Refers collectively to all types of
digital subscriber lines, the two main categories being
ADSL and
SDSL. Two other types of xDSL technologies are
High-data-rate DSL (HDSL) and
Very high DSL (VDSL).
DSL technologies use sophisticated modulation schemes to pack data onto copper wires. They are sometimes referred to as last-mile technologies because they are used only for connections from a telephone switching station to a home or office, not between switching stations.
xDSL is similar to ISDN inasmuch as both operate over existing copper telephone lines (POTS) and both require the short runs to a central telephone office (usually less than 20,000 feet). However, xDSL offers much higher speeds - up to 32 Mbps for upstream traffic, and from 32 Kbps to over 1 Mbps for downstream traffic.
Also see
Cable vs. DSL in Webopedia's "Did
You Know...?" section.
