In the 802.1X network access control model, the roles of the authenticator and the authentication server are distinct yet complementary. The authenticator acts as a RADIUS client, which is a network device, like a switch or wireless access point, that directly interfaces with the client machine (supplicant). The authentication server, typically a RADIUS server, is responsible for verifying the credentials provided by the supplicant through the authenticator. This setup helps in separating the duties where the authenticator enforces authentication but does not decide on the validity of the credentials, which is the role of the authentication server.
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IEEE 802.1X standard for network access control.