>...It is common for firewall software to have its own "idletimeout" value.
...

As always, excellent experience-based info from Wanda.

You might also look into the possibility of tuning the TCP keepalive
value for the client operating system.  For example, AIX has a network
tuning option called tcp_keepintvl, which defaults to 75 seconds.
Note that the client programming might also set the SO_KEEPALIVE
socket option.

  Richard Sims