Why do CIFS mounts disconnect after an idle period?

Issue

• CIFS mounts disconnecting after an period of idleness, why?
• After period of low activity the SMB share "hangs" when accessed via a df or ls or any other commands.
• The hang resolves itself after several minutes.
• During the issue the Windows File Server does not report a CIFS session from the application. When the issue is resolved, a session is reported.
• The current workaround is to touch or create a file every two minutes or so to maintain the CIFS session.
• CIFS mounts show a DISCONNECTED state in debugging
• CIFS filesystems hang in disconnected state
• CIFS filesystems routinely go into a DISCONNECTED state. Most of the time when they become active again, the reconnect just fine. But sometimes they don't and all commands hang.
• CIFS Mount hangs on this server and is fine when it is unmounted and mounted again