Let's look at a scenario. Say I have the domain foo.bar.cc and I'm attempting to connect via ssh:
ssh foo.bar.cc
But, in this scenario, foo.bar.cc:22 requires VPN access. So, this DNS entry is not visible to me. Seeing how I'd never be able to connect, the connection eventually TO's (times out).
Before the TO, what is happening under-the-hood while I am attempting to access the server? What is the connection loop process like during the connection attempt, and what system calls are called, and why? Eventually sshd bails out: how does it determine this? Again, which system calls typically come into play, etc.