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Update the firmware if yours is currently out of date.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.
The staffing of a maintenance crew that can fix problems associated with wireless
LANs is one step toward having successful maintenance. Being proactive is far
more important. The following offers some suggestions on preventative maintenance
tasks that you should perform with wireless LANs in order to minimize downtime:
- 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.
