[CentOS] Ethernet bandwith problem ...

"Petr \"Qaxi\" Klíma" qaxi at seznam.cz
Fri Mar 31 13:49:48 UTC 2006


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 at seznam.cz




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