802.11b: The LAN Option

802.11b wireless LANs finally have reached a point where we can safely say, "deploy them."

802.11b wireless LANs finally have reached a point where we can safely say, "deploy them." The best markets are retail, transportation and education, places where the end users are on the move—such as mobile classrooms and logistics. And you can look for the old buildings out there, where wiring is a problem because of asbestos or building codes.

But wireless LANs can benefit almost everyone. For you, the installations are cheaper and less complex than laying out Cat 5 cable. The facilities and IT staff dont need to worry about the patch panel during office moves. And anyone with a laptop will appreciate getting up and walking across the hall with their laptop firmly connected to the network.

Wireless LANs come in two flavors. The ad hoc network is a peer-to-peer connection of two or more clients, which is great for small workgroups or on-the-fly airport file sharing. Then, theres the more common infrastructure deployment. In this, you need an access point to the wired network. The 802.11b clients then connect to the LAN via the closest access point. Some access points even support wireless bridging so they can be daisy-chained via radio waves instead of Ethernet cable.

We looked at two shipping suites of products from Cisco (greater range and functionality) and Linksys (less expensive). We had no problems connecting any of the adapters to any of the access points. 802.11b handles only the physical layer and the medium access control (MAC) sublayer, so its the equivalent of Ethernet. Any protocol, network application or network operating system that runs on Ethernet will run on an 802.11b LAN.

Even though 802.11b calls for two types of radio technologies, direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum, most vendors have settled on DSSS for its higher throughput.

The primary limitations to signal strength and quality between client adapters and access points are distance and steel. We walked into our buildings elevator bay and lost our connection, even though we were only a few yards from the access point. On the other hand, we still got a link at the other side of the building, albeit a poor one.

Encryption plays havoc with throughput. Making matters worse, there are still interoperability issues with encryption. Fortunately, products from more than 42 vendors are playing nicely with each other, based on the Wireless Ethernet Compatibility Alliances interoperability tests (www.wi-fi.net).

And while 802.11b does define roaming—moving from one access point to another—it only goes so far as to identify the basic message formats. Cisco, Lucent and Digital Ocean developed the Inter-Access Point Protocol, which extends multivendor roaming interoperability.

Most of 802.11bs major kinks have been resolved. The 11Mbps rate is a vast improvement. However, our real test results were more in the area of 4Mbps to 6Mbps, which, while still double the original, is hardly five times the original.

The biggest problem, though, is that wireless networks simply are not secure. Security on a wired LAN is much more cut-and-dried than on a wireless network. On a wired system, a hacker would either have to blow through a firewall or gain physical entry to the office. But radio waves travel through walls, so your hacker might not even be in the building. The wireless LAN of your Wall Street office might be hacked into by someone riding a trolley car in San Francisco.

Granted, 802.11b security isnt completely wide open. At the most basic level, the service set identification codes—the network ID code necessary for access between an access point and a client—must match. The next tier of protection is the Wired Equivalent Privacy mechanism. As its name suggests, it was designed to provide the equivalent security of a wired LAN. It does this by offering both 40-bit and 128-bit encryption. Unfortunately, it lacks sophisticated key management, so a tenacious data thief could still hack her way through

Many vendors—Cisco for one—already have centralized key management built into their products. But until theres a standard, there wont be widespread security and interoperability. Until we get that, wireless LANs will continue to complement wired LANs rather than replace them.