File Transfer Protocol
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J. Postel, J. Reynolds · 1985-10
Abstract
The File Transfer Protocol (FTP) defines a standard network protocol for transferring files between a client and server over a TCP/IP network. FTP uses a dual-connection model with a separate control channel (port 21) for commands and a data channel (port 20 or negotiated) for file transfers. It supports authentication, directory navigation, and both ASCII and binary transfer modes.
Why This RFC Matters
FTP was one of the earliest and most widely deployed file transfer mechanisms on the Internet, predating the World Wide Web. Its dual-channel architecture introduced the concept of separating control and data planes, an approach later adopted by protocols like SIP and RTSP. Although largely superseded by SFTP, FTPS, SCP, and HTTPS-based file transfer for security-sensitive use cases, FTP remains in use for legacy systems and anonymous public software distribution. RFC 959 superseded the original FTP specifications in RFC 765 and RFC 354.