Stop Stumbling! Use This Diagnostics Tool for Wireless Connectivity

Wireless networks are becoming much more common in small-to-medium sized businesses, presenting a new revenue opportunity for system builders. Building wireless networks and getting them to work is not that difficult. But securing and maintaining wireless networks can be a different story. Without proper instrumentation for testing and monitoring wireless networks, meeting these responsibilities can quickly become complex and time-consuming.

It's a rare system builder who is prepared to act as their customers' network administrator, security officer, and wireless technical support/diagnostics person. Yet keeping a wireless network up and running involves many tasks. These tasks include proper configuration, correct placement, maximizing coverage areas and signal strengths, establishing and managing security protocols and authentication mechanisms, and systematic troubleshooting. Somebody has to do this work.

Fortunately, completing wireless tasks can be simplified with a new breed of software tools. One of the best, in my opinion, is NetStumbler. It's a freeware software offering that its developers describe as "beggarware"—meaning that while no payment is required to use the program, donations are both requested and gratefully accepted. NetStumbler is also the focus for this TechBuilder Recipe.

While NetStumbler does take some time to learn, we believe it is an indispensable tool for defining and diagnosing wireless connectivity. For this reason, NetStumbler should be an integral part of every system builder's wireless networking toolbox. NetStumbler's ease-of-use is inarguable, and it is well-suited for occasional yet extremely practical use.

NetStumbler lacks some of the more potent features of full-blown commercial suites, such as AiroPeek and AirMagnet security products, which offer such features as multi-layered protocol identification, packet trace decoding, and complete wireless security scans. But NetStumbler is sufficiently well-equipped to help install, document, and troubleshoot most wireless networks—especially small ones.

Benefits of Using NetStumbler

NetStumbler provides a turnkey solution for Windows-based test and measurement instrumentation to document and inspect wireless network installations. The NetStumbler tool can interrogate wireless devices and report information about their configurations and capabilities.

NetStumbler also documents Media Access Control (MAC) and identifies wireless communications channels and Service Set Identification (SSID) in use. These tasks are important: MAC addresses are unique, hardware-inscribed identification tags network devices, usually formatted as six-byte, colon-separated hexadecimal values such as: 0B:AD:CA:FE:F0:0D. An SSID is used to identify wireless network devices.

NetStumbler also does much more. It measures signal-to-noise (STN) ratios for all wireless access points (WAPs) it finds; describes the types of encryption being used; details sources of interference from nearby signal emitters; assists in detecting rogue access points and dead spots; and more.

Bottom line: NetStumbler is sufficiently general purpose enough to qualify for "Swiss Army Knife" status among wireless networking tools—and might even make Ron "Ronco" Popeil proud of its many capabilities!

If you're interested in automating wireless network assessments, NetStumbler also contains a basic scripting language that works with VBScript, Jscript, PERLScript, and Python input. Though NetStumbler lacks some features that other, more well-rounded commercial wireless network management applications provide—such as upper-layer protocol diagnostics and packet trace decoding (available in commercial products like WildPackets' AiroPeek NX)—NetStumbler performs well enough to be of great use to system builders and wireless-network installers alike.

In fact, system builders will find NetStumbler helpful when ensuring that systems are working and configured properly when finished (but not yet deployed). Wireless-network installers will find this tool invaluable for making sure wireless systems are configured and working properly, and complying with best security practices and security policies.

Ingredients

To get started working with NetStumbler, you'll need the following components:

• Any Windows-based PC with Windows 98SE or above. Wireless support for Windows 98 is virtually non-existent, as most modern wireless gear explicitly requires Windows 98SE or newer versions of Windows.

• A wireless access point.

• Any wireless card that work with NetStumbler. See the software's Release Notes for a complete list. Although NetStumbler may work to some degree on unsupported hardware, I recommend that you stick with supported cards for the best, most informative results.

• A copy of NetStumbler. (See our "Nine Steps" section below for details on how to download a copy.)

I recommend that you also bring along your own laptop and use it to run NetStumbler while installing or deploying wireless systems and gear. Even if the wireless adapter you're working with isn't on the NetStumbler supported list, as long as your laptop sports a supported wireless card, you can use NetStumbler for testing, documentation, and monitoring for just about any kind of 802.11 (whether a, b, or g) wireless network.

Currently, there are fewer than a handful of wireless standards amendments covered under the 802.11 heading. The variances between each are well beyond the scope of this article, but you should have a basic knowledge of which standards you're likely to encounter. Each amendment—such as 802.11a, 802.11b, and 802.11g—specifies, among other things, a maximal throughput rating, signal modulation techniques, and operational frequencies. Products bearing the Pre-N markings are nothing more than a pre-emptive solution to an amendment, 802.11n, which has not yet been finalized.

To research and write this TechBuilder Recipe, we used a D-Link USB 2.0 adapter (model number DWL-G132 hardware version A2) and a D-Link Access Point (model DWL-2100AP hardware version A3).

We also tried out two other wireless PC cards: a D-Link DWL-G650 and Belkin F5D8010, both of which returned mixed results. Using the Windows Zero Configuration utility, the D-Link card identified four wireless radios in access points in our vicinity, two of which were in effective communications range. Unfortunately, this same adapter failed to detect any of those same APs when running NetStumbler with Zero Configuration turned off. On the other hand, the Belkin card detected only a single radio with the Wireless Configuration active, but two when NetStumbler was active. Go figure!

Also, the D-Link card detected three to four radios (two of which were out of range), depending upon where the card was situated when we ran NetStumbler. In any case, systematic changes of device or antenna position can also assist you when deciding placement for wireless equipment to achieve optimal range and performance. More on that later in this Recipe.