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1. Background

The White Rabbit put on his spectacles. "Where shall I begin, please your Majesty?" he asked.

"Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop."

It's important to know a little ARPA net history to understand the Domain Name System ( DNS ). DNS was developed to address particular problems on the ARPA net, and the Internet - a descendant of the ARPA net - remains its main user.

If you've been using the Internet for years, you can probably skip this chapter. If you haven't, we hope it'll give you enough background to understand what motivated the development of DNS .

1.1 A (Very) Brief History of the Internet

In the late 1960s, the U.S. Department of Defense's Advanced Research Projects Agency, ARPA (later DARPA ), began funding an experimental wide area computer network that connected important research organizations in the U.S., called the ARPAnet . The original goal of the ARPA net was to allow government contractors to share expensive or scarce computing resources. From the beginning, however, users of the ARPA net also used the network for collaboration. This collaboration ranged from sharing files and software and exchanging electronic mail - now commonplace - to joint development and research using shared remote computers.

The TCP / IP (Transmission Control Protocol/Internet Protocol) protocol suite was developed in the early 1980s, and quickly became the standard host-networking protocol on the ARPA net. The inclusion of the protocol suite in the University of California at Berkeley's popular BSD UNIX operating system was instrumental in democratizing internetworking. BSD UNIX was virtually free to universities. This meant that internetworking - and ARPA net connectivity - were suddenly available cheaply to many more organizations than were previously attached to the ARPA net. Many of the computers being connected to the ARPA net were being connected to local networks, too, and very shortly the other computers on the local networks were communicating via the ARPA net as well.

The network grew from a handful of hosts to a network of tens of thousands of hosts. The original ARPA net became the backbone of a confederation of local and regional networks based on TCP / IP , called the Internet .

In 1988, however, DARPA decided the experiment was over. The Department of Defense began dismantling the ARPA net. Another network, funded by the National Science Foundation and called the NSFNET , replaced the ARPA net as the backbone of the Internet.

Even more recently, in the spring of 1995, the Internet made a transition from using the publicly-funded NSFNET as a backbone to using multiple commercial backbones, run by long-distance carriers like MCI and Sprint, and long-time commercial internetworking players like PSI Net and UUNET .

Today, the Internet connects millions of hosts around the world. In fact, a significant proportion of the non- PC computers in the world are connected to the Internet. Some of the new commercial backbones can carry a volume of 622 megabits per second, over ten thousand times the bandwidth of the original ARPA net. Tens of millions of people use the network for communication and collaboration daily.

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Acknowledgments Book Index 1.2 On the Internet and internets