In a fast-paced computer world dominated by telephone lines, T1 lines, Ethernet cabling and other physical media, wireless media is steadily gaining ground. Constant innovations are making wireless communication easier, less expensive, more efficient and, in some cases, more practical than physical media. Such challenges as long distances and immovable physical obstacles can often prove too rigorous for physical media. In these cases, wireless media may be used to overcome problems inherent with the physical.

When computers communicate "via the air waves," and without physical media like wires and cable, the transmission between the computers is considered "wireless." Wireless data transfer is also called "wireless communication."

Typical wireless communication modes include infrared waves, radio waves and microwaves. At present, there are three main wireless communication categories.

1. Wireless LAN Communications — used within a company's facility on private equipment.
2. Wireless Bridging and Internetworking — used for connecting buildings and facilities on campuses, within metropolitan areas or between offices in different planetary locations by satellite.
3. Wireless Mobile Communications — designed for use on the road, using public carrier resources including radio, cellular networks and satellite stations.

In this chapter, various wireless LAN devices are described focusing on the functions performed by the device as well as the different operating modes and options for each device. You will also learn about the different Service Sets (SSs) defined for 802.11 networks and their corresponding topologies. The focus is on the primary physical topologies associated with wireless Access Points (APs) and their clients. Finally, the chapter will discuss some wireless topologies.

Upon completion of this chapter, students will be able to:

1. Explain how Access Points are used on a WLAN
2. Explain how wireless bridges work
3. Explain how wireless gateways work
4. Describe the primary topologies of WLAN networks
5. Differentiate between wireless bridges and wireless repeaters