Uninformed: Informative Information for the Uninformed

Vol 5» 2006.Sep

What is 802.11?

802.11 is a link-layer protocol standard ratified by the IEEE. The first version of the standard was ratified in 1997 and the most recent revision was ratified in 1999 and reaffirmed in June 2003 [2]. Alternative data rates and PHY-layer protocols are specified in amendments 802.11b-1999 and 802.11a-1999 respectively. The Wireless LAN Edition is a compilation of the standard and its amendments. Many people equate "Wi-Fi" with 802.11. Wi-Fi is a term created by the Wi-Fi assocation[3]. It is quite possible for a device to be Wi-Fi compliant without fully complying with the 802.11 standard.

IEEE Std 802.11 is a Media Access Control (MAC) and Physical Layer (PHY) standard governing wireless local area networks operating in the ISM band which is unlicensed radio spectrum. This required the 802.11 Task Group to deal with problems that have no simple analogy in the wired world.

One of the most obvious problems is the unreliability of a wireless link. The standard operates in unlicensed spectrum and therefore competes with cordless phones and other wireless networks for the medium. Different wireless networks using the same frequency must co-exist. The designers had to take into account various means to stop independent networks from unfairly impacting the performance of each other. The 802.11 standard includes features to address this problem. These include positive acknowledgement with retransmission, and special medium access control frames called Request To Send (RTS) and Clear To Send (CTS).

In summary, the 802.11 standard is in many ways more complicated than its wired-Ethernet counterpart due to issues that arise in a wireless environment. It has to deal with many problems that have no wired-side analogy. Ultimately, it is this complexity that leads implementations to vary, making fingerprinting possible.