Check the Obvious

Check the Obvious
Sometimes, what’s causing you trouble is something simple — and which you
can fix simply.
For instance, one of us (and we won’t say who . . . Pat) was surprised that his
access point (AP) just stopped working one day. The culprit was his beagle,
Opie, who had pulled the plug out of the wall. As obvious as this sounds, it
took the unnamed person (Pat) an hour to figure it out. Now if someone told
you, “Hey, the AP just stopped working,” you’d probably say, “Is it plugged
in?” The moral: Think of the obvious and check that first.
Following are a couple more simple problems to think of first. . . .
Problem: The power goes out and then comes back on. Different equipment
takes different periods of time to reset and go through to restart, causing loss
of connectivity and logical configurations in your network.
Solution: Sometimes you need to just turn everything off and then turn
them back on in order — from the wide area network (WAN) connection
(your broadband modem, for instance) back to your machine — allowing
each device to start up with everything upstream properly in place and
turned on.
Problem: Your AP is working fine, with great throughput and a strong signal
footprint, until one day when it all just drops off substantially. No hardware
problem. No new interferers installed at home. No new obstructions. No
changes of software. Nothing. End cause: The next door neighbor got an
access point and was using his on the same channel.
Solution: This is hard to debug in the first place. How the heck do you
find out who is charging invisible interference — by going door to door?
“Uh, pardon me, I’m going door to door to try to debug interferers on my
access point. Are you suddenly emitting any extraneous radio waves? No,
I’m not wearing an aluminum foil hat, why?” Often with debugging performance
issues, you need to try a lot of the one-step solutions, such as changing
channels, to see whether that has an effect. If you can find the solution,
you will have a lot of insight as to what the problem was. (If changing channels
solved the problem, someone nearby was probably using the same channel,
and you can then start tracking down whom!)
The wireless utility for the adapter might have a tab listing the APs in range
called a Site Survey or Station List. It might show your neighbor’s AP and the
channel that it’s on.
And before you chase a performance issue, make sure that there is one. The
advertised rates for throughput for the various wireless standards are pretty
misleading. What starts out at 54 Mbps for 802.11a is really more like a maximum
of 36 Mbps in practice (less as distance grows). For 802.11b, it’s more
like 6 Mbps at best, rather than the 11 Mbps that you hear bandied about.
You will occasionally see the high levels (like when you’re within a few yards
of the access point), but that’s rare. The moral: If you think that you should
be getting 54 Mbps but you’re only getting 38 Mbps, consider yourself lucky.