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I have a weird issue on my Dell server. When I check the bandwidth using the tool Iperf against my Amazon Server I get bandwidth of 11 Mbps over Windows 7 Professional. On the same machine when I use Ubuntu against my Amazon server I receive speeds of 90 Mbps - a huge leap of bandwidth.

Can anyone tell me why I am experiencing such drastic differences in bandwidth speeds?

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Bandwidth != Speed. – joeqwerty Apr 4 '12 at 10:51

You are quite possibly running into problems with Windows's TCP Chimney Offload, Receive Side Scaling, and/or Network Direct Memory Access. Inspect Microsoft KB951037 for more information about each of those features and how to disable them.

I've also come across issues with Windows Network Task Offload. I had to disable it using an obscure registry key:


Add a new DWORD and give it the name DisableTaskOffload. Set the value on the new DWORD to 1. For more info, see a blog post I wrote titled "Fixing Exceptionally Slow Remote Desktop Performance to Windows Server 2008."

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Thanks Wesley. I have tried that but it hasnt helped me. I am still unable to increase the bandwidth speed over Windows. – Rak Apr 4 '12 at 3:45
Did you make sure to reboot after each change to the stack? – Wesley Apr 4 '12 at 3:47
Yes Sir.Did that as well but no luck. The bandwidth still shows as 11 odd mbps where i have a 100mbps connection – Rak Apr 4 '12 at 3:50
Are both ends a Windows machine? I'm not sure if the endpoint that the Windows 7 machine is trying to communicate with is also a Windows machine. These steps should be taken on both ends of the communication as part of troubleshooting. I had to disable Network Task Offloading on server and client to get my connection speeds to even out. – Wesley Apr 4 '12 at 3:52
The amazon end is a Linux machine while the server on my end is a Windows 7 machine. When I use Ubuntu instead of Windows everything is hunky-dory. – Rak Apr 4 '12 at 3:58

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