The UE-UE protocol stacks for discovery and PC5 link management as defined in
clause 6.1.1.2 apply to 5G ProSe Remote UE, 5G ProSe Intermediate UE-to-Network Relay and 5G ProSe Layer-3 UE-to-Network Relay. There could be zero, one or multiple 5G ProSe Intermediate UE-to-Network Relay(s) between the 5G ProSe Remote UE and the 5G ProSe UE-to-Network Relay. If there is no 5G ProSe Intermediate UE-to-Network Relay, the IP connection and the PC5 link is between the 5G ProSe Remote UE and the 5G ProSe UE-to-Network Relay.
Additionally, when N3IWF is supported by the 5G ProSe Layer-3 UE-to-Network Relay, the following control plane protocol stack apply.
The UE-UE protocol stacks for discovery and PC5 signalling defined in
clause 6.1.1.2 apply to 5G ProSe Remote UE and 5G ProSe Layer-2 UE-to-Network Relay.
Figure 6.1.1.7.2-1 illustrates the protocol stack of the NAS connection for the 5G ProSe Layer-2 Remote UE for NAS-MM and NAS-SM. The NAS messages are transparently transferred between the 5G ProSe Layer-2 Remote UE and NG-RAN over the 5G ProSe Layer-2 UE-to-Network Relay using:
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PDCP end-to-end connection between the 5G ProSe Layer-2 Remote UE and NG-RAN, where the role of the 5G ProSe Layer-2 UE-to-Network Relay is to relay the PDUs over the signalling radio bear without any modifications and using the functionality of the adaptation layer as specified in TS 38.300.
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Connection between NG-RAN and AMF over N2.
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Connection between AMF and SMF over N11.
The control plane protocol stack used by the 5G ProSe Layer-2 UE-to-Network Relay is defined in
clause 8.2.2 of TS 23.501.