Cable Internet

Cable Internet

In telecommunications, cable Internet is a form of broadband Internet access that uses the cable television infrastructure. Like digital subscriber lines and fiber optic networks, cable Internet bridges the last kilometre or mile from the Internet provider to the subscriber. It is layered on top of the existing cable television network infrastructure; just as DSL uses the existing telephone network. Cable networks and telephone 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

Downstream, which goes toward the user, bit rates can be as much 50 megabits per second for business connections, and two to twenty megabits for consumers depending on the country. Upstream, which goes from the user rates range from 384Kbit/s to more than 20Mbit/s.

Broadband cable Internet access requires a cable modem at the customer premises and a CMTS (Cable Modem Termination System) at a cable operator facility (typically a headend or hub location). The two are connected via coaxial cable or, more commonly, a Hybrid Fiber Coaxial plant. While access networks are sometimes referred to as "last-mile" (or "first-mile") technologies, cable Internet systems can typically operate where the distance between the modem and CMTS is up to convert|100|mi|km.

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 uploaded to the modem using the Trivial File Transfer Protocol, when the modem first establishes a connection to the provider's equipment.Fact|date=April 2008


Like all residential broadband technologies, such as DSL, FTTX, Satellite Internet, or WiMAX, a population of users share a fixed channel capacity. Some share only their core network, while some including Cable Internet share also share the access network. Users in a particular neighborhood may share only a single coaxial cable line. So, the service can become sluggish if many people are using the service at the same time. This arrangement allows the network operator to take advantage of statistical multiplexing, a bandwidth sharing technique which is employed to distribute bandwidth fairly, in order to provide an adequate level of service at an acceptable price. However, the operator has to monitor usage patterns and scale the network appropriately, to ensure that customers receive adequate service even during peak-usage times. Some operators, such as Virgin Media in the UK, use a bandwidth cap, or other bandwidth throttling technique. In the case of Virgin Media, the user's download speed is limited during peak times, if they have downloaded a large amount of data that day.cite web | last =WHO | authorlink =PC Pro | title =Virgin Media cuts broadband speeds for the heavy downloaders |date=May 2007 | url =]

Many cable Internet providers offer Internet access without tying it to a cable television subscription. This is achieved by charging higher rates than if one bundles it with a cable television subscription. The extra cost is to cover the cable line access, much like phone companies charge a small line access fee for having DSL Internet service without a phone subscription (naked DSL). The cable line tap outside the residence is adjusted to prevent analog cable television channels from being transmitted through. The customer does not receive any cable television channels, including the basic channels. Internet Service Providers who resell high-speed Internet access from or through cable companies, such as Earthlink and AOL, are generally not subject to these higher rates. They can as well provide you Internet service without a cable television subscription. However, it is likely that the bill will be sent by the cable company on behalf of the Internet Service Provider.

One downstream channel can handle hundreds of cable modems. As the system grows, the CMTS can be upgraded with more downstream and upstream ports. If the HFC network is vast, the CMTS can be grouped into hubs for efficient management. Some usersFact|date=April 2008 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. Uncapping is almost always a violation of the Terms of Service agreement.Fact|date=February 2007

See also

* List of cable Internet providers
* Cable modem


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