ssh-agent: How to use it properly?

[rz1a at nwgsm.ru]

Hello list,

 Again not sure if this is a right place to ask.

 I read the "Snail book" (SSH, The secure shell. The definitive guide.
 1st ed.) and try to figure out whether I need a copy of the ssh-agent
 running on a host through which I try connect further.

 The Snail book recommends running the ssh-agent on the remote host
 always if the TTY is allocated (i.e. I not just remote-execute a
 command there).

 My feel is that I need an agent only if I'm on /dev/con not on
 /dev/tty, i.e. logged-in locally.

 Please comment.
-- 
Best regards,
 Anthony