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full Contents for  TS 23.502  Word version:   16.4.0

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1…   4.2.2.2.2   4.2.2.2.3…   4.2.3…   4.2.3.3   4.2.4…   4.2.6   4.2.7…   4.2.9…   4.3…   4.3.2.2…   4.3.2.2.2   4.3.2.2.3…   4.3.3   4.3.4   4.3.5…   4.3.5.2…   4.3.5.4…   4.3.5.6…   4.3.6…   4.4…   4.5…   4.9…   4.9.1.3…   4.9.2…   4.11…   4.11.1.2.2…   4.11.1.3…   4.11.1.4…   4.11.1.5…   4.11.2   4.11.3…   4.12…   4.12.6…   4.12a   4.12b   4.13…   4.13.4…   4.13.6…   4.14…   4.15…   4.15.4…   4.16…   4.16.4…   4.16.8…   4.17…   4.17.9…   4.18…   4.19…   4.23…   4.23.7…   4.23.9…   4.23.11…   4.24   4.25   4.26…   5…   5.2.3…   5.2.5…   5.2.6…   5.2.7…   5.2.8…   5.2.9…   5.2.12…   A…   E…   F…

 

4.15  Network ExposureWord-p. 284
4.15.1  General
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.
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 Receving 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 subscripton 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.
NOTE 1:
The Notification Correlation ID is allocated by the consumer NF that subscribes to event reporting and the Subscription Correlation ID is allocated by the NF that notifies when the event is met. Both correlation identifiers can be assigned the same value, although in principle they are supposed to be different, as they are optimized for finding the subscription related context within each NF.
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 mode
Mode of reporting - e.g reporting up to a maximum number of reports, periodic reporting along with periodicity, reporting up to a maximum duration
mandatory
Maximum number of reports
Maximum number of reports after which the event subscription ceases to exist
(see NOTE 2)
Maximum duration of reporting
Maximum duration after which the event subscription ceases to exist
(see NOTE 2)
Immediate reporting flag
The Event provider NF notifies the current status of the subscribed event, if available, immediately to the consumer NF.
Sampling ratio
Percentage of sampling (1%..100%) among impacted UEs.
optional (see NOTE 3)
Group Reporting Guard Time
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.
optional

NOTE 2:
The requester shall include 2) Maximum number of reports or 3) Maximum duration of reporting, or both, depending on 1) Event reporting mode.
NOTE 3:
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 4:
Explicit unsubscribe by the NF consumer is still possible.
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 parameter is applied to each individual member UE. The count of number of reports is per Event Type granularity.
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 both Maximum Number of reports and Maximum duration of reporting are included then the subscription is considered to expire 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 not managed by the event provider NF any more. A UE newly managed by the NF may become selected.
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.
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.
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 output message, if corresponding information is available at the reception of the subscription request of the event.
The optional parameter MTC Provider Information as used e.g. in clause 4.25.3, 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.
NOTE 5:
The MTC Provider Information can be used by Service Providers for, e.g. to distinguish their different customers.
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4.15.2  External Exposure of Network CapabilitiesWord-p. 286
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]
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 NEF
4.15.3.1  Monitoring Events
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, I-NEF may be deployed as defined in clause 6.2.5a of TS 23.501. If I-NEF is deployed, the AMF and SMF in the VPLMN provide the configuration for a given Monitor Event at I-NEF and make monitoring event reported via the I-NEF, the I-NEF is aware of the monitoring event and make it reported via 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 and the GMLC enables NEF to configure a given Monitor Event at UDM, AMF, SMF or GMLC, and reporting of the event via UDM and/or AMF, SMF or GMLC. Depending on the specific monitoring event or information, it is the AMF, GMLC 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).
AMF
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.
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.
AMF, UDM
The AF may provide the following parameters:
1) Maximum Latency;
2) Maximum Response Time;
3) Suggested number of downlink packets. (see NOTE 5).
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).
AMF, GMLC
It indicates 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 the Current Location. 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 Last Known Location only One-time Reporting is supported
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.
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 when the UE's current roaming status (the serving PLMN and/or whether the UE is in its HPLMN) and notification when that status changes. (see NOTE 2).
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.
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).
AMF
It indicates the number of UEs that are in the geographic 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).
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:
SMF
- 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
UE reachability for SMS delivery
This event is detected when an SMSF is registered for a UE. This enables the UE to receive an SMS.
UDM: reachability for SMS
HSS can subscribe to notifications about SMSF registration events in UDM for a given UE as defined in TS 23.632.
User State Information in 5GS
Provides user state information in 5GS.
AMF

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.
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".

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4.15.3.2  Information flowsWord-p. 290
4.15.3.2.1  AMF service operations information flow
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. If AMF receives Monitoring event subscription for roaming UEs and I-NEF is deployed as defined in clause 6.2.5a of TS 23.501, clause 4.15.3.2.3a applies after step 2.
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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. As 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 flow
The procedure is used by the NEF to subscribe to notifications and to explicitly cancel a previous subscription. 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. If AMF receives Monitoring event subscription for roaming UEs and I-NEF is deployed as defined in clause 6.2.5a of TS 23.501, clause 4.15.3.2.3a applies after step 3.
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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.
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Step 2a.
[Conditional] Some events (e.g. loss of connectivity), 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).
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).
NOTE:
The same notification endpoint of UDM is to help the AMF identify whether the subscription for the requested group event is same or not when a new group member UE is registered.
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Step 2b.
[Conditional] AMF acknowledges the execution of Namf_EventExposure_Subscribe.
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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 within this group is included in the acknowledgement.
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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.
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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.
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 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.
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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. 292
The procedure is used by the AF to subscribe to notifications and to explicitly cancel a previous subscription. 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. If AMF or SMF receive Monitoring event subscription for roaming UEs and I-NEF is deployed as defined in clause 6.2.5a of TS 23.501, clause 4.15.3.2.3a applies after step 5.
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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.
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 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.
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).
NOTE 1:
The same notification endpoint of UDM is to help the AMF identify whether the subscription for the requested group event is same or not when a new group member UE is registered.
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.
NOTE 2:
In the home routed case, the UDM sends the subscription to the V-SMF via the H-SMF.
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 is included in the acknowledgement.
Step 5.
NEF acknowledges the execution of Nnef_EventExposure_Subscribe to the requester that initiated the request.
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.
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.
For both step 6a and step 6b, 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 6b, 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 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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4.15.3.2.3a  I-NEF service operations information flow [R16]Word-p. 295
The procedure is used by the NF (AMF, SMF) in VPLMN to provision monitoring configurations and to explicitly cancel a previous monitoring configuration at I-NEF. Cancelling is done by sending Ninef_EventExposure_UnSubscribe request identifying the monitoring configuration to cancel. The notification steps 3 to 5 are not applicable in cancellation case.
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Step 1.
NEF or UDM subscribe or unsubscribe to the notification of monitoring events at SMF or AMF as refered to steps 1 to 2 in clause 4.15.3.2.1, steps 1 to 3 in clause 4.15.3.2.2, and steps 1 to 5 in clause 4.15.3.2.3.
Step 2.
AMF or SMF determines that the UE is in roaming, it requests to provision or delete monitoring configuration on I-NEF in Ninef_EventExposure_Subscribe or Ninef_EventExposure_UnSubscribe request. The monitoring configuration on I-NEF includes the notification endpoint information of the NEF. I-NEF acknowledges the execution of Ninef_EventExposure_Subscribe or Ninef_EventExposure_UnSubscribe request. When AMF provisions the monitoring configuration on I-NEF, the I-NEF updates the monitoring event subscription on AMF with the notification endpoint information of the I-NEF by means of Namf_EventExposure_Subscribe message.
Step 3.
[Conditional- depending on the Event] refer to step 6e in clause 4.15.3.2.3.
Step 4.
The AMF detects the related event occurs, it sends the event report by means of Namf_EventExposure_Notify message to the I-NEF.
Step 5.
The I-NEF performs normalization of reports and generation of charging/accounting information as defined in clause 6.2.5a of TS 23.501. The I-NEF sends the event report by means of Ninef_EventExposure_Notify message to the NEF.
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4.15.3.2.3b  Specific NEF service operations information flow for loss of connectivity and UE reachability [R16]
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.
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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.
  • For UE reachability, the subscription request may include Maximum Latency, Maximum Response Time and/or Suggested number of downlink packets.
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.
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 newly received suggested number of downlink packets is higher than the provided suggested number of downlink packet, the UDM shall set the suggested number of downlink packets using the newly received suggested number of downlink packets.
If the subscribed periodic registration timer, subscribed Active Time and/or the suggested number of downlink packets 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 AMF receives a subscribed active time value from the UDM, it allocates the subscribed value to the UE. If the AMF receives a suggested number of downlink packets, the AMF provides it to the SMF. 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.
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. 297
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.
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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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4.15.3.2.5  Information flow for downlink data delivery status with SMF buffering [R16]Word-p. 299
The procedure is used if the SMF requests the UPF to forward downlink data packets that are subject of extended buffering in the SMF. The procedure describes a mechanism for the Application Function to subscribe downlink data delivery status notifications. The downlink data delivery status notifications relates to high latency communication, see also clauses 4.24.2 and 4.2.3.3.
Cancelling the subscription is done by sending Nnef_EventExposure_Unsubscribe request identifying the subscription to cancel with Subscription Correlation ID in the same order as indicated in figure 4.15.3.2.5-1 for the corresponding subscribe requests. Step 0 and the notification steps 7 to 9 are not applicable in cancellation case.
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Step 0.
The SMF (in the non-roaming case the SMF, in the roaming case the V-SMF, in the case of PDU session with I-SMF the I-SMF) configures the relevant UPF to forward downlink data packets towards the SMF as described in clause 5.8.3 in TS 23.501. The SMF decides to apply this behavior based on the "expected UE behaviour". Alternatively, step 0 is triggered by step 3,
Step 1.
The AF sends Nnef_EventExposure_Subscribe Request to NEF requesting notification for event "Downlink data delivery status" with traffic descriptor (e.g. the source of the downlink IP or Ethernet traffic) for a UE or group of UEs. If the reporting event subscription is authorized by the NEF, the NEF records the association of the event trigger and the requester identity. The Downlink data delivery status events include:
  • First downlink Packet in extended buffering event:
    • This event is triggered when the first new downlink data packet is buffered with extended buffering matching the traffic descriptor.
    • in notifications about this Downlink data delivery status, the SMF provides the Extended Buffering time as determined in clause 4.2.3.3.
  • First downlink Packet discarded:
    • This event occurs when the first packet matching the traffic descriptor is discarded because the Extended Buffering time, as determined by the SMF, expires or the amount of downlink data to be buffered is exceeded.
  • First Downlink Packet transmitted:
    • This event occurs when the first packet matching the traffic descriptor is transmitted after previous buffering or discarding of corresponding packet(s) because the UE of the PDU Session becomes ACTIVE, and buffered data can be delivered to UE according to clause 4.2.3.3.
Step 2.
The NEF sends the Nudm_EventExposure_Subscribe Request to UDM. Identifier of the UE or group of UEs, the traffic descriptor, monitoring event received from AF in step 1, and notification endpoint of the NEF are included in the message. 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 5 indicating failure.
Step 3.
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. If the UDM is able to derive the applicable DNN and S-NSSAI from the traffic descriptor via configured information, the UDM may send Nsmf_EventExposure_Subscribe Request messages only to SMFs with PDU sessions with that DNN and S-NSSAI for such UEs and includes the Identifier of the UE or Internal-Group-Id, traffic descriptor, monitoring event and the notification endpoint of NEF received in step 2 are included in the message. If the UDM becomes aware that such a UE has a PDU session established with the DNN and S-NSSAI corresponding to the traffic descriptor at a later time than when receiving step 2, the UDM then executes step 3.
In the case of home-routed PDU session or PDU session with I-SMF, the UDM sends the Nsmf_EventExposure_Subscribe Request message to each H-SMF or SMF, and the H-SMF or SMF further sends Nsmf_EventExposure_Subscribe Request message to each related V-SMF or I-SMF. Steps 7-8 are performed by V-SMF or I-SMF.
Step 4.
The SMF sends the Nsmf_EventExposure_Subscribe Response message to the UDM.
Step 5.
The UDM send sends the Nsmf_EventExposure_Subscribe response message to the NEF.
Step 6.
The NEF sends the Nsmf_EventExposure_Subscribe response to the AF.
Step 7.
The SMF detects a change in Downlink Data Delivery Status event as described in clause 4.2.3. The SMF becomes aware that Downlink Packet(s) require extended buffering via a Namf_Communication_N1N2MessageTransfer service operation with the AMF. If the SMF decides to discard packets, the "Downlink Packet(s) discarded event" is detected. The SMF detects that previously buffered packets can be transmitted by the fact that the related PDU session becomes ACTIVE.
Step 8.
The SMF sends the Nsmf_EventExposure_Notify with Downlink Delivery Status event message to NEF.
Step 9.
The NEF sends Nnef_EventExposure_Notify with Downlink Delivery Status event message to AF.
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4.15.3.2.6  GMLC service operations information flow [R16]Word-p. 300
The procedure is used by the NF to subscribe to notifications and to explicitly cancel a previous subscription. The GMLC service operations information flow is defined in clause 6.1.2 and clause 6.3 of TS 23.273.
4.15.3.2.7  Information flow for Availability after DDN Failure with SMF buffering [R16]
The procedure is used if the SMF requests the UPF to forward packets that are subject of buffering in the SMF. The procedure describes a mechanism for the Application Function to subscribe to notifications about availability after downlink data notification failure. The Availability after Downlink Data Notification failure event is related to high latency communication, see also clauses 4.24.2 and 4.2.3.3.
Cancelling the subscription is done by sending EventExposure_Unsubscribe requests identifying the subscription to cancel with the Subscription Correlation ID in the same order as indicated in figure 4.15.3.2.7-1 for the corresponding subscribe requests. Step 0 and the notification steps 9 to 13 are not applicable in the cancellation case.
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Step 0.
The SMF (in the no-roaming case the H-SMF. in the roaming case the V-SMF, in the case of PDU session with I-SMF the I-SMF) configures the relevant UPF to forward packets to the SMF as described in clause 5.8.3 in TS 23.501. The SMF decides to apply this behavior based on the "expected UE behaviour". Alternatively, step 0 is triggered by step 5.
Step 1.
The AF sends Nnef_EventExposure_Subscribe Request to the NEF requesting notifications for "Availability after DDN Failure" for a UE or group of UEs and providing a traffic descriptor identifying the source of the downlink IP or Ethernet traffic. If the reporting event subscription is authorized by the NEF, the NEF records the association of the event trigger and the requester identity.
Step 2.
The NEF sends the Nudm_EventExposure_Subscribe Request to UDM. Identifier of the UE or group of UEs, the traffic descriptor, monitoring event received from AF at step 1, and notification endpoint of the NEF are included in the message. 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 7 indicating failure.
Step 3.
The UDM sends Namf_EventExposure_Subscribe messages to the AMF(s) which serve the UE(s) identified in step2 to subscribe to "Availability after DDN Failure". The UDM includes the DNN and S-NSSAI as well as the Traffic Descriptor if available A separate subscription is used for each UE. The NEF notification endpoint received in step 2 is included in the message. If the UDM becomes aware that such a UE is registered at a later time than when receiving step 2, the UDM then executes step 3.
Step 4.
The AMF acknowledges the execution of Namf_EventExposure_Subscribe.
Step 5.
If PDU Session exists for the DNN and S-NSSAI, the AMF subscribes to DDN Failure status notification by sending the Nsmf_PDUSession_UpdateSMContext Request message to each SMF, requesting the SMF to notify DDN Failure. The AMF also includes in Nsmf_PDUSession_UpdateSMContext the Traffic Descriptor and NEF correlation ID if received from the UDM. For new PDU Session establishment towards a DNN and S-NSSAI, the AMF subscribes to DDN Failure status notification in Nsmf_PDUSession_CreateSMContext Request message if the UDM has subscribed to Availability after DDN Failure event.
In the case of home-routed PDU session or PDU session with I-SMF, the AMF sends Nsmf_PDUSession_UpdateSMContext Request message(s) to the related V-SMF(s) or I SMF(s). Steps 9-10 are performed by those V-SMF(s) or I-SMF(s).
Step 6.
The (I/V-)SMF sends the Nsmf_PDUSession_UpdateSMContext response message to the AMF.
NOTE:
Step 7 can happen any time after step 4.
Step 7.
The UDM sends the Nudm_EventExposure_Subscribe response to the NEF.
Step 8.
The NEF sends the Nsmf_EventExposure_Subscribe response to the AF.
Step 9-10.
The SMF is informed that the UE is unreachable via a Namf_Communication_N1N2MessageTransfer service operation. The SMF then decides to discard downlink packets received from the UPF. By comparing those discarded downlink packets received from the UPF with the Traffic Descriptor(s) received in the event subscription(s), the SMF determines whether DDN Failure due to any traffic from an AF is to be notified to the AMF and if so, the SMF sends the DDN Failure status, by means of Nsmf_PDUSession_SMContextStatusNotify message including NEF Correlation ID, to the AMF.If the UE is not reachable after the AMF received the DDN Failure notification from the SMF, the AMF shall set a Notify-on-available-after-DDN-failure flag corresponding to the NEF Correlation ID.
Step 11-12.
[Conditional] The AMF detects the UE is reachable and sends the event report(s) based on the Notify-on-available-after-DDN-failure flag, by means of Namf_EventExposure_Notify message(s), only to the NEF(s) indicated as notification endpoint(s) identified via the corresponding subscription in step 3. In this way, only the AF(s) for which DL traffic transmission failed are notified.
Step 13.
The NEF sends Nnef_EventExposure_Notify message with the "Availability after DDN Failure" event to AF.
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4.15.3.2.8  Information flow for downlink data delivery status with UPF buffering [R16]Word-p. 302
The procedure is used if the SMF requests the UPF to buffer packets. The procedure describes a mechanism for the Application Function to subscribe to notifications about downlink data delivery notification. The data delivery status notifications relates to high latency communication, see also clauses 4.24.2 and 4.2.3.3.
Cancelling is done by sending Nnef_EventExposure_Unsubscribe request identifying the subscription to cancel with Subscription Correlation ID.
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Step 1.
AF interacts with NEF to subscribe DDD status as described in clause 4.15.3.2.5.
Step 2.
If the UPF is configured to apply extended buffering, step 2 is executed immediately after step 1. Otherwise, step 2 is executed when the SMF is informed that the UE is unreachable via a Namf_Communication_N1N2MessageTransfer service operation as described in clause 4.2.3, and the SMF then also updates the PDR(s) for flows requiring extended buffering to requests the UPF to buffer downlink packets. If the DDDs status event with traffic descriptor has been received in the SMF in step 1, if extended DL Data buffering in the UPF applies, the SMF provides the Traffic Descriptor in a PDR and requests the UPF to report when there are corresponding buffered downlink packets or discarded packets in the UPF as defined in Clause 4.2.3. If PCC is not used and there is no installed PDR with the exact same traffic descriptor, the SMF copies the installed PDR that would have previously matched the incoming traffic described by the traffic descriptor in the notification subscription, but provides that traffic descriptor, a higher priority, and a buffer notification action within. If PCC is used. the SMF checks if the Policy Control Trigger Request are set to report the reception of a subscription to DDD status and then SMF requests PCC Rules to the PCF before contacting the UPF.
Step 3.
The UPF reports when there is buffered or discarded traffic matching the received PDR to the SMF and the SMF sends the corresponding event report, by means of Nsmf_EventExposure_Notify message. The SMF detects that previously buffered packets can be transmitted by the fact that the related PDU session becomes ACTIVE.
Step 4.
The SMF sends the Nsmf_EventExposure_Notify with Downlink Delivery Status event message to NEF.
Step 5.
The NEF sends Nnef_EventExposure_Notify with Downlink Delivery Status event message to AF.
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4.15.3.2.9  Information flow for Availability after DDN Failure with UPF buffering [R16]Word-p. 303
The procedure is used if the SMF requests the UPF to buffer packets. The procedure describes a mechanism for the Application Function to subscribe to notifications about availability after DDN failure.
Cancelling is done by sending Nnef_EventExposure_Unsubscribe request identifying the subscription to cancel with Subscription Correlation ID.
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Step 0.
The SMF (in the non-roaming case the H-SMF, in the roaming case the V-SMF, in the case of PDU session with I-SMF the I-SMF) configures the relevant UPF to buffer packets as described in clause 5.8.3 in TS 23.501.
Step 1.
AF interacts with NEF to subscribe availability after DDN failure subscription procedure as described in clause 4.15.3.2.7.
Step 2-3.
If the SMF is informed the UE is unreachable via a Namf_Communication_N1N2MessageTransfer service operation, the SMF provides the Traffic Descriptor in the PDR and requests the UPF to report when there are corresponding discarded packets in the UPF. When the UPF determines to discard DL data matching the received PDR, it reports the corresponding event to the SMF and the SMF sends the event reports the DDN Failure status with NEF Correlation ID, by means of Nsmf_PDUSession_SMContextStatusNotify Nsmf_EventExposure_Notify message, to the AMF indicated as notification endpoint. If the UE is not reachable after the AMF received the notification from the SMF, the AMF shall set a Notify-on-available-after-DDN-failure flag corresponding to the Notification Correlation Id and the identifier of the UE if available.
Step 4-5.
[Conditional] The AMF detects the UE is reachable and sends the event report(s) based on the Notify-on-available-after-DDN-failure flag, by means of Namf_EventExposure_Notify message(s), only to the NEF(s) indicated as notification endpoint(s) identified via the corresponding subscription in step 3. In this way, only the AF(s) for which DL traffic transmission failed are notified.
Step 6.
The NEF sends Nnef_EventExposure_Notify message with the "Availability after DDN Failure" event to AF.
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4.15.3.3Void

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