The default connection timeout in IIS7 is 2 minutes. Click on your web site in IIS Mgr, click Advanced Settings, and expand Connection Limits. The Connection Timeout (Seconds) setting is what governs this. If IIS doesn’t receive activity on a connection for this duration then it will time the connection out. This is regardless of whether or not the connection was requested as a keep-alive. You will, of course, have to have keep-alives enabled for this to be a “keep-alive timeout”. Keep-alive is enabled by default in IIS.
You can also set it for the site in the applicationHost.config file using the <limits> and the connectionTimeout attribute.
<limits connectionTimeout="00:02:00" />
This will set the timeout value to 2 minutes.