ath driver transmits frames only after a low watermark is filled

[Victor Semionov]

How is data transmission related to power management?

On Wednesday 19 July 2006 19:01, you wrote:
> Sounds like what always happens when crappy power management stuff is
> enabled either on the station or the ap.
> I would investigate that first.
>
> Victor Semionov wrote:
> > Hello list,
> >
> > I have a wireless card with an Atheros 5212 chipset and I'm experiencing
> > the following behavior under FreeBSD 6.1:
> >
> > TCP connections that consist of small short bursts of one-way
> > (transmission) traffic often stall until traffic is received over another
> > TCP connection. For example, if I try to load a small web page, located
> > on the FreeBSD box, over the wireless link, it doesn't load completely,
> > unless I hit return in a concurrent terminal session, or until I request
> > some other file hosted on the FreeBSD box, or until I wait 20 seconds or
> > so. The signal is not low, the two wireless boxes are in the same room.
> >
> > Higher-bandwidth connections rarely stall. This makes me think there is
> > some kind of low watermark functionality in the hardware/driver that
> > doesn't send frames until a certain number of them have been queued for
> > transmission, or until a frame has been received. Also, I guess this is
> > the reason that the ath module caused the system to freeze at shutdown or
> > when the module is unloaded, unless I do an "ifconfig ath0 down" before
> > unloading - the unloading code is probably waiting for all queued frames
> > to be transmitted, but that never happens.
> >
> > Sorry for the weak conclusion that is based on assumptions. I'm not
> > familiar with the OS/driver internals and don't know how to investigate
> > further. Is there a sysctl or other setting that controls this behavior,
> > or some other workaround? Any help would be greatly appreciated.
> >
> > Best regards,
> > Victor Semionov
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