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The 802.11 standard defines a link layer wireless protocol and is managed by the Institute of Electrical and Electronics Engineers (IEEE). Many people think of Wi-Fi when they hear 802.11, but they are not quite the same thing. In recent years, Wi-Fi and 802.11 have exploded in popularity, and every new laptop comes with a builtin Wi-Fi adapter. This popularity has led to a surge of research into the security of the 802.11 standard, which is outlined in Chapters 4 through 8. This chapter lays the groundwork for a strong understanding of the 802.11 protocol. If you have some background with 802.11 and are interested in specific ways to attack or defend your network, you can probably skip this chapter. If you have never seen Wireshark (formerly Ethereal) display an 802.11 packet, or you are interested in some of the interesting features in the 802.11 Media Access Control (MAC), read on.
The first 802.11 standard was approved in 1997 and allowed transmission speeds that topped out at 2 Mbps. This version of the standard allowed two different methods for encoding information at a physical level, Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS). These two different encoding schemes are incompatible, however, and the choice led to a lot of confusion in the marketplace.
In 1999, the IEEE released 802.11b, an amendment to the original 802.11 standard. The 802.11b standard used DSSS and increased the maximum transmission speed to a much faster 11 Mbps. Also released in 1999 was 802.11a, which allowed 802.11 to run outside of the crowded 2.4-GHz industrial, scientific, and medical (ISM) band and in the 5-GHz Unlicensed National Information Infrastructure (UNII) band. Due to increased cost and reduced signal propagation, 802.11a was never widely adopted by consumers despite the increased speed it offered (54 Mbps).
Increasing the speed of 802.11 has been a consistent priority for the 802.11 committee, so in 2003, they released another speed boost, 802.11g, which brought 54 Mbps while also utilizing the 2.4-GHz band. The next speed increase is 802.11n, which allows speeds of 100 Mbps.
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Some people wonder if you can use the IR port built in to many laptops to talk 802.11. In fact, the standard does include support for an IR physical layer (PHY), so theoretically, it is possible. However, very few products have been produced that actually implement the IR physical layer. The infrared ports on laptops are compatible with protocols designed by the Infrared Data Association (IrDA).
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Wi-Fi is a subset of the 802.11 standard that is managed by the Wi-Fi Alliance. Because the 802.11 standard is so large, and the process required to update the standard can take awhile (it's run by a committee), nearly all of the major wireless equipment manufacturers decided they needed a smaller, more nimble group dedicated to maintaining interoperability among vendors. This resulted in the creation of the Wi-Fi Alliance.
The Wi-Fi Alliance assures that all products with a Wi-Fi-certified logo work together. This way if any ambiguity in the 802.11 standard crops up, the Wi-Fi Alliance defines the "right thing" to do. It also allows vendors to implement important subsets of draft standards (standards that have not yet been ratified). The most well-known example of this is Wi-Fi Protected Access (WPA) or "draft" 802.11n equipment.
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