ZyXEL Communications P-334WT Support Notes page 198

However, if during bootup, the supplicant does not receive an EAP-request/identity frame from the Wireless AP, the client can initiate
authentication by sending an EAPOL-Start frame, which prompts the switch to request the supplicant's identity. In above case,
authenticator co-locate with authentication server. When the supplicant supplies its identity, the authenticator directly exchanges
EAPOL to the supplicant until authentication succeeds or fails. If the authentication succeeds, the port becomes authorized. If the
authentication fails, the port becomes unauthorized. When the supplicant does not need Wireless access any more, it sends EAPOL-
Logoff packet to terminate its 802.1x session, the port state will become unauthorized. The following figure shows the EAPOL
exchange ping-pong chart.
The EAPOL packet contains the following fields: protocol version, packet type, packet body length and packet body. Most of the fields
are obvious. The packet type can have four different values, and these values are described below: