File eXchange Protocol
From Free net encyclopedia
| Layer | Protocols |
|---|---|
| Application | DNS, TLS/SSL, TFTP, FTP, HTTP, IMAP, IRC, NNTP, POP3, SIP, SMTP, SNMP, SSH, TELNET, BitTorrent, RTP, rlogin, ENRP, … |
| Transport | TCP, UDP, DCCP, SCTP, IL, RUDP, … |
| Network | IP (IPv4, IPv6), ICMP, IGMP, ARP, RARP, … |
| Link | Ethernet, Wi-Fi, Token ring, PPP, SLIP, FDDI, ATM, DTM, Frame Relay, SMDS, … |
File eXchange Protocol (FXP) is a method of data transfer which uses the FTP protocol to transfer data from one remote server to another without routing this data through the client's connection. Conventional FTP involves a single server and a single client; all data transmission is done between these two. In an FXP session, a client maintains a standard FTP connection to two servers, and can direct either server to connect to the other to initiate a data transfer. The advantage of using FXP over FTP is evident when a high-bandwidth server demands resources from another high-bandwidth server, but only a low-bandwidth client, such as a network administrator working away from location, has the authority to access the resources on both servers.
Contents |
Risk
Enabling FXP support, however, can make a server vulnerable to an exploit known as FTP bounce. FXP is also frequently used for warez trafficking. As a result of this FTP server software often disables FXP by default.
FXP over SSL
Some advanced FTP Servers such as glFTPd and RaidenFTPd support negotiation of a secure data channel between two servers using either the (File Transfer Protocol)FTP protocol extension commands CPSV or SSPN. This normally works by the client replacing the PASV command with one of these commands which instruct the server to create either a SSL or TLS connection.
Technical
Although FXP may be classed as its own "protocol", it is in fact merely an extension of FTP and is specified in RFC 959:
User-PI - Server A User-PI - Server B
------------------ ------------------
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 standardized as a subset of RFC 0959 by the IETF as:
- RFC 0959 File Transfer Protocol (FTP). J. Postel, J. Reynolds. Oct-1985. (Format: TXT, 147316 bytes at http://www.ietf.org/rfc/rfc959.txt ) This obsoleted the preceding RFC 765 and earlier FTP RFCs back to the original RFC 114.
See also
- File Transfer Protocol (FTP)
- Trivial File Transfer Protocol (TFTP)
- SSH file transfer protocol (sftp), a protocol running over SSH
- Secure FTP (SFTP), FTP run over SSL
- Simple File Transfer Protocol (SFTP), the historic protocol RFC 913
- FTP client
- List of FTP clients
- FTP server
- List of FTP serversde:File Exchange Protocol