TCP/IP Tutorial and Technical Overview - IBM Redbooks

Figure 23-3 illustrates the controlled port status after a successful authentication
from a resulting EAPoL session.
Figure 23-3 Authorized port
Extensible Authentication Protocol over LANs (EAPoL)
Extensible Authentication Protocol (EAP) is used for the exchange of
authentication information between the supplicant and the authentication server.
IEEE 802.1x defines an encapsulation protocol called EAP over LAN (EAPoL) to
carry these EAP packets between the supplicant and the network port. The
supplicant and authenticator use EAPoL for authentication and authorization
communication. The authenticator then repackages these EAP packets using the
RADIUS protocol and forwards them to the authentication server. The network
port and authentication server use EAP over RADIUS for communication. The
network port exchanges EAP authentication packets between the supplicant and
authentication server with proper encapsulation, that is, EAPoL for the packets
that are meant for the supplicant and RADIUS for the packets that are meant for
the authentication server.
Note: EAPoL, defined in the 802.1x standard, is just an encapsulation
protocol to exchange EAP authentication information between the supplicant
and authenticator.
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