4.2.15 Architecture to support WLAN connection using 5G credentials without 5GS registration

23.5013GPPRelease 18System architecture for the 5G System (5GS)TS

The reference architecture shown with reference point representation in Figure 4.2.15-1 and with Service Based Interface (SBI)-representation in Figure 4.2.15-2, enables a UE to connect to a WLAN access network using its 5GS credentials without registration to 5GS. This architecture is based on the Non-Seamless WLAN Offload Function (NSWOF), which interfaces to the WLAN access network using the SWa interface as defined in TS 23.402 [43], and interfaces to the AUSF using the Nausf SBI. The functionality of the NSWOF and the procedures applied for supporting a WLAN connection using 5GS credentials for Non-seamless WLAN offload are further defined in TS 33.501 [29] Annex S. The roaming architectures are shown with reference point representation in Figure 4.2.15-3 and with SBI representation in Figure 4.2.15-4. The architecture in Figure 4.2.15-1 and Figure 4.2.15-2 applies to UEs with PLMN or SNPN credentials.

NOTE 1: For a UE with SNPN credentials it is assumed that the realm part of UE identifier in SUCI format is defined in a way that enables routing of SWa requests from the WLAN AN to the NSWOF in the SNPN’s 5GC.

The UE can also connect to a WLAN access network using 5GS credentials by performing the 5GS registration via Trusted non-3GPP access procedure defined in clause 4.12a.2.2 of TS 23.502 [3]. With this procedure, the UE connects to a WLAN access network using 5GS credentials and simultaneously registers in 5GS. However, the architecture defined in Figure 4.2.15-1, Figure 4.2.15-2, Figure 4.2.15-3 and in Figure 4.2.15-4, enables a UE to connect to a WLAN access network using 5GS credentials but without registration in 5GS.

If the WLAN is configured as Untrusted Non-3GPP access, in the case that the WLAN supports IEEE 802.1x, the UE may first use the 5G NSWO procedure to obtain a connection with and the local IP address from the WLAN, and any time after that, the UE may initiate the Untrusted Non-3GPP Access to obtain the access to 5GC.

Figure 4.2.15-1: Reference architecture to support authentication for Non-seamless WLAN offload in 5GS

Figure 4.2.15-2: Service based reference architecture to support authentication for Non-seamless WLAN offload in 5GS

Figure 4.2.15-3: Roaming reference architectures to support authentication for Non-seamless WLAN offload in 5GS

NOTE 2: Configuration 2) in Figure 4.2.15-3 is a deployment variant of configuration 1)

Figure 4.2.15-4: Service based Roaming reference architecture to support authentication for Non-seamless WLAN offload in 5GS