It is a port based authentication Which uses protocol EAPOL which is known as Extensible Authentication Protocol over LAN used to transport EAP packets between Supplicant and an Authenticator over Local Area Network (LAN). Client – The client is the end user workstation or device that requests access to the LAN and it responds to requests from the switch.  The client must run compliant client software Authenticator – The authenticator is what physically controls access to the network based on the authentication status of the client.  It is an intermediary between the client and the authentication server such as a RADIUS server.  When the switch receives the EAPOL frames, it relays them to the authentication server Authentication Server – The server that performs the actual authentication of the request.  It sends a reply back to the switch as to whether or not the authentication request is valid and if the client is validated to access the network and other switch services.