Networking with no strings attached

If your agency or department is like most, chances are you've at least given some thought to augmenting your existing infrastructure by setting up a wireless local-area network.

From cellular phones to digital media, wireless technology is now being used in just about every sector of professional life, and many organizations see the value of allowing wireless devices to tap into their existing networks.

In addition to the obvious benefits — such as increased mobility and faster deployment times — wireless LANs enable administrators to upgrade, reconfigure or extend an existing network without the hassle and cost of installing cable. Not only does this mitigate the problem of wiring existing buildings, it also eliminates a potential failure point — the wire itself.

What's more, wireless LANS are growing increasingly attractive as speeds increase and prices drop.

But that's not to say that the wired backbone is on its way out just yet. The costs of wireless solutions are dropping, but they still cost more than wired solutions. An Ethernet card, for example, costs less than $50 per card, compared to around $200 for a wireless LAN Network Interface Card. And on top of that $200, you'll have to provide an Ethernet tap, wall plate and Category 5 cabling.

A wireless network also brings new security vulnerabilities, including a higher potential for theft of client devices and the pirating of signals via packet analyzer tools.

There are, of course, ways to mitigate these vulnerabilities. The risk of a stolen device providing unauthorized access to the network can be controlled by using access lists or Remote Authentication Dial-In User Service servers, which require users of remote devices to log in before accessing the network. And the theft of pirated signals can be deterred by use of the Wired Equivalent Privacy protocol's built-in encryption. Both solutions, however, require additional funds and staff time to implement.

Interoperability is another concern. Network administrators are used to the conveniences and maturity of Ethernet and its ability to use just about any vendor's network card with just about any vendor's connecting hardware. However, although devices in the wireless world are improving, they do not always work together as well as they should. Be prepared for the potential for reduced capability and increased calls to the help desk. Finally, if your new wireless warriors will be connecting via laptop computers, you need to think about battery longevity because wireless network adapters, especially those offering higher-speed throughput, often have a voracious appetite for power.

For all these reasons, most agencies and departments in the foreseeable future will look to wireless to supplement, rather than replace, a broader wired network.

Planning for Wireless

As with any project, planning is imperative. Neglecting to detail all of the major as well as minor steps will more often than not lead to poor performance, overall failure or even unhappy end users. When constructing a wireless LAN, give careful thought to how users will connect to the network — on which coverage area and at what performance level — and what security is needed.

Choosing a standard is often the first step. Currently, three specifications reign supreme — the older 802.11; the newer 802.11b, affectionately dubbed "Wi-Fi"; and the even newer 802.11a.

Both the 802.11 and 802.11b specifications operate at frequencies in the 2.4 GHz region of the radio spectrum and enable optimal throughput of 2 megabits/sec and 11 megabits/sec, respectively, using either direct-sequence spread spectrum (DSSS) or frequency-hopping spread spectrum (FHSS) modulation techniques.

Although both techniques use spread spectrum technology, which prevents congestion by transmitting data across a range of frequencies, each handles it in different ways.

A good example of this is DSSS, which combines a data signal with a chipping code, or redundant bit pattern, to increase its resistance to interference, while also providing a mechanism for recovery from damaged transmissions. In contrast, FHSS combines a data signal with a carrier signal that "hops" in random but known sequences from frequency to frequency.

On the other hand, the 802.11a specification, while still in its infancy, operates at frequencies between 5 GHz and 6 GHz with optimal throughput as high as 54 megabits/sec using Orthogonal Frequency Division Multiplexing. OFDM, which actually dates to the 1970s, splits a signal into several channels at different frequencies to provide higher data rates, while tolerating transmission distortions from propagation and radio frequency interference.

So why not just go with the higher performance of 802.11a? For starters, 802.11a is only now being implemented seriously by device manufacturers, and those devices are more costly, consume more power and require more access points.

A recent study by the META Group Inc. showed that those implementing a network on this standard require almost 40 percent to 50 percent more access points than those required for an 802.11b-based implementation. For now, then, 802.11a will appeal mostly to those who must deliver wireless access to power users who are accustomed to fast Ethernet connections. For most agencies and departments, however, 802.11b-based networks offer economies that make them more attractive.

Before settling on one or the other, however, you must conduct a radio frequency survey of the environment. This enables you to predict whether obstacles such as walls, desks and filing cabinets will decrease the expected range of a device, regardless of the vendor's claims. It also aids in determining how many access points are required. This proves especially important for those considering an 802.11a-based network.

It's a safe bet that the majority of those who already have wireless LANs use the 802.11b specification, unless they bought their equipment quite a while ago. If I were to recommend a wireless network, I would definitely go with 802.11b because it offers more vendor choices. I would also most likely look at mixed standard access points and upgrade incrementally to the higher specification over time, as the technology matures.

Although each of the standards generally does not work with the others, new products such as the Harmony family from Proxim Inc. (www.proxim. com) and MobileLAN access from Intermec Technologies Corp. (www.inter enable a wireless LAN to have multistandard capabilities at the access point, allowing users to upgrade to the higher speed specification over time while still maintaining a current 802.11b user base.

Lastly, keep in mind the maturity of the standard you choose, as well as the availability of products and support. Although technologies such as Bluetooth and HiperLAN/2 are also available, we did not include them in our reviews. The first deals primarily with short-range client connections, and the second is not yet strongly supported by vendors in the United States.

Selecting products that are compatible, scalable and, most important, nonproprietary is also a sure step toward success. However, evaluating the many choices available today will often prove to be the most time-consuming part of any analysis. To assist in your efforts, we have provided reviews of the highest-cost and lowest-cost solutions, from Cisco Systems Inc. and D-Link Systems Inc., respectively.

Fielden is a freelance writer. He can be reached at tfielden


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