What is DSL?

DSL delivers high-speed internet access to businesses and homes using standard telephone lines that run from a telephone company facility called a central office (CO). What transforms these copper lines into DSL lines is special equipment installed at the CO and DSL Customer Premise Equipment (CPE) at a business.

How does it work?

Normal telephone switches and standard telephone lines, while ideal voice communication, limit maximum allowable bandwidth for data transmission to 56 kbps. DSL uses these standard telephone lines but bypasses the normal telephone switches, enabling ultra-high data bandwidth transmission.

DSL works on a telephone line connected between DSL CPE and a Digital Subscriber Line Access Multi-plexer (DSLAM). The DSLAM concentrates multiple lines into an asynchronous transfer mode (ATM) or frame relay data network. Internet Service Providers (ISP's) connect to the ATM or frame relay cloud to create permanent virtual circuits. The resulting end-to-end circuit provides dedicated high-speed links to the Internet, corporate local area networks (LANs), or stand-alone computers.

Types of DSL

Promising speeds up to 200 times faster than other access methods, DSL comes in several versions, including ADSL,IDSL, and SDSL which transmit data at multiple symmetric or asymmetric speeds ranging from 32 kbps to 53 mbps. Speed decreases as distance from the Central Office (CO) increases.

Because SDSL and IDSL provide symmetrical access and compatibility with T1 and ISDN 2B1Q line encoding, they have been the fastest to be deployed by ISP's to business-class users. Residential users have seen the most rapid deployment of ADSL, because it is geared for downloading only and is not appropriate for hosting servers or providing other business services to the Internet.