Problems with TCP Chimney Offload (TOE)

Over the past few years, several of my servers have had odd intermittent network connection issues where user sessions would “Time-Out” immediately, even when their timeout was set to 30 seconds (or more).  After digging into the problem from multiple angles with my network guys, I stumbled onto an article that showed promise.  I am re-publishing this information here for quick reference and in case someone else has a need to investigate this as a possible issue/solution.  Please see this TechNet entry for more information.

The TCP Offload Engine (TOE) is intended to alleviate problems with high connections by offloading certain workloads onto hardware.  While this is a great idea in theory, in practice it can sometimes cause more problems than solutions.  It is fairly non-interruptive to try turning the TCP Chimney Offload off to test if this is a cause of a strange network connection issue you may be having, so it is worth a try.

First, check to see if you have TCP Chimney Offload enabled:

netsh int tcp show global

A list of global parameters will be returned, look for the one that says, “Chimney Offload State”.  If it is set to anything other than “disabled”, try setting the parameter to “disabled”.  You will need to be in an elevated command prompt to issue the following command:

netsh int tcp set global chimney=disabled

After issuing this command, observe your system to see if you have a change, either for better or worse, with regard to your network connections.  Again, please see this TechNet entry for more information.

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