Digital Subscriber Line

digital subscriber line

[¦dij·əd·əl səb′skrīb·ər ‚līn] (communications) A system that provides subscribers with continuous, uninterrupted connections to the Internet over existing telephone lines, offering a choice of speeds ranging from 32 kilobits per second to more than 50 megabits per second. Abbreviated DSL.

Digital Subscriber Line

(communications, protocol)(DSL, or Digital Subscriber Loop,xDSL - see below) A family of digital telecommunicationsprotocols designed to allow high speed data communicationover the existing copper telephone lines between end-usersand telephone companies.

When two conventional modems are connected through thetelephone system (PSTN), it treats the communication thesame as voice conversations. This has the advantage thatthere is no investment required from the telephone company(telco) but the disadvantage is that the bandwidth availablefor the communication is the same as that available for voiceconversations, usually 64 kb/s (DS0) at most. Thetwisted-pair copper cables into individual homes or officescan usually carry significantly more than 64 kb/s but thetelco needs to handle the signal as digital rather thananalog.

There are many implementation of the basic scheme, differingin the communication protocol used and providing varyingservice levels. The throughput of the communication can beanything from about 128 kb/s to over 8 Mb/s, the communicationcan be either symmetric or asymmetric (i.e. the availablebandwidth may or may not be the same upstream anddownstream). Equipment prices and service fees also varyconsiderably.

The first technology based on DSL was ISDN, although ISDN isnot often recognised as such nowadays. Since then a largenumber of other protocols have been developed, collectivelyreferred to as xDSL, including HDSL, SDSL, ADSL, andVDSL. As yet none of these have reached very widedeployment but wider deployment is expected for 1998-1999.

http://cyberventure.com/~cedpa/databus-issues/v38n1/xdsl.html.

2Wire DSL provider lookup.

["Data Cooks, But Will Vendors Get Burned?", "SupercommSpotlight On ADSL" & "Lucent Sells Paradine", Wilson & Carol,Inter@ctive Week Vol. 3 #13, p1 & 6, June 24 1996].

digital subscriber line

Digital Subscriber Line