[Cerowrt-devel] what is the right way to do, and rationale, for wifi channel scans?

[Cerowrt-devel] what is the right way to do, and rationale, for wifi channel scans?

[Dave Taht]

I finally tracked down the source of many of the anomalies I'd
seen thus far... channel scans.

For the related rant, see:

http://blog.cerowrt.org/post/disabling_channel_scans/

Still haven't been able to kill it off entirely.

-- 
Dave Täht
Let's go make home routers and wifi faster! With better software!
http://blog.cerowrt.org

Re: [Cerowrt-devel] [Make-wifi-fast] what is the right way to do, and rationale, for wifi channel scans?

[Aaron Wood]

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wpa_supplicant?  I've seen some atrocious behavior from wpa_supplicant in
the past (especially the closed-source versions from some chipset
companies).

One reason it's likely to be scanning is that it's looking for alternate
APs for the same SSID, which are "better".

I saw one implementation that would do an all-channel wildcard ssid scan
(elicting a response from every AP in range), and then would proceed to
scan every channel for just the ssid it was configured to use (hardcoded in
the wifi config).  Why it was doing a broadcast for all APs, I don't know.
But once you get enough APs in a small enough area, that behavior causes a
broadcast storm as the probe responses (all at 1Mbps) flood the air, and
then cause other STAs to miss beacons, and re-scan, and it death-spirals
from there.

-Aaron

On Fri, May 13, 2016 at 5:19 PM, Dave Taht <dave.taht@gmail.com> wrote:

> I finally tracked down the source of many of the anomalies I'd
> seen thus far... channel scans.
>
> For the related rant, see:
>
> http://blog.cerowrt.org/post/disabling_channel_scans/
>
> Still haven't been able to kill it off entirely.
>
> --
> Dave Täht
> Let's go make home routers and wifi faster! With better software!
> http://blog.cerowrt.org
> _______________________________________________
> Make-wifi-fast mailing list
> Make-wifi-fast@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/make-wifi-fast
>

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Re: [Cerowrt-devel] [Make-wifi-fast] what is the right way to do, and rationale, for wifi channel scans?

[Dave Taht]

The discussion on the g+ thread for the channel scan issue got hot and
heavy, here:

https://plus.google.com/u/0/107942175615993706558/posts/WA915Pt4SRN

On Fri, May 13, 2016 at 8:19 PM, Aaron Wood <woody77@gmail.com> wrote:
> wpa_supplicant?  I've seen some atrocious behavior from wpa_supplicant in
> the past (especially the closed-source versions from some chipset
> companies).
>
> One reason it's likely to be scanning is that it's looking for alternate APs
> for the same SSID, which are "better".
>
> I saw one implementation that would do an all-channel wildcard ssid scan
> (elicting a response from every AP in range), and then would proceed to scan
> every channel for just the ssid it was configured to use (hardcoded in the
> wifi config).  Why it was doing a broadcast for all APs, I don't know.  But
> once you get enough APs in a small enough area, that behavior causes a
> broadcast storm as the probe responses (all at 1Mbps) flood the air, and
> then cause other STAs to miss beacons, and re-scan, and it death-spirals
> from there.
>
> -Aaron
>
> On Fri, May 13, 2016 at 5:19 PM, Dave Taht <dave.taht@gmail.com> wrote:
>>
>> I finally tracked down the source of many of the anomalies I'd
>> seen thus far... channel scans.
>>
>> For the related rant, see:
>>
>> http://blog.cerowrt.org/post/disabling_channel_scans/
>>
>> Still haven't been able to kill it off entirely.
>>
>> --
>> Dave Täht
>> Let's go make home routers and wifi faster! With better software!
>> http://blog.cerowrt.org
>> _______________________________________________
>> Make-wifi-fast mailing list
>> Make-wifi-fast@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/make-wifi-fast
>
>



-- 
Dave Täht
Let's go make home routers and wifi faster! With better software!
http://blog.cerowrt.org