Sluggish performances with Linux

[Laurent Goujon]

Hi all,

Currently I have a two computers : 
- The first one is my gateway. It's running Freebsd 5.2 stable, has two
networks cards, a realtek 8139 and a broadcom 4401
- The second one is my laptop and it's running most of the time Linux
(Mandrake cooker with a 2.6 kernel), sometimes winxp (because of the
lack of support for some hardware components) and has a sis900 network
adapter

My problem is :
I have very poor performances with tcp streams from my server to my
laptop (0.35 Mb/s), but throughput is normal from the laptop to the
server (90Mb/s) and also (my favorite one) from Internet to my laptop
(~4Mb/s).
When I'm running WinXP, all is quite normal.

I've tried to invert network cards on my server, to bypass my switch :
no result

Any idea ?

Laurent Goujon