Connection time out from Database

Hi,

   Hi we have application running on Unix Server\(solaris10\), which establishes connection\(sessions\) with DATABASE\(oracle 10g\) which is on another server and firewal is there in between. After some time i am usually getting connection time out\(oarcle error 3114/3113\) in some of my processes which were idle for sometime.

we have set idle time UNLIMITED in our database.Is there any rules in firewal??
Also i am using cluster Ip for both application and for database. I mean there is a clustering for Application as well as database.

thnks and regards
Ajay Sahoo