Wi-Fi (short for Wireless Fidelity, pronounced "why-fie") networks use radio signals instead of Ethernet cables to connect computers and other devices to a LAN. Wi-Fi is a convenient alternative to conventional wired networks because any wireless-enabled computer within range of the Wi-Fi signal can join the network; there's no need to find a network outlet. This can be particularly useful when it's not practical to pull data cables through walls, ceilings, and floors, and when a user wants to connect a laptop computer or a handheld device such as an iPhone or BlackBerry to an existing network or through a LAN to the Internet. And of course, thousands of Wi-Fi hotspots in public spaces such as airports, coffee shops, libraries, and schools offer easy access to the Internet when you're away from your own home or office.
However, Wi-Fi connections are far less secure than wired networks, because the same data that moves between a computer and a base station by radio can be intercepted by another computer. Even if the data is encrypted, a dedicated intruder with enough time can steal passwords, credit card numbers, and other personal information. However, the latest security tools, including WPA encryption and virtual private networks (VPNs), can go a long way toward making a Wi-Fi network secure.
This chapter describes the types of Wi-Fi networks and explains how to add a Wi-Fi hotspot to your LAN, how to select and use a Wi-Fi network interface with your computer, and how to keep your Wi-Fi network as secure as possible.
Wi-Fi networks use the IEEE (Institute of Electrical and Electronics Engineers) 802.11 family of standards to define the radio frequencies, data formats, and other technical details that are necessary to establish a wireless LAN. Today, there are four types of 802.11 networks, as shown in Table 8-1.
Table 8-1. Wireless Network Standards
Type | Maximum Speed | Maximum Range (outdoors) | Radio Frequency Band |
|---|---|---|---|
802.11b | 11 Mbps | 300 feet (100 meters) | 2.4 GHz |
802.11a | 54 Mbps | 75-100 feet (23-30 meters) | 5.2 GHz |
802.11g | 54 Mbps | 300 feet (100 meters) | 2.4 GHz |
802.11n | 248 Mbps | 750 feet (250 meters) | 2.4 GHz/5.2 GHz |
The useful distance that an access point can reach is often considerably less than the promised maximum, especially when the path between the access point and a computer's wireless adapter is indoors. Walls, furniture, and other objects between the two antennas can all reduce the signal strength. 802.11b networks were the first to appear, and they were the most common type until the faster 802.11g version became available. 802.11a uses different radio frequencies, but many network adapters are compatible with both 2.4 GHz and 5.2 GHz access points. Today, the new 802.11n standard is beginning to replace all three older versions.
The three systems that use channels in the 2.4 GHz frequency band are backward compatible. In other words, if your Wi-Fi network interface adapter uses 802.11b only, it will continue to work with an 802.11g or 802.11n base station; both 802.11b and 802.11g adapters will work with an 802.11n base station.
The missing letters—802.11c, d, e, and so forth—describe other wireless data characteristics and enhancements that apply to wireless data networks. They're important to hardware designers and manufacturers, but as a network manager or user, you don't have to worry about them.
You might also see some Wi-Fi access points and network adapters identified as extreme or enhanced, or with some other word which suggests that they work at faster speeds than a standard network. Most often these systems use a proprietary method that involves two or more parallel channels to increase their data-handling capacity. Enhanced systems usually work as advertised, but only when the adapter and access point were both made by the same company. When you're building a wireless network that will use network adapters made by different manufacturers, or if you plan to allow users of laptops and other portable devices to connect to your network, there's not much benefit to having an enhanced network.
The Wi-Fi Alliance (http://www.wi-fi.org/), the industry group that promotes these networks, conducts periodic "bake-offs" where many manufacturers demonstrate that their products will work correctly with equipment made by their competitors. A network adapter or access point that carries the Wi-Fi logo has been tested and certified for compatibility by the Wi-Fi Alliance.