Windows 2008 TCP autotuning and java applets

Windows 2008, Vista and Windows 7 contains some enhancements of the TCP stack compared to earlier versions of Windows.
Among them, are the TCP autotuning option which by default is enabled. (For more info, see
During installation of a two-server remote desktop farm, I installed Sun Java runtime, and routinely set out to test the functionality by connecting to the testpage ( The test failed, leaving the java plugin window with the spinning circle.
This probleme was evident on both physical and virtual (hyper-v) servers on the network, but only on various flavours of Windows 2008, not Windows 2003 etc.
After heavy testing and a lot of google abuse searching for “applet download fail” and striking out, it dawned on me that I was looking at it from the wrong perspective. I had to be a response problem, and it had to be a delay thing. I searched for “windows 2008 applet download slow”, and came upon this page that put me on to the soluton:
After disabling autotuning, java applets started to load normally.
This issue might also have affected other applications on the remote desktop servers, so this is not a java runtime specific issue.
Edit: In hindsight, the error was not really related to Windows 2008 R2 or autotuning. After a few months, the customers old firewall (A Linksys VPN router), died and was replaced with a new firewall. On a hunch, I decided to test java again from an unmodified server. It worked. It was the old firewall that was to blame….

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