16.1.3 Reference points

23.4023GPPArchitecture enhancements for non-3GPP accessesRelease 18TS

16.1.3.1 STa reference point

In addition to STa reference point features specified for any non-3GPP IP access network, STa reference point specification is enhanced with the following features for the support of EPC access through S2a over Trusted WLAN:

– A way for the TWAN to provide the 3GPP AAA server with following information:

– An indication on whether the TWAN supports S2a, non-seamless offload or both;

– An indication on whether the TWAN supports Transparent Single-Connection, Single-Connection mode or Multi-Connection mode or a combination of them;

– The PDN addresses provided by the PGW for EPC access in Single-Connection mode;

– The TWAG control plane IP address to be used for WLCP if the TWAN supports the Multi-Connection Mode;

– The SSID selected by the UE to access the TWAN;

– A Session Management back-off timer to be sent to the UE in Single-Connection mode;

– An indication on whether the TWAN supports emergency sessions.

– A way for the 3GPP AAA server to provide the TWAN with following information:

– Whether access to EPC is allowed for the UE on the TWAN;

– As for any Trusted Non-3GPP Access, when the UE is allowed to access EPC via TWAN, the subscription data of the user including the default APN to be associated with the user for EPC access; the TWAN uses the default APN to establish the PDN connection with the PDN GW in the absence of UE signalling of the APN it desires to reach over the Trusted WLAN. Based on the HPLMN operator configuration the HSS may provide the 3GPP AAA server with a default APN for Transparent Single-Connection mode different from the 3GPP access default APN;

– An indication on whether the Single-Connection mode or Multi-Connection mode is selected for the UE. No indication provided by the 3GPP AAA server implies Transparent Single-Connection mode of operation.

16.1.3.2 SWw reference point

The SWw reference point connects the WLAN UE to the WLAN Access Network per IEEE Std 802.11-2012 [64]. The definition of IEEE Physical and Medium Access Control layers protocols (e.g. Layer 1 and Layer 2 defined by IEEE Std 802.11-2012 [64]) is out of the scope of 3GPP.

The SWw reference point also includes:

– The support of EAP (IETF RFC 3748 [11]) and EAP-AKA’ (IETF RFC 5448 [72]) for UE authentication and authorization, as well as extensions to EAP-AKA’ described in clause 16.1.4A.1;

– The support of WLCP signalling protocol used for establishment / release of PDN connections in the case of Multi-Connection mode;

– The support of multiple TWAG MAC addresses as user plane transport mechanism for the multiplexing of multiple PDN connections multiple bearers’ user data in the case of Multi-Connection mode.

16.1.3.3 S2a reference point

The S2a reference point connects the TWAN to the PDN GW. It supports two possible protocol variants: GTP and PMIPv6, to be chosen by the TWAN.