ASP.Net SQL Server Session management

Hi All,

I am experiencing an issue with my hosted application that is throwing Authentication Failed Exception. Here is a background of the issue:

Our application is hosted on two servers with Load balancer in the front. Obviously, we had to manage the session outside the servers and we chose SQL server to do this job.

Our timeout value is set to 60 minutes. But, if I leave my application in idle state for about 20 minutes and then click on a link or try to navigate to another page, it registers a 401 exception as below and returns to the login page. Please find the fiddler response below:

Please help me with some insight into this issue. Can there be scenarios where a session is cleared off the SQL server before the timeout interval? I checked in the table for the session and the timeout field there is displaying correct data

HTTP/1.1 401 Unauthorized
Cache-Control: private
Content-Type: application/json; charset=utf-8
Server: Microsoft-IIS/7.5
jsonerror: true
X-Powered-By: ASP.NET
Date: Thu, 19 Jun 2014 07:00:55 GMT
Content-Length: 105

{"Message":"Authentication failed.","StackTrace":null,"ExceptionType":"System.InvalidOperationException"}
Thank you.

Regards,

Krishna Chaduvula