CCNA Cisco Certified Network Associate Study Guide - FTP Server

670 Glossary
DDP Datagram Delivery Protocol: Used in the AppleTalk suite of protocols
as a connectionless protocol that is responsible for sending datagrams
through an internetwork.
DDR dial-on-demand routing: A technique that allows a router to automatically
initiate and end a circuit-switched session per the requirements of
the sending station. By mimicking keepalives, the router fools the end station
into treating the session as active. DDR permits routing over ISDN or telephone
lines via a modem or external ISDN terminal adapter.
DE Discard Eligibility: Used in Frame Relay networks to tell a switch that
a frame can be discarded if the switch is too busy. The DE is a field in the
frame that is turned on by transmitting routers if the Committed Information
Rate (CIR) is oversubscribed or set to 0.
default route The static routing table entry used to direct frames whose
next hop is not spelled out in the dynamic routing table.
delay The time elapsed between a sender’s initiation of a transaction and
the first response they receive. Also, the time needed to move a packet from
its source to its destination over a path. See also: latency.
demarc The demarcation point between the customer premises equipment
(CPE) and the telco’s carrier equipment.
demodulation A series of steps that return a modulated signal to its original
form. When receiving, a modem demodulates an analog signal to its
original digital form (and, conversely, modulates the digital data it sends into
an analog signal). See also: modulation.
demultiplexing The process of converting a single multiplex signal, comprising
more than one input stream, back into separate output streams. See
also: multiplexing.
designated bridge In the process of forwarding a frame from a segment
to the route bridge, the bridge with the lowest path cost.
designated port Used with the Spanning-Tree Protocol (STP) to designate
forwarding ports. If there are multiple links to the same network, STP will
shut a port down to stop network loops.