Glossary
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destination address
The address for the network devices that will receive
a packet.
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.
digital
A digital waveform is one where distinct ones and zeros provide the
data representation. See also: analog.
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.
discovery mode
Also known as dynamic configuration, this technique is
used by an AppleTalk interface to gain information from a working node
about an attached network. The information is subsequently used by the
interface for self-configuration.
distance-vector routing algorithm
In order to find the shortest path, this
group of routing algorithms repeats on the number of hops in a given route,
requiring each router to send its complete routing table with each update,
but only to its neighbors. Routing algorithms of this type tend to generate
loops, but they are fundamentally simpler than their link-state counterparts.
See also: link-state routing algorithm and SPF.
distribution layer
Middle layer of the Cisco three-layer hierarchical
model, which helps you design, install, and maintain Cisco hierarchical net-
works. The distribution layer is the point where access layer devices connect.
Routing is performed at this layer.
distribution lists
Access list used to filter incoming and outgoing route
table entries on a router.
DLCI
Data-Link Connection Identifier: Used to identify virtual circuits in a
Frame Relay network.
DNS
Domain Name System: Used to resolve host names to IP addresses.
DSAP
Destination Service Access Point: The service access point of a network
node, specified in the destination field of a packet. See also: SSAP and SAP.
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