Bad host-vased AP performace -- and qouple of questions about FreeBSD WiFi stack tuning

[Adrian Chadd]

2011/8/9 Lev Serebryakov <lev at serebryakov.spb.ru>:
> Hello, Adrian.
> You wrote 8 августа 2011 г., 22:11:03:
>
>> Can you verify when "bad" and "good" performance occured? Can you
>> narrow it down to FreeBSD versions in particular?

>   I'm afraid, that will be difficult. I could try 8.2-RELEASE and
>  even 8.0-RELEASE (but I'll need to build NanoBSD images for them).
>  I'm sure, that 7-STABLE gives me 3.2MiB/s regularly, but noteboks
>  were changed from these times. I'll try to build 7-STABLE NanoBSD
>  image, but it will need some more effort, as config files changes from
>  these times :)

Hi,

That's definitely required knowledge. 8.0-RELEASE is a good starting point.
I'm afraid it's going to be difficult for me to narrow down what's
changed without you doing a bit of legwork to find which kernel
version(s) introduced the performance regression.
Once we narrow that down, I'll fix it. :)

Please keep everything else the same though, including the laptop. :)

>> 2) not sure, it's late and I'm not knee-deep in the beacon frame
>> format. But I bet it's ok?
>  It is "not accurate enough" :) Many APs, seen in my apartments,
>  announce all speeds up to 54Mb :) But, of course, It is practically Ok till
>  clients can connect on higher speeds.

Hm, that's odd. The 11b rates should show up  (1 -> 11), the rest are
11g rates. I can't think of why the AP wouldn't advertise all 11g
rates, but then, I haven't gone digging in that code lately.

>> 3) txpower is in dBm units, based on what the card is supposed to be
>> putting out of the antenna socket, before antennas
>  Ok, so 30 means 1:1 (according to dBm definition) and means "full
>  power".

Well, some cards "lie". You program in x dBm, you get x+constant dBm.
That's how so high powered cards work - you program in some lower
value that fits inside regulatory limits (say, 23dBm) and you then get
(say) a +6 dBm boost no matter what you program in. So a 23 dBm
txpower would equal 29dBm. 0dBm txpower would equal 6dBm. etc, etc.

The only real way to know is a spectrum analyser. :)


Adrian