Page 736

710

Glossary

Enhanced IGRP

Enhanced Interior Gateway Rout-

ing Protocol: An advanced routing protocol created by
Cisco, combining the advantages of link-state and dis-
tance-vector protocols. Enhanced IGRP has superior
convergence attributes, including high operating effi-
ciency. See also: IGP, OSPF, and RIP.

enterprise network

A privately owned and oper-

ated network that joins most major locations in a large
company or organization.

EPROM

Erasable Programmable Read-Only Mem-

ory: Programmed after their manufacture, these non-
volatile memory chips can be erased if necessary using
high-power light and reprogrammed. See also:
EEPROM, PROM.

error control

The control mechanism for verifica-

tion of contiguous and non-erroneous packets.

ESF

Extended Superframe: Made up of 24 frames

with 192 bits each, with the 193rd bit providing other
functions including timing. This is an enhanced ver-
sion of SF. See also: SF.

Ethernet

A baseband LAN specification created by

the Xerox Corporation and then improved through
joint efforts of Xerox, Digital Equipment Corpora-
tion, and Intel. Ethernet is similar to the IEEE 802.3
series standard and, using CSMA/CD, operates over
various types of cables at 10Mbps. Also called: DIX
(Digital/Intel/Xerox) Ethernet. See also: 10BaseT,
Fast Ethernet, and IEEE.

EtherTalk

A data-link product from Apple Com-

puter that permits AppleTalk networks to be con-
nected by Ethernet.

excess rate

In ATM networking, traffic exceeding a

connection's insured rate. The excess rate is the max-
imum rate less the insured rate. Depending on the
availability of network resources, excess traffic can be
discarded during congestion episodes. Compare with:
maximum rate.

expansion

The procedure of directing compressed

data through an algorithm, restoring information to
its original size.

expedited delivery

An option that can be specified

by one protocol layer, communicating either with
other layers or with the identical protocol layer in a
different network device, requiring that identified data
be processed faster.

explorer packet

An SNA packet transmitted by a

source Token Ring device to find the path through a
source-route-bridged network.

extended addressing

The technique used by

AppleTalk Phase 2 to assign multiple network
addresses to a single segment.

extended IP access list

IP access list that filters the

network by logical address, protocol field in the Net-
work layer header, and even the port field in the
Transport layer header.

extended IPX access list

IPX access list that filters

the network by logical IPX address, protocol field in
the Network layer header, and even the socket number
in the Transport layer header.

Extended Setup

Used in setup mode to configure

the router with more detail than Basic Setup mode.
Allows multiple-protocol support and interface con-
figuration.

extended ping

The enhanced version of PING that

allows user interaction to choose options when exe-
cuting the PING command. This resource requires
enable access to the router.

fact gathering

The process of using diagnostic tools

to collect information specific to the network and net-
work devices involved in a problem. Additional infor-
mation should include data that excludes other
possibilities and helps pinpoint the actual problem.

failure domain

The region in which a failure has

occurred in a Token Ring. When a station gains infor-
mation that a serious problem, such as a cable break,
has occurred with the network, it sends a beacon
frame that includes the station reporting the failure, its
NAUN, and everything between. This defines the fail-
ure domain. Beaconing then initiates the procedure
known as autoreconfiguration. See also: autoreconfig-
uration and beacon.

fallback

In ATM networks, this mechanism is used

for scouting a path if it isn't possible to locate one
using customary methods. The device relaxes require-
ments for certain characteristics, such as delay, in an
attempt to find a path that meets a certain set of the
most important requirements.

Fast Ethernet

Any Ethernet specification with a

speed of 100Mbps. Fast Ethernet is ten times faster
than 10BaseT, while retaining qualities like MAC

www.sybex.com