There are many different ways your computer can connect to the Internet, ranging from dial-in connections to LANs (local area networks) to wireless connections to connections over cable TV wires, to DSL connections that use phone wires but connect you at high speed.
At one time, most people connected to the Internet via what is becoming an increasingly antiquated wayusing a dial-up modem. Typically, when you use your modem to connect to the Internet, you dial in to an Internet service provider (ISP), for example EarthLink or America Online. When you dial in to and connect to your ISP, you're in fact connecting to a modem attached to a more powerful computer called a server. ISPs typically have banks of hundreds or thousands of modems that accept dial-ins from subscribers trying to connect. Modems are controlled by your computer and communications software by a set of commands called the AT command set (also known as the Hayes command set, named after one of the original modem manufacturers, Hayes). It's a language that instructs the modem on what to do at various points during a communications session, such as opening up a line and sending out tones that the telephone system can understand.
But there's a major problem with connecting this wayit's too slow to be of much use. Websites use many graphics and multimedia features, and dial-up connections are so slow that the Web can seem unusable.
Much faster than dial-up are so-called broadband connections. A broadband connection is a generic name for a high-speed connection to the Internet, most notably cable modems and Digital Subscriber Line (DSL) connections. (For a look at how cable modems work, see "How Cable Modems Work," in Chapter 8, "How Internet/Television Connections Work.")
Several types of DSL technologies are available, but they all work on the same principles. They enable you to use your existing telephone lines to access the Internet at very high speeds.
DSL technologies require that DSL modems be used on each end of the phone line. In fact, the term DSL doesn't really refer to a phone line because an ordinary, existing copper phone line can be used for DSL. Instead, it refers to the DSL modems themselves. More confusing still, DSL modems aren't really traditional modems at all. They don't attach to a serial port, as do traditional modems. And they don't dial your telephone, as do traditional modems. Instead, they connect to your computer via a much higher-speed port, either an Ethernet port or a USB port, and they maintain an always-on connection over your phone line. So, you always have an Internet connection when they are plugged into your PC and turned on.
DSL technology has one drawback; it requires that your house (and DSL modem) be located within a certain distance from the telephone company office and its DSL modem. In cities, this should not be a major problem, but it could be a problem in rural areas. The exact distance required depends on the type and speed of DSL service you use. Higher speeds require that you be closer to the phone company office.