The Data Collection from NFs is used by NWDAF to subscribe/unsubscribe at any 5GC NF to be notified for data on a set of events.
The Data Collection from NFs is based on the services of AMF, SMF, UDM, PCF, NRF and AF (possibly via NEF):
This data collection service is used directly in order to retrieve behaviour data for individual UEs or groups of UEs (e.g. UE reachability), and also to retrieve global UE information (e.g. Number of UEs present in a geographical area).
The present document specifies that NWDAF can collect some UPF input data for deriving analytics, but how NWDAF collects these UPF input data is not defined in this Release of the specification.
To retrieve data related to a specific UE, the NWDAF shall first determine which NF instances are serving this UE as stated in Table 220.127.116.11-2
unless the NWDAF has already obtained this information due to recent operations related to this UE.
The UDM instance should be determined using NRF as described in clause 4.17.4 of TS 23.502
and factors to determine as described in clause 6.3.8 of TS 23.501
The AMF, SMF instances should be determined using a request to UDM providing the SUPI or the group identity. To determine the SMF serving a PDU session, the NWDAF should in addition provide the DNN and S-NSSAI of this PDU Session; otherwise the NWDAF will obtain a list of possibly multiple SMFs (e.g. one per PDU session).
The BSF instance should be discovered using NRF thanks to optional request parameters (e.g. DNN list, IP domain list, IPv4 address range, IPv6 prefix range) as stated in clause 4.17.4 of TS 23.502
, or based on local configuration at the NWDAF.
The PCF instance serving UE PDU Session(s) should be determined using a request to BSF with the allocated UE address, DNN and S-NSSAI.
When NWDAF receives a request addressed to an Internal Group ID from a consumer, NWDAF may need to initiate data collection from several 5GC NFs, such as AMF, SMF, UDM, PCF, NEF/AF, etc. NWDAF may first discover the instances of the required 5GC NFs deployed in the network, e.g. by querying NRF.
For discovering the UDM, NWDAF can query the NRF with the Internal Group ID as the target of the query. For discovering AMF, SMF, PCF, NEF, and AF, NWDAF may need to discover all the instances in the network by using the Nnrf_NFDiscovery
It is assumed that all members of an Internal Group ID belong to the same UDM Group ID. NWDAF can select a UDM instance supporting the UDM Group ID of the Internal Group ID.
Then, if data needs to be collected from AMF, SMF, UDM, and PCF, NWDAF may initiate the data collection with the Internal Group ID as the target, e.g. subscribing to the event exposure in all the instances of a given type of network function. This subscription to all the instances of required source of event exposure handles, e.g. mobility of UEs across AMFs, or initiation of new PDU sessions with different allocated SMFs.
For collecting data from AMF and SMF, NWDAF may collect the data directly from AMF and/or SMF, or indirectly via UDM, according to TS 23.502, clause 18.104.22.168.3
The NEF instance that is serving a specific network slices and/or applications of a UE should be determined using NRF using optional request parameters as defined in clause 6.3.14 of TS 23.501
If NWDAF needs to collect data from an AF deployed outside the operator's domain, the NWDAF shall contact NEF with a SUPI or Internal Group ID as the target of the data collection. NEF is responsible for translation of SUPI to GPSI, or internal to external group identifiers, by querying UDM, prior to contacting the AF.
The procedure in Figure 22.214.171.124-1
is used by NWDAF to subscribe/unsubscribe at NFs in order to be notified for data collection on a related event (s), using Event Exposure Services as listed in Table 126.96.36.199-1
The procedure in Figure 188.8.131.52-1
is used by NWDAF to collect information from AFs via the NEF.
In this release, AF registers its available data to NWDAF via OAM configuration at NEF.
The AF collectable data information includes: AF identification, AF service identification (e.g., endpoint information of Naf_EventExposure
), available data to be collected per application (e.g., identified by Event ID(s)).
After the registration of AF available data at the NEF, NEF generates an event exposure with new EventID to be associated with available data to be collected from AF. NEF invokes Nnrf_NFManagement_NFUpdate_request service operation to update its registration information (i.e., NEF Profile) including the generated Event IDs, and associated AF identification, Application ID(s).
NRF stores the received NEF registration information including available data to be collected from AF.
NRF sends Nnrf_NFManagement_NFUpdate_response message to NEF.
When NWDAF needs to discovery the available data from AFs and the appropriated NEF to collect this data, NWDAF invokes Nnrf_NFDiscovery_Request_request service operation using as parameter the NEF NF Type, a list of Event ID(s), and optionally AF identification, application ID.
NRF matches the requested query for available data in AFs with the registered NEF Profiles and sends this information via Nnrf_NFDiscovery_Request_response
message to NWDAF.
After the registration and discovery procedure described in step 1, NWDAF identifies the available data per AF per application and the proper NEF to collect such data.
The NWDAF subscribes to or cancels subscription to data in AF via NEF by invoking the Nnef_EventExposure_Subscribe
service operation. If the event subscription is authorized by the NEF, the NEF records the association of the event trigger and the NWDAF identity.
User consent for retrieving user data in AF via NEF is not specified in this Release.
Based on the request from the NWDAF, the NEF subscribes to or cancels subscription to data in AF by invoking the Naf_EventExposure_Subscribe/ Naf_EventExposure_Unsubscribe service operation.
If the NEF subscribes to data in AF, the AF notifies the NEF with the data by invoking Naf_EventExposure_Notify service operation.
If the NEF receives the notification from the AF, the NEF notifies the NWDAF with the data by invoking Nnef_EventExposure_Notify service operation.
The NWDAF may use NRF services and Network Function service framework procedures as defined in TS 23.502, clause 5.2.7
and clause 4.17
NF/NF service discovery procedures (in TS 23.502, clause 4.17.4) and Nnrf_NFDiscovery service (in TS 23.502, clause 184.108.40.206) in order to dynamically discover the NF instances and services of the 5GC. Such discovery may be performed on a periodic basis, or under specific circumstances.
NF/NF service status subscribe/notify procedures (in TS 23.502, clause 4.17.7) and Nnrf_NFManagement service (in TS 23.502, clause 220.127.116.11) in order to be notified about the change of status of an NF. The service operations for obtaining status information are NFStatusSubscribe and NFStatusNotify, from the Nnrf_NFManagement service.
The information provided by the NRF to the NWDAF with the Nnrf_NFDiscovery_Request
and the Nnrf_NFManagement_NFStatusNotify
operations are the NFProfile and the NFService. Such information can be used to set-up and maintain a consistent network map for data collection and also, depending on use cases, in order to perform estimations:
NF profile: NF capacity, NF load information, NF status, NF recovery time, NF locality;
NF service: service capacity, service load information, service status, service recovery time.
The NWDAF shall subscribe (and unsubscribe) to the Event exposure service from NF(s) reusing the framework defined in TS 23.502, clause 4.15
. This framework supports the possibility for the NWDAF to indicate / request:
Events-ID: one or multiple Event ID(s) defined in TS 23.502, clause 4.15.1
Target of Event Reporting defined in TS 23.502, clause 4.15.1: the objects targeted by the Events. Within a subscription, all Event ID(s) are associated with the same target of event reporting. In the case of NWDAF, the objects can be UE(s), UE group(s), any UE.
Event Filter Information defined in TS 23.502, clause 4.15.1. This provides Event Parameter Types and Event Parameter Value(s) to be matched against.
A Notification Target Address and a Notification Correlation ID as defined in TS 23.502, clause 4.15.1, allowing the NWDAF to correlate notifications received from the NF with this subscription.
Event Reporting Information described in TS 23.502 Table 4.15.1-1.
Expiry time as defined in TS 23.502, clause 4.15.1.
The notifications from NFs/AFs contain on top of the Event being reported (and of dedicated information being reported for this event):
the Notification Correlation Information provided by the NWDAF in its request,
(when applicable to the event) the Target Id e.g. UE ID (SUPI and if available GPSI), and
a time stamp.