Default time out in digest authentication was one of the issues which struggled me for days.
I activated digest authentication in my web application hosted in IIS.I was getting continuous complaints from my client that the login window is popping up in every 5 minutes or even in lesser time and is a complete annoyance.
I tried various techniques to fix the issue.Increased the timeout of the session to 30 min.Disabled the fail-over time.But nothing worked in my favor.
Finally, After a lot of googling, I found that the timeout of digest authentication is by default set to 300 seconds if not explicitly mentioned in the registry.
It required change this default setting by having explicit entries in the registry.
Time out in Digest Authentication
For changing this default setting you need to edit the registry as below,
Got to registry edit then select HKEY_LOCAL_MACHINE
Go To SYSTEM > CurrentControlSet > Services > InetInfo
Click on Parameters and add a new DWORD value by right clicking in the right pane.
Set Name DigestContextCacheTTL and data type as REG_DWORD.
Double click on it and change the decimal value as your need in milliseconds.
If you want to further read on various similar global registry entries please see article Global Registry entries.