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Intelecommunications,cable Internet access, shortened tocable Internet, is a form ofbroadband internet access which uses the same infrastructure ascable television. Likedigital subscriber line (DSL) andfiber to the premises, cable Internet access provides network edge connectivity (last mile access) from theInternet service provider to an end user. It is integrated into the cable television infrastructure analogously to DSL, which uses the existingtelephone network. Cable TV networks andtelecommunications networks are the two predominant forms of residential Internet access. Recently,[when?] both have seen increased competition fromfiber deployments,wireless, andsatellite internet access.
Broadband cable Internet access requires acable modem at the customer's premises and acable modem termination system (CMTS) at acable operator facility, typically acable television headend. The two are connected viacoaxial cable to ahybrid fibre-coaxial (HFC) network. Whileaccess networks are referred to aslast-mile technologies, cable Internet systems can typically operate where the distance between the modem and the termination system is up to 160 kilometres (99 mi). If the HFC network is large, the cable modem termination system can be grouped into hubs for efficient management. Several standards have been used for cable internet, but the most common is Data Over Cable Service Interface Specification (DOCSIS).[1]
A cable modem at the customer is connected via coaxial cable to an optical node, and thus into an HFC network. An optical node serves many modems as the modems are connected with coaxial cable to a coaxial cable "trunk" via distribution "taps" on the trunk, which then connects to the node, possibly using amplifiers along the trunk. The optical node converts the radio frequency (RF) signal in the coaxial cable trunk into light pulses to be sent through optical fibers in the HFC network. At the other end of the network, an optics platform or headend platform converts the light pulses into RF signals in coaxial cables again using transmitter and receiver modules,[2][3] and the cable modem termination system (CMTS) connects to these coaxial cables. An example of an optics platform is the Arris CH3000. There are two coaxial cables at the CMTS for each node: one for the downstream (download speed signal), and the other for the upstream (upload speed signal).[3] The CMTS then connects to the ISP's IP (Internet Protocol) network.[4]
Downstream, the direction toward the user, bit rates can be as high as 1Gbit/s.[5] Upstream traffic, originating at the user, ranges from 384kbit/s to more than 50 Mbit/s, although maximum effective range seems to be unknown. One downstream channel can handle hundreds of cable modems. As the system grows, the CMTS can be upgraded with more downstream and upstream ports, and grouped into hub CMTSs for efficient management.
Most 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 theTrivial File Transfer Protocol, when the modem first establishes a connection to the provider's equipment.[6] Some users[specify] have attempted to override the bandwidth cap and gain access to the full bandwidth of the system by uploading their own configuration file to the cable modem, a process calleduncapping.
In most residential broadband technologies, such as cable Internet,DSL,satellite internet, orwireless broadband, a population of users share the availablebandwidth. Some technologies share only theircore network, while some including cable internet andpassive optical network (PON) also share theaccess network. This arrangement allows the network operator to take advantage ofstatistical multiplexing, abandwidth 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. If the network operator does not provide enough bandwidth for a particular neighborhood, the connection would become saturated and speeds would drop if many people are using the service at the same time, or drop out completely. Operators have been known to use abandwidth cap, or otherbandwidth throttling technique; users' download speed is limited during peak times, if they have downloaded a large amount of data that day.[7]
