- 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.
E.164
- ITU-T recommendation for international
telecommunication numbering, especially in ISDN, BISDN, and SMDS. An
evolution of standard telephone numbers.
- 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.
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.
- European Academic Research
Network. European
network connecting universities and research institutes. EARN merged
with RARE to form TERENA. See also RARE
and TERENA.
- 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.
- 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.
- 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.
echo channel
- See E
channel.
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.
- European Computer
Manufacturers Association.
Group of European computer vendors who have done substantial OSI
standardization work.
- 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.
edge card control
- See ECC.
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.
- Electronic data interchange.
The electronic communication of operational data such as orders and
invoices between organizations.
- Electronic Data Interchange
for Administration, Commerce, and Transport.
Data exchange standard administered by the United Nations to be a
multi-industry EDI standard.
- Electrically erasable
programmable read-only memory.
EPROM that can be erased using electrical signals applied to
specific pins. See also EPROM.
- 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.
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.
- 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.
- 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.
- 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.
- 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.
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.
EIGRP
- See Enhanced
IGRP.
- 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.
- Extended Industry-Standard
Architecture. 32-bit bus
interface used in PCs, PC-based servers, and some UNIX workstations
and servers. See also ISA.
- 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.
electromagnetic interference
- See EMI.
electromagnetic pulse
- See EMP.
electrically erasable programmable
read-only memory
- See EEPROM.
electronic data interchange
- See EDI.
Electronic Data Interchange for
Administration, Commerce, and Transport
- See EDIFACT.
Electronic Industries Association
- See EIA.
- 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.
Electronic Messaging Association
- See EMA.
electrostatic discharge
- See ESD.
- 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.
e-mail
- See electronic
mail.
- Electromagnetic interference.
Interference by electromagnetic signals that can cause reduced data
integrity and increased error rates on transmission channels.
- 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.
- 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.
emulated LAN
- See ELAN.
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.
- 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.
enable-password
- Command used to restrict access to the
privileged EXEC mode.
enable-secret
- Password from the System Configuration
Dialog to setup global parameters uses a Cisco-proprietary
encryption process to alter the password character string.
- 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.
- Carries Ethernet frames from one
router to another across disparate media, such as serial and FDDI
lines. Contrast with translational
bridging.
encoder
- Device that modifies information into
the required transmission format.
encoding
- Process by which bits are represented
by voltages.
- 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.
end node
- See EN.
end of transmission
- See EOT.
end point
- Device at which a virtual circuit or
virtual path begins or ends.
end system
- See ES.
End System-to-Intermediate System
- See ES-IS.
Energy Sciences Network
- See ESnet.
- 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.
Enhanced Interior Gateway Routing
Protocol
- See Enhanced
IGRP.
Enterprise Management Architecture
- See EMA.
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.
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.
Enterprise System Connection
- See ESCON.
Enterprise System Connection channel
- See ESCON
channel.
- Generally, an individual, manageable
network device. Sometimes called an alias.
- End of transmission.
Generally, a character that signifies the end of a logical group of
characters or bits.
- 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.
equalization
- Technique used to compensate for
communications channel distortions.
erasable programmable read-only memory
- See EPROM.
erase startup-config
- Command used to delete the backup
configuration file in NVRAM.
error control
- Technique for detecting and correcting
errors in data transmissions.
error-correcting code
- Code having sufficient intelligence
and incorporating sufficient signaling information to enable the
detection and correction of many errors at the receiver.
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.
- 1. End system.
Generally, an end-user device on a network.
2. End system. Nonrouting host or node in an OSI network.
- 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.
- 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.
ESCON Multiple Image Facility
- See EMIF.
- 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.
- 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.
- End System-to-Intermediate
System. OSI protocol
that defines how end systems (hosts) announce themselves to
intermediate systems (routers). See also IS-IS.
- 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.
- 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.
Ethernet Interface Processor
- See EIP.
EtherTalk
- AppleTalk protocols running on
Ethernet.
- European Telecommunication
Standards Institute.
Organization created by the European PTTs and the European Community
(EC) to propose telecommunications standards for Europe.
- European Internet.
European commercial Internet service provider. EUnet is designed to
provide electronic mail, news, and other Internet services to
European markets.
European Academic Research Network
- See EARN.
European Computer Manufacturers
Association
- See ECMA.
European Telecommunication Standards
Institute
- See ETSI.
European Internet
- See EUnet.
- 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.
Excess Burst
- See Be.
- 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.
exchange identification
- See XID.
EXEC
- The interactive command processor of
the Cisco IOS software.
- 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.
expectational acknowledgment
- Type of confirmation scheme in which
the acknowledgment (ACK) number refers to the octet that will be
sent next.
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.
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.
explorer frame
- Frame sent out by a networked device
in a SRB environment to determine the optimal route to another
networked device.
- 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.
Extended Binary Coded Decimal
Interchange Code
- See EBCDIC.
Extended Industry-Standard
Architecture
- See EISA.
Extended Superframe Format
- See ESF.
exterior gateway protocol
- 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.
Exterior Gateway Protocol
- See EGP.
- 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.