Telnet Session Drops after 5 minutes despite Settings

[jllidc]

All telnet sessions via the internet to a UNIX computer behind Wingate 5.23 running on a Windows XP Pro computer drop after 5 minutes of inactivity regardless of the session settings in Extended Networking or in the Services time limit screen. We have tried both a simple redirection from within ENS for port 23 and a combination of a Telnet Service pointing to the UNIX Server plus an allow in ENS for port 23. Telnet session to the UNIX Server from within the network (even from the computer running Wingate) do not exhibit this problem. What other setting could be causing this condition???