Slow Ubuntu ssh login

I once experienced slow login to my Ubuntu box.  After ssh user@my-box, the password prompt delays several seconds.  This is very annoying.  Then I did,

1) append

UseDNS no

to /etc/ssh/sshd_config.  It's a local network, so I don't worry too much of certain security.

2) restart sshd

/etc/init_d/ssh restart

The problem is now solved.