF along with the time stamp. NEF may store the information in the UDR along with the time stamp using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.
If Nudm_EventExposure_Subscribe with update is received in step 2 indicating removal of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the UDM shall stop the event notification for the impacted UEs. If Maximum number of Reports is applied, the UDM shall set the number of reports of the indicated UE(s) to Maximum Number of Reports for the events monitored by UDM.
If Nudm_EventExposure_Subscribe with update is received in step 2 indicating addition of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the UDM shall create subscription to the event notification for the impacted UEs so as to detect the monitored event and send the event report for such impacted UEs.
Step 6c - 6d.
[Conditional - depending on the Event] The AMF detects the event occurs and sends the event report, by means of Namf_EventExposure_Notify message to associated notification endpoint of the NEF along with the time stamp. NEF may store the information in the UDR along with the time stamp using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.
If the AMF has a maximum number of reports stored for the UE or the individual member UE, the AMF shall decrease its value by one for the reported event.
If Namf_EventExposure_Subscribe with update is received in step 3a indicating removal of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the AMF shall stop the event notification for the impacted UEs. If Maximum number of Reports is applied, the AMF shall set the number of reports of the indicated UE(s) to Maximum Number of Reports.
If Namf_EventExposure_Subscribe with update is received in step 3a indicating addition of event notification subscription for certain UEs in a group of UEs for which there is an event notification subscription, the AMF shall create subscription to the event notification for the impacted UEs so as to detect the monitored event and send the event report for such impacted UEs.
For both step 6a and step 6c, when the maximum number of reports is reached and if the subscription is applied to a UE, The NEF unsubscribes the monitoring event(s) to the UDM and the UDM unsubscribes the monitoring event(s) to AMF serving for that UE.
For both step 6a and step 6c, when the maximum number of reports is reached for an individual group member UE, the NEF uses the Number of UEs received in step 4 and the Maximum number of reports to determine if reporting for the group is complete. If the NEF determines that reporting for the group is complete, the NEF unsubscribes the monitoring event(s) to the UDM and the UDM unsubscribes the monitoring event(s) to all AMF(s) serving the UEs belonging to that group.
When the Maximum duration of reporting expires in the NEF, the UDM and the AMF, then each of these nodes shall locally unsubscribe the monitoring event.
Step 6e - 6f.
[Conditional - depending on the Event] When the SMF detects a subscribed event, the SMF sends the event report, by means of Nsmf_EventExposure_Notify message, to the associated notification endpoint of the NEF provided in step 3c. NEF may store the information in the UDR along with the time stamp using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.
Step 7.
[Conditional - depending on the Event in steps 6a-6f] The NEF forwards to the AF the reporting event received by either Nudm_EventExposure_Notify and/or Namf_EventExposure_Notify. In the case of the PDU Session Status event, the NEF maps it to an PDN Connectivity Status notification when reporting to the AF.
Step 8.
[Conditional - depending on the Event] The AMF detects the subscription change related event occurs, e.g. Subscription Correlation ID change due to AMF reallocation or addition of new Subscription Correlation ID due to a new group UE registered, it sends the event report, by means of Namf_EventExposure_Notify message to the associated notification endpoint of the UDM.
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4.15.3.2.3aVoid
4.15.3.2.3b  Specific NEF service operations information flow for loss of connectivity and UE reachability |R16|Word‑p. 340
The procedure is used by the AF to subscribe to notifications and to explicitly cancel a previous subscription for loss of connectivity and UE reachability.
Reproduction of 3GPP TS 23.502, Figure 4.15.3.2.3b-1: Nnef_EventExposure_Subscribe, Unsubscribe and Notify operations or loss of connectivity and UE reachability
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Step 1.
Step 1 to step 3b of Figure 4.15.3.2.3-1 are performed with the following differences:
  • For Loss of Connectivity, the subscription request may include Maximum Detection Time (see Table 4.15.3.1-1).
  • For UE reachability, the subscription request may include Maximum Latency, Maximum Response Time and/or Suggested number of downlink packets (see Table 4.15.3.1-1). In step 3a of Figure 4.15.3.2.3-1, the UDM may include Maximum Response Time in the subscription request to the AMF.
  • For UE reachability, the AF may include Idle Status Indication request. If Idle Status Indication request is included, the NEF includes it in Nudm_EventExposure_Subscribe message. If the UDM receives Idle Status Indication request, it includes it in Namf_EventExposure_Subscribe message. If the NEF does not support the requested Idle Status Indication, then depending on operator policies, the NEF rejects the request.
Step 2.
[Conditional] If the subscribed periodic registration timer has not been set according to any subscription request, or a Network Configuration as defined in clause 4.15.6.3a the UDM shall set the subscribed periodic registration timer using the Maximum Detection Time or Maximum Latency; otherwise if the subscribed periodic registration timer was previously set by a different subscription identified by a different Notification Target Address (+ Notification Correlation ID), or set by a different Network Configuration identified by a different NEF reference ID for the same UE, and if the newly received Maximum Detection Time or Maximum Latency is lower than the provided subscribed periodic registration timer, the UDM shall set the subscribed periodic registration timer using the newly received Maximum Detection Time or Maximum Latency.
If Nudm_EventExposure_Unsubscribe request is performed in step 1, the UDM shall recalculate the subscribed periodic registration timer based on the remaining event subscriptions and/or Network Configurations.
In addition for UE reachability subscription, if the newly received Maximum Response Time is longer than the provided subscribed Active Time (i.e. previously provided Maximum Response Time), the UDM shall set the subscribed Active Time using the newly received Maximum Response Time. If the suggested number of downlink packets is newly received, the UDM shall add the newly received suggested number of downlink packets to the currently used value of suggested number of downlink packets if the aggregated value is within the operator defined range.
If Nudm_EventExposure_Unsubscribe request is performed in step 1, the UDM shall recalculate the subscribed Active Time and/or Suggested Number of Downlink Packets based on the remaining event subscriptions and/or Network Configurations.
If the subscribed periodic registration timer or the subscribed Active Time are set or modified, the UDM sends the Nudm_SDM_Notification request to related serving AMF(s). If the AMF receives a subscribed periodic registration timer value from the UDM, it allocates the received value to the UE as the periodic registration timer at subsequent Registration procedure. The AMF starts monitoring of the expiration of the mobile reachable timer for Loss of Connectivity (if required) and starts monitoring of the UE entering connected mode for UE reachability (if required).
If the suggested number of downlink packets are set or modified, the UDM sends the Nudm_SDM_Notification request to related serving SMF(s). The SMF configures the data buffer at the SMF/UPF according the suggested number of downlink packets.
If the provided value is updated by the UDM, the UDM may notify the NEF (which then notifies the AF) of the actual value that is being applied in the 3GPP network.
Step 3.
Step 4 to step 5 of Figure 4.15.3.2.3-1 are performed.
Step 4.
Step 6c to step 6d of Figure 4.15.3.2.3-1 are performed with the following differences:
  • For Loss of Connectivity, the event is detected when the mobile reachability timer expires.
  • For UE reachability, the event is detected when the UE changes to connected mode or when the UE will become reachable for paging.
  • For UE reachability, if Idle Status Indication request was included in step 1 and the AMF supports Idle Status Indication, the AMF includes also the Idle Status Indication.
Step 5.
Step 8 of Figure 4.15.3.2.3-1 is performed.
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4.15.3.2.4  Exposure with bulk subscriptionWord‑p. 341
Based on operator configuration NEF may perform bulk subscription with the NFs that provides necessary services. This feature is controlled by local policies of the NEF that control which events (set of Event ID(s)) and UE(s) are target of a bulk subscription.
When the NEF performs bulk subscription (subscribes for any UE (i.e. all UEs), group of UE(s) (e.g. identifying a certain type of UEs such as IoT UEs)), it subscribes to all the NFs that provide the necessary services (e.g. In a given PLMN, NEF may subscribe to all AMFs that support reachability notification for IoT UEs). Upon receiving bulk subscription from the NEF, the NFs store this information. Whenever the corresponding event(s) occur for the requested UE(s) as in bulk subscription request, NFs notify the NEF with the requested information.
The following call flow shows how network exposure can happen for one UE, groups of UE(s) (e.g. identifying a certain type of UEs such as IoT UEs) or any UE.
Reproduction of 3GPP TS 23.502, Figure 4.15.3.2.4-1: NF registration/status notification and Exposure with bulk subscription
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Step 1.
NEF registers with the NRF for any newly registered NF along with its NF services.
Step 2.
When an NF instantiates, it registers itself along with the supported NF services with the NRF.
Step 3.
NRF acknowledges the registration
Step 4.
NRF notifies the NEF with the newly registered NF along with the supported NF services.
Step 5.
NEF evaluates the NF and NF services supported against the pre-configured events within NEF. Based on that, NEF subscribes with the corresponding NF either for a single UE, group of UE(s) (e.g. identifying a certain type of UEs such as IoT UEs), any UE. NF acknowledges the subscription with the NEF.
Step 6 - 7.
When the event trigger happens, NF notifies the requested information towards the subscribing NEF along with the time stamp. NEF may store the information in the UDR along with the time stamp using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.
Step 8.
Application registers with the NEF for a certain event identified by event filters. If the registration for the event is authorized by the NEF, the NEF records the association of the event and the requester identity.
Step 9 - 10.
When the event trigger happens, NF notifies the requested information towards the subscribing NEF. NEF may store the information in the UDR using either Nudr_DM_Create or Nudr_DM_Update service operation as appropriate.
Step 11a-b.
NEF reads from UDR with Nudr_DM_Query, and notifies the application along with the time stamp for the corresponding subscribed events.
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