After reading this blog post by Ben Strong, I started looking on the internet for information on how the Initial Window size could be manipulated on Microsoft Windows Server 2003 (R2, 64bit in case it matters).

Turns out that there is some information on tuning TCP/IP for Windows, but I couldn't find anything that would allow me to change the Initial Window size. Does anyone know if there is a TCPIP tuning guide for Windows-web servers, or at least some information on how to accomplish this specific feat?

  • I don't believe that this is possible in 2003. The good news is that since 2003 R2 will be end of extended support relatively soon, you should be planning to migrate to something modern like Windows Server 2012, which can do this natively :) – MDMarra May 23 '13 at 20:00

Be aware that there are typically two windows with TCP: The receive window (receiver controlled flow control) and the congestion window (sender controlled flow control).

In this case, he is talking about the initial congestion window (often called initcwnd in the case of Linux.)

At least in 2008 R2 with a hotfix this can be set (source):

netsh interface tcp set supplemental template=custom icw=10
netsh interface tcp set supplemental template=custom

You could try this and see if it exists in 2003, but I would guess you might be out of luck. Either way, you should fire up wireshark with a higher latency connection to see if it is working once you have applied the change (if it lets you apply this).

  • I found that info and a little more pretty well summed up here. As mentioned in the original post, I'm looking for information specifically related to Windows 2003. Thanks though – DRCRON May 24 '13 at 13:28

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