The Network Exposure Function (NEF) provides a secure and robust programmable gateway between the 5G network and the external world.
It allows for secure provisioning of Network Functions based on information received from applications that are external to the 5G network through programmable interfaces.
It exposes internal information like Network Function capabilities, events, subscriber information and other in a secure way to 3rd parties.
This allows the 5G network to become effectively a programmable network, that enables the development of 3rd party applications to make use of network and subscriber information.
It can also be used to provide external information to the NWDAF to further enhance network analytics.
A use case that can easily be imagined is for Asset Tracking.
A car rental company installs a SIM based tracking solution into their cars to allow to localize the vehicles at any time.
The current position of the car is followed by the AMF, which is an internal 5G Core Network Function.
The car rental company has an application that permanently monitors and registers the location of the cars.
Through the API’s exposed by the NEF the company application can track the locations in real-time.
In the background the NEF will obtain the information from the AMF, translates it into a secure format that hides 5GC internal information and presents the information to the 3rd party application.