cable modem

A device used to provide fast Internet access over cable TV lines. The increased speed is made possible because coaxial cables (which transmit TV signals) have much greater bandwidth than standard telephone lines.

When it became available in late 1996, cable modem service had a few major problems. First, cable modems were unstandardized and incompatible; if you bought one from your cable company and then moved to another area, it probably wouldn’t work. Second, a rush of new subscribers bogged down the system and made it much slower than advertised. These problems were mostly resolved when cable companies accepted the DOCSIS standard and began splitting neighborhoods into smaller, more manageable network segments.

Of course, developing any sort of cable modem service was a challege. Old coaxial cables only supported 1-way TV transmissions, while Internet service absolutely requires a 2-way signal. Thus, before cable modem service could be offered in an area, the cable lines in the streets and on telephone poles had to be upgraded. The prohibitive cost of such an upgrade led many cable companies to offer "1-way" or "telco-return" service, in which the cable modem was used for downloads and a standard telephone modem was used for uploads.

Fortunately, telco-return service has become increasingly uncommon as upgrades have brought full 2-way service to most areas in the United States.

category 5

Also called Cat-5. A standard for network cable with four twisted pairs of copper wire terminated by RJ45 plugs. Maximum length is 100 meters (328ft). Due to its low cost and high performance, it is used in almost all LANs.

Cat-5e is the same kind of cable, and can be used wherever Cat-5 is needed. However, Cat-5e is specially manufactured to meet the stringent demands of 1000Base-T networking.


A computer that is served by another computer or device.

In the context of Internet connection sharing, client computers rely on a server computer or a router to provide ("serve") their Internet connection.


Cable Modem Termination System. A device at the cable company’s network center that connects the cable infrastructure to the Internet. Having more CMTS boxes creates more connections between these two networks, which (generally) increases performance. This is why a cable company often adds a CMTS when a neighborhood gains too many subscribers.


A cable that consists of a center wire surrounded by thick insulation and a wire mesh that shields from interference. Most frequently used for cable TV.


A situation where two computers on the same network have the same IP address.


A category 5 cable in which the internal wires have opposite arrangements at each end. Crossover cables can be used to connect a computer directly to another computer without the use of a hub, or to substitute for an uplink port.