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COMmunications, protocol> (DSL, or Digital Subscriber Loop, xDSL - see below) A family of
digital teleCOMmunications protocols designed to allow high speed data
COMmunication over the existing
copper telephone lines between end-users and telephone
COMpanies. When two conventional
modems are connected through the telephone system (
PSTN), it treats the
COMmunication the same as voice conversations. This has the advantage that there is no investment required from the telephone
COMpany (telco) but the disadvantage is that the
bandwidth available for the
COMmunication is the same as that available for voice conversations, usually 64 kb/s (
DS0) at most. The
twisted-pair copper cables into individual homes or offices can usually carry significantly more than 64 kb/s but the telco needs to handle the signal as digital rather than analog. There are many implementation of the basic scheme, differing in the
COMmunication
protocol used and providing varying
service levels. The throughput of the
COMmunication can be anything from about 128 kb/s to over 8 Mb/s, the
COMmunication can be either symmetric or asymmetric (i.e. the available bandwidth may or may not be the same
upstream and
downstream). Equipment prices and service fees also vary considerably. The first technology based on DSL was
ISDN, although ISDN is not often recognised as such nowadays. Since then a large number of other protocols have been developed, collectively referred to as xDSL, including
HDSL,
SDSL,
ADSL, and
VDSL. As yet none of these have reached very wide deployment but wider deployment is expected for 1998-1999.
.
2Wire DSL provider lookup . ["Data Cooks, But Will Vendors Get Burned?", "Super
COMm Spotlight On ADSL" & "Lucent Sells Paradine", Wilson & Carol, Inter@ctive Week Vol. 3 #13, p1 & 6, June 24 1996]. (2001-04-30)
In addition suitable contents:
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