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Glossary
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.
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.
designated router (DR)
An OSPF router that creates LSAs for a multi-
access network and is required to perform other special tasks in OSPF
operations. Multiaccess OSPF networks that maintain a minimum of two
attached routers identify one router that is chosen by the OSPF Hello protocol,
which makes possible a decrease in the number of adjacencies necessary on a
multiaccess network. This in turn reduces the quantity of routing protocol
traffic and the physical size of the database.
destination address
The address for the network devices that will receive
a packet.
DHCP
Dynamic Host Configuration Protocol: DHCP is a superset of the
BootP protocol. This means that it uses the same protocol structure as BootP,
but it has enhancements added. Both of these protocols use servers that
dynamically configure clients when requested. The two major enhancements
are address pools and lease times.
dial backup
Dial backup connections are typically used to provide redun-
dancy to Frame Relay connections. The backup link is activated over an
analog modem.
directed broadcast
A data frame or packet that is transmitted to a specific
group of nodes on a remote network segment. Directed broadcasts are
known by their broadcast address, which is a destination subnet address
with all the bits turned on.
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