Are there tweaks I can use to tune TCP/IP performance on Windows?

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Question

On Windows operating systems the TCP/IP stack by default introduces a 200ms delay when acknowledging TCP commands. This can have the effect of considerably slowing down the responsiveness of Windows systems but has the benefit of keeping CPU usage down to a minimum level.

Therefore any changes made must balance responsiveness against increases in CPU usage.

Answer

You can increase TCP performance by acknowledging incoming TCP segments much more quickly. To do so open regedt32.exe and navigate to:

 HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParametersInterfaces

On the Edit menu, click Add Value, and create the following registry value:

Value name: TcpDelAckTicks
Data type: REG_DWORD
Value data: 1

Restart your Windows operating system.

You may need to experiment somewhat with the value data used above to achieve the correct balance between speed and CPU usage.

The Value data has a range of 0 to 6 (100 millisecond intervals) with the default value being 2. Setting it to a value of 1 is telling Windows to use a delay of 100 milliseconds as opposed to a default of 200 milliseconds. In our testing we have found that a value of 0 leads to very high CPU usage so we would not recommend this.

Note: Editing of the registry can seriously affect the operation of Windows and must be done with great care.

See Also:

Keywords:tune TCP/IP stack Windows

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