PFCP Session Establishment Procedure

The PFCP Session Establishment procedure establishes a PFCP session between SMF and UPF. It also configures rules in UPF for handling incoming packets. In addition, the SMF sends Create URR Information Element (IE), which comprises of triggers and thresholds that are intended for reporting.

The following call flow depicts the PFCP Session Establishment procedure.

StepDescription
1The SMF receives the trigger to establish a new PDU Session or change the UPF for an established PDU Session.
2The SMF sends the PFCP Session Establishment Request message to the UPF. This message contains the structured control information, which defines the UPF's behavior.
3The SMF provisions URR with Create URR IE. The Create URR associates with PDRs by adding URR-ID IE in Create PDR IE. It includes various triggers and thresholds for usage reporting.
4When the same URR is associated with multiple PDRs, URRs are linked with another URR. Therefore, if a report for an URR is sent, its linked URR is also reported.
5The UPF responds with the PFCP Session Establishment Response message to the SMF. For instance, Created PDR IE, in which UPF Flow-TEID is sent to gNB for GTP-u encap for data traffic.
6The SMF interacts with the network function, which triggered this procedure. For instance, AMF or PCF.