Network too intelligent

Lately, working with Windows 7 I noticed a cruel transmission rate of 200 B/s while fetching a file from a local server over a highspeed connection. No, I didn’t have a typing error in there, it’s 200 Bytes per second; that’s even slower than GPRS!

I guess we agree on the fact that there’s something wrong on the network. Server? Switch? Client? The former ones are easy to exclude from our calculation due to the other users talking about weather and coffee both being quite tasteless. The common trick of disabling auto neg. at the switch didn’t help – so it’s time to look through the Technet stuff.

A few mouseclicks later and three hours (which did feel as if it was just 15 minutes) I stumbled over some suspect auto tuning of the network which is done by Windows 7 to improve speed. Yes, it should improve the network connection. Please mind the word ‘should’.

Diving into it, I opened a command prompt with admin permissions, checking the TCP parameters:

netsh interface tcp show global

Shaking my head about that output I thought about disabling the tuning features all together:

netsh interface tcp set global autotuninglevel=disabled

That was it: The network connection is as fast as it should be. In other words, the tuning logic was too intelligent for itself…

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