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I have a Windows 2008 Server. Its maximum connection backlog limit (TCP) is 200. Is there any way to increase this limit to a higher value – say 1000 or 2000?

In this article you will find description of parameters to change in the registry under this key:

  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AFD\Parameters

The relavant values should be these:

  • EnableDynamicBacklog (DWORD)
  • MinimumDynamicBacklog (DWORD)
  • MaximumDynamicBacklog (DWORD)
  • DynamicBacklogGrowthDelta (DWORD)

I have tried using different sets of values like

  • EnableDynamicBacklog = 1
  • MinimumDynamicBacklog = 250
  • MaximumDynamicBacklog = 20000
  • DynamicBacklogGrowthDelta = 100


  • EnableDynamicBacklog = 1
  • MinimumDynamicBacklog = 20
  • MaximumDynamicBacklog = 1000
  • DynamicBacklogGrowthDelta = 10

but no matter what I do I am still limited to a backlog of 200 connections. (And yes I have rebooted the server between configuration changes.)

Any ideas?

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Syn Attack protection has been implemented in TCP/IP stack of Vista and later OS. Therefore these registry parameters are no longer relevant.

Please refer to this technet article for more information about Syn Attack protection.

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I don't see how this is in any way related to the question. – Gabe Jul 1 '15 at 5:29

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