The Illustrated Network- P55:In this chapter, you will learn about the protocol stack used on the global public Internet and how these protocols have been evolving in today’s world. We’ll review some key basic defi nitions and see the network used to illustrate all of the examples in this book, as well as the packet content, the role that hosts and routers play on the network, and how graphic user and command line interfaces (GUI and CLI, respectively) both are used to interact with devices. | CHAPTER File Transfer Protocol 20 What You Will Learn In this chapter you will learn how FTP provides a method to move files around the Internet. We ll examine various aspects of FTP as a protocol and as an application showing how commands translate to protocol actions. You will learn about the differences between FTP s active and passive modes of operation. We ll discuss how security concerns affect the operation of FTP. The original Internet boasted three applications electronic mail remote computer access and remote file access. Over time not only have these three been joined by a host of others but the original applications have evolved to keep pace with expansion of the Internet and the environment of the modern world. As a simple example of this trend these applications have all moved beyond their simple commands typed in at a prompt to graphical front ends. These GUIs make the applications more accessible to novices but at the same time mask the details of protocol operation from users. Yet in most cases the original protocols are still there running behind the scenes as this look at the File Transfer Protocol FTP will show. FTP transfers a copy of a file. The original file is usually still present on the source host available for copying over and over as remote users request it. Copying files between two different computer systems has always been more difficult than it seems. Today most users are familiar with the differences between Windows file formats and those used by Apple which is why one can t usually take a floppy or CD from one and load it on the other. When other file systems are considered such as the varieties of Unix and older formats used by minicomputer and mainframe vendors many of which could not be copied between computer models from the same vendor it is no wonder the FTP is one of the most elaborate and robust applications in TCP IP although format conversion is much less of a concern than it used to be . 510 PART IV Application Level .
