|While Russell is correct, there are reasons to not beacon SSID.
One possibly good reason to disable broadcast SSID is simply to avoid confusing
clients that you do not want to connect (and that have no desire to connect to
you). My clients started acting odd when a neighboring motel set up some
public access points in spite of the fact that my clients were set up to use
only my own SSID. It turned out that they were getting hung up timing out on
association attempts with these public access points (and counting up SSID
mismatches) when they should have been talking to my access point. Clearly
it's pretty stupid of the firmware to keep trying the wrong SSID on an access
point that is willing to tell its SSID, but that's what they did. The resulting
delay caused the client in my car to fail to associate with my own access point
before I turned into the driveway, confusing my home automation system. I
ended up restricting the clients to my specific access points which is kind of
a pain since MAC addresses have to be everywhere...
|That is,
|to keep junk out of the air.
I'm not sure it accomplishes this one. As far as I can tell, most access
points that allow you to disable "broadcast SSID" mean that they will not
accept the null (= broadcast) SSID from clients in probes. The setting does
not change the rate of packets generated at idle. Having just ordered one
of the sniffer boxes advertised here recently, maybe I'll be able to see for
certain soon. :) (For some access points--like the ones mentioned above--
allowing broadcast SSID seems to make them accept any SSID rather than just
the null and configured ones. At least in some contexts. Very confusing...)
|In a congested environment (like here in
|Cambridge) this can make a difference. At the least, set your beacon
|interval to something reasonable (2 per second is good).
I've experimented with long beacon intervals and they kill PSP clients. I
don't quite understand what is going on yet, but the clients just sort of
grind to a halt if the beacon interval is significantly longer than the
default 100Kusec on my Aironet access point.
|I think a patch to allow disabling the beacon would be a good idea.
How do you convince the clients that the lack of beacons doesn't indicate
that the access point is dead? The active beacon seems to be on of those
unfortunate things which wasn't absolutely necessary for DSSS in the first
place (active probes are fine, no?) but which has come to be depended on for a
variety of functionality. Some of that could be changed, but PSP's dependence
is pretty deep...
Dan Lanciani
ddl@danlan.*com
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