ZyXEL Communications PLA-470 V2 - V3.0.5 Przewodnik Instalacji Pobierz pdf (Strona 100)

RADIUS and Diameter

802.1x does not define a particular authentication protocol on the server side. Two cli-

ent-server authentication protocols, RADIUS and Diameter, can be used. The simplest one,

RADIUS, has become the default server of any 802.1x architecture. The main constraint of

diameter is that it is based on the SCTP (Stream Control Transmission Protocol) transport

layer which is not implemented as much as TCP.

EAP (Extensible Authentication Protocol)

EAP was defined originally for the PPP (point-to-point protocol) as an extension to

the existing PAP (password authentication protocol) and CHAP (challenge hand-

shake authentication protocol). Compared with these two protocols, EAP provides

many authentication methods in a relatively simple way. This simplicity is due to

the fact that EAP is only an envelope for the transport of these authentication

methods.

Within the framework of a 802.1x PLC architecture, five EAP authentication

methods are used:

•

EAP-MD5. This solution is based on the hash function (MD5). For authenti-

cation, the user gives a login-password, the MD5 digest of which is transmit-

ted for authentication purposes to the server. This solution is deemed not to be

very reliable though only the digest is transmitted over the network and not

the login-password. It is no longer supported by Windows XP SP1.

•

EAP-TLS. TLS (transport layer security) is a mechanism used to implement a

secured connection. The mutual authentication between the client and the

server, the data encryption, and the dynamic management of keys constitute

its functionalities. TLS is the basis of SSL 3.0, which is found in HTTPS, a pro-

tocol used by many Web sites (banks, online reservation sites, and so forth).

IEEE 802.1x and Improvements to PLC Network Security 81

Figure 4.13 IEEE 802.1x authentication architecture

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ZyXEL Communications PLA-470 V2 - V3.0.5 Przewodnik Instalacji Strona 100