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Glossary
attenuation
In communication, weakening or loss
of signal energy, typically caused by distance.
AURP
AppleTalk Update-based Routing Protocol:
A technique for encapsulating AppleTalk traffic in the
header of a foreign protocol that allows the connec-
tion of at least two noncontiguous AppleTalk internet-
works through a foreign network (such as TCP/IP) to
create an AppleTalk WAN. The connection made is
called an AURP tunnel. By exchanging routing infor-
mation between exterior routers, the AURP maintains
routing tables for the complete AppleTalk WAN.
See
also: AURP tunnel.
AURP tunnel
A connection made in an AURP WAN
that acts as a single, virtual link between AppleTalk
internetworks separated physically by a foreign net-
work such as a TCP/IP network.
See also: AURP.
authority zone
A portion of the domain-name tree
associated with DNS for which one name server is the
authority.
See also: DNS.
auto duplex
A setting on Layer-1 and -2 devices
that sets the duplex of a switch or hub port automati-
cally.
automatic call reconnect
A function that enables
automatic call rerouting away from a failed trunk line.
autonomous confederation
A collection of self-
governed systems that depend more on their own net-
work accessibility and routing information than on
information received from other systems or groups.
autonomous switching
The ability of Cisco rout-
ers to process packets more quickly by using the cisco-
Bus to switch packets independently of the system
processor.
autonomous system (AS)
A group of networks
under mutual administration that share the same rout-
ing methodology. Autonomous systems are subdi-
vided by areas and must be assigned an individual 16-
bit number by the IANA. See also: area.
autoreconfiguration
A procedure executed by
nodes within the failure domain of a Token Ring,
wherein nodes automatically perform diagnostics, try-
ing to reconfigure the network around failed areas.
auxiliary port
The console port on the back of Cisco
routers that allows you to dial the router and make
console configuration settings.
B8ZS
Binary 8-Zero Substitution: A line-code type,
interpreted at the remote end of the connection, that
uses a special code substitution whenever eight consec-
utive zeros are transmitted over the link on T1 and E1
circuits. This technique assures ones density indepen-
dent of the data stream. Also known as bipolar 8-zero
substitution. Contrast with: AMI. See also: ones
density.
backbone
The basic portion of the network that
provides the primary path for traffic sent to and initi-
ated from other networks.
back end
A node or software program supplying
services to a front end. See also: server.
bandwidth
The gap between the highest and lowest
frequencies employed by network signals. More com-
monly, it refers to the rated throughput capacity of a
network protocol or medium.
baseband
A feature of a network technology that
uses only one carrier frequency, for example Ethernet.
Also named "narrowband." Compare with: broad-
band.
baseline
Baseline information includes historical
data about the network and routine utilization infor-
mation. This information can be used to determine
whether there were recent changes made to the net-
work that may contribute to the problem at hand.
Basic Management Setup
Used with Cisco routers
when in setup mode. Only provides enough manage-
ment and configuration to get the router working so
someone can telnet into the router and configure it.
baud
Synonymous with bits per second (bps), if each
signal element represents one bit. It is a unit of signal-
ing speed equivalent to the number of separate signal
elements transmitted per second.
B channel
Bearer channel: A full-duplex, 64Kbps
channel in ISDN that transmits user data. Compare
with: D channel, E channel, and H channel.
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