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Cable Internet access
In telecommunications, cable Internet access, shortened to cable Internet, is a form of broadband Internet access that uses the cable television infrastructure. Like digital subscriber line and fiber to the premises services, cable Internet access provides network edge connectivity (last mile access) from the Internet service provider to an end user. It is integrated into the cable television infrastructure analogously to DSL which uses the existing telephone network. Cable TV networks and telecommunications networks are the two predominant forms of residential Internet access. Recently, both have seen increased competition from fiber deployments, wireless, and mobile networks.
==Hardware and bit rates==
Broadband cable Internet access requires a cable modem at the customer's premises and a cable modem termination system at a cable operator facility, typically a cable television headend. The two are connected via coaxial cable or a Hybrid Fiber Coaxial (HFC) plant. While access networks are sometimes referred to as ''last-mile'' technologies, cable Internet systems can typically operate where the distance between the modem and the termination system is up to . If the HFC network is large, the cable modem termination system can be grouped into hubs for efficient management.
Downstream, the direction toward the user, bit rates can be as much as 400 Mbit/s for business connections, and 250 Mbit/s for residential service in some countries. Upstream traffic, originating at the user, ranges from 384 kbit/s to more than 20 Mbit/s. One downstream channel can handle hundreds of cable modems. As the system grows, the cable modem termination system (CMTS) can be upgraded with more downstream and upstream ports, and grouped into hubs CMTS for efficient management.
Most ''Data Over Cable Service Interface Specification'' (DOCSIS) cable modems restrict upload and download rates, with customizable limits. These limits are set in configuration files which are downloaded to the modem using the Trivial File Transfer Protocol, when the modem first establishes a connection to the provider's equipment. Some users have attempted to override the bandwidth cap and gain access to the full bandwidth of the system (often as much as 30 Mbit/s), by uploading their own configuration file to the cable modem - a process called uncapping.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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