UPF chaining and ULCL (uplink classifier)

Multi-UPF Architectures

A single PDU session can span multiple UPFs connected in a chain. The PDU Session Anchor UPF holds the UE IP address and connects to the central data network. An Intermediate UPF can be inserted between the gNB and the anchor for local traffic breakout. The SMF orchestrates this chaining by programming each UPF with appropriate forwarding rules and establishing GTP-U tunnels on the N9 interface between them. This architecture enables flexible traffic routing where some traffic stays local at the edge while other traffic traverses the full path to the central data center, all within a single…