cable modem - Computer Definition
A modem designed to support high speed data communications over hybrid fiber/coax (HFC) CATV networks. Cable modems are positioned at the customers' premises and in a cable modem termination system (CMTS) at the service provider's headend. The initial Data over Cable Service Interface Specification (DOCSIS), released in 1997, standardized cable modems. Continuing research and development efforts directed at cable modems and related CATV network standards are largely the responsibility of CableLabs. See also CableLabs, CATV, CMTS, DOCSIS, HFC, and modem.
A technology for connecting users to the Internet through the TV-cable network and has the advantage of high-speed bandwidth 10–50 times as high (up to 5 megabits per second) as dial-up modems, which have 56 kilobits per second and use the telephone networks. TV-cable providers have to upgrade their network infrastructure to offer the service, whereas the dial-up modems need just a telephone line for connectivity. An alternative to the usage of cable-modems is DSL (Digital Subscription Line). DSL makes use of existing telephony lines and achieves approximately the same transmission speeds as cable modems.
See Also: DSL Modem; Network.
A device used to connect a single computer or a network to a cable company's service for Internet access. The same physical cable coming into the house or office also provides TV and voice (VoIP) service. Compared to analog dial-up, cable Internet dramatically increases the bandwidth between the user's computer and the Internet (see broadband). In order to prevent users with lower-cost cable access from hosting high-traffic Web servers, the upload speed is approximately five times slower than the download speed. Cable operators also routinely change IP addresses assigned to users to prevent Web hosting (see DDNS). Connect Via Ethernet or USB Cable modems typically connect to the computer or network router via an Ethernet port; however, some cable modems have a USB port for hookup to the computer but not the network. Cable Internet is a shared service, and the individual user's speed will vary depending on how many customers are sending or receiving data on that cable segment at the same time. For example, when kids come home from school in the afternoon, many neighborhood users experience slower speeds. See DOCSIS, cable Internet, Internet appliance and MSN TV.