NSSF: Network Slice Selection Function

NSSF — Slice Selector

The Network Slice Selection Function determines which network slices a UE is permitted to use. During registration, the UE provides its Requested NSSAI containing the S-NSSAI values for the slices it wants to access. The AMF forwards this request to the NSSF over the N22 interface along with the subscription information. The NSSF evaluates the request against the subscriber profile, operator policy, and available slices in the serving area, then returns the Allowed NSSAI which is the final list of slices the UE can actually use. It also indicates which AMF set should serve each slice.