1-2z The authenticator system, residing at the other end of the LAN segment link, is the entity thatauthenticates the connected supplicant system. The authenticator system is usually an802.1x-supported network device. It provides ports (physical or logical) for the supplicant system toaccess the LAN.z The authentication server system is the entity that provides authentication services to theauthenticator system. The authentication server system, normally a RADIUS server, serves toperform AAA (authentication, authorization, and accounting) services to users. It also stores userinformation, such as user name, password, the VLAN a user should belong to, priority, and anyACLs (access control list) to be applied.There are four additional basic concepts related to 802.1x: port access entity (PAE), controlled port anduncontrolled port, the valid direction of a controlled port and the access control method of a port.Port access entityA PAE (port access entity) is responsible for implementing algorithms and performing protocol-relatedoperations in the authentication mechanism.z The authenticator system PAE authenticates the supplicant systems when they log into the LANand controls the status (authorized/unauthorized) of the controlled ports according to theauthentication result.z The supplicant system PAE responds to the authentication requests received from theauthenticator system and submits user authentication information to the authenticator system. Italso sends authentication requests and disconnection requests to the authenticator system PAE.Controlled port and uncontrolled portThe Authenticator system provides ports for supplicant systems to access a LAN. Logically, a port ofthis kind is divided into a controlled port and an uncontrolled port.z The uncontrolled port can always send and receive packets. It mainly serves to forward EAPoLpackets to ensure that a supplicant system can send and receive authentication requests.z The controlled port can be used to pass service packets when it is in authorized state. It is blockedwhen not in authorized state. In this case, no packets can pass through it.z Controlled port and uncontrolled port are two properties of a port. Packets reaching a port arevisible to both the controlled port and uncontrolled port of the port.The valid direction of a controlled portWhen a controlled port is in unauthorized state, you can configure it to be a unidirectional port, whichonly sends packets out to supplicant systems.By default, a controlled port is a unidirectional port.Port access control methodA port of the device can control user accesses in the following two ways.z Port-based control. When a port works in the port-based control mode, all the supplicant systemsconnected to the port can access the network without being authenticated after one supplicantsystem among them passes the authentication. And when the authenticated supplicant systemgoes offline, the others are denied as well.z MAC-based control. When a port works in the MAC-based control mode, all supplicant systemsconnected to the port have to be authenticated individually in order to access the network. Andwhen a supplicant system goes offline, the others are not affected.
