TCP/IP Tutorial and Technical Overview - IBM Redbooks

permits only the exchange of authentication traffic, or more specifically, EAPoL
frames.
Figure 23-2 illustrates the operation of a controlled port in an unauthorized state.
Figure 23-2 Unauthorized port
The authentication traffic that is passed represents traffic where the supplicant
tries to establish its credentials through EAPoL (see “Extensible Authentication
Protocol over LANs (EAPoL)” on page 894) to the authentication server using the
“uncontrolled” port. The authenticator acts as a passage for the authentication
traffic between the supplicant and authentication server. The authentication
server verifies and validates the authenticity of the supplicant to access the
network resources. The authenticator grants or rejects access for the supplicant
based on the resulting inquiry from the authentication server (RADIUS server).
After the supplicant authenticates successfully with the authentication server, the
network port moves the controlled port to the “authorized” state, allowing the
supplicant to access the computing resources.
Chapter 23. Port based network access control 893