Fixed Wireless Technology

Wireless LAN Tools Part 3: Discovery and Planning — continued

by Lisa Phifer VP Core Competence, Inc. [August 10, 2004]

Monitoring network activity
After AP installation, watch what happens as test stations begin to connect to your network and try to send data. In Part 4, we'll take a closer look at security and performance analysis and usage monitoring, trending, and reporting. But initially, you'll probably just need overall visibility as you debug AP placement and configuration.

Many WLAN analyzers include a dashboard that presents "at a glance" network utilization, throughput, and error rate summaries. For example, this dashboard from Network General Sniffer Wireless offers gauges and real-time graphs, with drill-down to break summary counts into components (see image at right). As you start to test connectivity, dashboards help you see whether traffic is flowing and errors are occurring. Some error is not unusual, but as we'll discuss in Part 4, excessive errors can require further analysis.

At this point, you may be surprised to see traffic from sources other than stations under test, and traffic that you didn't expect to be sending. WLAN analyzers can summarize what they see in many different ways; we'll dig into this more in Part 4. For now, we'll mention just a few tools that can be very handy during early network testing:

• A real-time channel activity graph, like this one generated by AiroPeekNX, can help you eyeball channel signal strength and utilization (see image at right). For example, if you're having trouble connecting, is the average signal for the desired channel under 20 to 30 percent? Note that transmissions are strongest at a given channel's center but do overlap adjacent channels; in this graph, the strongest APs are tuned to channel 6.
  
  
• A real-time Top Senders graph, like this one generated by Baseband's LinkFerret, can help you to quickly spot active stations. For example, if you're trying to monitor or capture traffic from your test station but don't see it show up in this list, then perhaps you are listening to the wrong channel or have your filter configured incorrectly.
  
  
• A real-time network protocol graph, like this one produced by the open source Packetyzer, can help you determine whether test stations are not just associating, but actually sending application traffic effectively through your network. If you're attempting to send test traffic and you don't see that traffic here, make sure you're looking in the right place first. Then you can start drilling down to diagnose AP, station, or network configuration errors.