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Glossary
DE bit
The DE bit marks a frame as discard eligible on a Frame Relay net-
work. If a serial link is congested and the Frame Relay network has passed
the Committed Information Rate (CIR), then the DE bit will always be on.
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 orig-
inal 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, com-
prising more than one input stream, back into separate output streams. See
also: multiplexing.
denial-of-service attack
A denial-of-service attack, or DoS, blocks access
to a network resource by saturating the device with attacking data. Typi-
cally, this is targeted against the link (particularly lower bandwidth links) or
the server. DDoS attacks, or distributed denial-of-service attacks, make use
of multiple originating attacking resources to saturate a more capable
resource.
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.
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