 keys derived from a master key. The EAPOL-Key message is transmitted with a Key Descriptor message body containing the information necessary for key establishment. 6.1.1.4. EAPOL-Encapsulated-ASF-Alert message The EAPOL-Encapsulated-ASF-Alert message is transmitted by the supplicant during authentication. It usually contains information specific to each constructor. 6.1.1.5. EAPOL-Announcement message The EAPOL-Announcement message was introduced in version 3 for the transmission by the authenticator of information concerning network access conditions. The message body is composed of TLV structures. The Network Identity TLV structure contains the identification of the network being subjected to access control. This structure can also be present in EAPOL-Start and EAPOL-Announcement-Req messages. The Access Information TLV structure contains access information (access status, EAPOL messages processed). This structure can also be present in EAPOL-Start and EAPOL-Announcement-Req messages. Mutual Authentication The Key Management Domain TLV structure contains the key-management domain name associated with a network name. 6.1.1.6. EAPOL-Announcement-Req message The EAPOL-Announcement-Req message was introduced in version 3. If the message body is absent or the least significant bit of the first byte of the message body is positioned at ONE, the receiver of the EAPOL- Announcement-Req message must make an announcement. As for the EAPOL-Start message, the other bytes of the message body, if present, have a TLV structure that gives information on access conditions. Unlike the EAPOL-Start message, the EAPOL-Announcement-Req message does not initiate the authentication procedure. 6.1.2. EAP The EAP is deployed for the access of a supplicant (network host) to the authenticator (switch or access point) and the authentication server. It enables the transport of authentication data and does not require Internet Protocol (IP) connectivity. The structure of the EAP is shown in Figure 6.4. Request 0000 0001 Response 0000 0010 S