http://www.rfc-editor.org/rfc/rfc1579.txt
RFC 1579: Firewall-Friendly FTP, S. Bellovin1994-02-01T23:00:00-00:00This memo describes a suggested change to the behavior of FTP client programs. This document provides information for the Internet community. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind.