So it appears that if I idle on a TCP connection a TCP RST takes place. At first I thought this was something in my software, then I assumed it was something in pppd. After a discussion on #openmoko I think this is something happening at the Vodafone NAT/router. It is easy to simulate by simply ssh’ng to a remote server and remaining idle. After several minutes (not timed yet) your ssh session will be disconnected but the ppp link remains active. I was able to exhibit the same behaviour on my Neo and my Eee PC connected with a different phone. I wonder if this is Vodafone specific or other networks are implementing this? It seems a bit annoying to have to periodically send traffic over a metered network to keep a TCP session alive! Will have to do some more research…