What you need to know about 802.1x

The Institute of Electrical and Electronics Engineers (IEEE) 802.1x standard is and why you should care means understanding three separate concepts: PPP, EAP and 802.1x itself.

Point-to-Point Protocol

Most people are familiar with PPP – Point-to-Point Protocol. PPP is most commonly used for dial-up Internet access. PPP is also 
used by some ISPs for DSL and cable modem authentication, in the form of PPP over Ethernet. PPP is part of Layer 2 Tunneling 
Protocol, a core part of Microsoft’s secure remote access solution for Windows 2000 and beyond.

PPP evolved beyond its original use as a dial-up access method and iis now used all over the Internet. One piece of PPP defines an authentication mechanism. With dial-up Internet access, that’s the username and password you’re used to using. PPP authentication is used to identify the user at the other end of the PPP line before giving them access.

Extensible Authentication Protocol

Most enterprises want to do more for security than simply employing user names and passwords for access, so a new authentication  protocol, called the Extensible Authentication Protocol (EAP), was designed. EAP sits inside of PPP’s authentication protocol and  provides a generalized framework for several different authentication methods. EAP is supposed to head off proprietary authentication systems and let everything from passwords to challenge-response tokens and public-key infrastructure certificates all work smoothly.

With a standardized EAP, interoperability and compatibility of authentication methods becomes simpler. For example, when you dial a remote-access server and use EAP as part of your PPP connection, the RAS doesn’t need to know any of the details about your authentication system. Only you and the authentication server have to be coordinated. By supporting EAP authentication a RAS server gets out of the business of acting as middle man, and just packages and repackages EAP packets to hand off to a RADIUS server that will do the actual authentication.

This brings us to the IEEE 802.1x standard, which is simply a standard for passing EAP over a wired or wireless LAN. With 802.1x, you package EAP messages in Ethernet frames and don’t use PPP. It’s authentication and nothing more. That’s desirable in situations in which the rest of PPP isn’t needed, where you’re using protocols other than TCP/IP, or where the overhead and complexity of using PPP is undesirable.

802.1x uses three terms that you need to know. The user or client that wants to be authenticated is called a supplicant. The actual 
server doing the authentication, typically a RADIUS server, is called the authentication server. And the device in between, such as 
a wireless access point, is called the authenticator. One of the key points of 802.1x is that the authenticator can be simple and 
dumb – all of the brains have to be in the supplicant and the authentication server. This makes 802.1x ideal for wireless access 
points, which are typically small and have little memory and processing power.

The protocol in 802.1x is called EAP encapsulation over LANs (EAPOL). It is currently defined for Ethernet-like LANs including  802.11 wireless, as well as token ring LANs such as FDDI. EAPOL is not particularly sophisticated. There are a number of modes of operation, but the most common case would look something like this: The authenticator sends an “EAP-Request/Identity” packet to the supplicant as soon as it detects that the link is active (e.g., the supplicant system has associated with the access point).


Down and dirty with Wireless LAN security

The 13-year-old Wired Equivalent Privacy (WEP) protocol has been discredited so thoroughly that its authentication and encryption capabilities are not considered sufficient for use in enterprise networks. In response to the WEP fiasco, many wireless LAN vendors have latched onto IEEE 802.1x standard to help authenticate and secure both wireless and wired LANs. The wildcard with 802.1x protocol is interoperability.



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