Digital Subscriber's Line


Tracy Pettigrue
Tracy Pettigrue
Sep 28, 2009
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DSL or xDSL, is a family of technologies that provide digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop, although in recent years, many[attribution needed] have adopted digital subscriber line as a more marketing-friendly term for the most popular version of consumer-ready DSL, ADSL.
Typically, the download speed of consumer DSL services ranges from 256 kilobits per second (kbit/s) to 24,000 kbit/s, depending on DSL technology, line conditions and service level implemented. Typically, upload speed is lower than download speed for Asymmetric Digital Subscriber Line (ADSL) and equal to download speed for Symmetric Digital Subscriber Line (SDSL).
The customer end of the connection consists of a DSL modem. This converts data from the digital signals used by computers into a voltage signal of a suitable frequency range which is then applied to the phone line.
In some DSL variations (for example, HDSL), the modem is directly connected to the computer via a serial interface, using protocols such as RS-232 or V.35. In other cases (particularly ADSL), it's common for the customer equipment to be integrated with higher level functionality, such as routing, firewalling, or other application-specific hardware and software. In this case, the entire equipment is usually referred to as a DSL router or DSL gateway.
Protocols and configurations
Many DSL technologies implement an asynchronous transfer mode ATM layer over the low-level bit stream layer to enable the adaptation of a number of different technologies over the same link.
DSL implementations may create bridged or routed networks.
DSL technologies:
Example DSL technologies (sometimes called xDSL) include:
  • High Data Rate Digital Subscriber Line (HDSL), also covered in this article
  • Symmetric Digital Subscriber Line (SDSL), a standardized version of HDSL
  • Asymmetric Digital Subscriber Line (ADSL), a version of DSL with a slower upload speed
  • ISDN Digital Subscriber Line (IDSL)
  • Rate-Adaptive Digital Subscriber Line (RADSL)
  • Very High Speed Digital Subscriber Line (VDSL)
  • Very High Speed Digital Subscriber Line 2 (VDSL2), an improved version of VDSL
  • Symmetric High-speed Digital Subscriber Line (G.SHDSL), a standardized replacement for early proprietary SDSL by the International Telecommunication Union Telecommunication Standardization Sector
  • Powerline Digital Subscriber Line (PDSL), a high speed powerline communications solution which modulates high speed data onto existing electricity distribution infrastructure
  • UDSL
  • Etherloop Ethernet Local Loop
Author's note: Digital_Subscribers_Line
Keywords: Digital_Subscribers_Line

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