Glossary of DSL Terms

What does "ADSL" mean? What does "upstream" refer to? What is NAT? Here you will find a list of many common terms used when referring to DSL service.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

- A -

ADSL (Asymmetric Digital Subscriber Line)

A term for one-way high speed transmission of signals over plain single twisted-pair wiring already run to residences. ADSL is provisioned with greater downstream than upstream rates (hence asymmetric). These rates are dependent on the distance of the user to the Central Office and can vary from as high as 6 Mbps to as low as 128 Kbps.

Adapter Card

An electronics board installed in a PC, which provides a network interface to and from that computer. Called a network interface card (NIC).

- B -

Bandwidth

The amount of information or data that can be sent over the Internet during a given period of time. Bandwidth is usually stated in bits per second (bps), kilobits per second (Kbps) or megabits per second (Mbps).

Bridge

A data communications device that connects two or more networks and forwards packets between them. Bridges read and filter packets and frames. Bridges do not require IP addresses and will pass broadcast traffic.

Broadband

A transmission medium or channel that has a wider bandwidth than one voice channel (with a carrier wave of a certain modulated frequency). It allows multiple services like voice, data, video, etc. to transit over the network.

- C -

CO (Central Office)

A circuit switch that terminates all the local access lines in a particular geographic serving area; a physical building where the local telephone company's switching equipment is found. DSL lines running from a subscriber's home connect at their serving Central Office.

CPE (Customer Premise Equipment)

Communications equipment that resides on the customer's premises. The CPE for DSL services is a DSL router or bridge.

- D -

Dedicated Line

A transmission circuit that is reserved by the provider for the full-time use of the subscriber.

Downstream

Refers to data flowing from the source, such as an Internet service provider (ISP), to the end user.

- E -

- F -

Filter

Filters that separate high frequency (ADSL) and low frequency telephone service (standard telephone service) signals at both the end user and central office end points.

FOC

Firm Order Confirmation

- G -

- H -

- I -

- J -

- K -

Kbps (Kilobits per second)

A measure of bandwidth capacity or transmission speed. The acronym stands for a thousand bits per second.

- L -

Local Loop

A generic term for the connection between the customer's premises (home, office, etc.) and the provider's serving Central Office.

- M -

Mbps (Million bits per second)

A measure of bandwidth capacity or transmission speed.

- N -

NIC (Network Interface Card)

The circuit board or other form of computer hardware that serves as the interface between a computer and the communications network.

- O -

- P -

- Q -

- R -

Router

The device that connects multiple computer networks by reading the address information on all data packets. The packet information is read, and the packets are then forwarded to the appropriate end station. Routers provide more functionality than bridges, which simply connect dissimilar networks.

- S -

SDSL (Symmetric Digital Subscriber Line)

Also called single line service, SDSL provides the same amount of bandwidth in both directions.

Splitter

See Filter.

- T -

- U -

Upstream

Refers to data flowing from the end user back to the Internet service provider.

- V -

- W -

- X -

xDSL

Generic acronym used to refer to any DSL service. The "x" can be replaced with a variety of letters, such as "a" for Asymmetric DSL and "s" for Symmetric DSL.

- Y -

- Z -

Z Blocker

See Filter

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