 for detaching the mobile, the procedure being at the initiative of the Wi-Fi access or the AAA server. The STa and SWa interfaces are used to renew mobile authentication. The procedure is initiated by the AAA server in the event that the subscriber's profile stored in the HSS entity is changed, or at the initiative of the Wi-Fi access that wants to verify that the subscriber's profile is not modified. Table 1.2 summarizes the DIAMETER messages exchanged on the STa and SWa interfaces. Messages Comments Wi-Fi access request to register and retrieve Authenticate and Authorize Request (AAR) the mobile profile AAA server response containing mobile Authenticate and Authorize Answer (AAA) profile AAA server request for mobile Re-Auth-Request (RAR) authentication renewal Re-Auth-Answer (RAA) Response from Wi-Fi access to RAR request Wi-Fi access request for ending the mobile Session Termination Request (STR) session Session Termination Answer (STA) AAA server response to STR request AAA server request for termination of Abort-Session-Request (ASR) mobile session Abort-Session-Answer (ASA) Response from Wi-Fi access to ASR request Wi-Fi access request used for the EAP-AKA Diameter-EAP-Request (DER) authentication procedure AAA server response used for the EAP-AKA Diameter-EAP-Answer (DEA) authentication procedure Table 1.2. DIAMETER messages on the STa and SWa interfaces The S6b interface is used by the PGW entity to communicate to the AAA server its address when the tunnel S2a, S2b or S2c is established. 18 Wi-Fi Integration to the 4G Mobile Network The S6b interface is used by the PGW entity to retrieve the subscriber's profile and the PMIPv6 and GTPv2 mechanism information. The S6b interface is used by the PGW entity to retrieve mobile authentication data for the DSMIPv6 mechanism. The authentication data is used to control the establishment of the IPSec mechanism to protect the DSMIPv6 signaling exchanged between the mobile and the PGW entity. The S6b interface is used for terminating the mobile session, the procedur