User's Manual

Prestige 645 ADSL Internet Access Router
D Glossary
computer equipment to digital transmission lines). The Channel Service Unit device connects
with the digital communication line and provides a termination for the digital signal. The
Data Service Unit device, sometimes called a digital service unit, is the hardware component
you need to transmit digital data over the hardware channel. The device converts signals
from bridges, routers, and multiplexors into the bipolar digital signals used by the digital
lines. Multiplexors mix voice signals and data on the same line.
DCE Data Communications Equipment is typically a modem or other type of communication
device. The DCE sits between the DTE (data terminal equipment) and a transmission circuit
such as a phone line.
DHCP Dynamic Host Configuration Protocol automatically assigns IP addresses to clients when
they log on. DHCP centralizes IP address management on central computers that run the
DHCP server program. DHCP leases addresses for a period of time which means that
addresses are made available to assign to other systems.
DNS Domain Name System links names to IP addresses. When you access Web sites on the
Internet, you can type the IP address of the site or the DNS name. When you type a domain
name in a Web browser, a query is sent to the primary DNS server defined in your Web
browser’s configuration dialog box. The DNS server converts the name you specified to an
IP address and returns this address to your system. From then on, the IP address is used in all
subsequent communications.
Domain
Name
The unique name that identifies an Internet site. Domain Names always have 2 or more parts,
separated by dots. The part on the left is the most specific, and the part on the right is the
most general.
DRAM Dynamic RAM that stores information in capacitors that must be refreshed periodically.
DSL Digital Subscriber Line technologies enhances the data capacity of the existing twisted-pair
wire that runs between the local telephone company switching offices and most homes and
offices. There are actually seven types of DSL service, ranging in speeds from 16 Kbits/sec
to 52 Mbits/sec. The services are either symmetrical (traffic flows at the same speed in both
directions), or asymmetrical (the downstream capacity is higher than the upstream capacity).
DSL connections are point-to-point dedicated circuits, meaning that they are always
connected. There is no dial-up. There is also no switching, which means that the line is a
direct connection into the carrier’s frame relay, ATM (Asynchronous Transfer Mode), or
Internet-connect system.
DSLAM A Digital Subscriber Line Access Multiplexer (DSLAM) is a network device, usually at a
telephone company central office, that receives signals from multiple customer Digital
Subscriber Line connections and puts the signals on a high-speed backbone line using
multiplexing techniques. Depending on the product, DSLAM multiplexers connect DSL
lines with some combination of asynchronous transfer mode ATM, frame relay, or IP