Which protocol is used by 802.1X for supplicant to authenticator and authenticator to authentication server?

The Extensible Authentication Protocol (EAP) is used for authentication between the supplicant and the authenticator. It is also used inside of the requests to the RADIUS server from the authenticator. The process begins by the EAP frame first being transmitted over the layer 2 connection via EAP over LAN (EAPoL). The switch (authenticator) then sends the EAP message to the RADIUS server encapsulated in a UDP packet for authentication. 802.1X authentication headers are used between the supplicant and the authenticator, such as the switch or wireless access point (WAP). IPsec is not commonly used with 802.1X. The RADIUS server is commonly the AAA authentication server.