Using a Windows 2008 R2 Server that runs IIS and that is part of a NLB cluster, the following error may occur in the System Log:

NLB cluster []: Timer starvation has been detected. This might be due to a denial of service attack or a very high server load. During this period, some connections might fail. If this problem recurs frequently, analyze the threat and take appropriate measures and/or add more servers to the cluster. An informational event log entry will be logged when the attack has subsided. Event 105, NLB

This Microsoft article shows that the TCP Chimney Offload does not work together with Network Load Balancing: http://support.microsoft.com/kb/951037

In Windows 2008 R2, TCP Chimney Offload is set to automatic by default. To disable it run the following command :

netsh int tcp set global chimney=disabled

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