The Illustrated Network- P50: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 Dynamic Host Configuration Protocol 18 What You Will Learn In this chapter you will learn how IP addresses are assigned in modern IP networks. You will learn how the Dynamic Host Configuration Protocol DHCP and related protocols such as BOOTP combine to allow IP addresses to be assigned to devices dynamically instead of by hand. You will learn how users often struggle to find printers and servers whose IP addresses jump around and you will learn means of dealing with this issue. When TCP IP first became popular configuration was never trivial and often complex. Whereas many clients needed only a handful of parameters servers often required long lists of values. Operating systems had quickly outgrown single floppies and most hosts now needed hard drives just to boot themselves into existence. Routers were in a class by themselves especially when they connected more than two subnets and in the days of expensive memory and secondary storage hard drives routers usually needed to load not only their configuration from a special server but often their entire operating systems. A once-popular movement to diskless workstations hyped devices that put all of their value into hefty processors while dispensing with expensive and failure-prone hard drives altogether. Semiconductor memory was not only prohibitively expensive in adequate quantities but universally volatile meaning that the content did not carry over a power failure if shut down. How could routers and diskless workstations find the software and configuration information they needed when they were initially powered on RFC 951 addressed this situation by defining BOOTP the bootstrap protocol to find servers offering the software and configuration files routers and other devices needed on the subnet. The basic functions were extended in RFC 1542 which described relay agents that could be used to find BOOTP servers almost anywhere on a network. BOOTP did a good job at router software loading but the .
