SMF : Session Management Function
SMF is responsible for setting up the connectivity for the UR towards the Data Networks.
It also manages user plane for that connectivity.
SMF manages the establishment, modification and release of sessions.
It allocates IP address to UE depending on the type of IPV4 or IPV6 request.
SMF will communicate indirectly with UE through AMF that will relay session-related information messages.
SMF will interact with other network elements using SB interface.
SMF will also interact with Policy Control Function to retrieve policies for a UE. They are configured in UPF.
SMF will also collect charging data for both online and offline.
Downlink data notification for idle UEs.
It is similar to PGW-C and SGW when compared with EPS.
PGW-U is similar to UPF.
AMF will select SMF, SMF will select the UPF.
Services Provided by SMF
SMF provides 2 services:
1. Nsmf_PDUSession service
2. Nsmf_EventExposure service