A broad understanding of how Wi-Fi networks operate is important for you to understand how the security mechanisms work. This chapter has reviewed IEEE 802.11 from the basic topology down to an outline of the protocol messages. We have seen how the Wi-Fi LAN fits into a stack of layers between the operating system and the wireless medium. Wi-Fi provides the lower layers of communication, while higher layers such as TCP/IP ensure delivery of data from end to end.

We looked at the way Wi-Fi LAN are organized, showing how there are two modes of operation?ad-hoc (IBSS) and infrastructure (ESS). The most common mode is ESS, which uses an access point.

Operation of the Wi-Fi LAN is coordinated by a stream of management and control messages in addition to data messages. This chapter has reviewed the main message types and how the management messages enable wireless devices to find each other and form connections. The security mechanisms are tied up with the process of making connections and passing data. The next chapter looks in detail at the original security method WEP, whose operation was closely tied to the Wi-Fi management messages.

    Part II: The Design of Wi-Fi Security