For some time we had a problem with IRC sessions running between screen(ed) irssi(s) on gallifrey and the irc_service timing out. This was not down to a networking problem, but to a feature of screen, where it “waits until the display restarts to accept the output”http://www.linuxmanpages.com/man1/screen.1.php#lbAH. This was happening when ssh timeouts occurred or when a user pressed ctrl+s and was rather annoying for other IRC users.

The solution, suggested by Patrick (not bung), was to add 'defnonblock on' to /etc/screenrc so that screen's default behaviour was to use an internal 1s timeout on the “display” (ssh in this case). Once this timeout is reached, screen will restart accepting output from its children and buffer it as it would if the screen were detached.