The 5G-RG can be connected to 5GC via W-5GAN, NG RAN or via both accesses.
The two N2 instances apply to a single AMF for a 5G-RG which is simultaneously connected to the same 5G Core Network over 3GPP access and Wireline 5G Access Network.
The two N3 instances in Figure 4.2.8. 4-1 may apply to different UPFs when different PDU Sessions are established over 3GPP access and Wireline 5G Access Network.
Figure 4.2.8.4-1: Non-roaming architecture for 5G Core Network for 5G-RG with Wireline 5G Access network and NG RAN
The N1 for the FN-RG, which is not 5G capable, is terminated on W-AGF which acts on behalf of the FN-RG.
The FN-RG can only be connected to 5GC via W-5GAN.
Figure 4.2.8.4-2: Non-roaming architecture for 5G Core Network for FN-RG with Wireline 5G Access network and NG RAN
4.2.8.5.1 General
The devices that do not support 5GC NAS signalling over WLAN access are referred to as "Non-5G-Capable over WLAN" devices, or N5CW devices for short. A N5CW device is not capable to operate as a 5G UE that supports 5GC NAS signalling over a WLAN access network, however, it may be capable to operate as a 5G UE over NG-RAN.
4.2.8.5.2 Reference Architecture 
Figure 4.2.8.5.2-1: Non-roaming and LBO Roaming Architecture for supporting 5GC access from N5CW UEs
4.2.8.5.3 Network Functions Word-p. 51
Trusted WLAN Access Point (TWAP): It is a particular type of a Trusted Non-3GPP Access Point (TNAP) specified in
clause 4.2.8.2, that supports a WLAN access technology, e.g. IEEE 802.11. This function is outside the scope of the 3GPP specifications.
Trusted WLAN Interworking Function (TWIF): It provides interworking functionality that enables N5CW devices to access 5GC. The TWIF supports the following functions:
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Terminates the N1, N2 and N3 interfaces.
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Implements the AMF selection procedure.
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Implements the NAS protocol stack and exchanges NAS messages with the AMF on behalf of the N5CW device.
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On the user plane, it relays protocol data units (PDUs) between the Yw interface and the N3 interface.
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May implement a local mobility anchor within the trusted WLAN access network.
4.2.8.5.4 Reference Points
The Yt and Yw reference points are both outside the scope of the 3GPP specifications.
The Yt reference point transports WLAN messages (e.g. IEEE 802.11 messages).
The Yw reference point:
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Shall be able to transport authentication messages between the TNAP and the TWIF for enabling authentication of a N5CW device;
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Shall allow the N5CW device to request and receive IP configuration from the TWIF, including an IP address, e.g. with DHCP.
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Shall support the transport of user-plane traffic for the N5CW device.
