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Chapter 1: TCP/IP: Its Basis and BackgroundWith the runaway growth of the Internet in the last few years, the term TCP/IP has rocketed from obscurity to celebrity. It's become a "must-know" concept. This transport protocol, or network language, bears some similarities to NetBEUI, SNA, IPX/SPX, or X.25, with one very important difference: Most of these transport protocols are designed to work well in either a LAN environment or a WAN environment-not in both. By contrast, TCP/IP is highly effective in either one. As you'll see in this chapter, it's this multi-platform versatility that's one of its greatest strengths.
Here's what to expect from this chapter. In it, we'll accomplish several things:
- Explain TCP/IP and the Internet
- Introduce you to some important tools for locating information on the Internet
- Clarify the Internet's development through RFCs
- Explore the design goals of TCP/IP and discover its purpose
A Brief History of TCP/IPLet's start off by asking, "What is TCP/IP?" Transmission Control Protocol/Internet Protocol is a collection of software created over the years, much of its development subsidized by large infusions of government research money. Originally, TCP/IP was intended for the Department of Defense (DoD). Putting our tax dollars to good use, the DoD tends to buy a lot of equipment, and much of that equipment is incompatible with other equipment. For example, back in the late '70s when the work that conceived TCP/IP began, it was nearly impossible to get an IBM mainframe to talk to a Burroughs mainframe. That was because the two computers were designed with entirely different protocolssomething like Figure 1.1....
...To get some idea of what the DoD was facing, imagine picking up the phone in the U.S. and calling someone in Spain. You have a perfectly good hardware connection, as the Spanish phone system is compatible with the American phone system. But despite the hardware compatibility, you face a software incompatibility. The person on the other end of the phone is expecting a different protocol for communication; that is, they likely speak Spanish. It's not that one language is better or worse than the other-they're simply different, and so, fluent understanding between the English and Spanish speakers just isn't going to happen. Rather than force the Spanish speaker to learn English or the English speaker to learn Spanish, we could teach them both a new language like Esperanto, the "universal language" designed in 1888. If Esperanto were used in our telephone example, it's likely that neither speaker would use it at home, but they would when communicating with each other.
That was how TCP/IP began-as a simple, alternative communications language. As time went on, TCP/IP evolved into a mature, well-understood, robust set of protocols, with many sites adopting it as their main communication language.
ARPANET and the Birth of the InternetAlthough it was an important goal of the first defense intranetwork, the original DoD network wasn't intended to just link military sites. Much of the basic research in the U.S. was funded by an arm of the Defense Department called the Advanced Research Projects Agency, or ARPA. ARPA gave, and still gives, a lot of money to university researchers to study all kinds of things. ARPA thought it would be useful for these researchers to be able to communicate with one another, as well as with the Pentagon. Figures 1.2 and 1.3 illustrate networking both before and after ARPANET implementation....
...The new network, dubbed ARPANET, was designed and put in place by a private contractor called Bolt, Barenek and Newman. For the first time, it linked university professors both to themselves and to their military and civilian project leaders around the country. Because ARPANET was a network that linked separate, private university networks with distant military networks, it was a "network of networks."
ARPANET ran atop a protocol called the Network Control Protocol (NCP). NCP was later refined into two components, the Internet Protocol (IP) and the Transmission Control Protocol (TCP). The change from NCP to TCP/IP is the technical difference between ARPANET and the Internet. On January 1, 1983, ARPANET packet-switching devices stopped accepting NCP packets and only passed TCP/IP packets, so, in a sense, that date can be thought of as the "official" birthday of the Internet.
The primordial Internet goo known as ARPANET became the Internet after a few evolutionary steps. Probably the first major development occurred in 1974, when Vinton Cerf and Robert Kahn proposed the protocols that would become TCP and IP. (We say "probably" because the Internet didn't grow through a centralized effort, but rather through the largely disconnected efforts of several researchers, university professors, and graduate students, most of whom are still alive-and almost all of whom have a different perspective on what the "defining" aspects of Internet development were.) Over its more than 20-year history, the Internet and its predecessors have gone through several stages of growth and adjustment. Ten years ago, the Internet could only claim a few thousand users. At last count, five million computers and 100 million users were on the Internet. The Internet appears to double in size about every year. It can't do that indefinitely, so it's certainly a time of change for this huge network of networks. As with life forms, adaptability facilitates both change and survival, so it's easy to appreciate why TCP/IP's versatility is so important.
Internet growth is fueled not by an esoteric interest in seeing how large a network the world can build, but rather by just a few applications that require the Internet to run. One of the most important is Internet e-mail, followed closely by the World Wide Web, with File Transfer Protocol (FTP) bringing up the: rear. We'll discuss these more thoroughly later in this chapter.
Originally, Internet protocols were intended to support connections between mainframe-based networks-basically the only type that existed through most of the 1970s. Then came the 1980s which saw the growth of UNIX workstations, microcomputers, and minicomputers. Since the development of the Berkeley version of UNIX was funded mostly with government money, the government said, "Put the TCP/IP protocol suite in that thing." There was some resistance at first, but adding IP as a built-in part of Berkeley UNIX has helped both UNIX and...