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Glossary

ELAP

EtherTalk Link Access Protocol: In an EtherTalk network, the link-

access protocol constructed above the standard Ethernet Data Link layer.

encapsulation

The technique used by layered protocols in which a layer

adds header information to the Protocol Data Unit (PDU) from the layer
above. As an example, in Internet terminology, a packet would contain a
header from the Physical layer, followed by a header from the Network layer
(IP), followed by a header from the Transport layer (TCP), followed by the
application protocol data.

encryption

The conversion of information into a scrambled form that

effectively disguises it to prevent unauthorized access. Every encryption
scheme uses some well-defined algorithm, which is reversed at the receiving
end by an opposite algorithm in a process known as decryption.

Endpoints

See: BGP neighbors.

end-to-end VLANs

VLANs that span the switch-fabric from end to end;

all switches in end-to-end VLANs understand about all configured VLANs.
End-to-end VLANs are configured to allow membership based on function,
project, department, and so on.

Enhanced IGRP

Enhanced Interior Gateway Routing Protocol: An

advanced routing protocol created by Cisco, combining the advantages of
link-state and distance-vector protocols. Enhanced IGRP has superior con-
vergence attributes, including high operating efficiency. See also: IGP,
OSPF, and RIP.

enterprise network

A privately owned and operated network that joins

most major locations in a large company or organization.

EPROM

erasable programmable read-only memory: Programmed after

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

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
version of SF. See also: SF.

Ethernet

A baseband LAN specification created by the Xerox Corpora-

tion and then improved through joint efforts of Xerox, Digital Equipment
Corporation, and Intel. Ethernet is similar to the IEEE 802.3 series standard

www.sybex.com