Browsing: E
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E1 |
Wide-area digital transmission scheme
used predominantly in Europe that carries data at a rate of 2.048
Mbps. E1 lines can be leased for private use from common carriers.
Compare with
T1.
See also DS-1.
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E.164 |
ITU-T recommendation for international
telecommunication numbering, especially in ISDN, BISDN, and SMDS. An
evolution of standard telephone numbers.
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E3 |
Wide-area digital transmission scheme
used predominantly in Europe that carries data at a rate of 34.368
Mbps. E3 lines can be leased for private use from common carriers.
Compare with
T3.
See also DS-3.
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early token release |
Technique used in Token Ring networks
that allows a station to release a new token onto the ring
immediately after transmitting, instead of waiting for the first
frame to return. This feature can increase the total bandwidth on
the ring. See also
Token
Ring.
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EARN |
European Academic Research
Network. European
network connecting universities and research institutes. EARN merged
with RARE to form TERENA. See also
RARE
and TERENA.
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EBCDIC |
Extended binary coded decimal
interchange code. Any of
a number of coded character sets developed by IBM consisting of
8-bit coded characters. This character code is used by older IBM
systems and telex machines. Compare with
ASCII.
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ECC |
Edge card control.
Process on the NP of a LightStream 2020 ATM switch that performs
per-card processing for an edge card. Such processing includes
protocol management (ATM connection management) and media-specific
(Ethernet and FDDI) management tasks, internetworking operations
such as packet forwarding and filtering, and network management
tasks. See also
edge
card,
LCC,
and NP
card.
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E channel |
Echo channel.
64-kbps ISDN circuit-switching control channel. The E channel was
defined in the 1984 ITU-T ISDN specification, but was dropped in the
1988 specification. Compare with
B
channel,
D
channel, and
H
channel.
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echo channel |
See
E
channel.
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echoplex |
Mode in which keyboard characters are
echoed on a terminal screen upon return of a signal from the other
end of the line indicating that the characters were received
correctly.
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ECMA |
European Computer
Manufacturers Association.
Group of European computer vendors who have done substantial OSI
standardization work. |
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edge card |
Line card on the LightStream 2020 ATM
switch that is configured to communicate with devices outside the
ATM network. Edge cards offer Ethernet, FDDI, frame forwarding,
Frame Relay, OC-3c, and UNI interfaces. See also
trunk
card.
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edge card control |
See
ECC.
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edge device |
Network entity such as a LAN segment,
host, or router that connects to a LightStream 2020 ATM switch via
an edge card. Edge devices send and receive the data that passes
through the ATM network.
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EDI |
Electronic data interchange.
The electronic communication of operational data such as orders and
invoices between organizations.
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EDIFACT |
Electronic Data Interchange
for Administration, Commerce, and Transport.
Data exchange standard administered by the United Nations to be a
multi-industry EDI standard.
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EEPROM |
Electrically erasable
programmable read-only memory.
EPROM that can be erased using electrical signals applied to
specific pins. See also
EPROM.
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EGP |
Exterior Gateway Protocol.
Internet protocol for exchanging routing information between
autonomous systems. Documented in RFC 904. Not to be confused with
the general term exterior gateway protocol. EGP is an
obsolete protocol that has been replaced by BGP. See also
BGP.
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EIA |
Electronic Industries
Association. Group that
specifies electrical transmission standards. The EIA and TIA have
developed numerous well-known communications standards, including EIA/TIA-232
and EIA/TIA-449. See also
TIA.
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EIA-530 |
REFers to two electrical
implementations of EIA/TIA-449: RS-422 (for balanced transmission)
and RS-423 (for unbalanced transmission). See also
RS-422,
RS-423,
and EIA/TIA-449.
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EIA/TIA-232 |
Common physical layer interface
standard, developed by EIA and TIA, that supports unbalanced
circuits at signal speeds of up to 64 kbps. Closely resembles the
V.24 specification. Formerly known as RS-232.
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EIA/TIA-449 |
Popular physical layer interface
developed by EIA and TIA. Essentially, a faster (up to 2 Mbps)
version of EIA/TIA-232 capable of longer cable runs. Formerly called
RS-449. See also
EIA-530.
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EIA/TIA-568 |
Standard that describes the
characteristics and applications for various grades of UTP cabling.
See also Category
1 cabling,
Category
2 cabling,
Category
3 cabling,
Category
4 cabling,
Category
5 cabling, and
UTP.
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EIA/TIA-606 |
Administration standard for the
telecommunications infrastructure of commercial buildings. It
includes the following administration areas: terminations, media,
pathways, spaces, and bounding and grounding.
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EIGRP |
See
Enhanced
IGRP.
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EIP |
Ethernet Interface Processor.
Interface processor card on the Cisco 7000 series routers. The EIP
provides high-speed (10-Mbps) AUI ports that support Ethernet
Version 1 and Ethernet Version 2 or IEEE 802.3 interfaces, and a
high-speed data path to other interface processors.
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EISA |
Extended Industry-Standard
Architecture. 32-bit bus
interface used in PCs, PC-based servers, and some UNIX workstations
and servers. See also
ISA.
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ELAN |
Emulated LAN.
ATM network in which an Ethernet or Token Ring LAN is emulated using
a client-server model. ELANs are composed of an LEC, an LES, a BUS,
and an LECS. Multiple ELANs can exist simultaneously on a single ATM
network. ELANs are defined by the LANE specification. See also
BUS,
LANE,
LEC,
LECS,
and LES.
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electromagnetic interference |
See
EMI.
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electromagnetic pulse |
See
EMP.
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electrically erasable programmable
read-only memory |
See
EEPROM.
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electronic data interchange |
See
EDI.
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Electronic Data Interchange for
Administration, Commerce, and Transport |
See
EDIFACT.
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Electronic Industries Association |
See
EIA.
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electronic mail |
Widely used network application in
which mail messages are transmitted electronically between end users
over various types of networks using various network protocols.
Often called e-mail.
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Electronic Messaging Association |
See
EMA.
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electrostatic discharge |
See
ESD.
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EMA
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1. Enterprise Management
Architecture. Digital Equipment Corporation network
management architecture, based on the OSI network management model.
2. Electronic Messaging Association. Forum devoted
to standards and policy work, education, and development of
electronic messaging systems such as electronic mail, voice mail,
and facsimile.
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e-mail |
See
electronic
mail.
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EMI |
Electromagnetic interference.
Interference by electromagnetic signals that can cause reduced data
integrity and increased error rates on transmission channels.
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EMIF |
ESCON Multiple Image Facility.
Mainframe I/O software function that allows one ESCON channel to be
shared among multiple logical partitions on the same mainframe. See
also ESCON.
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EMP |
Electromagnetic pulse.
Caused by lightning and other high-energy phenomena. Capable of
coupling enough energy into unshielded conductors to destroy
electronic devices. See also
Tempest.
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emulated LAN |
See
ELAN.
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emulation mode |
Function of an NCP that enables it to
perform activities equivalent to those performed by a transmission
control unit. For example, with CiscoWorks, the NetView PU 2
emulates the IBM 3274.
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EN |
End node.
APPN end system that implements the PU 2.1, provides end-user
services, and supports sessions between local and remote CPs. ENs
are not capable of routing traffic and rely on an adjacent NN for
APPN services. Compare with
NN.
See also CP.
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enable-password |
Command used to restrict access to the
privileged EXEC mode.
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enable-secret |
Password from the System Configuration
Dialog to setup global parameters uses a Cisco-proprietary
encryption process to alter the password character string.
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encapsulation |
The wrapping of data in a particular
protocol header. For example, Ethernet data is wrapped in a specific
Ethernet header before network transit. Also, when bridging
dissimilar networks, the entire frame from one network is simply
placed in the header used by the data link layer protocol of the
other network. See also
tunneling.
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encapsulation
bridging |
Carries Ethernet frames from one
router to another across disparate media, such as serial and FDDI
lines. Contrast with
translational
bridging.
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encoder |
Device that modifies information into
the required transmission format.
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encoding |
Process by which bits are represented
by voltages.
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encryption |
The application of a specific
algorithm to data so as to alter the appearance of the data making
it incomprehensible to those who are not authorized to see the
information. See also
decryption.
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end node |
See
EN.
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end of transmission |
See
EOT.
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end point |
Device at which a virtual circuit or
virtual path begins or ends.
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end system |
See
ES.
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End System-to-Intermediate System |
See
ES-IS.
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Energy Sciences Network |
See
ESnet.
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Enhanced IGRP |
Enhanced Interior Gateway
Routing Protocol.
Advanced version of IGRP developed by Cisco. Provides superior
convergence properties and operating efficiency, and combines the
advantages of link state protocols with those of distance vector
protocols. Compare with
IGRP.
See also IGP,
OSPF,
and RIP.
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Enhanced Interior Gateway Routing
Protocol |
See
Enhanced
IGRP.
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Enterprise Management Architecture |
See
EMA.
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Enhanced Monitoring Services |
Set of analysis tools on the Catalyst
5000 switch, consisting of an integrated RMON agent and the SPAN.
These tools provide traffic monitoring, and network segment analysis
and management. See also
RMON
and SPAN.
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enterprise network |
Large and diverse network connecting
most major points in a company or other organization. Differs from a
WAN in that it is privately owned and maintained.
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Enterprise System Connection |
See
ESCON.
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Enterprise System Connection channel |
See
ESCON
channel.
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entity |
Generally, an individual, manageable
network device. Sometimes called an alias.
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EOT |
End of transmission.
Generally, a character that signifies the end of a logical group of
characters or bits.
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EPROM |
Erasable programmable
read-only memory.
Nonvolatile memory chips that are programmed after they are
manufactured, and, if necessary, can be erased by some means and
reprogrammed. Compare with
EEPROM
and PROM.
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equalization |
Technique used to compensate for
communications channel distortions.
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erasable programmable read-only memory |
See
EPROM.
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erase startup-config |
Command used to delete the backup
configuration file in NVRAM.
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error control |
Technique for detecting and correcting errors in data transmissions.
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error-correcting code |
Code having sufficient intelligence and incorporating sufficient
signaling information to enable the detection and correction of many
errors at the receiver.
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error-detecting code |
Code that can detect transmission errors through analysis of
received data based on the adherence of the data to appropriate
structural guidelines.
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ES |
End system (ES) refers to any non-routing host or node. ES lives in
a particular area. See also IS,
ES-IS,
IS-IS.
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ESCON |
Enterprise System Connection.
IBM channel architecture that specifies a pair of fiber-optic
cables, with either LEDs or lasers as transmitters and a signaling
rate of 200 Mbps.
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ESCON channel |
IBM channel for attaching mainframes to peripherals such as storage
devices, backup units, and network interfaces. This channel
incorporates fiber channel technology. The ESCON channel replaces
the bus and tag channel. Compare with
parallel channel. See also
bus and tag channel.
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ESCON Multiple Image Facility |
See
EMIF.
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ESD |
Electrostatic discharge.
A flow or spark of electricity that originates from a static source
such as a carpet and arcs across a gap to another object.
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ESF |
Extended Superframe Format.
Framing type used on T1 circuits that consists of 24 frames of 192
bits each, with the 193rd bit providing timing and other functions.
ESF is an enhanced version of SF. See also
SF.
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ESH |
End System Hello (ESH) is an IS-IS hello
packet type. It is part of the ES-IS spec 9542; similar to ICMP
Router Discovery Protocol (IRDP) in TCP/IP; used for routers (ISs)
and End Systems (ESs) to detect each other and form adjacencies.
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ES-IS |
End System-to-Intermediate System (ES-IS) ES-IS discovery protocols
used for routing between end systems and intermediate systems. ES-IS
is an analogous to Address Resolution Protocol (ARP) in IP. Although
not technically a routing protocol, ES-IS is commonly used with
routing protocols to provide end-to-end data movement through an
internetwork. Routing between end systems and intermediate systems
is sometimes referred to as Level 0 routing. See also
ES, IS,
IS-IS.
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ESnet |
Energy Sciences Network.
Data communications network managed and funded by the U.S.
Department of Energy Office of Energy Research (DOE/OER).
Interconnects the DOE to educational institutions and other research
facilities.
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Ethernet |
Baseband LAN specification invented by Xerox Corporation and
developed jointly by Xerox, Intel, and Digital Equipment
Corporation. Ethernet networks use CSMA/CD and run over a variety of
cable types at 10 Mbps. Ethernet is similar to the IEEE 802.3 series
of standards. See also
10BASE2,
10BASE5,
10BASE-F,
10BASE-T,
10Broad36, and
IEEE 802.3.
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Ethernet Interface Processor |
See
EIP.
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EtherTalk |
AppleTalk protocols running on Ethernet.
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ETSI |
European Telecommunication Standards Institute.
Organization created by the European PTTs and the European Community
(EC) to propose telecommunications standards for Europe.
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EUnet |
European Internet.
European commercial Internet service provider. EUnet is designed to
provide electronic mail, news, and other Internet services to
European markets.
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European Academic Research Network |
See
EARN.
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European Computer Manufacturers
Association |
See
ECMA.
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European Telecommunication Standards
Institute |
See
ETSI.
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European Internet |
See
EUnet.
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event |
Network message indicating operational irregularities in physical
elements of a network or a response to the occurrence of a
significant task, typically the completion of a request for
information. See also
alarm and
trap.
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Excess Burst |
See
Be.
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excess rate |
Traffic in excess of the insured rate for a given connection.
Specifically, the excess rate equals the maximum rate minus the
insured rate. Excess traffic is delivered only if network resources
are available and can be discarded during periods of congestion.
Compare with
insured rate and
maximum rate.
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exchange identification |
See
XID.
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EXEC |
The interactive command processor of the Cisco IOS software.
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expansion |
The process of running a compressed data set through an algorithm
that restores the data set to its original size. Compare with
companding and
compression.
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expectational acknowledgment |
Type of acknowledgment scheme in which the acknowledgment number
refers to the octet expected next.
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expedited delivery |
Option set by a specific protocol layer telling other protocol
layers (or the same protocol layer in another network device) to
handle specific data more rapidly.
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explicit route |
In SNA, a route from a source subarea to a destination subarea, as
specified by a list of subarea nodes and transmission groups that
connect the two.
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explorer frame |
Frame sent out by a networked device in a SRB environment to
determine the optimal route to another networked device.
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explorer packet |
Generated by an end station trying to find its way through a SRB
network. Gathers a hop-by-hop description of a path through the
network by being marked (updated) by each bridge that it traverses,
thereby creating a complete topological map. See also
all-routes explorer packet,
local explorer packet, and
spanning explorer packet.
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Extended Binary Coded Decimal Interchange
Code |
See
EBCDIC.
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Extended Industry-Standard Architecture |
See
EISA.
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Extended Superframe Format
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See
ESF.
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exterior gateway protocol
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Any internetwork protocol used to exchange routing information
between autonomous systems. Not to be confused with Exterior
Gateway Protocol (EGP), which is a particular instance of an
exterior gateway protocol.
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Exterior Gateway Protocol |
See
EGP.
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exterior router |
Router connected to an AURP tunnel, responsible for the
encapsulation and deencapsulation of AppleTalk packets in a foreign
protocol header (for example, IP). See also
AURP and
AURP tunnel.
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