Digital Subscriber Line (DSL) is a family of technologies that provides
digital data transmission over the wires of a local telephone network.
DSL originally stood for digital subscriber loop. In telecommunications
marketing, the term Digital Subscriber Line is widely understood to mean
Asymmetric Digital Subscriber Line (ADSL), the most commonly installed
technical varieties of DSL. DSL service is delivered simultaneously with
regular telephone on the same telephone line as it uses a higher
frequency band that is separated by filtering.

The data throughput of consumer DSL services typically ranges
from 384 KB/s to 20 MB/s in the direction to the customer,
depending on DSL technology, line conditions, and service-level implementation
Typically, the data throughput in the reverse direction, i.e. in the direction to the
service provider is lower, hence the designation of asymmetric service, but the
two are equal for the Symmetric Digital Subscriber Line (SDSL) service.