File eXchange Protocol

File eXchange Protocol (FXP) and (FXSP) is a adjustment of abstracts alteration which uses FTP to alteration abstracts from one limited server to addition (inter-server) after acquisition this abstracts through the client's connection. Conventional FTP involves a individual server and a individual client; all abstracts manual is done amid these two. In the FXP session, a applicant maintains a accepted FTP affiliation to two servers, and can absolute either server to affix to the added to admit a abstracts transfer. The advantage of application FXP over FTP is axiomatic if a high-bandwidth server demands assets from addition high-bandwidth server, but alone a low-bandwidth client, such as a arrangement ambassador alive abroad from location, has the ascendancy to admission the assets on both servers.

Risk

Enabling FXP abutment can accomplish a server accessible to an accomplishment accepted as FTP bounce. As a aftereffect of this, FTP server software generally has FXP disabled by default.

FXP over SSL

Some FTP Servers such as glFTPd, cuftpd, RaidenFTPD, drftpd, and wzdftpd abutment agreement of a defended abstracts approach amid two servers application either of the FTP agreement addendum commands; CPSV or SSCN. This commonly works by the applicant arising CPSV in lieu of the PASV command—or by sending SSCN above-mentioned to PASV transfers—which instructs the server to actualize either a SSL or TLS connection. However, both methods—CPSV and SSCN—may be affected to man-in-the-middle attacks, if the two FTP servers do not verify anniversary other's SSL certificates. SSCN was aboriginal alien by RaidenFTPD and SmartFTP in 2003 and has been widelycitation bare adopted now.when?

Technical

Although FXP is generally advised a audible protocol, it is in actuality alone an addendum of the FTP agreement and is defined in RFC 959:

User-PI - Server A (Dest) User-PI - Server B (Source)

------------------ ------------------

C->A : Connect C->B : Connect

C->A : PASV

A->C : 227 Entering Passive Mode. A1,A2,A3,A4,a1,a2

C->B : PORT A1,A2,A3,A4,a1,a2

B->C : 200 Okay

C->A : STOR C->B : RETR

B->A : Connect to HOST-A, PORT-a

References

This "protocol" is connected as a subset of RFC 0959 by the IETF as:

RFC 959 File Transfer Protocol (FTP). J. Postel, J. Reynolds. Oct-1985. This obsoleted the above-mentioned RFC 765 and beforehand FTP RFCs aback to the aboriginal RFC 114.