Digital Subscriber Line

Introduction

Digital Subscriber Line or DSL is a family of technologies that provide digital data transmission over the wires of a local telephone network. Typically, the download speed of DSL ranges from 128 kilobits per second (kbit/s) to 24,000 kbit/s depending on DSL technology and service level implemented. Upload speed is lower than download speed for Asymmetric Digital Subscriber Line (ADSL) and equal to download speed for Symmetric Digital Subscriber Line (SDSL).

DSL technologies
The line length limitations from telephone exchange to subscriber are more restrictive for higher data transmission rates. Technologies such as VDSL provide very high speed, short-range links as a method of delivering "triple play" services (typically implemented in fiber to the curb network architectures). Example DSL technologies (sometimes called xDSL) include:

• High Data Rate Digital Subscriber Line (HDSL)

• Symmetric Digital Subscriber Line (SDSL), a standardised version of HDSL

• Asymmetric Digital Subscriber Line (ADSL), a version of DSL with a slower upload speed

• Rate-Adaptive Digital Subscriber Line (RADSL)

• Very-high-bit-rate Digital Subscriber Line (VDSL)

• Very-high-bit-rate Digital Subscriber Line 2 (VDSL2), an improved version of VDSL

• G. Symmetric High-speed Digital Subscriber Line (G.SHDSL), a standardised replacement for early proprietary SDSL by the International Telecommunication Union Telecommunication Standardization Sector

• Powerline Digital Subscriber Line (PDSL), a high speed powerline communications solution which modulates high speed data onto existing electricity distribution infrastructure