FTP, the Protocol

FTP is short for File Transfer Protocol, and that's just what FTP is: the file transfer protocol in the Internet's TCP/IP protocol suite. You use FTP to copy (not really transfer) files from one computer to another. Both computers have to be connected to the Internet or another computer network using the Internet's TCP/IP communications protocols (like the ADN-ii), and your local computer and the remote computer that you're exchanging files with must "talk" FTP.

Larger machines like CMS and the ACCC UNIX workstations run an FTP demon to hold their end of an FTP conversation. No, that's not a "demon" as in a malicious elf; it's a service machine demon. A demon (a.k.a. daemon) is a service program that you start once and leave running; afterwards it performs its tasks on demand.

What is a "protocol suite"? A network communications protocol suite is a set of rules that collectively govern how information is exchanged on a network; each protocol in the suite defines a different component of the communications process.

Why bother with protocols? It's useful to think of network communications protocols as defining the "language" of the network, but they define more than just its words and grammar. They also define the physical features of the network's language -- the "sounds" it uses and the mechanics of how the sounds travel. This complete and thorough definition of network communications protocols allows the TCP/IP software written by different software manufacturers to work together with minimal difficulty.

FTP is an "application protocol" in the TCP/IP protocol suite; it defines how files are sent and received on a TCP/IP network.

TCP/IP's name comes from two other of its protocols; TCP (Transmission Control Protocol) and IP (Internet Protocol) are "lower level protocols" that define the organization of the "data packets" that carry data over the network and how they physically travel.

Applications protocols define tasks that people using a network are likely to do -- FTP file transfer, for example, and Telnet, the standard Internet terminal emulation protocol, and SMTP, Simple Mail Transfer Protocol. It's useful to know the names of the application protocols because their names (or initials) are often used as the name of the command used to execute that protocol. So when you transfer files using FTP, you'll use the ftp command or FTP software. (Not on Macs though; fetch is the most common Mac TCP/IP software.)

Want to learn more? Check out Quick Introduction to FTP.