freebsd security - Jan 2006 - limiting concurrent scp/rsync sessions (over ssh)

Hello,

I have a file server that serves files over rsync and scp (all over ssh -
in fact, ssh is the only service listening)

I would like to limit each user to no more than X concurrent ssh sessions
(regardless of what they are doing (interactive login, scp, rsync, etc.))

I have read the documentation and man pages and it looks like I need to
set this in /etc/pam.d/sshd, but I don't know exactly what to put in place
where.

Can someone tell me the steps needed to do this ?

Thank you very much.