Feature Description
For Custom Slice selection without NSSF, AMF now supports SMF selection based on S-NSSAIs received from UE (Requested S-NSSAI) during PDU session establishment procedures.
AMF supports SNNSAI-based SMF selection only using NRF (Network Repository Function).
During PDU session establishment procedure, AMF queries the necessary NRF serving PLMN by issuing the Nnrf_NFDiscovery_Request including SNSSAI to select SMF.
The NRF serving PLMN provides a set of the discovered SMF instances or Endpoint Addresses of SMF service instance(s) in Nnrf_NFDiscovery_Request response message. AMF uses the information provided by NRF and connects to the necessary SMF for further interactions.