...back-channels.

By turning off the PORT command, we can eliminate the back-channel problem for get requests, but it remains for dir.

...public.

Indeed, our expendable firewall machine provides the homepage for the footbag competition. A group alumnus is a footbag competition organizer, but his employer's firewall implementation does not enable him to make documents available to the public. He has a guest account on our expendable host through which he periodically refreshes the footbag web pages.

...machine.

Currently, all users in the internal mail server's /etc/passwd file must have entries in the expendable server's /etc/passwd file, though the external account shell is typically set to /bin/false. We are currently exploring ways to simplify this aspect of the setup.

...connect.

The TCP specification [17] (page 45) requires that the server be able to bind the client host as the foreign address on the local socket before initiating the passive TCP open. However, the BSD socket API does not provide this functionality, so the server must explicitly verify that the accepted connection actually originated from the expected client host.

Sandeep Singhal
Thu Nov 30 01:58:58 PST 1995