Planning WLAN Operational Support, Part IV
October 31, 2003
Due to the use of radio waves, wireless LANs have unique maintenance requirements. Learn what you should consider for maintaining a Wi-Fi network as part of this continuing series focusing on operational support planning.
When deploying a wireless LAN, be certain to have a plan for fixing problems if they arise after the network becomes operational. In fact, even try to proactively find trouble spots and mend them before they affect users. This reduces downtime, which certainly makes users much happier.
These types of efforts fall into what most companies call the maintenance function. Effective maintenance staffs include hands-on people who are capable of troubleshooting problems and applying appropriate fixes.
The maintenance staff should be ready to repair the following types of wireless LAN problems:
- Inoperative access points. Firmware bugs sometimes cause access points to fail. Often, a solution to getting things back to normal is to just reboot the access point. This will generally put the access point back on the air. With the access point in this "holding pattern," determine whether updates to the firmware are available and report the problem to the vendor. Update the firmware if yours is currently out of date. In some cases, you might need to replace the access point.
- Poor performance. Wireless LANs are difficult to design and install in a way that provide good performance at all times, especially when there are lots of users or when high performance applications (e.g., video streaming) are in use. The shared medium access protocols of the 802.11 ("Wi-Fi") standard makes throughput vary widely as conditions on the network change. As a result, maintenance staff needs to be ready to respond to users complaining about sluggish performance. Possible remedies to this include ensuring there's adequate coverage, implementing bandwidth control mechanisms, possibly upgrading to 802.11g or 802.11a, or using a wireless LAN switch architecture.
- Poor coverage. As I've covered in a previous tutorial, you should always perform an RF site survey to properly position the access points and determine whether there are any harmful interference sources present that will disturb performance. Often, however, companies either don't perform a survey or alterations made within the facility change the propagation and coverage of the wireless LAN. Thus, users may eventually complain about having poor coverage in certain parts of the building. Maintenance staff will then need to evaluate the areas having poor coverage and reorient the access points in a way that satisfies required coverage.
- Broken hardware. The two primary components of an access point that break are antennas and cable connectors. If a telephone technician rewiring phones accidentally clips off an antenna from an access point, then poor coverage will result. The access point will still probably continue to operate, but the range will be lessened without the antenna. A broken data cable, however, completely disables the access point, especially when using 802.3af power-over-Ethernet (PoE)to supply electricity. These mishaps will happen sooner or later, so have adequate numbers of spare antennas and cables on hand. A spare access point or two is also a good idea.
- Monitor access points. Implement continual network monitoring and incorporate alerts that inform maintenance staff when an access point is not operating properly (or not operating at all). An access point can be down for days, weeks, or months without anyone knowing. Keep a close eye on this and take corrective actions when necessary, hopefully before partial coverage affects users too badly.
- Keep firmware up-to-date. Instead of waiting for an access point to fail, update the firmware when new releases become available. This ensures that the access point operates with the latest features and freedom from defects in order to maximize performance and security of the network. Before moving access points to a new release of firmware, however, be sure to adequately review and test the new firmware. New releases have been known to cause more problems than the previous versions.
- Monitor performance. Be sure to review actual utilization of the access points, and track the average and peak values. The trends provide valuable information that you can use to determine whether you should begin implementing methods to increase throughput available for each user.
- Verify coverage. Don't wait until users complain about spotty coverage. The maintenance group should periodically perform tests to ensure that the access points are properly covering the building at applicable levels of performance. If discrepancies are found, then reposition or add new access points.
- Inspect access points. It's also important to walk around and visually inspect the access points at least monthly. For preventative maintenance purposes, check for any existing or potential damage. I remember walking through a large medical center a few months and found several access points dangling by their data cables over some beams. A construction company had come in to replace ceiling tiles and left the access points in these vulnerable positions for several days. Ideally, the access points should be neatly tucked away above the ceiling or securely mounted to beams or walls. It's also best if the access points are out of easy reach to avoid security problems.
In order to complete maintenance tasks, tools are necessary. You'll at least need test equipment that measure radio parameters, such as signal strength and signal-to-noise ratio, and have the ability to capture 802.11 frames and display throughput.
With wireless LANs, maintenance personnel need to have experience with radio systems, which is not common among most IT groups. In most cases, existing IT staff will require wireless LAN training that focuses on radio frequency fundamentals, troubleshooting wireless LANs, and related test equipment. Maintenance staff should obtain applicable training from specific access point vendors and also consider independent certification, such as the Certified Wireless Network Professional (CWNP) program.
Stay tuned! In part V of this series, we'll take a look at reengineering wireless LANs.
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.