ss point), used to identify the supplicant. RADIUS messages are encrypted and checked in their entirety using a secret shared between the two end points. Wi-Fi Integration to the 4G Mobile Network 6.1.3.1. Access-Request message The RADIUS Access-Request message is transmitted by the authenticator to the authentication server. This message is used to start the authentication procedure. 6.1.3.2. Access-Challenge message The RADIUS Access-Challenge message is exchanged between the authenticator and the authentication server. This message is used to roll through the procedure for the authentication method. 6.1.3.3. Access-Accept message The RADIUS Access-Accept message is one of the responses of the authentication server at the end of the authentication procedure. In this message, the authentication server accepts the supplicant's authentication request. Upon receipt of this message, the authenticator unblocks the supplicant's access. 6.1.3.4. Access-Reject message The RADIUS Access-Reject message is one of the responses of the authentication server at the end of the authentication procedure. In this message, the authentication server rejects the supplicant's authentication request. Upon receipt of this message, the authenticator continues to block the supplicant's access. 6.1.4. Authentication procedure Prior to the 802. 1x authentication procedure, the supplicant must connect to the authenticator: - if the supplicant is connected to an Ethernet switch, the 802.1x procedure starts when its interface is activated; - if the supplicant is connected to a Wi-Fi access point, the 802.1x procedure starts at the end of the association phase with the Wi-Fi access point. Whatever the authentication method used, the procedure is initiated by the supplicant, which transmits the EAPOL-Start message (Figure 6.5). Mutual Authentication Authentication Supplicant Authenticator server Connection EAPOL-Start EAP-Method Identity EAP Request EAPOL EAP-Method Identity EAP-Method Identity EAP Response EAP Response EAPOL RADIUS Access-Req