Enabling ServerAliveInterval by default

[Damien Miller]

On Fri, 14 Dec 2007, Nadav Har'El wrote:

> It turns out that recent versions of OpenSSH clients already have an option
> that solves this problem - ServerAliveInterval.
> 
> Is there a reason why OpenSSH shouldn't enable ServerAliveInterval in the
> default client configuration, with some interval of, say, 120 seconds?

Activating protocol-level keepalives is not without costs:
{Client,Server}AliveInterval is not just a keepalive - it is also a
"make dead" that will kill a connection that has experienced packet loss
for AliveInterval*AliveCountMax, but which TCP would otherwise have been
able to recover from.

-d