6.2.5.0 NEF functionality

The Network Exposure Function (NEF) supports the following independent functionality:

• Exposure of capabilities and events:

NF capabilities and events may be securely exposed by NEF for e.g. 3rd party, Application Functions, Edge Computing as described in clause 5.13.

NEF stores/retrieves information as structured data using a standardized interface (Nudr) to the Unified Data Repository (UDR).

• Secure provision of information from external application to 3GPP network:

It provides a means for the Application Functions to securely provide information to 3GPP network, e.g. Expected UE Behaviour, 5G-VN group information, CAG information, time synchronization service information, PDU Set based Handling service specific information and Non-3GPP Device Identifier Information. In that case the NEF may authenticate and authorize and assist in throttling the Application Functions.

• Translation of internal-external information:

It translates between information exchanged with the AF and information exchanged with the internal network function. For example, it translates between an AF-Service-Identifier and internal 5G Core information such as DNN, S-NSSAI, as described in clause 5.6.7.

In particular, NEF handles masking of network and user sensitive information to external AF's according to the network policy.

• Redirecting the AF to a more suitable NEF/L-NEF e.g. when serving an AF request for local information exposure and detecting there is a more appropriate NEF instance to serve the AF's request.
• The Network Exposure Function receives information from other network functions (based on exposed capabilities of other network functions). NEF stores the received information as structured data using a standardized interface to a Unified Data Repository (UDR). The stored information can be accessed and "re-exposed" by the NEF to other network functions and Application Functions and used for other purposes such as analytics.
• A NEF may also support a PFD Function: The PFD Function in the NEF may store and retrieve PFD(s) in the UDR and shall provide PFD(s) to the SMF on the request of SMF (pull mode) or on the request of PFD management from NEF (push mode), as described in TS 23.503 [45].
• A NEF may also support a 5G-VN Group Management Function: The 5G-VN Group Management Function in the NEF may store the 5G-VN group information in the UDR via UDM as described in TS 23.502 [3].
• Support management of ECS Address Information.
• Support management of relationship between DNAI and EAS Address Information.
• Exposure of analytics:

NWDAF analytics may be securely exposed by NEF for external party, as specified in TS 23.288 [86].

• Retrieval of data from external party by NWDAF:

Data provided by the external party may be collected by NWDAF via NEF for analytics generation purpose. NEF handles and forwards requests and notifications between NWDAF and AF, as specified in TS 23.288 [86].

• Support of Non-IP Data Delivery:

NEF provides a means for management of NIDD configuration and delivery of MO/MT unstructured data by exposing the NIDD APIs as described in TS 23.502 [3] on the N33/Nnef reference point. See clause 5.31.5.

• Charging data collection and support of charging interfaces.
• Support of Member UE selection assistance functionality:
• NEF may provide one or more list(s) of candidate UE(s) (among the list of target member UE(s) provided by the AF) and additional information to the AF based on the parameters contained in the request from the AF as described in clause 5.46.2. NEF supports the translation of the member UE selection filtering criteria parameters received from the AF to the corresponding event or analytics filters that can be understood by the 5GC NFs for events or analytics related data collection. NEF interacts with 5GC NFs using existing services in order to collect the corresponding data and then derive the list(s) of candidate UE(s) and other assistance information as described in clause 4.15.13 of TS 23.502 [3].
• Support of Multi-member AF session with required QoS for a set of UEs identified by a list of UE addresses:
• Details are specified in clause 4.15.6.13 of TS 23.502 [3].
• Support of UAS NF functionality:

Details are defined in TS 23.256 [136].

• Support of EAS deployment functionality:

Details are defined in TS 23.548 [130].

• Support of SBI-based MO SM transmit for MSISDN-less MO SMS:

Details are defined in TS 23.540 [142].

• Support PDU Set based Handling as defined in clause 5.37.5.
• Support management of common EAS and common DNAI:

Details are defined in TS 23.548 [130].

• Support of Vertical Federated Learning (VFL):

Details are defined in TS 23.288 [86].

• Support energy related functionality as defined in clause 5.51.

A specific NEF instance may support one or more of the functionalities described above and consequently an individual NEF may support a subset of the APIs specified for capability exposure.

NOTE: The NEF can access the UDR located in the same PLMN as the NEF.

The services provided by the NEF are specified in clause 7.2.8.

For external exposure of services related to specific UE(s), the NEF resides in the HPLMN. Depending on operator agreements, the NEF in the HPLMN may have interface(s) with NF(s) in the VPLMN.

When a UE is capable of switching between EPC and 5GC, an SCEF+NEF is used for service exposure. See clause 5.17.5 for a description of the SCEF+NEF.