1.1   What is the Internet?

In this book we use the public Internet, a specific computer network (and one which probably most readers have used), as our principle vehicle for discussing computer networking protocols. But what is the Internet? We would like to give you a one-sentence definition of the Internet, a definition that you can take home and share with your family and friends. Alas, the Internet is very complex, both in terms of its hardware and software components, as well as the services it provides.

A Nuts and Bolts Description

Instead of giving a one-sentence definition, let's try a more descriptive approach. There are a couple of ways to do this. One way is to describe the nuts and bolts of the Internet, that is, the basic hardware and software components that make up the Internet. Another way is to describe the Internet in terms of a networking infrastructure that provides services to distributed applications. Let's begin with the nuts-and-bolts description, using Figure 1.1-1 to illustrate our discussion.

Some pieces of the Internet
Figure 1.1-1: Some "pieces" of the Internet

The public Internet (i.e., the global network of networks discussed above) is the network that one typically refers to as the Internet. There are also many private networks, such as certain corporate and government networks, whose hosts are not accessible from (i.e., they can not exchange messages with) hosts outside of that private network. These private networks are often referred to as intranets, as they often use the same "internet technology" (e.g., the same types of host, routers, links, protocols, and standards) as the public Internet.

A Service Description

The discussion above has identified many of the pieces that make up the Internet. Let's now leave the nuts and bolts description and take a more abstract, service-oriented, view:

Our second description of the Internet – in terms of the services it provides to distributed applications – is a non-traditional, but important, one. Increasingly, advances in the "nuts and bolts" components of the Internet are being driven by the needs of new applications. So it's important to keep in mind that the Internet is an infrastructure in which new applications are being constantly invented and deployed.

We have given two descriptions of the Internet, one in terms of the hardware and software components that make up the Internet, the other in terms of the services it provides to distributed applications. But perhaps you are even more confused as to what the Internet is. What is packet switching, TCP/IP and connection-oriented service? What are routers? What kinds of communication links are present in the Internet? What is a distributed application? What does the Internet have to do with children's toys? If you feel a bit overwhelmed by all of this now, don't worry – the purpose of this book is to introduce you to both the nuts and bolts of the Internet, as well as the principles that govern how and why it works. We will explain these important terms and questions in the subsequent sections and chapters.

Some Good Hyperlinks

As every Internet researcher knows, some of the best and most accurate information about the Internet and its protocols is not in hard copy books, journals, or magazines. The best stuff about the Internet is in the Internet itself! Of course, there's really too much material to sift through, and sometimes the gems are few and far between. Below, we list a few generally excellent WWW sites for network- and Internet-related material. Throughout the book, we will also present links to relevant, high quality URL's that provide background, original (i.e., a citation), or advanced material related to the particular topic under study. Here is a set of key links that you will want to consult while you proceed through this book:

Internet Engineering Task Force (IETF): The IETF is an open international community concerned with the development and operation of the Internet and its architecture. The IETF was formally established by the Internet Architecture Board (IAB) in 1986. The IETF meets three times a year; much of its ongoing work is conducted via mailing lists by working groups. Typically, based upon previous IETF proceedings, working groups will convene at meetings of the IETF to discuss the work of the IETF working groups. The IETF is administered by the Internet Society, whose WWW site contains lots of high-quality, Internet-related material.

The World Wide Web Consortium (W3C): The W3C was founded in 1994 to develop common protocols for the evolution of the World Wide Web. This an outstanding site with fascinating information on emerging Web technologies, protocols and standards.

The Association for Computing Machinery (ACM) and the Institute of Electrical and Electronics Engineers (IEEE): These are the two main international professional societies that have technical conferences, magazines, and journals in the networking area. The ACM Special Interest Group in Data Communications (SIGCOMM), the IEEE Communications Society, and the IEEE Computer Society are the groups within these bodies whose efforts are most closely related to networking.

Connected: An Internet Encyclopedia: An attempt to take the Internet tradition of open, free protocol specifications, merge it with a 1990s Web presentation, and produce a readable and useful reference to the technical operation of the Internet. The site contains material on over 100 Internet topics.

Data communications tutorials from the online magazine Data Communications: One of the better magazines for data communications technology. The site includes many excellent tutorials.

Media History Project: You may be wondering how the Internet got started. Or you may wonder how electrical communications got started in the first place. And you may even wonder about what preceded electrical communications! Fortunately, the Web contains an abundance of excellent resources available on these subjects. This site promotes the study of media history from petroglyths to pixels. It covers the history of digital media, mass media, electrical media, print media, and even oral and scribal culture.


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Copyright Keith W. Ross and Jim Kurose 1996–2000