5G SMF Calls

Downlink Data Notification - 5G UE

When UE turns to Idle state in the 5G call mode, SMF sends Sx_Modify_Request with FAR Apply Action set to BUFFER value. For every QFI (default/dedicated), the FAR Apply Action is set to BUFFER value.

Once the Downlink packet is received from the server, UPF sends the Sx_Report_Request with Downlink Data Notification with Rule Id (PDR Id)/QFI as per packet rulematch. UPF continues buffering packets until the packet limit reaches 5 for every FAR.

When UE is active, Sx_Modify_Request reaches UPF with FAR Apply Action set to FWD (Forward) and TEID (Tunnel Endpoint Identifier). UPF debuffers the packets and sends them to UE as FIFO. For each packet, rule match will take place after the debuffering process.