Using IPTABLES to simulate router dropping TCP connection

Hi All,

I'm trying to figure out a way to simulate the behaviour described here:
http://tldp.org/HOWTO/TCP-Keepalive-HOWTO/overview.html in section 2.4. Basically I want to be able to get the firewall on my local system to behave in a similar way. Why would I want to do this? Well I'm trying to get GNOME's Nautilus/gvfs to handle this scenario better as it does happen in real world scenarios, and I need a way to simulate this. Ideally it would be great if I could do this to any connection that is idle after 30 seconds.

Thanks for you time,
Tim