PFD (Packet Flow Description) is responsible to define the characteristics of a certain application traffic flow in the 5G mobile network.

It includes information such as source/destination IP addresses, port numbers, and protocol types.

Various components in the 5G mobile core network, such as the Session Management Function (SMF) and the Policy Control Function (PCF), uses PFD to apply the appropriate policies and QoS treatments to the traffic flows.

The SMF retrieves the PFD information from the Policy Control Function (PCF), or from the Application Function (AF) through the Network Exposure Function (NEF) . So that the SMF can use these PFD information to configure the appropriate QoS policies and traffic handling rules in the UPF.

When a PCC rule is provided for an Application Identifier corresponding to the PFD(s), the SMF shall provide the corresponding PFD(s) to the UPF.