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TERM
|
DEFINITION |
|
10BASE2 |
IEEE 802.3 specification
thin coaxial cable that
can support 10 Mbps and
has a maximum distance of
185 meters (607 feet) per
segment. Also called thinwire
and cheapernet. |
|
10BASE5 |
IEEE
802.3 specification thick
coaxial cable that can support
10 Mbps and has a maximum
distance of 500 meters (1604
feet) per segment. Also
called thickwire.
|
10BASE-FL
|
IEEE 802.3
specification fibre optic
cable that can support 10
Mbps and has a maximum distance
of 2000 meters (6561 feet).
|
10BASE-T
|
IEEE 802.3
specification unshielded
twisted pair cable that
can support 10 Mbps and
has a maximum distance of
100 meters (328 feet). This
cable meets EINTIA category
3 wire specifications. |
100BASE-FX
|
IEEE 802.3
specification fibre optic
cable that can support 100
Mbps and has a maximum distance
of 412 meters (1352 feet)
|
100BASE-T
|
IEEE 802.3
specification unshielded
twisted pair cable that
can support 100 Mbps and
has a maximum distance of
100 meters (328 feet). This
cable meets EIA/TIA category
5 wire specifications. |
| Adapter |
A circuit board that provides
communication capabilities
between a computer or computer
system and a communication
network. Also called network
interface card (NIC). |
|
Address |
Data structure used to identify
a unique entity (process,
network location, etc.).
|
|
Agent |
Software that processes
queries and returns replies
on behalf of an application.
In network managed systems,
agents reside in all managed
devices and report the values
of specified variables to
management work stations.
|
API
|
Application programming
interface. A specification
of function call conventions
that defines an interface
to a service. |
AppleTalk®
|
A series of related communications
protocols introduced and
maintained by Apple Computer.
Two phases currently exist:
Phase I and Phase II. Phase
II, which includes support
for internetworks, is the
most recent version.
|
Application layer
|
Layer seven of the OSI reference
model. This layer is implemented
by various network applications
including electronic mail,
file transfer, and terminal
emulation.
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ARCnet®
|
Attached resource computer
network. A 2.5 Mbps token
bus LAN network developed
in the late 1970s and early
1980s by Datapoint Corporation.
Primary characteristics
include simplicity, ease
of use, and relative low
cost.
|
ARP
|
Address resolution protocol.
An Internet protocol used
to bind an IP address to
Ethernet /IEEE 802.3 addresses.
Defined in RFC 826.
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ARPANET
|
A packet switching network
developed in the early 1970s
by BBN (Bolt, Beranek, and
Newman Inc.) and funded
by ARPA (advanced research
projects agency). The ARPANET
evolved into the Internet,
and the term ARPANET was
officially retired in 1990.
|
ASCII
|
American standard code for
information interchange.
An eight bit (seven bits
plus parity) code for character
representation.
|
ASN.1
|
Abstract syntax notation
one. An OS1 language for
describing data types in
a manner independent of
particular computer structures
and representation techniques.
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Asynchronous transmission
|
Operation of a network system
wherein events occur without
precise clocking. In such
systems, individual characters
are usually encapsulated
in control bits called start
and stop bits, which designate
the beginning and ending
of characters.
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ATM
|
Asynchronous transfer mode.
The CCITT standard for cell
relay wherein information
for multiple types of services
(voice, video, data) is
conveyed in small, fixed
size cells. Also, a BISDN
transfer mode wherein an
accelerated version of asynchronous
time division multiplexing
(ATDM) is used to move multiple
streams of information across
a communication channel.
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Attenuation
|
Loss of communication signal
energy.
|
AUI
|
Attachment unit interface.
An IEEE 802.3 cable connecting
the MAU (media access unit)
to the networked device.
The term AUI also can be
used to refer to the host
back panel connector to
which an AUI cable (transceiver
cable) attaches.
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Backbone network
|
A network acting as a primary
conduit for traffic that
is often both sourced from,
and destined for, other
networks.
|
Balun
|
Balanced, unbalanced. Device
used for matching impedance
between a balanced and unbalanced
line (usually twisted pair
and coaxial cable).
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Bandwidth
|
The difference between the
highest and lowest frequencies
available for network signals.
The term is also used to
describe the rated throughput
capacity.
|
Baseband
|
Characteristic of a network
technology where only one
carrier frequency is used.
Baseband is the opposite
of broadband. Ethernetis
an example of a baseband
network.
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Baud
|
A unit of signalling speed
equal to the number of discrete
conditions or signal events
per second. Baud is synonymous
with bits per second if
each signal event represents
exactly one bit.
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BISDN
|
Broadband ISON. Communication
standards being developed
by the CCITT to handle high
bandwidth applications such
as video. BISDN will use
ATM technology over SONET-based
transmission circuits to
provide data rates of 155
Mbps to 622 Mbps and beyond.
|
Bit
|
Smallest unit of information
recognised by a computer
and its associated equipment.
|
BNC connector
|
Standard connector used
to connect IEEE 802.3 1
OBASE2 coaxial cable to
a transceiver.
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BootP
|
A protocol used by a network
node to determine the IP
address of its Ethernet
interfaces, in order to
effect network booting.
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Boot PROM
|
Boot programmable read-only
memory. A chip mounted on
a printed circuit board
used to provide executable
boot instructions to a computer
device.
|
Bridge
|
A device that connects and
passes packets between two
network segments. Bridges
operate at layer two (data
link) of the 031 reference
model and are insensitive
to upper layer protocols.
|
Broadband
|
A transmission system that
multiplexes multiple independent
signals onto one cable,
Broadband is the opposite
of baseband.
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Broadcast
|
A message sent to all network
destinations.
|
Broadcast storm
|
Undesirable network event
in which many broadcasts
are sent all at the same
time, using substantial
network bandwidth and, typically,
causing network time-outs.
|
Bus topology
|
Linear LAN architecture
in which transmissions from
network stations propagate
the whole length of the
medium and are received
by all other stations.
|
Byte
|
A series of consecutive
binary digits that are operated
upon as a unit (for example,
an eight bit byte).
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Carrier
|
A signal suitable for modulation
by another signal containing
information to be transmitted.
|
CCITT
|
Consultative committee for
international telegraph
and telephone. An international
organisation that develops
communication standards.
|
Cell
|
The basic unit for ATM switching
and multiplexing. Each cell
consists of a five byte
header and 48 bytes of payload.
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Cell relay
|
Network technology based
on the use of small, fixed-size
packets, or cells. Cells
contain identifiers that
specify the data stream
to which they belong. Because
the cells are fixed length,
they can be processed and
switched in hardware at
very high speeds.
|
Cheapernet
|
IEEE 802.3 1 OBASE2 standard
or the cable specified in
that standard. Thinnet,
also used to describe this
standard, specifies a less
expensive, thinner version
of Ethernet cable.
|
Client
|
A node or software program
(front end device) that
requests services from a
server.
|
Client-server computing
|
Distributed processing (computing)
network systems in which
transaction responsibilities
are divided into the client
(front end) part and the
server (back end) part.
Both client and server can
be applied to both software
programs or actual computing
devices.
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Coaxial cable
|
A cable consisting of a
hollow outer cylindrical
conductor that surrounds
a single inner wire conductor.
|
Concentrator
|
A device that serves as
the hub of a star-topology
network. Also, sometimes
used to refer to a device
that contains multiple modules
of network and internetwork
equipment.
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Connectionless
|
Data transfer without the
existence of a virtual circuit.
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CRC
|
Cyclic redundancy check.
An error checking technique
in which the frame recipient
calculates a remainder by
dividing frame contents
by a prime binary divisor
and compares the calculated
remainder (which itself
is often called a CRC) to
a value stored in the frame
by the sending node.
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CSMA/CD
|
Carrier sense multiple access
with collision detection.
A channel access mechanism
wherein devices wishing
to transmit first check
the channel for a carrier.
If no carrier is sensed
for some period of time,
devices can transmit. If
two devices transmit at
once, a collision occurs
and is detected by all colliding
devices, which subsequently
delay their retransmission
for some random length of
time.
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Datagram
|
A logical grouping of information
sent as a network-layer
unit over a transmission
medium without prior establishment
of a virtual circuit. The
terms packet, frame, segment,
and message are also used
to describe logical information
groupings at various layers
of the OSI reference model
and in various technologies.
IP datagrams are the primary
information units in the
Internet.
|
Data link layer
|
Layer two of the OSI reference
model. This layer takes
a raw transmission facility
and transforms it into a
channel that appears, to
the network layer, to be
free of transmission errors.
Its main services are addressing,
error detection, and flow
control.
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DCS
|
Distributed control system.
|
DECnet
|
A group of communications
products (including a protocol
suite) developed and supported
by Digital Equipment Corporation.
The most recent iteration
is DECnet Phase V, which
is largely based upon the
OSI protocols.
|
DNS
|
Domain name system. Distributed
name system used in the
Internet.
|
DTE
|
Data terminal equipment.
The part of a data station
that serves as a data source,
destination, or both, and
that provides for the data
communications control function
according to protocols.
DTE includes computers,
protocol translators, and
multiplexers.
|
Emulation mode
|
Function of a network control
program that enables it
to perform activities equivalent
to those performed by a
transmission control unit.
|
Encryption
|
The application of a specific
algorithm to data so as
to alter the appearance
of the data to make it incomprehensible
to those who might attempt
to misuse the information.
|
|
Enterprise network |
A network (usually large,
diverse) connecting most
major points in a company.
Differs from WAN network
in that it is typically
private and contained within
a single organisation.
|
Ethernet
|
A baseband LAN specification
invented by Xerox Corporation
and developed jointly by
Xerox®, Intel®, and Digital
Equipment Corporation.
|
FDDI
|
Fibre distributed data interface.
An ANSI defined standard
specifying a 100 Mbps token
passing network using fibre
optic cable.
|
Fibre optic cable
|
Thin, flexible, medium capable
of conducting modulated
light transmission.
|
File server
|
A networked computer system
that stores files for network
users and provides network
access to the files.
|
Flash EPROM
|
A EPROM (electronically
programmable read-only memory)
technology developed by
Intel and licensed to other
semiconductor companies,
Flash EPROM is non-volatile
storage that can be electrically
erased in the circuit and
reprogrammed.
|
Fragment
|
A piece of a larger packet
that has been broken down
to smaller units.
|
Fragmentation
|
The process of breaking
a packet into smaller units
when transmitting over a
network medium that cannot
support the original size
of the packet.
|
Frame
|
A logical grouping of information
sent as a link layer unit
over a transmission medium.
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Frame relay
|
A protocol used across the
interface between user devices
(hosts and routers) and
network equipment (switching
nodes).
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FTP
|
File transfer protocol.
An IP application protocol
for transferring files between
network nodes.
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Full duplex
|
A capability for simultaneous
transmission of data in
both directions.
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GAN
|
Global area network. A network
that spans the globe.
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Gateway
|
In the past, this referred
to a routing device. Today,
this refers to a special
purpose device that performs
a layer seven conversion
of information from one
protocol stack to another.
|
|
Hardware address |
A data link layer address
associated with a particular
network device. Also called
physical address or MAC
layer address.
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Header
|
Control information added
(before data) when encapsulating
the data for network transmission.
|
Hop
|
The passage of a packet
through one router.
|
|
Hop count |
A routing metric used to
measure the distance between
a source and a destination.
|
Host
|
Computer system on a network.
Similar to the terms device
or node except that host
usually implies a computer
system, whereas device and
node generally apply to
any networked system, including
communication servers and
routers.
|
Hub
|
A device that serves as
the centre of a star topology
network. In Ethernet/IEEE
802.3 terminology, a hub
is an Ethernet multiple
port repeater (sometimes
called concentrator). Hub
is also used to refer to
a hardware/software device
that contains multiple independent
but connected modules of
network and internetwork
equipment.
|
Hybrid network
|
An internetwork made up
of more than one type of
network technology, including
LAN and WAN networks.
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ICMP
|
Internet control message
protocol. A network layer
Internet protocol that provides
message packets to report
errors and other information
relevant to Internet protocol
packet processing.
|
Interface
|
A connection between two
systems or devices.
|
International standards
organisation
|
Expansion of the acronym
ISO.
|
Internet
|
The world's largest internetwork,
connecting thousands of
networks world-wide and
having a "culture" based
upon simplicity, research,
and standardisation based
on real-life use.
|
Internet address
|
A 32 bit address assigned
to hosts using TCP/IP. The
address is written as four
octets separated with periods
(dotted decimal format)
that are made up of a network
section, an optional subnet
section, and a host section.
Also called IP address.
|
Internetwork
|
A collection of networks
interconnected by routers
that functions (generally)
as a single network. Sometimes
called an internet, which
is not to be confused with
the Internet.
|
Internetworking
|
The industry that has arisen
around the problem of connecting
networks together.
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Interoperability
|
The ability of computing
equipment manufactured by
different vendors to communicate
successfully over a network,
|
IP
|
Internet protocol. A layer
three (network layer) protocol
that contains addressing
information and some control
information that allows
packets to be routed.
|
IP address
|
Refer to Internet address.
|
IPX
|
Internetwork packet exchange.
Novell layer three protocol
similar to XNS and IP that
is used in NetWare® networks.
|
ISDN
|
Integrated services digital.network
Communication protocols
proposed by telephone companies
to permit telephone networks
to carry data, voice, and
other source material.
|
ISO
|
International organisation
for standardisation. Often
incorrectly referred to
as the international standards
organisation. An international
organisation that is responsible
for a wide range of standards,
including those relevant
to networking.
|
lsochronous transmission
|
Asynchronous (start-stop)
transmission over a synchronous
data link.
|
LAN
|
Local area network. A network
covering a relatively small
geographic area (usually
not larger than a floor
or small building).
|
LAT
|
Local area transport. A
network virtual terminal
protocol developed by Digital
Equipment Corporation.
|
Latency
|
The amount of time between
when a device requests access
to a network and when it
is granted permission to
transmit.
|
Leased line
|
A transmission line reserved
by a communications carrier
for the private use of a
customer.
|
Line driver
|
Inexpensive amplifier/signal
converter that conditions
digital signals to insure
reliable transmissions over
extended distances.
|
MAC layer address
|
Refer to hardware address
or physical address.
|
MAC sublayer
|
Media access control sublayer.
The lower portion of the
OSI reference model data
link layer that Is concerned
with media access issues,
such as whether token passing
or contention will be used.
|
MAN
|
Metropolitan area network.
A network that spans a metropolitan
area.
|
MAU
|
Medium attachment unit (IEEE
802.3) or multi-station
access unit (IEEE 802.5).
In IEEE 802.3, a device
that performs IEEE 802.3
onto the network. A MAU
is referred to as a transceiver
in the Ethernet specification.
|
Mbps
|
Megabits per second.
|
Media
|
The physical environment
through which transmission
signals pass. Common network
media include twisted pair,
coaxial, fibre optic cable,
and the atmosphere.
|
MMF
|
Multi-mode fibre optic cable.
|
Modem
|
Modulator-demodulator. A
device that converts digital
signals into a form suitable
for transmission over analogue
communication facilities
and vice versa.
|
MTU
|
Maximum transmission unit.
The maximum packet size,
in bytes, that a particular
interface will handle.
|
Multi-mode fibre
|
Optical fibre supporting
propagation of multiple
frequencies of light.
|
Multiplexing
|
Putting multiple signals
on a single channel.
|
Name server
|
A server provided on the
network that resolves network
names into network locations
or addresses..
|
Netbios
|
Network basic input/output
system. A session layer
interface for work stations
networks from IBMand Microsoft
|
NetView®
|
IBM network management architecture
and related applications.
|
NetWare
|
The world's most popular
distributed file system
that provides transparent
remote file access and numerous
other distributed network
services.
|
Network
|
A collection of computers
and other devices that are
able to communicate with
each other over some network
medium.
|
Network address
|
A network layer address
referring to a logical,
rather than a physical,
network device. Also called
protocol address.
|
Network layer
|
Layer three of the OSI reference
model. Layer three is the
layer at which routing occurs.
|
Network management
|
Systems or actions that
help maintain, characterise,
or troubleshoot a network.
|
NIC
|
Network interface card.
A circuit board that provides
communication capabilities
between a computer or computer
system and a communication
network. Also called adapter.
|
Node
|
An entity that can access
a network. Also called device.
|
NOS
|
Network operating system.
Distributed file systems
such as NetWare, Banyan®
VINES NFS, LAN Manager,
etc.
|
Null modem
|
Small box or cable used
to join computing devices
directly, rather than over
a network.
|
NVRAM
|
Non-volatile RAM. Random
access memory that retains
its contents when a Unit
is powered oft.
|
Open architecture
|
An architecture according
to which third-party developers
can legally develop products
and for which public domain
specifications exist.
|
OSI
|
Open system interconnection.
An international standardisation
program created by ISO and
CCITT to develop standards
for data networking, that
facilitates multiple vendor
equipment interoperability.
|
|
OSI reference model |
A network architectural
model developed by ISO and
CCITT, The model consists
of seven layers, each of
which specifies particular
network functions such as
addressing, flow control,
error control, encapsulation,
and reliable message transfer.
The highest layer (the application
layer) is closest to the
user. The lowest layer (the
physical layer) is closest
to the media technology.
The OSI reference model
is used universally as a
method for teaching and
understanding network functionality.
|
Packet
|
A logical grouping of information
that includes a header and
(usually) user data.
|
Packet buffer
|
Storage area to hold incoming
data until the receiving
device can process the data.
|
Packet switching
|
Network on which nodes share
bandwidth with each other
by intermittently sending
logical information units
(packets).
|
