Question about AP hopping

Dan Williams dcbw at redhat.com
Fri Jun 1 12:11:14 EDT 2007


On Fri, 2007-06-01 at 11:32 -0400, Aric D. Blumer wrote:
> Suppose that I have two APs, fairly close to each other.  They have the
> same SSID but are on different channels.  One is set to have low power
> transmit.
> 
> A network card running the hostap driver is associated with the
> low-power AP while the other AP is turned off.  Then the other AP is
> turned on, and the card is able to scan both APs.  It remains associated
> with the lower-power AP.
> 
> As I walk away from them, I lose connection with the low-power AP, but I
> would expect a reassociation to occur to the higher-power AP.  This does
> not occur.  Isn't that how 802.11 supposed to work?  Does anything need
> to be set in the hostap driver on the mobile device in order to
> reassociate to the other AP?

Depends on quite a few things.  If the firmware does the roaming, it's
all up to the firmware.  If you've specified a particular BSSID, then
the driver/card should hang onto that BSSID forever.  I'm not sure if
hostap has driver-level roaming support, but if the firmware doesn't do
roaming for you (it's true that many do) then you'll need a userspace
tool to work it all out.

Dan

> Thanks for any insight you might have.
> Aric.
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