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"Windows Scaling heuristics" changes my TCP autotuning level ?

It is sometimes possible for Windows Vista/7 to change the TCP autotuning level on its own, even after it being user-configured. When that happens, the "netsh int tcp show global" command displays the following message:

** The above autotuninglevel setting is the result of Windows Scaling heuristics
overriding any local/policy configuration on at least one profile.

To prevent that behavior and turn off heuristics, before setting the TCP Receive Window auto-tuning level you should execute the following command:

netsh int tcp set heuristics disabled

Note this should be executed in elevated command prompt (as administrator). If the command is accepted by the OS you should see an "Ok." on a new line.

For more information and TCP tweaks, see our Vista/Windows 7 tweaking article.


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by MDK - 2012-12-11 09:01
If you are doing anything with windows 7, (hosting a server, etc) and you seem to be having issues even though you know your firewall isl setup correctly, this is the command to fix it. I was trying to setup a source dedicated server and could not figure out why the server kept dropping offline after it initially showed online with the game trackers.
Thanks!!
by KEiGHT - 2015-02-16 04:37
There is another hotfix for this issue ; http://support.microsoft.com/kb/2780879

To enable TCP window scaling after the second retransmission of a SYN packet:

netsh int tcp set heuristics enabled enabled

or to set only Window Scaling without heuristics

netsh int tcp set heuristics wsh=disabled forcews=enabled

RESTART !
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