Page 474

442

Glossary

attenuation

In communication, weakening or loss of signal energy, typi-

cally caused by distance.

AURP

AppleTalk Update-based Routing Protocol: A technique for encap-

sulating AppleTalk traffic in the header of a foreign protocol that allows the
connection of at least two noncontiguous AppleTalk internetworks through
a foreign network (such as TCP/IP) to create an AppleTalk WAN. The con-
nection made is called an AURP tunnel. By exchanging routing information
between exterior routers, the AURP maintains routing tables for the com-
plete 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 for-
eign network such as a TCP/IP network. See also: AURP.

authentication

The first component in the AAA model. Users are typically

authenticated via a username and password, which are used to uniquely
identify them.

authority zone

A portion of the domain-name tree associated with DNS

for which one name server is the authority. See also: DNS.

authorization

The act of permitting access to a resource based on authen-

tication information in the AAA model.

auto duplex

A setting on Layer 1 and 2 devices that sets the duplex of a

switch or hub port automatically.

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 network accessibility and routing information
than on information received from other systems or groups.

autonomous switching

The ability of Cisco routers to process packets

more quickly by using the ciscoBus to switch packets independently of the
system processor.

autonomous system (AS)

A group of networks under mutual adminis-

tration that share the same routing methodology. Autonomous systems are
subdivided by areas and must be assigned an individual 16-bit number by the
IANA. See also: area.

www.sybex.com