User plane protocol stack (GTP-U, UDP, IP)

The User Plane Protocol Stack

User data in 5G traverses a multi-layered protocol stack that differs on each segment of the path. On the radio interface between UE and gNB, the application data flows through SDAP for QoS flow mapping, PDCP for encryption and integrity protection, RLC for segmentation and ARQ, MAC for scheduling and multiplexing, and PHY for over-the-air transmission. At the gNB, the inner IP packet is extracted from the radio protocols and encapsulated in GTP-U for transport across the backhaul to the UPF over the N3 interface. This tunneling preserves the original user IP packet intact throughout the core…