UPF packet processing: PDR, FAR, QER, URR

UPF Rule-Based Packet Processing

The UPF processes every incoming packet through a pipeline of rules installed by the SMF via PFCP on the N4 interface. These rules form a processing chain that handles detection, forwarding, quality enforcement, and usage accounting. Each PDU session has its own set of rules, enabling granular per-session and per-flow treatment. When a packet arrives at the UPF, it is first matched against Packet Detection Rules, then processed according to the associated Forwarding Action Rule, shaped by the QoS Enforcement Rule, and counted by the Usage Reporting Rule. This rule-based architecture makes the…