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Connecting to the Internet

Until a few years ago, the prevalent method for connecting to the Internet was through POTS (plain old telephone services). These dial-up connections are still popular, but they are of limited capacity. Increasingly, Internet users are migrating to broadband services provided by the telephone and cable TV companies, as well as satellite and cellular companies.

Figure 1.3 shows an example of a machine that can connect users’ computers to the Internet. It is called by various names because it provides a multitude of services. First, it is a modem. A modem (from modulator/demodulator) provides the physical transmissions for the connection, such as voltages and frequencies. Second, it acts as a firewall; that is, it attempts to block unwelcome visitors from intruding into users’ computers and files. Third, it performs the functions of a router. For example, this machine can support several computers’ Internet sessions with both remote and local computers. It “routes” traffic back and forth by examining addresses in each packet. Fourth, it is a wireless (cellular) machine. The antenna and associated components in the machine send and receive traffic within a LAN—in this situation, our home or office.

Figure 1.3

Figure 1.3 A router and attached links

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