On Fri, Mar 26, 2010 at 8:02 PM, Jouni Malinen
<[email protected]> wrote:
> On Fri, 2010-03-26 at 16:16 -0700, Pavel Roskin wrote:
>> I confirm that scan_freq is accepted by the current wpa_supplicant but
>> has no reliable effect.  Both ath5k and ath9k connected to an AP on the
>> channel 6 when "scan_freq=2412" was in the configuration file.
>
> scan_freq is not supposed to limit the association to specific channels;
> it is only to limit scan requests made by wpa_supplicant. You may still
> find BSSes on other channels either due to scan requests made by other
> programs or by receiving Beacon/Probe Response frames on another
> channel.
>
> If there is interest for limiting the association to specific channels,
> it should be trivial addition to wpa_supplicant (with nl80211).

Wireless vendors have started to realize the problem here and have
begun implementing features to help.  An example from the latest Cisco
Controller configuration guide for 802.11n AP's:

...Configuring Band Selection

The 2.4-GHz band is often congested. Clients on this band typically
experience interference from Bluetooth devices, microwave ovens, and
cordless phones as well as co-channel interference from other access
points because of the 802.11b/g limit of three non-overlapping
channels. To combat these sources of interference and improve overall
network performance, controller software release 6.0 enables you to
configure band selection on the controller. This feature enables
client radios that are capable of dual-band (2.4- and 5-GHz) operation
to move to a less congested 5-GHz access point...

> I don't
> know whether I would fully agree on this being a useful thing for
> general use, but I can understand it at least as a testing tool

Yes, how can one accurately simulate an end user problem when their
client is on a different band than yours and you have no control over
which band your client lands on.

>(which
> people may then misuse for other things ;-).

Years ago Intel (and I think some Broadcom) made that same decision
with many of their Windows drivers, and now recently Microsoft with
Vista and Windows 7 thought it was important enough to at least have
the option.  Agreed ...it is not on the first page of the
configuration, but it is an option for those of us looking hard enough
to find it.

...Especially if it is "trivial" ...please consider adding.  For me,
it's the only reason I occasionally have to boot Windows.

Thanks,

Curtis
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