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.
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