PC5-U: The SDAP/PDCP/RLC/MAC/PHY functionality is specified in TS 38.300.
PDCP SDU types of IP, Ethernet, Unstructured and Address Resolution Protocol are supported. For IP PDCP SDU type, both IPv4 and IPv6 are supported.
The packets from ProSe application layer are handled by the ProSe layer before transmitting them to the AS layer, e.g. ProSe layer maps the IP, Ethernet and Unstructured packets to PC5 QoS Flow and marks the corresponding PFI.
GPRS Tunnelling Protocol for the user plane (GTP-U): This protocol tunnels user data between NG-RAN node and UPF as well as between the UPFs in the backbone network (not shown in the Figure). GTP-U shall encapsulate all end user PDU packets.
SMF controls the user plane tunnel establishment and establishes User Plane Bearers between NG-RAN node and UPF.
UDP/IP: These are the backbone network protocols used for routing user data and control signalling.
Uu: The NR Uu radio protocols of NG-RAN between the UE-to-Network Relay and the NG-RAN node are specified in TS 38.300.
PC5-U: The radio protocols between the UE and the UE-to-Network Relay are specified in clause 22.214.171.124.
Figure 126.96.36.199.2-1 illustrates the protocol stack for the user plane transport, related to a PDU Session, including a 5G ProSe Layer 2 UE-to-Network Relay. The PDU layer corresponds to the PDU carried between the 5G ProSe Layer-2 Remote UE and the Data Network (DN) over the PDU session. The SDAP and PDCP protocols are specified in TS 38.300. PDCP end-to-end connection is between the 5G ProSe Layer-2 Remote UE and NG-RAN. The functionality of the adaptation layer is specified in TS 38.351.
Figure 188.8.131.52.1-1 illustrates user plane protocol stacks using a 5G ProSe Layer-2 UE-to-UE Relay. Security is established end-to-end between 5G ProSe End UEs as shown by the PDCP layer terminating in the 5G ProSe End UEs.