Digital subscriber line (DSL) is a family of technologies that provides internet access by transmitting digital data over the wires of a local telephone network. It operates at higher frequencies than the voice band, allowing standard telephone calls and internet traffic to share the same physical cable simultaneously. Telecom providers heavily relied on DSL to bridge the gap between dial-up and fiber-optic networks.
The customer is complaining about slow speeds, but they're at the absolute distance limit for copper DSL.
Related terms
ADSL
Asymmetric Digital Subscriber Line provides broadband internet access over traditional copper telephone lines.
POTS
Plain old telephone service is the traditional analog voice transmission network using copper wires.
Local loop
The physical wiring connecting a customer premises to the nearest telephone exchange.
Last mile
The final segment of a telecommunications network that physically reaches the customer premises.