Planning WLAN Operational Support, Part II

By Jim Geier

October 17, 2003

Wireless LANs behave much differently than wired networks. Learn what you should consider when monitoring them as we continue this series focusing on operational support planning.

By Jim Geier

In the previous instalment of this series, we explored what you should think about regarding configuration management of wireless LANs. Now, let's take a look at what you should consider when implementing network monitoring.

Network monitoring continuously measures attributes of the wireless LAN. This plays a key role in proactively managing the network in a way that enables smooth upsizing to support a growth of users and ability to solve issues before they hamper performance and security. Until recently, there have not been very many companies selling network monitoring tools for wireless LANs. There is a plethora of vendors now, such as AirDefense, AirMagnet, Airwave, Roving Planet, WildPackets, and many others, offering network monitoring tools that operate across multiple vendor access points.

When planning operational support for a wireless LAN, consider monitoring the following elements:

  • Performance. Continually measure the usage of access points to provide valuable information necessary to properly scale the wireless LAN as user traffic changes. The utilization of access points acts as a gauge to indicate when additional access points, access controllers, and Internet bandwidth are necessary. In addition, network monitoring should also keep an eye on sources of RF interference and raise flags when the interference is high enough to cause significant degradation in throughput.
  • Coverage. Alterations made to a facility, such as addition of new office partitions and influx of additional employees, cause attenuation and make radio waves propagate differently. This causes coverage of the wireless LAN to change, often limiting wireless user access to the network. In extreme situations, an access point may become inoperative due to a broken antenna or firmware fault, which requires maintenance or rebooting before users are able to associate with the access point. Because most companies deploy wireless LANs having access point range boundaries that radically overlap, however, total loss of connectivity may not occur. Instead, users experience lower performance in certain parts of the facility. In this case, users tend to not complain to strongly to the IT group about the problem, making it tricky for network administrators to determine whether an access point is down. Network monitoring is certainly a remedy to this problem.

  • Configuration settings. When installing access points, several configuration parameters, such as SSID, RF channel, and transmit power, are set. It's important to monitor these configuration settings over time. Network managers should be aware of the configuration of all access points in order to facilitate effective updates to the network. Documentation of the access point configurations can be easily lost. Monitoring of the configurations enables accurate, centralized records of the setting values.

    In addition, a hacker may attempt to reconfigure an access point to a default configuration that is insecure and comprises the security of the network. Tools should continuously monitor all of the access points in the network and alert the IT staff if anything strange is going on. The IT staff can set the performance and security thresholds at any value they wish and change them at any time. Some software packages also have auto-repair features, which automatically return the access points to their proper settings if someone tampers with the settings or a maintenance person reboots the access point due to a malfunction.

  • Rogue access points. Network monitoring should identify the presence of rogue access points to ensure there are no open, unprotected entry points into the corporate information system. This can be done by placing monitoring pods through out the facility to detect unauthorized access points, or monitoring can (ideally) be done over the Ethernet side of the network. Most vendors making wireless LAN management tools, such as AirDefense, AirMagnet, Airwave, and OptimumPath, include rogue access point detection. Vivato, a maker of a wireless LAN switch, takes advantage of independent beams to identify and give the approximate location of rogues.

If possible, a company should integrate the network monitoring function into tools in use for monitoring the existing Ethernet corporate network. Most access points offer simple network management protocol (SNMP) that provides an interface to existing wired network monitoring tools.

In part III of this series next week, we'll take a closer look at planning the security of a wireless LAN.

Jim Geier provides independent consulting services to companies developing and deploying wireless network solutions. He is the author of the book, Wireless LANs and offers training focusing on wireless LANs.

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