4.13 Support of NAS signalling using wireline access network

A 5G-RG, a W-AGF acting on behalf of an FN-RG or a W-AGF acting on behalf of an N5GC device can use wireline access network to access the 5GCN by using NAS signalling procedures as described in 3GPP TS 23.501 [8], 3GPP TS 23.502 [9] and 3GPP TS 23.316 [6D].

Wireline access is a type of non-3GPP access.

A 5G-RG simultaneously connected to the same 5GCN of a PLMN over a 3GPP access and a wireline access is connected to a single AMF.

5G-RG maintains the N1 NAS signalling connection with the AMF over the wireline access network after all the PDU sessions for the 5G-RG over that access have been released or handed over to 3GPP access.

The 5G-RG connected to 5GCN via NG-RAN is specified in 3GPP TS 23.316 [6D].

When accessing the 5GCN over 3GPP access, in addition to requirements specified for the 5G-RG in the present document, the 5G-RG shall also perform requirements (e.g, 5GMM, 5GSM related requirements) specified in the present document for a UE accessing 5GCN over 3GPP access. When accessing the 5GCN over wireline access, in addition to requirements specified for the 5G-RG in the present document, the 5G-RG shall also perform requirements (e.g, 5GMM, 5GSM related requirements) specified in the present document for a UE accessing 5GCN over non-3GPP access. If a requirement specified for the 5G-RG in the present document contradicts a requirement specified for the UE in the present document, the 5G-RG shall perform the requirement specified in the present document for the 5G-RG.

For the scenario of FN-RG, which does not support N1 mode, the W-AGF acting on behalf of the FN-RG exchanges NAS signalling messages with an AMF.

For the scenario of N5GC device, which does not support N1 mode, the W-AGF acting on behalf of the N5GC device exchanges NAS signalling messages with an AMF.

For the scenario of AUN3 device, which does not support N1 mode, the 5G-RG acting on behalf of the AUN3 device exchanges NAS signalling messages with an AMF. If the 5G-RG is not registered and connected to the 5GCN over wireline access, the 5G-RG acting on behalf of an AUN3 device shall not initiate the initial registration procedure on behalf of the AUN3 device.

NOTE 1: The 5G-RG acting on behalf of an AUN3 device maintains a 5GMM context for each AUN3 device behind it. The AMF maintains a 5GMM context for each AUN3 device. The AMF is not aware of any association between the 5GMM context of the 5G-RG and the 5GMM context of the AUN3 device.

When the 5G-RG acting on behalf of an AUN3 device initiates the initial registration procedure on behalf of the AUN3 device, the 5G-RG shall not include the requested NSSAI in the REGISTRATION REQUEST message.

For the scenario of NAUN3 device, which does not support N1 mode, the 5G-RG acting on behalf of a connectivity group consisting of one or more NAUN3 devices exchanges NAS signalling messages with an AMF.

NOTE 2: It is also possible for 5G-RG that is connected to 5GCN via NG-RAN to act on behalf of a connectivity group consisting of one or more NAUN3 devices as specified in 3GPP TS 23.316 [6D].

In addition to requirements specified for the W-AGF acting on behalf of the FN-RG (or on behalf of the N5GC device) in the present document, the W-AGF acting on behalf of the FN-RG (or on behalf of the N5GC device) shall also perform requirements specified in the present document for a UE accessing 5GCN over non-3GPP access. If a requirement specified for the W-AGF acting on behalf of the FN-RG (or on behalf of the N5GC device) in the present document contradicts a requirement specified for the UE in the present document, the W-AGF acting on behalf of the FN-RG (or on behalf of the N5GC device) shall perform requirement specified in the present document for the W-AGF acting on behalf of the FN-RG (or on behalf of the N5GC device).

The PDU session authentication and authorization procedure is not supported in a PDU session established by the W-AGF acting on behalf of the FN-RG or on behalf of the N5GC device.

The W-AGF acting on behalf of the N5GC device requests the establishment of a PDU Session on behalf of the N5GC device upon registration. Only one PDU session per N5GC device is supported.

The 5G-RG acting on behalf of an AUN3 device requests the establishment of a PDU Session on behalf of the AUN3 device upon registration. Only one PDU session per AUN3 is supported.

The 5G-RG acting on behalf of a connectivity group consisting of one or more NAUN3 devices requests the establishment of a PDU Session on behalf of the connectivity group. Only one PDU session per the connectivity group is supported, where all the NAUN3 devices in the connectivity group share the same PDU session.

A 5G-RG or an FN-RG provide a non-3GPP access network to UEs. A UE connected to a non-3GPP access network provided by the 5G-RG or the FN-RG can access to the 5GCN via the N3IWF or via the TNGF as described in 3GPP TS 23.316 [6D].

The 5G-RG or the W-AGF acting on behalf of the FN-RG shall indicate "ANDSP not supported by the UE" in the UE policy classmark IE during the UE-initiated UE state indication procedure as specified in clause D.2.2.

The 5G-RG or the W-AGF acting on behalf of the FN-RG shall indicate "Reporting URSP rule enforcement not supported by the UE" in the UE policy classmark IE during the UE-initiated UE state indication procedure as specified in clause D.2.2.

The Non-3GPP QoS Assistance Information (N3QAI) is introduced to enable a 5G-RG to perform the QoS differentiation for the UE behind the 5G-RG, the AUN3 device behind the 5G-RG or the NAUN3 device behind the 5G-RG. The network may provide the N3QAI associated with the QoS flow during the PDU session establishment procedure as defined in clause 6.4.1 or during the PDU session modification procedure as defined in clause 6.4.2.

NOTE 3: How the 5G-RG applies N3QAI is outside the scope of the present document.

If the AMF receives an indication from the W-AGF that there is no 5G-RG connected to the same wireline for an AUN3 device as specified in 3GPP TS 23.316 [6D], the AMF shall locally de-register the AUN3 device.