Glossary
EN/LZT 108 6429 R1
45 (47)
May 2003
Glossary
ADSL
Short for Asymmetric Digital Subscriber Line, a technology that allows more data to
be sent over existing copper telephone lines (POTS). ADSL support data rates of
fromm 1.5 to 9 Mbps when receiving data (known as the downstream rate) and from
16 to 640 Kbps when sending data (known as the upstream rate).
ATM
Short for Asynchronous Transfer Mode, a network technology based on transferring
data in cells or packets of a fixed size. The cell used with ATM is relatively small
compared to units used with older technologies. The small, constant cell size allows
ATM equipment to transmit video, audio, and computer data over the same network,
and assure that no single type of data hogs the line.
Device
Any machine or component that attaches to a computer. Examples of devices include
disk drives, printers, mice, and modems.
DHCP
Short for Dynamic Host Configuration Protocol, a protocol for assigning dynamic IP
addresses to devices on a network. With dynamic addressing, a device can have a
different IP address every time it connects to the network. In some systems, the
device's IP address can even change while it is still connected. Many ISP's use
dynamic IP addressing for dial-up users.
Downstream
The direction of a downstream signal is from the ISP/service provider to the user's
computer (downloading).
DSL
Short for Digital Subscriber Line, which is a data communications technology that
transmits information over the existing copper telephone lines (POTS). DSL takes
existing voice cables that connect customer premises (CPE) to the phone company's
central office (CO) and turns them into a high-speed digital linke. There are many
types of DSL and ADSL is one of them.
DSLAM
Short for Digital Subscriber Line Access Multiplexer, a mechanism at a phone
company's central location that links many customer DSL connections to a single
high-speed ATM line.
When the phone company receives a DSL signal, an ADSL modem with a POTS
splitter detects voice calls and data. Voice calls are sent to the PSTN, and data re sent
to the DSLAM, where it passes through the ATM to the Internet, then baack through
the DSLAM and ADSL modem before returning to the customer's PC.
Firmware
Software (programs or data) that has been written onto read-only memory (ROM).
Firmware is a combination of software and hardware.
G.dmt
A kind of asymmetric DSL technology, based on DMT modulation, that offers up to 8
megabits per second downstream bandwidth, 1.544 Megabits per second upstream
bandwidth. "G.dmt" is actually a nickname for the standard officially known as
ITU-T Recommendation G.992.1.
