CCNA Data Center DCICN 640-911 Official Cert Guide

Digital Subscriber Line

Digital subscriber line (DSL) creates a relatively short (miles long, not tens of miles) high-speed link WAN between a telco customer and an ISP. To do so, it uses the same single-pair telephone line used for a typical home phone line. DSL, as a technology, does not try to replace leased lines, which run between any two sites, for potentially very long distances. DSL instead just provides a short physical link from a home to the telco’s network, allowing access to the Internet.

First, to get an idea about the cabling, think about typical home telephone service in the United States, before adding DSL service. Each home has one phone line that runs from a nearby telco CO to the home. As shown on the left side of Figure 3-15 ...