[Shiunbird]

ssh has X11 forwarding, which may be what was called "tunneling". This sets the DISPLAY environment variable to point to the ssh connection, so that typing "xterm" in a ssh session will open a window on your screen instead of on the remote computer. It is set up with a config file, see "man ssh_config".

I recall doing X over telnet for HP-UX. Is there anything I am missing?
On the local machine, add remote machine to xhosts.
On the remote machine, set DISPLAY to the local machine, then start an application.