3Com 4200G 12-Port Configuration Manual page 220

EAP relay mode
This mode is defined in 802.1x. In this mode, EAP packets are encapsulated in higher level protocol
(such as EAPoR) packets to enable them to successfully reach the authentication server. Normally, this
mode requires that the RADIUS server support the two newly-added fields: the EAP-message field
(with a value of 79) and the Message-authenticator field (with a value of 80).
Four authentication ways, namely EAP-MD5, EAP-TLS (transport layer security), EAP-TTLS (tunneled
transport layer security), and Protected Extensible Authentication Protocol (PEAP), are available in the
EAP relay mode.
EAP-MD5 authenticates the supplicant system. The RADIUS server sends MD5 keys (contained in
EAP-request/MD5 challenge packets) to the supplicant system, which in turn encrypts the
passwords using the MD5 keys.
EAP-TLS allows the supplicant system and the RADIUS server to check each other's security
certificate and authenticate each other's identity, guaranteeing that data is transferred to the right
destination and preventing data from being intercepted.
EAP-TTLS is a kind of extended EAP-TLS. EAP-TLS implements bidirectional authentication
between the client and authentication server. EAP-TTLS transmit message using a tunnel
established using TLS.
PEAP creates and uses TLS security channels to ensure data integrity and then performs new EAP
negotiations to verify supplicant systems.
Figure 1-8 describes the basic EAP-MD5 authentication procedure.
1-6