Hello

I experienced strange problem with bandwith. My CentOS 4.3 x86_64 server is a gateway to Internet. The uplink is 20 Mbps full duplex Eth card is part of NForce4 chipset, the module is "forcedeth" As a testing tool we use "iperf" http://dast.nlanr.net/Projects/Iperf/

By test we decide downloda is only 10 Mbps (upload is 18-20 Mbps)

The first suspect was ISP, so we did test in cooperation. ISP Our site

FreeBSD ========= FreeBSD (ISP test machine)

TCP&UDP down 20 Mbps TCP&UDP up 20 Mbps TCP&UDP up 20 Mbps TCP&UDP down 20 Mbps

result: link is Ok

The second and final suspect was our gateway:

ISP Our site

FreeBSD ========= CentOS 4.3

UDP down 20 Mbps UDP up 20 Mbps UDP up 20 Mbps UDP down 20 Mbps

BUT

TCP down 20 Mbps TCP up 20 Mbps TCP up 10-12 Mbps TCP down 10-12 Mbps

SO: there is an problem with TCP ??? At the time of testing there was NO iptable rules or shaping enabled ...

Where to find? I realy do not know.

Petr Klíma

e-mail: qaxi@seznam.cz