This article applies to:

• WebMarshal
• Microsoft Windows Server or Workstation

Symptoms:

• One or more sites time out when using the WebMarshal proxy, but they load fast when not using WebMarshal
• WebMarshal is installed on Windows Server 2008 or above (or related Workstation OS)
• The behavior is not changed by adding the sites to the bypass list, disabling all connection rules, or disabling the cache
• WebMarshal on Windows 2003 server in the same LAN works well
• In a packet capture it appears that the sites refuse or reset the connection

Causes:

• This issue could be caused by the "TCP auto tuning" feature of networking in recent Windows operating systems.
• Auto-tuning is known to cause communication issues when used with devices that do not support auto-tuning. The Microsoft article (referenced below) states in part:
  
  "When the Receive Window Auto-Tuning feature is enabled for HTTP traffic, older routers, older firewalls, and older operating systems that are incompatible with the Receive Window Auto-Tuning feature may sometimes cause slow data transfer or a loss of connectivity."

Resolution:

To disable TCP Auto-tuning:

On the WebMarshal node server(s), open an elevated command prompt and run the command:

netsh int tcp set global autotuninglevel=disabled

Notes:

For more details of the auto-tuning functionality, see the following Microsoft Knowledge Base article:   http://support.microsoft.com/kb/947239