This specification is an easy fix (or hack) to support distributed transfers.
Rewriting all transfer commands is another option but it places much more burden on ftp client authors wanting to implement it. Possibly preventing them from implementing it too soon.
I wrote another specification for this but another client author suggested it was too much work to get everyone to implement it and this would be simpler.
http://drftpd.mog.se/wiki.phtml?titl...nsfer_commands
It has IPv6 support, and better NAT support for PORT transfer mode.