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Analog, ISDN, and DSL modems all use conventional telephone lines for communication. By contrast, a cable modem uses coaxial (copper) cable that in theory can provide high bandwidth (e.g., 10 Mbps or better) and more reliable communication than telephone lines. The cost for Internet service through a cable modem is comparable to that for DSL, and so cable modems represent an attractive option for homes already subscribing to cable television. The main drawback to cable modem technology is that most cable companies employ a bus topology, in which all of the subscribers in a given region/neighborhood share the same bandwidth. The result is poor scaleability, since all of the users must compete for the same (limited) bandwidth. To illustrate, if you are the only person in your region/neighborhood with a cable modem, you can expect to get great performance (e.g., 10 Mbps). However, if just 1000 other people in your region are using the same service, your performance will drop to 10 Mbps / 1000 = 10 Kbps, and every additional person will cause further degradation. For this reason, most people today believe that DSL represents a more cost-effective way to access the Internet than a cable modem. (Although if everyone else acts on this belief and avoids cable modems, you may be the only person with a cable modem in your region and get great performance! But if your cable company continues to support a program with such low demand . . .) |
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If you encounter technical errors, contact rit@calvin.edu. |
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