Re: asymetric capacity on windows on Linux everything is fine

Szymon Turkiewicz wrote:
Dnia Mon, 18 Aug 2008 17:30:30 +0200, John Oliver napisał(a):

On Mon, 18 Aug 2008 12:28:16 +0000 (UTC), Szymon Turkiewicz wrote:
Hi,

Lately I encounter quite interesting problem on my network. I have
512/512 kbit/s link from my isp and everything seems to be fine when
I'm uploading I have something about 512kb/s when I'm testing download
I have about 512kbit/s :). This works fine both on Windows XP and
Gentoo. Problem starts when I'm testing up/down simultaneously then I
have down ~500 and up ~ 200 kbit/s on widnows and ~500/500 on gentoo. I
wonder where is the difference between Windows and Linux and if there
is any chance to solve this problem.
Sounds like a driver issue. I'd look for a driver update for Windows.

I'm almost sure this is not the problem. I've made tests on few different notebooks and on WindowsXP and Windows2000.


How are you testing the speed? If you are using tcp connections, then for every transferred packet there is an acknowledge packet going in the opposite direction. There is also normally other traffic in both directions - things like DNS lookups and transfer handshakes. If windows is badly prioritising the packets so that all the bandwidth in one direction is completely filled with data packets, the other direction could quickly be stalled because the small but critical handshaking packets are delayed. You can read about this sort of thing on webpages about bittorrent clients - they normally recommend that you limit download and upload bandwidth to slightly lower than your full rate to avoid this sort of stalling.
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