Authentication using session.

Hello All, I would like a solution for the following We should accept a login and password in a login screen.These values should be Authenicated using a database.If it is a valid user then the username should be made a session variable.I would like to access different pages/screens using this session variable. In the logout screen I would like to destroy the session and the session variable so that to access any of the screens directly(by typing the URL) ,it checks for the session variable and since it is null should redirect to the login screen. I would also like to set a session timeout i.e for how long the session remains active before expiring. If possible please send a sample code. please reply, thanks in adv, kishor