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How the Internet Works

Now that you know what the Internet is, let's discuss how it works. First, let's assume that there's a computer somewhere out there in cyberspace that has some information you want. This computer is called a host. At a party, it's the function of the host to serve you (probably hors d'oeuvres). It's the same thing on the Internet: the host is there to serve you, in this case with the information you request (which is why hosts are sometimes called servers). If the "other" computer is the host, then who are you? Well, you are the user or client.

It would be a far simpler world if you, the client, could connect directly to the host over the Internet, but you can't. The host is connected to the Internet by special digital lines. Unless you work at a university or a large company that is connected to the Internet, you'll have to go through an intermediary to connect to the Internet and get information from the host—usually over a regular dial-up telephone line.

This intermediary is called an Internet Service Provider (ISP). Netcom, GTE, MCInet, AT&T, and UUNet are just a few of the better known, national ISPs. Your ISP might also be a local company, such as your phone company or even your electric company (particularly if you live in an area served by telephone or electric cooperatives). Your ISP could also be an on-line service such as America Online (AOL), CompuServe, or the Microsoft Network (MSN), which provides its own content in addition to what's available to everyone on the Net. For a more complete list of ISPs and on-line service providers, see Appendix A.

Like hosts, ISPs are always connected to the Internet, usually by special digital lines—lines to which you, as a personal or small-business user, probably don't have access. Instead, you'll have to use a line to which you do have access—usually your regular telephone line. There are special high-speed digital phone lines called Integrated Services Digital Network (ISDN) that can connect homes and businesses to the Net, and in some areas you may be able to connect by way of cable TV. However, most people use a regular phone line to connect to an ISP or on-line service to reach the Internet. "Mr. Sulu, Warp Factor 2"

Although most people will use a regular phone line to access the Internet, there are sportier ways to cruise the Net. In some areas, special digital lines, called ISDN lines, are available from the phone company. An ISDN line has a digital channel for voice and another digital channel for data—to give you both voice and data service. These channels can each carry 56 kilobits per second (kbs), and they can be combined to carry 128 kbs of data. An ISDN line costs several times as much as a regular analog phone line and requires a special interface device (regular modems used for standard phone lines won't work with ISDN lines). If you are interested in learning more about ISDN, call your phone company. Another option for higher speeds is to check with your cable TV company. Some are now offering high-speed Internet access through cable TV. The speed of this service varies, but can be between 50 and 300 times faster than a standard telephone line can handle. The costs are usually two or three times those charged by most dial-up ISPs, but anyone who has cruised the Internet at 1,5 megabits per second would want it—if they could afford it.

Although the telephone line is the most common way to connect to the Internet from home or most small businesses, the phone system was originally designed to carry the human voice—not the ones and zeros used by computers. For your computer to "talk" over a phone line, its ones and zeros must first be converted into sounds that the phone line can carry. This converter is called a modem. You'll have to have a modem on your end of the phone line, and of course your ISP will have one as well. So. to paraphrase that old song, our computer is connected to a modem, the ISP is connected to the Internet, and the Internet is connected to the host. And that's how it all works—more or less. 3y the way, this description may make the host computer—sound almost mythic or almost godlike. Some are truly large and powerful machines, but a host could also be an old 386 PC. The host-client relationship depends on who is serving whom, not on how large one computer is compared with another.

Date: 2015-12-18; view: 862

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