DSL and Its Types

To view other topics related to Computer. Click Here.

DSL

DSL stands for Digital Subscriber Line. It is a term used to describe a range of high-speed (broadband) communications services offered over the Public Switched Telephone Network (PSTN). The PSTN uses a pair of copper wires to connect your telephone service to the national telephony network. DSL technology enables high-speed communications over these same copper lines by making use of the frequencies not used by voice communications - the frequency spectrum (range) between 0kHz and 4kHz is used for your telephone service and 20kHz to 2.2MHz for your DSL (ADSL or ADSL2) service.

Types of DSL

ADSL (Asynchronous DSL)

ADSL (Asymmetric DSL) is a type of DSL where the upstream and downstream band widths are assigned different amounts of bandwidth. Typical configurations today are 2Mb downstream and 128Kb upstream.

Downstream refers to data which you are downloading across the network to your local systems. Upstream refers to data you are sending from your local systems across the network.

ADSL is the most common flavor of DSL.

HDSL (High bit-rate DSL)

HDSL (High bit-rate Digital Subscriber Line) is a variant of DSL which is not frequently implemented.

IDSL (ISDN over DSL)

IDSL (ISDN over DSL) is a 144Kb standard for DSL. IDSL is available where other forms of DSL, such as ADSL are not available.

IDSL is slow and relatively expensive, but it can sometimes be the best possible option.

RADSL (Rate-adaptive DSL)

RADSL (Rate Adaptive DSL) is an asymmetric DSL variant which can adjust the speed of the DSL connection depending on the distance from the Central Office (CO) and the quality of the connection.

SDSL (Symmetric DSL)

SDSL (Single line DSL) is a DSL variant where the upstream and downstream are both set to the same bandwidth.

SDSL typically operates at 1.5Mbps upstream and downstream.

SDSL is not nearly as common as ADSL.

VDSL (Very high bit-rate DSL)

VDSL (Very high bit-rate DSL) is an asymmetric version of DSL which operates at very high speeds.

VDSL operates at downstream speeds up to 55Mbps, but only at a distance of up to 1000 feet from the Central Office (CO).

At longer distances, VDSL transmission rates drop dramatically

DSL Lite

DSL Lite is an asymmetric variant of DSL which places the DSL splitter at the telco central office instead of in the customer premises.

G.SHDSL (Single-pair High-speed DSL)

G.SHDSL (Single-pair high-speed Digital Subscriber Line) is a variant of SDSL which is defined by ITU standard G.991.

G.SHDSL supports symmetric speeds from 192Kbps-2304Kbps on a single line pair and 384Kbps-4608Kbps over two pair.

Europeans refer to G.SHDSL as "SDSL", causing confusion with existing SDSL equipment.