What is FXP? (site to site transfer)

FXP is supported by RaidenFTPD FTP server software but What is FXP? Some people said it's File eXchange Protocol, however it isn't really a protocol because.
1. there is no rfc defined for FXP.
2. FXP operations are just making use of existing FTP commands.

What can FXP do for You?

FXP allows You to COPY files from and to FTP servers by operating a FTP(FXP) client software without actually owning the files You are COPYING to and from the servers.

FXP supports in RaidenFTPD?

RaidenFTPD FTP server software is fully compatible with FXP operations, additionally, it allows You to turn on or off FXP operations in user account settings.

Not only the standard FXP oprations, RaidenFTPD also supports SSCN secured FXP, it allows You to FXP files in a secured way, please read the document here.