Virgin Media Super Hub and ssh timeouts

After upgrading to a new "shiny" Virgin Media Super Hub I started to get annoying ssh timeouts on idle connections.  After some Googling around I discovered that it suffers from TCP connection timeouts and some users have suggested that there isn't much memory in the device, so it can't save much session data.

Well, how does one workaround this issue?  Setting the keep alive probe down to 50 seconds and then resending it every 10 seconds seems to do the trick for me. I also tweaked the TCP settings so that if no ACK response is received for 5 consecutive times, the connection is marked as broken.  Here's the quick one-liner fix:
 

 sudo sysctl -w net.ipv4.tcp_keepalive_time=50 \
 net.ipv4.tcp_keepalive_intvl=10 \
 net.ipv4.tcp_keepalive_probes=5  

Of course, to make these settings persistent across reboots, add them to /etc/sysctl.conf

I'm not sure if these settings are "optimal", but they do the trick. You're mileage may vary.

Faster ssh X11 Forwarding

I use ssh daily to connect to my servers and laptops around my home office. Most of the time I'm using ssh to login and build software, so it's plain and simple command line activity. However, sometimes I need to run an X11 application on a remote machine, in which case I use X forwarding to display the remote X application on my laptop. However, this can be slow. Today I stumbled on the following incantation to speed up X11 forwarding over ssh:

ssh -c arcfour,blowfish-cbc -X -C user@remotehost

Thanks to Samat Jain for this info.

The choice of cipher is based on some performance benchmarks as noted in LaunchPad bug #54180