Sometime you found that that ssh take more than 20 seconds before it ask for login.
The reason for the slow connections is that SSH is trying to use Kerberos, hangs
for about 10 seconds, then tries public key authentication, hangs for about
10 seconds, and then finally prompts for password. By setting the "GSSAPIAuthentication" option to false, either in /etc/ssh/ssh_config, or on the command line, everything works perfectly.