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What is the internet and how does it work?

The Internet is a loose association of thousands of networks and millions of computers across the world that all work together to share information.

On the Net, the main lines carry the bulk of the traffic and are collectively known as the Internet backbone. The backbone is formed by the biggest networks in the system, owned by major Internet service providers.

In the United States, there are five points--located in San Francisco, San Jose (California), Chicago, New York (actually, Pennsauken, New Jersey), and Washington, D.C.--where the main lines intersect. These Network access points use high-speed networking equipment to connect the backbone to other networks (see Figure 1). These networks are owned by smaller regional and local ISPs, which in turn lease access to companies and individuals in the areas they serve.

How do these networks talk to one another?

The secret of the Net is a network protocol called TCP/IP--that is, a kind of coding system that lets computers electronically describe and interpret (send and receive) data over the network.

The term actually refers to two separate parts: the transmission control protocol (TCP) and the Internet protocol (IP). Together they form the language of the Internet. Every computer that hooks to the Internet understands these two protocols and uses them to send and receive data from the next computer along the network.

TCP breaks down every piece of data--such as an email message or a web page--into small chunks called packets. The IP protocol then figures out how the data is supposed to get from point A to point B by passing through a series of routers--sort of like regular mail passes through several post offices on its way to a remote location.

Each router examines the destination addresses of the packets it receives and then passes the packets on to another router as they make their way to their final destination. If your web page was broken into ten packets, then each of those may have traveled a completely separate route. But you'll never know it, because as the packets arrive, TCP takes over again, identifying each packet and checking to see if it's intact. Once it has received all the packets, TCP reassembles them into the original. (See Figure 2.)

The World Wide Web?

Although the terms Web and Internet are often used synonymously, they're actually not the same thing. The World Wide Web is a subset of the Internet--a collection of interlinked documents that work together using a specific Internet protocol called HTTP(Hypertext Transfer Protocol). HTTP is just one of many protocols that are used on the internet. Others include simple mail transfer protocol (SMTP), file transfer protocol (FTP), and Telnet protocol, just to name a few.

As you can see from the map above, the web is not equally well developed around the world. In 1991, many countries did not have computer networks that could access to the WWW or other internet protocols. By 1997, (hold your mouse over the map to see newer image) more countries have access, however, there are still places on the globe that do not have access to the web.

The defining feature of the Web is its ability to graphically connect pages to one another--as well as to audio, video, and image files--with hyperlinks. The Web is based on a set of rules for exchanging text, images, sound, video, and other multimedia files, which is collectively known as HTTP, or hypertext transfer protocol.

Web pages can be exchanged over the Net because browsers (which read the pages) and Web servers (such are orion, which store the pages) both understand HTTP. Web pages are written in HTML, or Hypertext Markup Language, which tells the Web browser how to display the page and its elements.

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