E


E1

Generally used in Europe, a wide-area digital transmission scheme carrying data at 2.048Mbps. E1 transmission lines are available for lease from common carriers for private use.

E.164

1. Evolved from standard telephone numbering system, the standard recommended by ITU-T for international telecommunication numbering, particularly in ISDN, SMDS, and BIISDN.

2. Label of field in an ATM address containing numbers in E.164 format.

E channel

Echo channel: A 64Kbps ISDN control channel used for circuit switching. Specific description of this channel can be found in the 1984 ITU-T ISDN specification, but was dropped from the 1988 version. See also: B, D, and H channels.

ECNM

(Enterprise Composite Network Module) Cisco’s Enterprise Composite Network Modules approach has two main advantages: First, it allows the architecture to address the security relationship between the various modular blocks of the network. Second, it permits the designer to evaluate and implement security on a module-by-module basis, instead of attempting the complete architecture in a single phase.

edge device

A device that enables packets to be forwarded between legacy interfaces (such as Ethernet and Token Ring) and ATM interfaces based on information in the Data Link and Network layers. An edge device does not take part in the running of any Network layer routing protocol; it merely uses the route description protocol in order to get the forwarding information required.

EFCI

Explicit Forward Congestion Indication: A congestion feedback mode permitted by ABR service in an ATM network. The EFCI may be set by any network element that is in a state of immediate or certain congestion. The destination end-system is able to carry out a protocol that adjusts and lowers the cell rate of the connection based on value of the EFCI. See also: ABR.

EIGRP

See: Enhanced IGRP.

EIP

Ethernet Interface Processor: A Cisco 7000 series router interface processor card, supplying 10Mbps AUI ports to support Ethernet Version 1 and Ethernet Version 2 or IEEE 802.3 interfaces with a high-speed data path to other interface processors.

ELAN

Emulated LAN: An ATM network configured using a client/server model in order to emulate either an Ethernet or Token Ring LAN. Multiple ELANs can exist at the same time on a single ATM network and are made up of an LAN emulation client (LEC), an LAN emulation server (LES), a broadcast-and unknown server (BUS), and an LAN emulation configuration server (LECS). ELANs are defined by the LANE specification. See also: LANE, LEC, LECS, and LES.

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.

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 convergence attributes, including high operating efficiency. See also: IGP, OSPF, and RIP.

Enterprise Campus

A layer found in the Enterprise Composite Network Model, this layer contains four major modules. It applies to a single campus and can easily be replicated campus to campus.

Enterprise Edge

A layer found in the Enterprise Composite Network Model, this layer includes four modules. Each of these modules is connected to the Edge Distribution module of the Enterprise Campus functional area. This bridges the gap between the campus site and WAN connectivity.

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

EtherTalk

A data-link product from Apple Computer that permits AppleTalk networks to be connected by Ethernet.

excess rate

In ATM networking, traffic exceeding a connection’s insured rate. The excess rate is the maximum 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

A packet transmitted by a source device to find the path through a source-route-bridged network.




CCDA. Cisco Certified Design Associate Study Guide
CCDA: Cisco Certified Design Associate Study Guide, 2nd Edition (640-861)
ISBN: 0782142001
EAN: 2147483647
Year: 2002
Pages: 201

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