27.1 Introduction

FTP is another commonly used application. It is the Internet standard for file transfer. We must be careful to differentiate between file transfer, which is what FTP provides, and file access, which is provided by applications such as NFS (Sun's Network File System, Chapter 29). The file transfer provided by FTP copies a complete file from one system to another system. To use FTP we need an account to login to on the server, or we need to use it with a server that allows anonymous FTP (which we show an example of in this chapter).

Like Telnet, FTP was designed from the start to work between different hosts , running different operating systems, using different file structures, and perhaps different character sets. Telnet, however, achieved heterogeneity by forcing both ends to deal with a single standard: the NVT using 7-bit ASCII. FTP handles all the differences between different systems using a different approach. FTP supports a limited number of file types (ASCII, binary, etc.) and file structures (byte stream or record oriented).

RFC 959 [Postel and Reynolds 1985] is the official specification for FTP. This RFC contains a history of the evolution of file transfer over the years .