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Encyclopedia > File Transfer Protocol
The five-layer TCP/IP model
5. Application layer

DHCPDNSFTPGopherHTTPIMAP4IRCNNTPXMPPPOP3SIPSMTPSNMPSSHTELNETRPC • RTP • RTCPRTSPTLS/SSLSDPSOAPBGP • PPTP • L2TPGTPSTUNNTP • ... For FTP see the Internet File Transfer Protocol For file transfer protocols in general, see protocols for file transfer. ... FTP can refer to: File Transfer Protocol used on the Internet Federal Theater Project, a U.S. New Deal project Franc Tireurs Partisans (Partisan irregular riflemen), a Communist French Resistance movement during World War II Foiled twisted pair cabling FTP Software, the defunct network-software company of the 1990s For... The TCP/IP model or Internet reference model, sometimes called the DoD model (DoD, Department of Defense), ARPANET reference model, is a layered abstract description for communications and computer network protocol design. ... The application layer is the seventh level of the seven-layer OSI model. ... (DHCP) is a set of rules used by a communications device such as a computer, router or network adapter to allow the device to request and obtain an IP address from a server which has a list of addresses available for assignment. ... It has been suggested that this article be split into multiple articles. ... Gopher is a distributed document search and retrieval network protocol designed for the Internet. ... Hypertext Transfer Protocol (HTTP) is a communications protocol used to transfer or convey information on the World Wide Web. ... The Internet Message Access Protocol (commonly known as IMAP or IMAP4, and previously called Internet Mail Access Protocol, Interactive Mail Access Protocol (RFC 1064), and Interim Mail Access Protocol[1]) is an application layer Internet protocol operating on port 143 that allows a local client to access e-mail on... “IRC” redirects here. ... The Network News Transfer Protocol or NNTP is an Internet application protocol used primarily for reading and posting Usenet articles, as well as transferring news among news servers. ... Extensible Messaging and Presence Protocol, or XMPP, is an open, XML-based protocol for near real-time extensible messaging and presence events. ... In computing, local e-mail clients use the Post Office Protocol version 3 (POP3), an application-layer Internet standard protocol, to retrieve e-mail from a remote server over a TCP/IP connection. ... The Session Initiation Protocol (SIP) is an application-layer control (signaling) protocol for creating, modifying, and terminating sessions with one or more participants. ... Simple Mail Transfer Protocol (SMTP) is the de facto standard for e-mail transmissions across the Internet. ... The simple network management protocol (SNMP) forms part of the internet protocol suite as defined by the Internet Engineering Task Force (IETF). ... Secure Shell or SSH is a network protocol that allows data to be exchanged over a secure channel between two computers. ... This article or section includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... Remote procedure call (RPC) is a protocol that allows a computer program running on one computer to cause a subroutine on another computer to be executed without the programmer explicitly coding the details for this interaction. ... The Real-time Transport Protocol (or RTP) defines a standardized packet format for delivering audio and video over the Internet. ... RTP Control Protocol (RTCP) is a sister protocol of the Real-time Transport Protocol (RTP). ... The Real Time Streaming Protocol (RTSP), developed by the IETF and created in 1998 as RFC 2326, is a protocol for use in streaming media systems which allows a client to remotely control a streaming media server, issuing VCR-like commands such as play and pause, and allowing time-based... Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocols that provide secure communications on the Internet for such things as web browsing, e-mail, Internet faxing, instant messaging and other data transfers. ... Session Description Protocol (SDP), is a format for describing streaming media initialization parameters. ... This article is about the computer protocol. ... The Border Gateway Protocol (BGP) is the core routing protocol of the Internet. ... The Point-to-Point Tunneling Protocol (PPTP) is a method for implementing virtual private networks. ... In computer networking, the Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol used to support virtual private networks (VPNs). ... GPRS Tunneling Protocol (or GTP) is an IP based protocol used within GSM and UMTS networks. ... This article is about the Internet protocol. ... The Network Time Protocol (NTP) is a protocol for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. ...

4. Transport layer

TCPUDPDCCPSCTPRSVP • ... In computing and telecommunications, the transport layer is the second highest layer in the four and five layer TCP/IP reference models, where it responds to service requests from the application layer and issues service requests to the Internet layer. ... The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite, often simply referred to as TCP/IP. Using TCP, applications on networked hosts can create connections to one another, over which they can exchange streams of data using Stream Sockets. ... User Datagram Protocol (UDP) is one of the core protocols of the Internet protocol suite. ... The Datagram Congestion Control Protocol (DCCP) is a message-oriented transport layer protocol that is currently under development in the IETF. Applications that might make use of DCCP include those with timingconstraints on the delivery of data such that reliable in-order delivery, when combined with congestion control, is likely... In the field of computer networking, the IETF Signaling Transport (SIGTRAN) working group defined the Stream Control Transmission Protocol (SCTP) as a transport layer protocol in 2000. ... The Resource ReSerVation Protocol (RSVP), described in RFC 2205, is a transport layer protocol designed to reserve resources across a network for an integrated services Internet. ...

3. Network/Internet Layer

IP (IPv4IPv6) • IGMPICMPOSPFISISIPsecARPRARPRIP • ... The network layer is third layer out of seven in OSI model and it is the third layer out of five in TCP/IP model. ... The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ... Internet Protocol version 4 is the fourth iteration of the Internet Protocol (IP) and it is the first version of the protocol to be widely deployed. ... It has been suggested that IPv6 internet be merged into this article or section. ... The Internet Group Management Protocol is a communications protocol used to manage the membership of Internet Protocol multicast groups. ... The (ICMP) is one of the core protocols of the Internet protocol suite. ... The Open Shortest Path First (OSPF) protocol is a hierarchical interior gateway protocol (IGP) for routing in Internet Protocol, using a link-state in the individual areas that make up the hierarchy. ... Intermediate system to intermediate system (IS-IS), is an IGP routing protocol originally designed for CLNS as part of the OSI protocol stack and described in ISO 10589 . ... IPsec (IP security) is a suite of protocols for securing Internet Protocol (IP) communications by authenticating and/or encrypting each IP packet in a data stream. ... In computer networking, the Address Resolution Protocol (ARP) is the standard method for finding a hosts hardware address when only its network layer address is known. ... Reverse Address Resolution Protocol (RARP) is a network layer protocol used to obtain an IP address for a given hardware address (such as an Ethernet address). ... This article is chiefly about the Routing Information Protocol for IPv4 and IPv6. ...

2. Data link layer

802.11WiFiWiMAXATMDTMToken RingEthernetFDDIFrame RelayGPRS • EVDO • HSPA • HDLC • PPP • ... This article does not cite any references or sources. ... IEEE 802. ... Wi-Fi (or Wi-fi, WiFi, Wifi, wifi), short for Wireless Fidelity, is a set of standards for wireless local area networks (WLAN) currently based on the IEEE 802. ... WiMAX, the Worldwide Interoperability for Microwave Access, is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Dynamic synchronous Transfer Mode , or DTM for short, is a network protocol. ... Token-Ring local area network (LAN) technology was developed and promoted by IBM in the early 1980s and standardised as IEEE 802. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... In computer networking, fiber-distributed data interface (FDDI) is a standard for data transmission in a local area network that can extend in range up to 200 km (124 miles). ... In the context of computer networking, frame relay consists of an efficient data transmission technique used to send digital information quickly and cheaply in a relay of frames to one or many destinations from one or many end-points. ... General Packet Radio Service (GPRS) is a Mobile Data Service available to users of Global System for Mobile Communications (GSM) and IS-136 mobile phones. ... Evolution-Data Optimized or Evolution-Data only, abbreviated as EV-DO or EVDO and often EV, is one telecommunications standard for the wireless transmission of data through radio signals, typically for broadband Internet access. ... High-Speed Packet Access (HSPA) is a collection of mobile telephony protocols that extend and improve the performance of existing UMTS protocols. ... High-Level Data Link Control (HDLC) is a bit-oriented synchronous data link layer protocol developed by the International Organization for Standardization (ISO). ... In computing, the Point-to-Point Protocol, or PPP, is commonly used to establish a direct connection between two nodes. ...

1. Physical layer

Ethernet physical layerISDNModemsPLCSONET/SDHG.709OFDMOptical FiberCoaxial CableTwisted Pair • ... This article does not cite any references or sources. ... IEEE photograph of a diagram with the original terms for describing Ethernet drawn by Robert M. Metcalfe around 1976. ... // Integrated Services Digital Network (ISDN) is a circuit-switched telephone network system, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better quality and higher speeds than that is available with the PSTN system. ... A modem (from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. ... For other uses, see Power band. ... It has been suggested that this article be split into articles entitled Synchronous optical networking, SONET and Synchronous digital hierarchy. ... There are very few or no other articles that link to this one. ... Orthogonal frequency division modulation (OFDM, also called orthogonal frequency division multiplexing) is a technique for the modulation of digital information onto an analog carrier electromagnetic (e. ... Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length by confining as much light as possible in a propagating form. ... Coaxial Cable For the weapon, see coaxial weapon. ... 25 Pair Color Code Chart 10BASE-T UTP Cable Twisted pair cabling is a common form of wiring in which two conductors are wound around each other for the purposes of cancelling out electromagnetic interference known as crosstalk. ...

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FTP or File Transfer Protocol is used to transfer data from one computer to another over the Internet, or through a network.


Specifically, FTP is a commonly used protocol for exchanging files over any network that supports the TCP/IP protocol (such as the Internet or an intranet). There are two computers involved in an FTP transfer: a server and a client. The FTP server, running FTP server software, listens on the network for connection requests from other computers. The client computer, running FTP client software, initiates a connection to the server. Once connected, the client can do a number of file manipulation operations such as uploading files to the server, download files from the server, rename or delete files on the server and so on. Any software company or individual programmer is able to create FTP server or client software because the protocol is an open standard. Virtually every computer platform supports the FTP protocol. This allows any computer connected to a TCP/IP based network to manipulate files on another computer on that network regardless of which operating systems are involved (if the computers permit FTP access). There are many existing FTP client and server programs. FTP servers can be set up anywhere between game servers, voice servers, internet hosts, and other physical servers. The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet runs. ... An intranet is a private computer network that uses Internet protocols, network connectivity to securely share part of an organizations information or operations with its employees. ... The tower of a personal computer. ... This article does not cite any references or sources. ... In computing, a client is a system that accesses a (remote) service on another computer by some kind of network. ... The following tables compare general and technical information for a number of FTP clients, and related clients that use other file transfer protocols. ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ... In computing, an operating system (OS) is the system software responsible for the direct control and management of hardware and basic system operations. ...

Contents

Connection Methods

FTP runs exclusively over TCP. FTP servers by default listen on port 21 for incoming connections from FTP clients. A connection to this port from the FTP Client forms the control stream on which commands are passed to the FTP server from the FTP client and on occasion from the FTP server to the FTP client. For the actual file transfer to take place, a different connection is required which is called the data stream. Depending on the transfer mode, the process of setting up the data stream is different. The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite, often simply referred to as TCP/IP. Using TCP, applications on networked hosts can create connections to one another, over which they can exchange streams of data using Stream Sockets. ... TCP and UDP are transport protocols used for communication between computers. ...


In active mode, the FTP client opens a random port (> 1023), sends the FTP server the random port number on which it is listening over the control stream and waits for a connection from the FTP server. When the FTP server initiates the data connection to the FTP client it binds the source port to port 20 on the FTP server. An ephemeral port is a TCP or UDP port number that is automatically allocated from a predefined range by the TCP/IP stack software, typically to provide the port for the client end of a client-server communication. ...


In order to use active mode, the client sends a PORT command, with the IP and port as argument. The format for the IP and port is "h1,h2,h3,h4,p1,p2". Each field is a decimal representation of 8 bits of the host IP, followed by the chosen data port. For example, a client with an IP of 192.168.0.1, listening on port 1025 for the data connection will send the command “PORT 192,168,0,1,4,1”. The port fields should be interpreted as p1×256 + p2 = port, or, in this example, 4×256 + 1 = 1025.


In passive mode, the FTP server opens a random port (> 1023), sends the FTP client the server's IP address to connect to and the port on which it is listening (a 16 bit value broken into a high and low byte, like explained before) over the control stream and waits for a connection from the FTP client. In this case the FTP client binds the source port of the connection to a random port greater than 1023.


To use passive mode, the client sends the PASV command to which the server would reply with something similar to "227 Entering Passive Mode (127,0,0,1,78,52)". The syntax of the IP address and port are the same as for the argument to the PORT command.


In extended passive mode, the FTP server operates exactly the same as passive mode, however it only transmits the port number (not broken into high and low bytes) and the client is to assume that it connects to the same IP address that was originally connected to. Extended passive mode was added by RFC 2428 in September 1998.


While data is being transferred via the data stream, the control stream sits idle. This can cause problems with large data transfers through firewalls which time out sessions after lengthy periods of idleness. While the file may well be successfully transferred, the control session can be disconnected by the firewall, causing an error to be generated. Look up Data stream in Wiktionary, the free dictionary. ... Firewall separating zones of trust A firewall is a hardware or software device which is configured to permit, deny, or proxy data through a computer network which has different levels of trust. ...


The FTP protocol supports resuming of interrupted downloads using the REST command. The client passes the number of bytes it has already received as argument to the REST command and restarts the transfer. In some commandline clients for example, there is an often-ignored but valuable command, "reget" (meaning "get again") that will cause an interrupted "get" command to be continued, hopefully to completion, after a communications interruption.


Resuming uploads is not as easy. Although the FTP protocol supports the APPE command to append data to a file on the server, the client does not know the exact position at which a transfer got interrupted. It has to obtain the size of the file some other way, for example over a directory listing or using the SIZE command.


In ASCII mode (see below), resuming transfers can be troublesome if client and server use different end of line characters. In computing, EOL refers to the end-of-line character or signal. ...


The objectives of FTP, as outlined by its RFC, are: In internetworking and computer network engineering, Request for Comments (RFC) documents are a series of memoranda encompassing new research, innovations, and methodologies applicable to Internet technologies. ...

  1. To promote sharing of files (computer programs and/or data).
  2. To encourage indirect or implicit use of remote computers.
  3. To shield a user from variations in file storage systems among different hosts.
  4. To transfer data reliably, and efficiently.

A remote computer is a computer to which a user does not have physical access, but which he or she can access/manipulate via some kind of network from a local computer (one which the user does have physical access to). ... For other uses, see Data (disambiguation). ...

Criticisms of FTP

  1. Passwords and file contents are sent in clear text, which can be intercepted by eavesdroppers. There are protocol enhancements that circumvent this, for instance by using SSL or TLS.
  2. Multiple TCP/IP connections are used, one for the control connection, and one for each download, upload, or directory listing. Firewalls may need additional logic and or configuration changes to account for these connections.
  3. It is hard to filter active mode FTP traffic on the client side by using a firewall, since the client must open an arbitrary port in order to receive the connection. This problem is largely resolved by using passive mode FTP.
  4. It is possible to abuse the protocol's built-in proxy features to tell a server to send data to an arbitrary port of a third computer; see FXP.
  5. FTP is a high latency protocol due to the number of commands needed to initiate a transfer.
  6. No integrity check on the receiver side. If a transfer is interrupted, the receiver has no way to know if the received file is complete or not. Some servers support extensions to calculate for example a file's MD5 sum (e.g. using the SITE MD5 command) or CRC checksum, however even then the client has to make explicit use of them. In the absence of such extensions, integrity checks have to be managed externally.
  7. No date/timestamp attribute transfer. Uploaded files are given a new current timestamp, unlike other file transfer protocols such as SFTP, which allow attributes to be included. There is no way in the standard FTP protocol to set the time-last-modified (or time-created) datestamp that most modern filesystems preserve. There is a draft of a proposed extension that adds new commands for this, but as of yet, most of the popular FTP servers do not support it.

A password is a form of secret authentication data that is used to control access to a resource. ... In data communications, cleartext is the form of a message or data which is transferred or stored without cryptographic protection. ... To eavesdrop is to surreptitiously overhear a private conversation. ... Firewall separating zones of trust A firewall is a hardware or software device which is configured to permit, deny, or proxy data through a computer network which has different levels of trust. ... It has been suggested that this article or section be merged into Computer port (software). ... This article does not cite any references or sources. ... 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 clients connection. ... In cryptography, MD5 (Message-Digest algorithm 5) is a widely used cryptographic hash function with a 128-bit hash value. ... A cyclic redundancy check (CRC) is a type of function that takes as input a data stream of any length and produces as output a value of a certain fixed size. ... SFTP may refer to: Secure File Transfer Protocol, a network protocol designed by the IETF to provide secure file transfer and manipulation facilities over the secure shell (SSH) protocol. ...

Security problems

The original FTP specification is an inherently insecure method of transferring files because there is no method specified for transferring data in an encrypted fashion. This means that under most network configurations, user names, passwords, FTP commands and transferred files can be "sniffed" or viewed by anyone on the same network using a packet sniffer. This is a problem common to many Internet protocol specifications written prior to the creation of SSL such as HTTP, SMTP and Telnet. The common solution to this problem is to use either SFTP (SSH File Transfer Protocol), or FTPS (FTP over SSL), which adds SSL or TLS encryption to FTP as specified in RFC 4217. A packet sniffer (also known as a network analyzer or protocol analyzer or, for particular types of networks, an Ethernet sniffer or wireless sniffer) is computer software or computer hardware that can intercept and log traffic passing over a digital network or part of a network. ... Secure Sockets Layer (SSL) and Transport Layer Security (TLS), its successor, are cryptographic protocols which provide secure communications on the Internet. ... HTTP (for HyperText Transfer Protocol) is the primary method used to convey information on the World Wide Web. ... Simple Mail Transfer Protocol (SMTP) is the de facto standard for email transmission across the Internet. ... This article or section includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... In computing, the SSH File Transfer Protocol or SFTP is a network protocol that provides file transfer and manipulation functionality over any reliable data stream. ... FTPS is a name used to encompass a number of ways in which FTP software can perform secure file transfers. ... Secure Sockets Layer (SSL) and Transport Layer Security (TLS), its successor, are cryptographic protocols which provide secure communications on the Internet. ... Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocols that provide secure communications on the Internet for such things as web browsing, e-mail, Internet faxing, instant messaging and other data transfers. ... “Encrypt” redirects here. ...


FTP return codes

FTP server return codes indicate their status by the digits within them. A brief explanation of various digits' meanings are given below: Below is a list of all return codes that may be issued by an FTP server. ...

  • 1xx: Positive Preliminary reply. The action requested is being initiated but there will be another reply before it begins.
  • 2xx: Positive Completion reply. The action requested has been completed. The client may now issue a new command.
  • 3xx: Positive Intermediate reply. The command was successful, but a further command is required before the server can act upon the request.
  • 4xx: Transient Negative Completion reply. The command was not successful, but the client is free to try the command again as the failure is only temporary.
  • 5xx: Permanent Negative Completion reply. The command was not successful and the client should not attempt to repeat it again.
  • x0x: The failure was due to a syntax error.
  • x1x: This response is a reply to a request for information.
  • x2x: This response is a reply relating to connection information.
  • x3x: This response is a reply relating to accounting and authorization.
  • x4x: Unspecified as yet
  • x5x: These responses indicate the status of the Server file system vis-a-vis the requested transfer or other file system action

For other uses, see Syntax (disambiguation). ...

Anonymous FTP

Many sites that run FTP servers enable anonymous ftp. Under this arrangement, users do not need an account on the server. The user name for anonymous access is typically 'anonymous'. This account does not need a password. Although users are commonly asked to send their email addresses as their passwords for authentication, usually there is trivial or no verification, depending on the FTP server and its configuration. As modern FTP clients hide the login process from the user and usually don't know the user's email address, they supply dummy passwords, for example: The term FTP server can mean one of two things: a computer responsible for serving any kind of files, via the File Transfer Protocol to FTP clients which can also web browsers; a software program that implements the FTP protocol and is working as a daemon serving any kind of... Look up anonymous in Wiktionary, the free dictionary. ... A user in computing context is one who uses a computer system. ... E-mail, or email, is short for electronic mail and is a method of composing, sending, and receiving messages over electronic communication systems. ...

Internet Gopher has been suggested as an alternative to anonymous FTP, as well as Trivial File Transfer Protocol and File Service Protocol. Mozilla was the official, public, original name of Mozilla Application Suite by the Mozilla Foundation, nowadays called SeaMonkey suite. ... Konqueror is a file manager, web browser and file viewer, which was developed as part of the K Desktop Environment (KDE) by volunteers and runs on most Unix-like operating systems. ... Gopher is a distributed document search and retrieval network protocol designed for the Internet. ... Trivial File Transfer Protocol (TFTP) is a very simple file transfer protocol, with the functionality of a very basic form of FTP; it was first defined in 1980. ... File Service Protocol (or FTPs Sexy Partner) is a UDP-based variant of the File Transfer Protocol, designed for anonymous access over low quality networks. ...


Data format

While transferring data over the network, several data representations can be used. The two most common transfer modes are:

  1. ASCII mode
  2. Binary mode: In "Binary mode", the sending machine sends each file bit for bit and as such the recipient stores the bitstream as it receives it.

In "ASCII mode", any form of data that is not plain text will be corrupted. When a file is sent using an ASCII-type transfer, the individual letters, numbers, and characters are sent using their ASCII character codes. The receiving machine saves these in a text file in the appropriate format (for example, a Unix machine saves it in a Unix format, a Windows machine saves it in a Windows format). Hence if an ASCII transfer is used it can be assumed plain text is sent, which is stored by the receiving computer in its own format. Translating between text formats entails substituting the end of line and end of file characters used on the source platform with those on the destination platform, e.g. a Windows machine receiving a file from a Unix machine will replace the line feeds with carriage return-line feed pairs. Image:ASCII fullsvg There are 95 printable ASCII characters, numbered 32 to 126. ... A Hexdump of a JPEG image. ... This article is about the unit of information. ... Computer files can be divided into two broad categories: binary and text. ... In computing, EOL refers to the end-of-line character or signal. ... In computing, end-of-file, commonly abbreviated EOF, is a condition in a computer operating system where no more data can be read from a data source. ... In computing, line feed (LF) is a control character indicating that one line should be fed out. ... Originally, carriage return was the term for the key, lever, or mechanism on a typewriter that would cause the cylinder on which the paper was held (the carriage) to return to the left side of the paper after a line of text had been typed, and would often move it...


By default, most FTP clients use ASCII mode. Some clients try to determine the required transfer-mode by inspecting the file's name or contents.


The FTP specifications also list the following transfer modes:

  1. EBCDIC mode
  2. Local mode

In practice, these additional transfer modes are rarely used. They are however still used by some legacy mainframe systems. EBCDIC (Extended Binary Coded Decimal Interchange Code) is an 8-bit character encoding (code page) used on IBM mainframe operating systems, like z/OS, OS/390, VM and VSE, as well as IBM minicomputer operating systems like OS/400 and i5/OS. It is also employed on various non-IBM... It has been suggested that Legacy code be merged into this article or section. ... For other uses, see Mainframe. ...


FTP and web browsers

Most recent web browsers and file managers can connect to FTP servers, although they may lack the support for protocol extensions such as FTPS. This allows manipulation of remote files over FTP through an interface similar to that used for local files. This is done via an FTP URL, which takes the form ftp(s)://<ftpserveraddress>  (e.g., [1]). A password can optionally be given in the URL, e.g.:   ftp(s)://<login>:<password>@<ftpserveraddress>:<port>. Most web-browsers require the use of passive mode FTP, which not all FTP servers are capable of handling. Some browsers allow only the downloading of files, but offer no way to upload files to the server. An example of a Web browser (Konqueror) A Web browser is a software application that enables a user to display and interact with text, images, and other information typically located on a Web page at a website on the World Wide Web or a local area network. ... A screenshot of File Manager displaying a folder and the contents of the C drive. ... FTPS is a name used to encompass a number of ways in which FTP software can perform secure file transfers. ... A Uniform Resource Locator, URL (spelled out as an acronym, not pronounced as earl), or Web address, is a standardized address name layout for resources (such as documents or images) on the Internet (or elsewhere). ...


FTP and NAT devices

The representation of the IPs and ports in the PORT command and PASV reply poses another challenge for NAT devices in handling FTP. The NAT device must alter these values, so that they contain the IP of the NAT-ed client, and a port chosen by the NAT device for the data connection. The new IP and port will probably differ in length in their decimal representation from the original IP and port. This means that altering the values on the control connection by the NAT device must be done carefully, changing the TCP Sequence and Acknowledgment fields for all subsequent packets. In Computer Networking, the process of Network Address Translation (NAT, also known as Network Masquerading, Native Address Translation or IP Masquerading) involves re-writing the source and/or destination addresses of IP packets as they pass through a Router or firewall. ... The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite, often simply referred to as TCP/IP. Using TCP, applications on networked hosts can create connections to one another, over which they can exchange streams of data using Stream Sockets. ...


For example: A client with an IP of 192.168.0.1, starting an active mode transfer on port 1025, will send the string "PORT 192,168,0,1,4,1". A NAT device masquerading this client with an IP of 192.168.15.5, with a chosen port of 2000 for the data connection, will need to replace the above string with "PORT 192,168,15,5,7,208".


The new string is 23 characters long, compared to 20 characters in the original packet. The Acknowledgment field by the server to this packet will need to be decreased by 3 bytes by the NAT device for the client to correctly understand that the PORT command has arrived to the server. If the NAT device is not capable of correcting the Sequence and Acknowledgement fields, it will not be possible to use active mode FTP. Passive mode FTP will work in this case, because the information about the IP and port for the data connection is sent by the server, which doesn't need to be NATed. If NAT is performed on the server by the NAT device, then the exact opposite will happen. Active mode will work, but passive mode will fail.


It should be noted that many NAT devices perform this protocol inspection and modify the PORT command without being explicitly told to do so by the user. This can lead to several problems. First of all, there is no guarantee that the used protocol really is FTP, or it might use some extension not understood by the NAT device. One example would be an SSL secured FTP connection. Due to the encryption, the NAT device will be unable to modify the address. As result, active mode transfers will fail only if encryption is used, much to the confusion of the user.


The proper way to solve this is to tell the client which IP address and ports to use for active mode. Furthermore, the NAT device has to be configured to forward the selected range of ports to the client's machine.


FTP over SSH

FTP over SSH refers to the practice of tunneling a normal FTP session over an SSH connection. Secure Shell or SSH is a network protocol that allows data to be exchanged over a secure channel between two computers. ...


Because FTP uses multiple TCP connections (unusual for a TCP/IP protocol that is still in use), it is particularly difficult to tunnel over SSH. With many SSH clients, attempting to set up a tunnel for the control channel (the initial client-to-server connection on port 21) will only protect that channel; when data is transferred, the FTP software at either end will set up new TCP connections (data channels) which will bypass the SSH connection, and thus have no confidentiality, integrity protection, etc. The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite, often simply referred to as TCP/IP. Using TCP, applications on networked hosts can create connections to one another, over which they can exchange streams of data using Stream Sockets. ... Confidentiality has been defined by the International Organization for Standardization (ISO) as ensuring that information is accessible only to those authorized to have access and is one of the cornerstones of Information security. ... In telecommunication, the term data integrity has the following meanings: The condition that exists when data is unchanged from its source and has not been accidentally or maliciously modified, altered, or destroyed. ...


If the FTP client is configured to use passive mode and to connect to a SOCKS server interface that many SSH clients can present for tunneling, it is possible to run all the FTP channels over the SSH connection. SOCKS is an Internet protocol that allows client-server applications to transparently use the services of a network firewall. ...


Otherwise, it is necessary for the SSH client software to have specific knowledge of the FTP protocol, and monitor and rewrite FTP control channel messages and autonomously open new forwardings for FTP data channels. Version 3 of SSH Communications Security's software suite, and the GPL licensed FONC are two software packages that support this mode. SSH Communications Security is a Finnish company thats based in Helsinki and was founded by Tatu Ylönen in 1995. ... The GNU logo For other uses of GPL, see GPL (disambiguation). ...


FTP over SSH is sometimes referred to as secure FTP; this should not be confused with other methods of securing FTP, such as with SSL/TLS (FTPS). Other methods of transferring files using SSH that are not related to FTP include SFTP and SCP; in each of these, the entire conversation (credentials and data) is always protected by the SSH protocol. FTPS is a name used to encompass a number of ways in which FTP software can perform secure file transfers. ... In computing, the SSH File Transfer Protocol or SFTP is a network protocol that provides file transfer and manipulation functionality over any reliable data stream. ... Secure Copy or SCP is a means of securely transferring computer files between a local and a remote host or between two remote hosts, using the Secure Shell (SSH) protocol. ...


References

The protocol is standardised in RFC 0959 by the IETF as: Standardization, in the context related to technologies and industries, is the process of establishing a technical standard among competing entities in a market, where this will bring benefits without hurting competition. ... In internetworking and computer network engineering, Request for Comments (RFC) documents are a series of memoranda encompassing new research, innovations, and methodologies applicable to Internet technologies. ... The Internet Engineering Task Force (IETF) is charged with developing and promoting Internet standards. ...

  • RFC 959 File Transfer Protocol (FTP). J. Postel, J. Reynolds. Oct-1985. This obsoleted the preceding RFC 765 and earlier FTP RFCs back to the original RFC 114.
  • See also RFC 1579 Firewall-Friendly FTP.

See also

Archie was the first search engine ever invented, designed to index FTP archives, allowing people to find specific files. ... FTAM, an ISO 8571 standard, is an OSI Application layer protocol for File Transfer Access and Management. ... FTPFS (File Transfer Protocol FileSystem) is an obsoleted Linux kernel module that allows the user to mount a FTP server onto the local filesystem. ... This article is about the Internet protocol. ... Below is a list of all return codes that may be issued by an FTP server. ... Below is a list of FTP commands that may be sent to an FTP host, including all commands that are standardized in RFC 959 by the IETF. All commands below are RFC 959 based unless stated otherwise. ... A managed file transfer (MFT) application is a software product that provides organizations with a holistic solution to their file transfer needs. ... IrOBEX (or just OBEX) is a communications protocol that facilitates the exchange of binary objects between devices. ... In computing, a shared resource is a device or piece of information on a computer that is accessed from another computer via a network, as if it were a local resource. ... TCP Wrapper is a host-based Networking ACL system, used to filter network access to Internet Protocol servers on (Unix-like) operating systems such as Linux or BSD. It allows host or subnetwork IP addresses, names and/or ident query replies, to be used as tokens on which to filter...

FTP-like protocols

File Service Protocol (or FTPs Sexy Partner) is a UDP-based variant of the File Transfer Protocol, designed for anonymous access over low quality networks. ... FTPS is a name used to encompass a number of ways in which FTP software can perform secure file transfers. ... Gopher is a distributed document search and retrieval network protocol designed for the Internet. ... Secure Copy or SCP is a means of securely transferring computer files between a local and a remote host or between two remote hosts, using the Secure Shell (SSH) protocol. ... Secure Shell or SSH is a network protocol that allows data to be exchanged over a secure channel between two computers. ... The term SFTP has other meanings. ... In computing, the SSH File Transfer Protocol or SFTP is a network protocol that provides file transfer and manipulation functionality over any reliable data stream. ... Secure Shell or SSH is a network protocol that allows data to be exchanged over a secure channel between two computers. ... Trivial File Transfer Protocol (TFTP) is a very simple file transfer protocol, with the functionality of a very basic form of FTP; it was first defined in 1980. ... WebDAV was a working group of the Internet Engineering Task Force (IETF). ...

Software

The following tables compare general and technical information for a number of FTP clients, and related clients that use other file transfer protocols. ... Implementations of FTP servers (organized by the nature of the interface used to configure them) include: // ALFTP — proprietary, freeware, Windows only. ... iam here in the office . ...

External links

  • RFC 959 — File Transfer Protocol (FTP). J. Postel, J. Reynolds. Oct-1985.
  • RFC 1579 — Firewall-Friendly FTP
  • RFC 2228 — FTP Security Extensions
  • RFC 2428 — Extensions for IPv6, NAT, and Extended passive mode Sep-1998.
  • RFC 3659 — Extensions to FTP. P. Hethmon. March-2007.
  • FTP Reviewed — a review of the protocol notably from a security standpoint
  • Raw FTP command list
  • FTP Sequence Diagram (in PDF format)

The Portable Document Format (PDF) is the file format created by Adobe Systems in 1993 for document exchange. ...

Tutorial/overview


  Results from FactBites:
 
RFC 959 (rfc959) - File Transfer Protocol (15465 words)
For files sent with record or page structure a maximum record or page size (in logical bytes) might also be necessary; this is indicated by a decimal integer in a second argument field of RFC 959 October 1985 File Transfer Protocol the command.
RFC 959 October 1985 File Transfer Protocol In the first case, the server closes the data connection (if it is open) and responds with a 226 reply, indicating that the abort command was successfully processed.
FTP REPLIES Replies to File Transfer Protocol commands are devised to ensure the synchronization of requests and actions in the process of file transfer, and to guarantee that the user process always knows the state of the Server.
File Transfer Protocol - Wikipedia, the free encyclopedia (1640 words)
FTP or file transfer protocol is a commonly used protocol for exchanging files over any network that supports the TCP/IP protocol (such as the Internet or an intranet).
FTP is an extremely high latency protocol due to the number of commands needed to initiate a transfer.
Other methods of transferring files using SSH which are not related to FTP include SFTP or SCP; in both of these, the entire conversation (credentials and data) is always protected by the SSH protocol.
  More results at FactBites »

 
 

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