Section: 5.30.2.15 Access to SNPN services for N5CW devices
Content: Devices that do not support 5GC NAS signalling over WLAN access (referred to as "Non-5G-Capable over WLAN" devices, or N5CW devices for short), may access 5GC in an SNPN via a trusted WLAN access network that supports a TWIF function. To access SNPN services the N5CW device performs the following procedure: - A WLAN access network may advertise (e.g. with ANQP), not only the PLMNs with which "5G connectivity-without-NAS" is supported (as specified in clause 6.3.12a.1), but also the SNPNs with which "5G connectivity-without-NAS" is supported, as well as the related parameters and indications defined in clause 5.30.2.2 (i.e. human-readable network name(s), GIN(s), indication whether access using credentials from a Credentials Holder is supported, indication whether SNPN allows registration attempts from UEs that are not explicitly configured to select the SNPN). - The N5CW device initiates the access network selection procedure by sending an ANQP query to each discovered WLAN access network and constructs a list of available SNPNs with which "5G connectivity-without-NAS" is supported. This list contains the SNPNs with which "5G connectivity-without-NAS" is supported as advertised by all the discovered WLAN access networks. - The N5CW device selects an SNPN that is included in the list of available SNPNs with which "5G connectivity-without-NAS" is supported following the procedure in clause 5.30.2.4. - The N5CW device selects a WLAN access network (e.g. an SSID) that supports "5G connectivity-without-NAS" to the selected SNPN and initiates the "Initial Registration and PDU Session Establishment" procedure specified in clause 4.12b.2 of TS 23.502[ Procedures for the 5G System (5GS) ]  [3]. If there are multiple WLAN access networks that support "5G connectivity-without-NAS" to the selected SNPN, then the N5CW device selects the highest priority WLAN access network from this list. To determine the priority of a WLAN access network, the N5CW device shall apply the WLANSP rules (if provided), and the procedure specified in clause 6.6.1.3 of TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [45], "UE procedure for selecting a WLAN access based on WLANSP rules". If the N5CW device is not provided with WLANSP rules, the N5CW device determines the priority of a WLAN access network by using implementation means. NOTE: How the N5CW device selects credentials to use for SNPN access is implementation specific.