Is there anyway that we can extend session timeout

[Katsuyuki Michishita]

Is somebody have information for how to configure session timeout. I use Tomcat3.1. I belive I have to do something with server,xml.. but do not know how and where to configure it. Phone devise dose not have cookie, we dicided to extend timeout. If you have some other ways other than URL rewriting, please let me know.   Katsyuki