| |
|
D |
| DAC |
 |
Dual Attached Concentrator; also digital-to-analog
converter, a device that is attached to and allows
access to both rings in an FDDI network. |
| DAS |
|
Dual-Attached
Station, a station with two connections to an FDDI
network, one to each logical ring. If one of the rings
should fail, the network automatically reconfigures
to continue normal operation. |
| DASD |
|
Direct Access Storage Device |
| Data
Link |
|
A
logical connection between two nodes on the same circuit. |
| Data
Link Layer |
|
Layer
of two of the seven-layer OSI reference model for communication
between computers on networks.
This layer defines protocols for data packets and how
they are transmitted to and from each network device.
It is a medium-independent, link-level communications
facility on top of the Physical layer, and is divided
into two sublayers: medium-access control (MAC) and
logical-link control (LLC). |
| DCE |
|
Data Communication-terminate Equipment |
| DCE |
|
Data Circuit terminating Equipment, a communications
device that can establish, maintain and terminate a
connection (for example, a modem). A DCE may also provide
signal conversion between the data terminal equipment
(DTE) and the common carrier's channel. Contrast DTE. |
| D
Channel |
|
Full
duplex 16 Kbps (basic rate) or 64 Kbps (primary rate)
ISDN channel. |
| DDCMP |
|
Digital
Data Communications Message Protocol |
| DDN |
|
Digital Data Network |
| DDNS |
|
Dynamic Domain Name Server |
| DDP |
|
Datagram Delivery Protocol |
| DDS |
|
Digital Data Service |
| DECNet |
|
Digital Equipment Corporation's proprietary network
architecture, a system for networking computers. IT
runs on point-to-point, X.25 and Ethernet networks. |
| Dedicated
line |
|
A
transmission circuit installed between two sites of
a private network and "open," or available,
at all times. |
| Default
route |
|
Entry
in a routing table that can re-direct any frames for
which the table has no definitive listing
for the next hop. |
| Delay |
|
Amount of time a call spends waiting to be processed. |
| Demodulation |
|
Opposite
of modulation; the process of retrieving data from
a modulated carrier wave. |
| |
|
|
| DES |
|
Data
Encryption Standard |
| Designated
router |
|
In
OSPF, each multiaccess network with at least two attached
routers has a designated router. The designated router
has special duties in the running of the protocol,
such as generating a link state advertisement for the
multiaccess network. This concept helps reduce the
number of adjacencies required on a multiaccess network,
which cuts routing protocol traffic and the size of
the topological database. |
| DHCP |
|
Dynamic Host Configuration Protocol |
| Dial
on demand |
|
When
a router detects the need to initiate a dial-up connection
to a remote network, it does so
automatically according to pre-defined parameters set
by the network manager. |
| Dialback |
|
A security feature that ensures people do not log into
modems that they shouldn't have access to. When a connection
is requested, the system checks the user name for validity,
then "dials back" the number associated with
that user name. |
| Dial
up |
|
A
type of communication that is established by a switched-circuit
connection using the telephone network. |
| DLC |
|
Data Link Control, the SNA layer responsible for transmission
of data between
two nodes over a physical link. |
| DLCI |
|
Data Link Connection Identifier, a value in frame relay that identifies
a logical connection. |
| DLE |
|
Data Link Escape (Character) |
| DMT |
|
Discrete Multi-Tone |
| DNA |
|
Distributed Network Architecture (DEC) |
| DNS |
|
Domain Name System or Domain Name Server |
| Domain
Name |
|
A
domain name is a text name appended to a host name
to form a unique
host name across internets. |
| Download |
|
The
transfer of a file or information from one network
node to another. Generally refers to transferring a
file from a "big" node, such as a computer,
to a "small" node, such as a terminal server
or printer |
| DPA |
|
Demand
Protocol Architecture |
| DPLL |
|
Digital Phase-Lock Loop |
| DQDB |
|
Distributed Queue Dual Bus, communication protocol
proposed by IEEE 802.6 committee for use in MANs. |
| DRAM |
|
Dynamic
Random Access Memory |
| DRI |
|
Distributed Recovery Intelligence, the ability to track
down a network problem and automatically isolate the
malfunctioning node. |
| Drop
cabl |
|
e
A cable that connects a network device such as a computer
to a physical medium such as an Ethernet
network. Drop cable is also called transceiver cable
because it runs from the network node to a transceiver
(a transmit/receiver) attached to the trunk cable.
Compare AUI cable. |
| DS |
|
Directory Service |
| DS-1 |
|
Digital (transmission) System 1, or Digital Signal
level 1; refers to the 1.44 Mbps (JS) or 2.108 Mbps
(Europe) digital signal carried on a T1 circuit. |
| DS-3 |
|
Digital
(transmission) System 3, or Digital Signal level 3;
refers to the 44 Mbps digital signal carried
on a T3 circuit. |
| DSAP |
|
Destination
Service Access Point |
| DSL |
|
Digital Subscriber Loop |
| DSP |
|
Digital Signal Processor |
| DSU
DP |
|
Data
Service Unit Data Port |
| DTE |
|
Data Terminal Equipment, end-user equipment, typically
a terminal or computer, that can function as the source
or destination point of communication on the network.
Contrast DCE. |
| Dual
homing |
|
Method
used to connect a DAS or DAC to a pair of concentrators
on an FDDI ring; used when server
or station availability is critical topology or traffic. |
| DV |
|
Distance Vector |
| Dynamic
routing |
|
Routing
that adjusts automatically to changes in network topology
or traffic. |
| |
|
|
