Networking

Factors to consider when building a scalable WLAN

Before you take the plunge into wireless, or upgrade your existing 802.11b network, be sure to consider the scalability factors for each of the available technologies. There is no "one size fits all" solution; the best choice for your organization depends in large part on which is more important to you: compatibility and distance range or reliability.

Wireless technology provides convenience for users and makes it far easier to network computers that move around (notebooks and handhelds) and those located in places where cable hasn't been run. It also creates some extra administrative and security headaches. If you've weighed the pros and cons and decided to implement a wireless LAN (WLAN) for your organization, one consideration in choosing the right wireless technology and topology is how well it will scale to meet your future needs.

Here are some factors to keep in mind when you plan your wireless infrastructure.

Wireless options

Most wireless networks today use one of three variations of wi-fi technology:

  • 802.11b
  • 802.11a
  • 802.11g

We've listed them in chronological order of their introduction/adoption, rather than alphabetical order. The most common, least expensive and first to become widespread is 802.11b, which provides data transfer rates of 11 Mbps (or, in an "enhanced" version, 22 Mbps) and a typical distance range of approximately 300 feet. It operates at the 2.4 GHz radio frequency (as do many cordless phones, microwave ovens and other devices).

802.11a was developed to provide higher speed communications, up to 54 Mbps. Unfortunately, you sacrifice range to get that speed because the signal typically only reaches about half as far. However, it has another advantage in that it suffers less from interference. That's because it operates at the 5.8 GHz frequency, which is used by fewer common household and office devices.

802.11g in some ways gives you the "best of both worlds." You get the high speed of a 54 Mbps, with "enhanced" versions available that claim double that speed and a distance range closer to that of b. Since 802.11g is really an extension to its 802.11b cousin, it operates at the same frequency, 2.4 GHz.

Note that the speeds given are "stated maximum throughput." In practice, you will probably get transfer rates somewhat lower than these. But keep in mind that even the slowest (about 5 Mbps effective throughput on most 802.11b networks) is still faster than the typical broadband Internet connection.

There are other wireless networking technologies, such as BlueTooth (used for short range communications between devices in close proximity) and Wi-Max (being developed as a long-distance wireless solution to connect computers over distances greater than the scope of the typical LAN), not to mention satellite-based networking. In this article, we'll stick to the 802.11 variants that are commonly used to give wireless connectivity to a local network. (For more information, download TechRepublic's Wireless Technologies Scorecard.)

Speed and distance

Speed and distance can be important factors in scalability of a WLAN. As your organization grows, you will add more users. In addition, you'll most likely need more bandwidth for the transfer of larger files and for higher bandwidth technologies such as streaming audio/video, real-time conferencing, etc. That means the more bandwidth, the better.

802.11a and 802.11g provide more scalability in this regard than 802.11b, and with 802.11a you can combine channels to get even higher throughput.

Distance range can also be a factor in the scalability of your WLAN. As your office expands physically, you'll have to deploy more access points to reach the areas you need to reach with 802.11a than you would need with 802.11b or g.

Compatibility

Another factor that affects scalability is compatibility, and this is a two-pronged consideration: compatibility of wireless technologies with one another and compatibility with wireless devices, especially the network adapters built into many of today's notebook computers.

A big advantage of 802.11g over a is its backward compatibility with 802.11b. This means you can "start small" with an inexpensive 802.11b WAP and then later replace it with a WAP that supports both b and g. Computers that have 802.11b network adapters will still work, but at the lower 802.11b speeds. You can replace the NICs gradually, making for a smooth transition. If you switch to 802.11a, everything will have to be replaced immediately because it is not backwardly compatible with your old 802.11b equipment.

Another problem with 802.11a is that the built-in wireless equipment in notebooks is almost always of the more common 802.11b or g varieties. These will be useless with an 802.11a infrastructure; you'll have to turn off the built-in wireless and add 802.11a NICs via the PCMCIA (PC card) slot.

Finally, employees who connect to your wireless network may also want to connect to other wireless networks at their homes or at public access points ("hot spots") in hotels, airports and restaurants. Most home and public wireless networks use 802.11b technology, so they'll need to swap out two different NICs (or use built-in wireless for home/public networks and a separate NIC for the corporate wireless network).

(For a set of checklists to help you select, install, configure, and manager your network, download TechRepublic's Support and Configuration Checklists for Small/Midsize Networks.)

Reliability

Up to this point, it may seem that 802.11b/g is the clear choice, but there is one more important factor to consider. In order to scale to meet your networking needs, your WLAN must be reliable. An unreliable technology isn't scalable because it doesn't make sense to expand its deployment if you can't count on it to work properly.

This is where 802.11a has the home-court advantage. By virtue of its incompatibility — that is, because it operates on an entirely different frequency from other popular wireless networking and consumer communications technologies — it's far less prone to interference that can bring the network down or disrupt transmissions. Another aspect of reliability is security, and 802.11a enjoys a form of "security through obscurity." Simply because it's not as widely deployed and the equipment costs more, fewer hackers target networks based on 802.11a. (For more on wireless security, see Manage your company wireless network hardware to prevent security breaches.)

Weigh your options

Before you take the plunge into wireless, or upgrade your existing 802.11b network, be sure to consider the scalability factors for each of the available technologies. There is no "one size fits all" solution; the best choice for your organization depends in large part on which is more important to you: compatibility and distance range or reliability. Most organizations will probably opt for the 802.11b/g combination because of the ease of transition, but those who use wireless communications for mission critical tasks and who need more security may find 802.11a to be a better option.

About Deb Shinder

Debra Littlejohn Shinder, MCSE, MVP is a technology consultant, trainer, and writer who has authored a number of books on computer operating systems, networking, and security. Deb is a tech editor, developmental editor, and contributor to over 20 add...

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