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VPN-UPLINK - Encyclopedia: DSL
Digital Subscriber Line, or DSL, is a family of technologies that provide a digital connection over the copper wires of the local telephone network. Its origin dates back to 1988, when an engineer at Bell Labs devised a way to carry a digital signal over the unused frequency spectrum. This allows an ordinary phone line to provide digital communication without blocking access to voice services. Bell's management, however, were not enthusiastic about it, since it was not as profitable as renting out a second phone line for consumers who preferred to have access to the phone when dialing out. This changed in the late 1990s when cable companies started marketing broadband Internet access. Realising that most consumers would prefer broadband Internet to a second dial out line, Bell companies rushed out the DSL technology that they had been sitting on for the past decade as an attempt to slow broadband Internet access uptake, to win market share against the cable companies.

As of 2005, DSL provides the principal competition to cable modems for providing high speed Internet access to home consumers in Europe and North America; although on average, cable is much faster than DSL in most commercial situations. Older ADSL standards could deliver 8 Mbit/s over about one mile (2 km) of copper wire. The latest standard ADSL2+ can deliver over 20 Mbit/s per user over similar distances. However many copper lines are longer than one mile (2 km) reducing the amount of bandwidth that can be transmitted.

Example DSL technologies (sometimes called xDSL) include:

  • ADSL (Asymmetric Digital Subscriber Line)

  • HDSL (High Bit Rate Digital Subscriber Line)

  • RADSL (Rate Adaptive Digital Subscriber Line)

  • SDSL (Symmetric Digital Subscriber Line, a standardised version of HDSL)

  • VDSL (Very high bit-rate Digital Subscriber Line)

  • VDSL2 (Improved version of VDSL)

  • G.SHDSL (ITU-T Standardised replacement for early proprietary SDSL)

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Digital Subscriber Line".