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The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  TCP/IP Key Applications and Application Protocols            9  TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)                 9  TCP/IP General File Transfer Protocols (FTP and TFTP)                      9  File Transfer Protocol (FTP)

File Transfer Protocol (FTP) 1 2 FTP Concepts and General Operation

The TCP/IP protocol suite as we know it today was developed in the late 1970s and early 1980s, with the watershed event probably the publishing of the version 4 standards of the Internet Protocol and Transmission Control Protocol in 1980. Modern TCP/IP was the result of experimentation and development work that had been underway since the 1960s. This work included both the design and implementation of the protocols that would implement internetworks, and also the creation of the first networking applications to allow users to perform different tasks.

The developers of early applications conceptually divided methods of network use into two categories: direct and indirect. Direct network applications let a user access a remote host and use it as if it were local, creating the illusion that the network doesn't even exist (or at least, minimizing the importance of distance). Indirect network use meant getting resources from a remote host and using them on the local system, then transferring them back. These two methods of use became the models for the first two formalized TCP/IP networking applications: Telnet for direct access and the File Transfer Protocol (FTP) for indirect network use.

The first FTP standard was RFC 114, published in April 1971, before TCP and IP even existed. This standard defined the basic commands of the protocol and the formal means by which devises communicate using it. At this time the predecessor of TCP (called simply the Network Control Protocol or NCP) was used for conveying network traffic. There was no Internet back then. Its precursor, the ARPAnet, was tiny, consisting of only a small group of development computers.

A number of subsequent RFCs refined the operation of this early version of FTP, with revisions published as RFC 172 in June 1971 and RFC 265 in November 1971. The first major revision was RFC 354, July 1972, which for the first time contained a description of the overall communication model used by modern TCP, and details on many of the current features of the protocol. In subsequent months many additional RFCs were published, defining features for FTP or raising issues with it. RFC 542, August 1973, the FTP specification looks remarkably similar to the one we use today, over three decades later, except that it was still defined to run over NCP.

After a number of subsequent RFCs to define and discuss changes, the formal standard for modern FTP was published in RFC 765, File Transfer Protocol Specification, June 1980. This was the first standard to define FTP operation over modern TCP/IP, and was created at around the same time as the other primary defining standards for TCP/IP.

RFC 959, File Transfer Protocol (FTP), was published in October 1985 and made some revisions to RFC 765, including the addition of several new commands, and is now the base specification for FTP. Since that time a number of other standards have been published that define extensions to FTP, better security measures and other features. (Some of these are discussed in the general operation section in the appropriate places.)

File Transfer Protocol (FTP) 1 2 FTP Concepts and General Operation