User guide

Glossary
EN/LZT1083982 R4 81 (87)
2000-12-07
Default
A value or setting that a device or program automatically selects if you do not specify a
substitute.
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. DHCP also supports a mix of
static and dynamic IP addresses. Dynamic addressing simplifies network administration
because the software keeps track of IP addresses rather than requiring an administrator to
manage the task. This means that a new computer can be added to a network without the
hassle of manually assigning it a unique IP address. Many ISPs use dynamic IP
addressing for dial-up users.
DNS
Short for Domain Name System (or Service), an Internet service that translates domain
names into IP addresses. Because domain names are alphabetic, they are easier to
remember. The Internet however, is really based on IP addresses. Every time you use a
domain name, therefore, a DNS service must translate the name into the corresponding IP
address. The DNS system is, in fact, its own network. If one DNS server does not know
how to translate a particular domain name, it asks another one, and so on, until the correct
IP address is returned.
Downstream
The direction of a downstream signal is from the headend to the user's computer.
Driver
A program that controls a device. A driver acts like a translator between the device and
programs that use the device.
DSLAM
A Digital Subscriber Line Access Multiplexer is 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 are sent to
the DSLAM, where it passes through the ATM to the Internet, then back through the
DSLAM and ADSL modem before returning to the customer's PC.
DSL
xDSL refers collectively to all types of Digital Subscriber Lines, the two main categories
being ADSL and SDSL. DSL technologies use sophisticated modulation schemes to pack
data onto copper wires. They are sometimes referred to as last-mile technologies because
they are used only for connections from a telephone switching station to a home or office,