E1 The European standard
for high-speed data transmission at 2.048Mbit/s - 32 64Kbit/s
channels are provided.
Earth station Transmitting
or receiving point for satellite transmission.
EBCDIC (Extended Binary Coded Decimal Interchange
Code) An IBM-developed eight-bit binary
code that can represent 256 characters. It allows the representation
of control codes and graphics in a logical format. It was created
to represent data in particular types of data processing and communications
terminal devices.
Echo cancellation A
technique used in high-speed modems to isolate and remove unwanted
signal energy created by echoes of the transmitted signal. (An
echo is the return of a transmitted signal). It would be noticeable
by its absence on transatlantic or other time-differentiated phone
conversations.
ECMA (European Computer Manufacturers Association)
An organization dedicated to the co-operative
development of standards applicable to computer technology. It
works closely with certain ITU-TS Study Groups and ISO Sub-committees.
EDI (Electronic Data Interchange) The
interchange of trading information through the use of an electronic
messaging system. A form of paperless trading that is rapidly
expanding through organizations such as Geis.
EGP (Exterior Gateway Protocol) The
protocol used by a gateway in one autonomous system to advertise
the IP addresses of networks in that system to a gateway in another
autonomous system.
EIA/TIA The US Electronics
Industries Association and Telecommunications Industries Association
which have merged. The EIA is a US trade organization for the
electronics industry that concentrates on hardware interface standards.
Best known for the RS232C and RS422 standards that specify the
electrical characteristics of interconnections between terminals
and computers or between two computers.
EIA/TIA 568 The EIA/TIA's
most famous standard specifying a maximum horizontal cable run
of 90 meters, allowing 10 meters for hub and device attachment
resulting a total cable length of 1000 meters. Its related Service
Bulletins TSB 36 and 40 define three categories of cabling system
for data communications: Categories 3, 4 & 5.
EISA (Extended Industry Standard Architecture)
A 32-bit adaptation of the 8/16-bit buses
originally developed by IBM and now standard in almost all PCs
that use Intel's 8086 and 80X86 chips. The EISA bus is a joint
development from Compaq and other PC manufacturers. Contrast with
Microchannel and ISA.
Electronic mail, e-mail The
electronic transmission and reception of messages and text-based
information without the need for the recipient to be present at
the time of the transmission. Available either as a value-added
service from providers such as GEIS, IBM and MCI or on LAN systems
such as ccMail. De jure standards are evolving, but gateway software
in the interim is now sufficiently mature to cope with most interactivity.
EMS (Element Management System) The
level of a network management system concerned with collecting
network management information from, and setting parameters on
the network elements. Network elements consist of data communications
and telecommunications equipment.
Emulation Hardware
or software, or a combination of the two, that behaves like another
device or program, like PCs emulating dumb terminals.
Encapsulation The
process of sending data encoded in one protocol format across
a network operating a different protocol, where it is not possible
or desirable to convert between the two protocols. For example,
where Ethernet LANs attach to an FDDI backbone, it is not possible
to convert between the different packet formats, so the Ethernet
packet is encapsulated in its entirety inside an FDDI packet as
it crosses the bridge on to the FDDI network. When the encapsulated
Ethernet packet reaches the bridge connecting the destination
Ethernet LAN to the FDDI network, the Ethernet packet is stripped
out of the FDDI packet and put, unchanged, on to the destination
Ethernet LAN. Also known as protocol tunneling.
Entry point An IBM
network management term. An entry point provides management functions
for itself and the devices attached to it. It has to be an SNA-addressable
unit, allowing it to participate in network management by monitoring
its own environment and exchanging information and messages with
a Focal point.
Error control A means
of ensuring that information received across a transmission link
is correct. The techniques involved typically use error detection
to detect if the transmitted data has been corrupted. The error
control technique involves asking for data to be retransmitted
until a correct version is received.
Error correction A
technique to restore data integrity in received data that has
been corrupted during transmission. Error correction techniques
involve sending extra data along with the original data being
sent. It allows the correct form of the data to be reconstructed
from the extra information if the original has been corrupted.
This extra information is calculated using particular error correction
algorithms such as Hamming Code. It allow errors to be detected
and the original data reconstructed. This is sometimes termed
forward error correction.
Error detection A
set of techniques that can be used to detect errors in received
data. Techniques that are applicable include parity checks involving
parity bits, checksums or a Cyclic Redundancy Check.
Ethernet The most
widely LAN transmission network. Based on a bus network topology,
it runs at a maximum 10Mbit/s - in practice far less - and adopts
CSMA/CD techniques operating over convention co-axial cable, thin
wire co-axial cable and unshielded twisted pair cabling. A fiber-optic
implementation has also been defined. Originally developed by
Xerox, Intel and Dec, Ethernet has moved through V1 and V2 proprietary
definitions, and has now been standardized by the IEEE as the
IEEE 802.3 standard. This has several implementations - 10Base5
for use over conventional co-axial cable, 10BaseF for use over
optic fiber, and 10BaseT for use over Unshielded Twisted Pair
(UTP) cabling.
Ethernet switching A
technique inspired by Kalpana bringing the advantages of a parallel
networking architecture to current contention- based Ethernet
LANs. Each LAN can be segmented, each with its own 10Mbit/s path.
When users on different segments exchange data, an Ethernet switch
dynamically connects the two separate Ethernet channels without
interfering with other network segments. The switch can create
multiple independent connections between separate segments, allowing
multiple parallel data exchanges. This multiplies network bandwidth
without modification to Ethernet end station hardware or software.
Once disparaged by other vendors, it now forms part of the portfolio
of the major hub and router manufacturers.
Etsi (European Telecommunications Standards
Institute) A European standards body established
in 1988 by a decision of the CEPT. It has taken over the work
of the CEPT the area of developing the Net-Normes Europeene de
Telecommunication, Net standards.
Eutelsat Inter-governmental
organization founded in 1983 with the launch of Eutelsat 1, Eutelsat
aims to provide and operate a space segment for public intra-European
international telecommunications services. The segment is also
used to meet domestic needs by offering leased capacity, primarily
for television. UK and France are the main shareholders, with
about 25 members in total.
Ewos (European Workshop for Open Systems)
A forum aimed at promoting OSI standards and undertaking
the development of functional profiles. Its work includes OSI
Layers One to Four, FTAM, MHS, ODA, Directory Services and the
VT protocol.
