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208 CHAPTER 9: AAA AND RADIUS OPERATION
The LAN access control device needs to provide the Authenticator System of
802.1x. The computers need to be installed with the 802.1x client Supplicant
software, for example, the 802.1x client provided by Microsoft Windows XP. The
802.1x Authentication Server system normally stays in the carrier’s AAA center.
Authenticator and Authentication Server exchange information through EAP
(Extensible Authentication Protocol) frames. The Supplicant and the Authenticator
exchange information through the EAPoL (Extensible Authentication Protocol over
LANs) frame defined by IEEE 802.1x. Authentication data are encapsulated in the
EAP frame, which is encapsulated in packets of other AAA upper layer protocols
(e.g. RADIUS). This provides a channel through the complicated network to the
Authentication Server. Such procedure is called EAP Relay.
There are two types of ports for the Authenticator. One is the Uncontrolled Port,
and the other is the Controlled Port. The Uncontrolled Port is always in a
bi-directional connection state. The user can access and share the network
resources any time through the ports. The Controlled Port will be in a connecting
state only after the user passes the authentication. Then the user is allowed to
access the network resources.
Figure 55 802.1x System Architecture
Tasks for configuring 802.1x System Architecture is described in the following
sections:
■ 802.1x Authentication Process
■ Implement 802.1x on Ethernet Switch
802.1x Authentication Process
802.1x configures EAP frame to carry the authentication information. The
Standard defines the following types of EAP frames:
■ EAP-Packet: Authentication information frame, used to carry the
authentication information.
■ EAPoL-Start: Authentication originating frame, actively originated by the
Supplicant.
■ EAPoL-Logoff: Logoff request frame, actively terminating the authenticated
state.
Requester
Requester
system
Services offered by
Authenticator
system
Authenticator PAE
Authenticator
server
Authenticator
server system
Authenticator system
Controlled
port
Unauthorized
port
EAPol
LAN
EAP protocol exchanges
carried in higher layer
protocol