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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

Uniform Resource Names (URNs) 1 File and Message Transfer Overview and Application Categories

The purpose of networking applications is to allow different types of information to be sent between networked devices. In the world of computers, information is most often arranged into discrete units called files. When those files are created specifically for the purpose of communication, they are often called messages. One of the most important groups of TCP/IP applications is the one that describes the basic mechanisms for moving these files between internetworked devices: file and message transfer applications.

In this section I describe in detail the most important applications used in TCP/IP for file and message transfer, and the protocols that implement them. I begin with an overview of these applications, and a description of the differences between them. I then include four subsections that describe the four most important file/message transfer application families: explicit file transfer, electronic mail, network news (Usenet) and hypertext (the World Wide Web). I also provide a brief look at the Gopher protocol, which has fallen out of favor but is worth a quick mention, especially due to its role as an historical precursor of the Web.

Uniform Resource Names (URNs) 1 File and Message Transfer Overview and Application Categories