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Glossary of Internetworking Terms
10BASE2
A form of Ethernet standard and IEEE 802.3 that uses a thin coaxial
cable. Also called Thin Ethernet, ThinWire, ThinNet, and CheaperNet. It refers to 10Mbit/s
speed Baseband transmission over 200 metres maximum length - in practice 185m.
10BASE5:
A form of Ethernet standard and IEEE 802.3 that uses thick coaxial cable.
It refers to 10Mbit/s speed Baseband transmission and 500m maximum length.
10BASE-F
An Ethernet standard that uses optical fibers in a star topology.
10BASE-T
A form of Ethernet standard and IEEE 802.3 network cabling using twisted
pair cabling. It refers to 10Mbit/s speed Baseband transmission over twisted pair cable with a
maximum segment length of 100m.
100BASE-T
A high-speed version of Ethernet. IEEE 802.3U standard from proposals by
the Fast Ethernet Alliance (including 3Com and SynOptics). It will support Category 3,4 and 5
UTP cabling. Also known as Fast Ethernet, 100BASE-T transmits at 100Mbps.
100BASEVG:
A competing proposal to 100Base-T (promoted by Hewlett and Packard, IBM
and Protean) to the IEEE for a 100Mbit/s standard over voice-grade UTP - the cable most users
already have installed in existing 10BASET systems. Based on Quartet Signalling and demand
priority protocol, it preserves the infrastructure and will need only a new hub and upgraded
adapters in PCs/ workstations. It claims support for Category 3,4 and 5 UTP cabling for both
Ethernet and Token Ring as well as 10BASE-T networks at 100 Mbps.
23B+D
Integrated Services Digital Network; Primary Rate Interface or P.R.I in the
U.S. ISDN’s high-speed service provides 23 B channels and one 64-Kbps D channel (23B+D).
2B+D
ISDN’s basic service is called Basic Rate Interface, or BRI. BRI is made up
of two 64-Kbps B channels and one 16-Kbps D channel (2B+D).
Address
One or a group of characters specifying the recipient or originator of
transmitted data. An address can also denote the position of data in computer memory or the
data packet itself while in transit through a network. IEEE 802.3 and 802.5 recommend having a
unique address for each device world-wide.
ADSL (Asymmetric Digital Subscriber Line)
Uses a twisted copper pair to support
broadband transmission rates.
Agent
A software-driven process running on a communications or networking device
that allows that device to participate in a network management system. For example, an SNMP
agent running on a router provides the ability for the router to exchange information with an
SNMP network management system through the use of the SNMP protocol.
Aggregate Bandwidth
The total bandwidth of channel carrying a multiplexed bit
stream.
Alternate Routing
Safety technique enabling communication to continue in the event
of node failure or congestion. The network design allows for alternate paths through the
network to arrive at the same destination.
Analogue Loopback
A diagnostic test that returns the transmitted signal back to the
sending device after it had passed through a network or across a particular link. The returned
signal can then be compared to the transmitted one. The discrepancies between the two help to
trace the fault. When trying to locate a faulty piece of equipment, loopbacks will be repeated,
eliminating satisfactory machines until the problem is found.
Appleshare
Apple system software that turns a Macintosh into a file server.
AppleShare PC
Software from Apple that enables a PC to connect to an AppleTalk
network.
AppleTalk
A seven-layer protocol stack developed by Apple for communications
between its Apple Macintosh product range.
Application Layer
The top layer in the OSI Reference Model comprising the interface
between OSI environment and a user’s application. It does not contain applications, but provides
a link from application software on one system to applications on another, through the OSI
environment.
Applications Programming Interface (API)
Software designed to make computer
functions available to an application program - PC and network operating systems have them.
APIs in a network must be compatible to ensure programs are accessible to machines other than
those they reside in. Some APIs, such as NetBios, are de facto standards.ANSI
The American National Standards Institute.
ARP (Address Resolution Protocol)
A low-level TCP/IP protocol which is used to get
a node’s physical address when only its logical IP address is known. ARP operates only across a
single physical network and is limited to networks supporting hardware broadcast.
ARPANET (Advanced Research Projects Agency NETwork)
The first, large scale, packet
switched network - the precursor of today’s Internet.
ATM (Asynchronous Transfer Mode)
A cell-based data transfer technique in which
channel demand determines packet allocation. ATM offers fast packet technology, real-time,
demanded switching for efficient use of network resources. ATM is defined in the Broadband
ISDN (BISDN) standard and provides bandwidth on demand by charging customers for the amount
of data they send. Data rates are scaleable, starting as low as 1.5 Mbps with intermediate
speeds of 25, 51 and 100 Mbps, to high speeds of 155, 622 Mbps and up into the gigabit range.
Attenuation
The weakening of transmitted signals as they travel away from their
point of origin. Amplifiers can recharge the signal up to a point. It is a major factor in LAN
design and the lengths cables can run to.
AUI (Attachment Unit Interface)
The network interface used with standard Ethernet
and IEEE 802.3 - specified cable and connector used to attach devices to a MAU.
Autosensing
Automatically adjusts to different operating conditions. For example,
an autosensing power supply will provide the correct power level whether it’s plugged into
115- or 230-volt power.
Backbone
A high-capacity network that links other lower capacity networks together.
A local backbone network would typically be an FDDI network acting as an in-building backbone
to link together multiple LANs. A wide area backbone network would typically use digital leased
circuits and multiplexers or routers.
Bandwidth
The range of frequencies a transmission line or channel can carry.
For a digital channel this is defined in bit/s. For an analogue channel, it is dependent on
the type and method of modulation used to encode the data.
Bandwidth on Demand
Capability of an end user or network
device to access available network capacity at a rate as required by the
application being utilised for a specified period.
Banner
A banner is most often used as an advertising image
that usually spreads across the width of the Web page. Advertisers
sometimes count banner "views", or the number of times a banner graphic
image is downloaded over a period of time.
Baseband
A transmission where digital signals are placed onto a transmission line
with no change in their modulation and use the full-channel bandwidth. The digital input is
applied directly to the transmission media without the intervention of a modulating device,
which works well if there is wide bandwidth and distances no more than several hundred metres
are involved. All stations attached to the network have to participate in every transmission.
It permits only one conversation at a time as the whole of the band width is used to transmit
a single digital signal.
Basic Rate Access (BRA)
Two 64Kbit/s B channels + one 16Kbit/s D channel
(2B+D), carrying user traffic and signalling information respectively to the user via twisted
pair local loop.
B Channel (Bearer Channel)
A 64-Kbps ISDN user channel that carries digital data,
or a PCM-encoded digital voice.
Best Effort
The service model for standard Internet service.
In the face of congestion of a network interface, packets are discarded
without regard to user or application until traffic is reduced.
BISDN (Broadband ISDN)
A second generation ISDN standard, BISDN uses fibre-optic
cables to achieve speeds of 155 Mbps and higher. It promises universal coverage based on ATM/SDH
technologies and optical fibre, supporting data, voice and video traffic.
Bit ("Binary Digit")
A bit is the primary unit of electronic,
digital data. Written in base-2, binary language as a "1" or a "0".
BNC (Bayonet-Neill-Concelman)
A commonly used connector for coaxial cable, such as
10BASE2 thin wire Ethernet, and to link thin wire Ethernet to network interface cards,
transceivers and other network elements. Also referred to as Barrel Nut Connector.
Boundary Routing
A 3-Com proprietary name for a method of accessing remote networked
locations, such as a bank branch office. Effectively a form of bridging, the idea is to reduce
the need for technical expertise locally and the cost of equipment at the remote site and manage
the communications from head office.
Bps (Bits Per Second)
The basic unit of measurement for serial data-transmission
capacity; stands for the number of bits transmitted per second - bit/s.
BRI (Basic Rate Interface)
An ISDN service referred to as 2B+D, BRI provides two
64-Kbps, bearer digital channels, plus a 16-Kbps delta channel. ISDN Terminal Adapters replace
modems as the customer-premise connection to this service, for direct connections of data and
voice transmissions.
Bridge
A device that connects two LAN segments together, which may be similar or
dissimilar types, such as Ethernet and Token Ring. Once bridging is accomplished, the bridge
makes interconnected LANs look like a single LAN, passing data between the networks and
filtering local traffic. They control network traffic and security, filtering where necessary
to boost network performance and contain sensitive data to particular LAN areas.
Broadband
A technique for transmitting data, voice and video over long distances
using high-frequency transmission over coaxial or optical fibres. It allows multiple
simultaneous conversations, since the independent networks operate on different frequencies
and do not interfere with each other.
Broadcast
1. A method of transmitting messages to two or more stations at the same
time, such as over a bus type local area network or by satellite.
2. A protocol mechanism that supports group and universal addressing.
3. Any simultaneous transmission to many receiving locations.
Broadcast Storm
Excessive transmission of address verification requests in a
network. It can occur when multiple routers come online or synchronise themselves
simultaneously, each trying to identify all the connected nodes in the network.
Brouter
A communications device that provides the functions of a bridge and router. It supports
more than two LAN connections and uses Level Two addresses for routing. The term is mostly
used by bridge vendors.
Buffer
A temporary storage place for data, designed to compensate for a difference
in transmission speeds or to hold data when there is a difference in timing of events.
Burst Mode
A high-speed transmission mode in a communications or computer channel
which sends a burst of data at higher than the normal transmission speed.
Bursty
Refers to data transmitted in short, uneven spurts.
Bus
A common pathway, or channel, between multiple devices.
Busmastering
A bus design that enables add-in boards to process independently of the
CPU and access the computer’s memory and peripherals on their own.
Bus Topology
A type of network in which all the devices are connected in a line to
a single cable. A bus network has two distinct ends. All devices which are attached to a bus
network have equal access to it and they can see all the messages that are put on to the network.
Each device determines which messages are intended for it alone, and selects those.
Byte
The common unit of computer storage from micro to mainframe
(1) A set
of bits that represent a single character. A byte is composed of 8 bits.
(2) A bit
string that is operated upon as a unit and the size of which is independent of redundancy or
framing techniques.
Cable
A flexible metal or glass wire or group of wires. All cables used in
electronics are insulated with a material such a plastic or rubber.
Cable Modem
A modem used to connect a computer to a cable TV system that offers
online services.
Cache
A local temporary store of information.
Cascading Style Sheets(CSS)
This is a new technology which allows web designers to
have control over the elements on a web page and used to separate content from style. Style
sheets provide a flexible way to designate paragraphs, major headings, second-level headings
and so on. Use of style shhets has the advantages of maintainability, searchability and
flexibility.
Channel
1. A high-speed metal or fibre-optic pathway between the computer and the
control units of the peripheral devices used in mainframes and high-end machines.
2. The PC bus serves as a common, shared channel between all devices.
3. Any pathway between two computers or terminals. It can be the physical medium, such as
the cable, or the specific carrier frequency (subchannel) within a larger channel or wireless
medium.
Channel Aggregation
Combines multiple physical channels into one logical channel
of greater bandwidth. For example, with BRI ISDN connections, it combines the two 64 Kbps B
channels into a single, logical 128 Kbps channel.
CHAP (Challenge-Handshake Authentication Protocol)
An authentication protocol used
to verify a user’s name and password for PPP Internet connections, which performs a three-way
handshake while the link is established.
Cheapernet
Colloquial term for thin wire Ethernet.
Certificate Authority (CA)
A trusted third-party organisation
or company that issues digital certificates used to create digital
signatures and public-private key pairs. The role of the CA in this
process is to guarantee that the individual granted the unique certificate
is, in fact, who he or she claims to be. CAs are a critical component in
data security and electronic commerce because they guarantee the
identities of parties exchanging information.
Circuit Switched Connection
A temporary connection that is
established on request between two or more stations in order to allow the
exclusive use of that connection until it is released.
Client
1. A workstation or PC in a client/server environment.
2. One end of the spectrum in a request/supply relationship between programs.
3. A client can also be viewed as a program like Internet Explorer (a browser) or Eudora (a mail
reader). A client resides on your computer as you use the Internet.
Client/Server
An architecture in which the client workstation is the requesting
machine and the server is the supplying machine.
Client/Server Network
1. A communications network that uses dedicated servers.
2. A network that is processing applications designed for client/server architecture.
Coaxial Cable
A high-capacity cable used in communications and video which contains
an insulated solid or stranded wire surrounded by a solid or braided metallic shield, wrapped
in a plastic cover. It is difficult to add or remove devices from a coaxial LAN as the cable
is unwieldy and thick so is being superseded by UTP.
Collision
The result of two devices on a shared transmission medium, like Ethernet,
transmitting simultaneously. Data is corrupted and both devices must retry their transmissions.
A delay mechanism used by both senders drastically reduces the chances of another collision.
Collision Detection
Devices at each end of a link are designed to detect
collisions instantly and attempt to re-send. This is the principal on which CSMA/CD is based
and the access control method for Ethernet. An alternative is to re-send if there is no
acknowledgement of receipt from the remote device.
Communications
The electronic transfer of information from one location to another.
Communications Channel
1. Also called a circuit or line, it’s a pathway over
which data is transferred between remote devices.
2. The physical communication medium, such
as a telephone line; fibre-optic, coaxial, or twisted-pair cable.
3. One of several carrier frequencies transmitted simultaneously within a communication line.
Communications Protocol
Hardware and software standards that govern transmission
between two stations.
COM Port
A serial communications port on a PC.
Concentrator
Concentrator: A central chassis into which various modules, such as
bridging, supervisory, 10BaseT and FOIRL cards, are slotted.
Connection
1. An established data-communications path.
2. The process of establishing that path
3. A point of attachment for that path.
Connectionless Service
The transport of a single datagram or packet of information
from one network node to a destination node or multiple nodes without establishing a network
connection.
Connectivity
The capability to provide, to end users,
connections to the Internet or other communications networks.
Connector
A plug, or socket, or wire that links two devices together.
Console
1. A terminal used to monitor and control a computer or network.
2. Any display terminal.
Contention
The process whereby multiple users make requests for transmission
bandwidth across a transmission link but the pool of bandwidth is less than the aggregate amount
of bandwidth the users could request between them. Contention is used to resolve which users
gain access to the bandwidth.
Converter
A repeater that also converts from one media type to another, such as from fibre to
copper. Often called a media adapter.
Cookie
A mechanism for a Web server to store and retrieve
information from a client (browser). The cookie is generated by the server
and sent to the client. When it is accepted, the next time the client
connects to the service, the client's computer automatically sends this
information back to the server.
CRC (Cyclic Redundancy Check)
A method of detecting errors in the serial
transmission of data. A CRC for a block of data is calculated before it is sent, and is then
sent along with the data. A new CRC is calculated on the received data. If the new CRC does not
match the one that has been sent along with the data then an error has occurred.
Cross-pinned or Crossover CableA RS-232 cable that enables two DTE devices or two DCE
devices to be connected through serial ports and crosses the sending wire on one end to the
receiving wire on the other.
Cross-platform
Dealing with more than one platform.
Crosstalk
Unwanted interference from another adjacent communications channel. The
signal from the adjacent channel is inserted into the original communications channel.
CSMA (Carrier Sense Multiple Access)
A LAN contention protocol by which workstations
connected to the same channel are able to sense transmission activity on that channel and so
defer their own transmission while the channel is active.
CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance)
A LAN access method
in which contention between two or more stations is avoided, because a station listens first to
see if the channel is clear before transmitting.
CSMA/CD (Carrier Sense Multiple Access/Collision Detection)
All nodes are attached
to single cable and contend equally for access to the transmission medium. If two nodes attempt
to send data at the same time, they sense each other’s signal and immediately stop sending.
They will both try to send again after waiting a random number of microseconds.
Cut Through
A buffering technique in which messages or packets are not examined for
integrity before forwarding. The first six bytes (the destination address) are checked, then
forwarded regardless of what else the packet contains.
Daisychain
To connect devices in series, one after the other where the transmitted
signals go to the first device, then to the second and so on.
Data Bus
An internal pathway across which data is transferred to and from the
processor.
Datagram
A TCP/IP message unit that contains Internet source and destination
addresses and data. It is a method of sending data in which parts of the message are sent in
random order. The recipient machine has the task of reassembling the parts in the correct order.
The datagram is a connectionless, single package message or item of data that can traverse a
network at OSI Level Three, the Network Layer. It typically does not involve end-to-end session
establishment or delivery confirmation acknowledgement.
Data Integrity
1. The process of preventing accidental erasure or adulteration in a
database.
2. A measure of data-communications performance, indicating a scarcity (or,
ideally, the absence) of undetected errors.
Data Link
A direct serial data communications path between two devices without
intermediate switching nodes.
Data-Link Layer
Layer Two of the ISO OSI model is responsible for the transmission
of information over a physical medium. After establishing the link it ensures the error-free
delivery of the information through the use of error detection, error recovery and flow control.
Data-Link Protocol
The transmission of a unit of data from one node to another
(OSI Layer Two).
Data-Over-Voice
A frequency-division multiplexing technique, which combines data and
voice on the same line by assigning a portion of the unused bandwidth to the data. It’s usually
implemented on twisted-pair cables in-house telephone-system wiring.
Data PABX
A PABX used solely for data. It’s used to set up and break connections on
demand between computers, terminals, and peripherals.
Data Packet
One frame in a packet-switched message.
Data Rate, Data Signalling Rate
1. The data-transfer speed within the computer or
between a peripheral and computer.
2. The data-transmission speed in a network.
Data Stream
The continuous flow of data from one place to another.
Data Switch
A switch box that routes one line to another; for example, to connect
two computers to one printer.
Data Transfer
1.The movement of data within a computer system.
2.Data is transferred within a computer, but it’s transmitted over a communications network.
Data Transmission
Sending data over a communications network.
D Channel (Delta Channel)
This 16-Kbps channel is used to signal the telephone
company computer to make calls, put them on hold, and activate features such as conference
calling and call forwarding. It also receives information about incoming calls, as in Caller
ID.
DDE (Dynamic Data Exchange)
A Microsoft messaging specification. When DDE-compliant
applications are combined, dynamic documents can be created which update each other as data
changes.
Dedicated Line
A private communications channel leased from a common carrier.
Ordered in pairs, providing a four-wire channel for full duplex transmission.
Demodulation
Technique for retrieving information from a modulated signal.
Demonstrated by the eponymous modem (modulator/demodulator).
Device Driver
In the context of computer networking a device driver is a software
module forming part of a computer operating system, or software that interacts with the
operating systems. It aims to control communications equipment, such as a LAN network
adapter card and facilitate the transfer of information to and form the network. Other
examples of device driver programs include software to support the activities of printers,
disks and mice.
DHCP (Dynamic Host Configuration Protocol)
Software included in Windows NT and Windows
95 that assigns IP addresses (TCP/IP) to stations in a network.
Dialup Network
The switched telephone network regulated by government and
administered by common carriers.
Digital certificate (also, digital signature)
An attachment to an
electronic message used for security purposes. The most common use of a
digital certificate is to verify that a user sending a message is who he
or she claims to be, and to provide the receiver with the means to encode
a reply.
DIP (Dual In-Line Package)
A common rectangular chip housing with leads (pins) on
the base of both sides.
DIP Switch (Dual In-Line Package Switch)
A set of tiny toggle switches built into
a DIP, mounted directly on a circuit board.
Distributed Architecture
1. LAN architecture that uses a shared communications
medium such as bus or ring LANs.
2. Any computer system that uses shared access methods.
Distributed Computing
Computed power is concentrated more at individual workstations
, rather than one central processing system.
Distributed Processing
An approach that allows one application program to execute on
multiple computers linked together by a network. The networked computers share the work between
them.
DLC (Data-Link Control)
The set of protocols used by two nodes or stations on a
network to perform an orderly exchange or information.
DLCI (Data-Link Connection Identifier)
A header field in a Frame-Relay packet that
identifies the destination of the package.
Domain
A group of nodes on a network that form an administrative entity. It could
also be a number of servers grouped together and named to simplify network administration and
security. Every computer on the LAN belongs to at least one domain. Being logged in on one
domain, however, does not limit resources in other domains to which the user has access
permissions.
Domain Name
The registered name of an individual or
organisation eligible to use the Internet. Domain names have at least two
parts and each part is separated by a dot. The name to the left of the dot
is unique for each top-level domain name, which is the name that appears
to the right of the dot. For instance, the International Telecommunication
Union's domain name is itu.int. "ITU" is a unique name within the gTLD
"int".
Domain Name System (DNS)
Databases located throughout the
Internet that contain Internet naming information, including tables that
cross reference domain names with their underlying IP numbers. When an end
user enters a domain name, the network converts the domain name of its
destination into the corresponding IP number, and the IP number is used
for routing purposes.
Downlink
Transmission from satellite to an Earth Station.
Drop
A connection point between a communicating device and communications network;
a single connection (or node) on a multipoint line.
Drop Cable
In LANs, a cable that connects the main network cable, or bus, and the data
terminal equipment (DTE). Also called an Attachment Unit Interface cable or transceiver cable.
Duplex
Simultaneous, two-way independent transmission of data.
Dynamic Node Address
An Apple-patented feature of Apple Talk under which each node
assigns itself a unique address code each time it is initialised. Conventionally, nodes are
assigned fixed addresses that do not change.
Dynamic Routing
A process for selecting the most appropriate path or route for a
packet or datagram to travel around a network. At the end of each leg of the journey of the
packet across the network, the router decides on the most appropriate path for the packet or
datagram to follow if there are multiple routes available. This is done using network status
information gathered from around the Internet and passed from router to router through the use
of routing information protocols.
E1
The European standard for high-speed digital transmission at 2.048 Mbps, with
31 64-KB channels available for traffic. Also called 2-Meg, European T1, or Conference European
Post Telecom.
Earth Station
Transmitting or receiving point for satellite transmission.
EDI (Electronic Data Interchange)
Business-to-business interactions handled
exclusively with electronic communications a form of paperless trading.
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.
Electronic Data Interchange (EDI)
Electronic Data Interchange
(EDI) is the computer- to-computer exchange of business documents between
companies, using a public standard format. Rather than preparing paper and
sending it through the mail, or using other communications methods such as
fax, EDI users exchange business data directly between their respective
computer systems.
EMI (Electro-Magnetic Interference)
Electromagnetic waves that emanate from an
electrical device.
Empty-Slot Ring
A ring LAN in which a free packet circulates through every station.
Encryption
The translation of data into a secret code.
Encryption is the most effective way to achieve data security. To read an
encrypted file, one must have access to a secret key or password that
enables it to be decrypted.
End user
The individual or organisation that originates or is
the final recipient of information carried via the Internet (i.e., the
consumer).
Enterprise Networking
The networking infrastructure in a large organisation with multiple
computer systems and networks.
Ethernet
A local area network (LAN) developed by Xerox, Digital Equipment Corp.
and Intel (IEEE 802.3). Ethernet connects up to 1024 nodes at 10 Mbps over twisted-pair, coax and
fibre-optic cable. When a station is ready to send, it transmits its data packets onto the
network, which is common to all nodes. All stations hear the data. The station that matches the
destination address in the packet is the one that responds, while the others do nothing.
Ethernet is a data-link protocol and functions at the data-link and physical levels of the
OSI model (Layers 1 and 2). The following is a chart of the different cabling and topologies
supported within Ethernet networks.
| Segment | Ethernet Type |
Length | Maximum
Devices | Topology |
| 10BASE5 | Thick | 1640
ft. | 100 | Bus |
| 10BASE2 | Thin | 607 ft.
| 30 | Bus |
| 10BASE-T | Twisted Pair |
328 ft. | 2 | Star |
| 10BASE-F | Fiberoptic |
1.2 mi. | 2 | Star |
Ethernet Address
A 48-bit number maintained by the IEEE, an Ethernet Address is a
unique number assigned to each Ethernet network adapter.
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, or 100 Mbps, 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.
EtherTalk
Macintosh software from Apple that accompanies its Ethernet Interface NB
Card and adapts the Mac to Ethernet networks.
Euro-ISDN
The European implementation of ISDN.
Exchange point
Points within a network at which IP packets
are exchanged between ISPs.
Extranet
An extranet is an intranet that is partially
accessible to authorised outsiders, through the use of passwords.
Fast Ethernet
LAN technology (IEEE 802.3U) which operates at 100 Mbps, using a baseband
signal over a standard shared cable. It requires a star topology, has a more limited collision
domain than standard Ethernet and needs shorter cable lengths. Fast Ethernet is rapidly becoming
the standard Ethernet technology on the desktop.
Fast Packet
Any of several streamlined packet technologies including Frame Relay,
Asynchronous Transfer Mode, and Basic Rate Integrated Services Digital Network.
Fat Client
A client machine in a client/server environment that performs most or all
of the application processing with little or none performed in the server.
Fat Server
A server in a client/server environment that performs most or all of the
application processing with little or none performed by the client.
Fault Tolerance
A method of making a computer system or network resilient to faults
or breakdowns to avoid lost data and downtime. For servers this involves such techniques as disk
mirroring, dish duplexing or mirrored servers. For LANs and WANs it may involve the use of
multiple redundant transmission links.
Fax/Modem
A combination fax board and data modem available desktop unit that plugs
into the serial port or as an expansion board for internal installation. It includes fax switch
that routes the call to the fax or data modem.
FDDI (Fibre-Distributed Data Interface)
An ANSI standard token passing network that
uses fibre-optic cabling and transmits at 100 Mbps up to two kilometres. An FDDI network has two modes of
attachment; a device may be a Single Attach Station attached to one ring or a Dual Attach
Station attached to both rings. Typical applications of FDDI are in the area of the high speed
LAN backbones.
FDSE (Full-Duplex Switched Ethernet)
A type of switched Ethernet that uses full-
duplexed network adapters and provides 20-Mbps, or 200 Mbps, bi-directional transmission between
nodes. Fibre Loss
The amount of attenuation of signal in a fiberoptic
transmission.
Fibre Optics
A technology that uses light as a digital information carrier through
a medium made up of small strands of glass, each of which provides a path for light rays that
carry the data signal.
File ServerA high-speed computer in a LAN that stores the programs and data files
shared by users on the network; it acts more like a remote disc drive. Also called a network
server.
Filter
An arrangement of electronic components designed to pass signals in one or
several frequency bands and to attenuate signals in other frequency bands.
Filtering
Discarding packets in a LAN that do not meet the criteria forwarding.
Firewall
A network node set up as a boundary to prevent traffic from one segment to
cross over to another. Firewalls are used to improve network traffic, as well as for security
purposes.
Firmware
A category of memory chips that hold their content without electrical
power and include ROM, PROM, EPROM, and EEPROM technologies.
Flash
Flash is a vector-graphics format that produces lean, resolution-independent,
vector-based art work. It is especially good for detailed line art. Of course, you have to get
and install the Flash player (which comes with the Shockwave plug-in) to see Flash illustrations.
Flash graphics resize on on the fly as the web browser window resizes, a key capability, since
designers cannot know in advance how big a web surfer's browser window will be or how it might
change during viewing.
Flash Memory
A memory chip that holds its content without power, but must be erased
in fixed blocks rather than single bytes. Block sizes typically range from 512 bytes up to 256
KB. FOIRL (Fibre Optic Inter Repeater Link)
Defined in IEEE 802.3 and
implementing over two fibre links, transmit and receive, this medium may be up to 500m and
1 kilometre long depending on the number of repeaters in the network.
Fragment Free
A buffering technique, which represents the middle ground between cut-through and store-and-forward. The first 64 bytes of a packet are read to check that the packet meets the minimum size requirement before forwarding.
Frame: A fixed block of data transmitted as a single entity.
Frame Buffer
An area of memory used to hold a frame of data.
Frame Relay
A high-speed packet-switching protocol used in wide area networks (WANs)
. Frame Relay provides for a granular service up to DS1 rates of 1.544 Mbps and is suited for
data and image transfer. It derives its name from using the Data Link or frame OSI layer Two to
route or relay a packet directly to its destination instead of terminating the packet at each
switching node. It does not have error detection and error control within the network, which
helps to speed up the protocol.
FTP (File Transfer Protocol)
The basic way of transferring files across the Internet
. If you want to get files from another computer then you will need an FTP client (available as
shareware or there is one built into most WWW browsers).
Full-Duplex (FDX)
A channel capable of transmitting in both directions at the same
time.
Full-Duplex Ethernet(FDE)
A type of switched Ethernet that uses full-duplexed
network adapters and provides a 20-Mbps, or 200 Mbps, bi-directional transmission between nodes.
Gateway
Network interconnection device and software that operate at OSI Layer Seven.
A gateway supports a full stack of the relevant protocol, such as SNA, DecNet, ISO, TCP/IP, and
can convert to a non-seven layer protocol, such as async or BSC. It is typically used to provide
access to wide area networks over asynchronous or X.25 links from a LAN environment.
GGP (Gateway-to-Gateway Protocol)
The protocol that cores gateways use to exchange
routing information, GGP implements a distributed shortest path routing computation.
Gigabit Ethernet
Technology (IEEE 802.32) that adapts the Ethernet model for data
transmission at 1 Gbps or higher.
GIF
GIF (pronounced with a hard g) is the acronym for Graphics Interchange Format,
the ubiquitous image format of the web. GIF handles indexed images of up to 8 bits (256 colours)
. The GIF format uses a compression algorithm called Lempel-Ziv-Welch, or LZW. This
compression scheme is lossless, which means the resulting decompressed image looks exactly the
same as the original. The average compression ratio is 4:1. GIF is most useful for type, line art
or small photographs.
Half-Circuit
A component of an international circuit that
originates or terminates between countries and terminates or originates at
a theoretical midpoint between countries.
Half-Duplex (HDX)
The transmission of data in both directions, but only one
direction at a time.
Handshaking
Signals transmitted back and forth over a communications network that
establishes a valid connection between two stations.
HDSL (High Bit-Rate Digital Subscriber Line)
It uses a twisted copper pairto support
broadband transmission rates.
Heartbeat
A test for Ethernet LANs; after the computer has sent a transmission onto
the local area network, the transceiver sends a collision test signal back to the Ethernet card.
Also called Signal Quality Error.
Hierarchical Routing
Breaking a network into a hierarchy of networks to make them
smaller and thus simplify routing.
Hop
One router-to-router leg of a packet’s journey to reach a network from sender
to receiver.
Host
Any computer that can function as the beginning and end
point of data transfers. Each Internet host has a unique Internet address
(IP address) associated with a domain name.
Hot Swapping
The ability of a device to have parts removed after, for example, a
slot-in card or fan failure, without affecting its operation.
HTML (Hyper Text Mark-up Language)
The language used to create documents on the
World Wide Web.
Hub
The centre of a star topology network or cabling system. A multi-node network
topology that has a central multiplexer with many nodes feeding into and through the multiplexer
or hub. The other nodes do not usually directly interconnect. LAN hubs are losing popularity
with the introduction of lower cost Ethernet switches.
IAB (Internet Activities Board)
The technical body that sets policy and standards
for TCP/IP and the connected Internet suite of protocols. Its task forces are the IETF and IRTF.
IC
Integrated Circuit
IEEE (Institute of Electrical and Electronic Engineers)
A membership organisation
that includes engineers, scientists and students in electronics and allied fields. It sets
standards for computers and communications.
IEEE 802.2
The Data Link standard for use with IEEE 802.3, 802.4 and 802.5 standards
. It specifies how the basic data connection should be set up over the cable.
IEEE 802.3
The IEEE standard for Ethernet. A Physical Layer definition that includes
specification for physical cabling plus the method of transmitting data and controlling access
to the cable. It uses the CSMA/CD access method on a bus topology LAN.
IEEE 802.4
The IEEE standardisation of Token Bus. A Physical Layer standard that
uses the Token Ring passing access method on a bus topology LAN. Used by LANs implementing the
Manufacturing Automation Protocol.
IEEE 802.5
The IEEE standardisation of IBM Token Ring. A LAN Physical Layer standard
that uses the Token Ring passing access method on a ring topology LAN.
IEEE 802.12
The draft standard for 100BASEVG networking.
IETF
Internet Engineering Task Force.
IFG
Interframe gap.
IGP (Interior Gateway Protocol)
The term applied to any protocol used to propagate
network reachability and routing information within an autonomous system. There is no single
standard IGP, but RIP is one of the most common.
In-band Signalling
A communications technique in which the part of a signal bearing
the data control information is contained within the bandwidth of the signal it is controlling.
Intelligent Hub: A central connecting device in a network that performs a variety of processing
functions such as network management, bridging, routing, and switching.
Intelligent Modem
Originally developed by Hayes, a modem that responds to commands
and can accept new instructions during online transmission.
Internal Bus
A data pathway between closely connected components, such as between
the CPU and memory.
Internet
1. Any large network made up of several smaller networks.
2. A group of networks that are interconnected so that they appear to be one continuous large
network, and can be addressed seamlessly at the OSI model NetworkLayer through routers.
3. The industry name for the network. Based upon the original Arpanet network, it’s used
as a reference resource, for e-mail, and an on-line chat room for users around the world.
Internet Access Provider
An organisation that provides access to the Internet.
Internet Backbone
The high-speed, high capacity lines or
series of connections that form a major pathway and carry aggregated
traffic within the Internet.
Internet Content Provider
A person or organisation, that
provides information via the Internet either with a price or free of
charge.
Internet Service Provider (ISP)
ISPs provide end users, and
other ISPs, access to the Internet. ISPs may also offer their own
proprietary content and access to online services such as e-mail.
Intranet
An intranet is a network, based on TCP/IP protocols,
accessible only by the organisation's employees, or other authorised
users. Intranet websites are similar to other websites, but are surrounded
by firewalls that prevent unauthorised access from the public Internet.
IP (Internet Protocol)
The protocol used in gateways to connect networks at the OSI
Network Level (Layer 3) and above. IP routes a message across networks. It includes the ICMP
control and error message protocol as an integral part.
IP Address
The 32-bit address assigned to hosts that want to participate in a TCP/IP
Internet.
IP numbers
An IP number (also referred to as IP address
number) are the addresses of hosts or other intelligent devices on the
Internet. All servers and users connected to the Internet have an IP
number.
IPNG (Internet Protocol New Generation or IPv6)
It is not that IP does not work, but the
current 32 bit IP addressing scheme will soon be unable to cope with the increasing number of
computers on the Net. IPNG consists of 128 bits so it will allow for a quadrillion addresses on
a trillion networks. However, it is not yet fully defined and is still the subject of IETF
working parties.
IPX (Internetwork Packet Exchange)
A communication protocol in Novell NetWare that
creates, maintains and terminates connections between network devices, such as workstations and
servers.
IRL (Inter-Repeater Link)
An Ethernet segment connecting two repeaters and not
containing network stations.
IRTF (Internet Research Task Force)
A technical group working on problems related
to TCP/IP and the connected Internet. The IRTF is divided into a set of research groups. The IRTF
chairperson is a member of the IAB.
ISDN (Integrated Services Digital Network)
An international telecommunications
standard for transmission over digital lines running at 64 Kbps. ISDN uses 64-Kbps circuit-
switched channels, called B channels, or “bearer” channels, and a separate D channel, or “delta”
channel, for control signals.
ISDN Terminal Adapter
A device that attaches a computer and an analogue or telephone
to a digital ISDN line.
ISO (International Standards Organisation)
A voluntary organisation that is
responsible for setting international standards known as ISO standards.
Jabber
Random data broadcast continuously on an Ethernet LAN as a result of a faulty
adapter card.
Jack
A receptacle into which a plug is inserted.
Java
Java (from Sun Microsystems) is a cross-platform programming language which
makes programming much easier in a networked environment. Java applets are small programs that
download quickly and execute on a web surfer's system (the client).
JavaScript
JavaScript (not related to Java) is a scripting language from Netscape
Communications. It is used for controlling elements on a web page. The most popular use of
JavaScript is to create gratuitous rollovers that causes images to change when the mouse moves
across a hot spot on a web page. Other uses include changing colour of some GIF text, scrolling
text, pop-up windows and validation of forms. Microsoft's version is called JScript.
Jitter
Slight movement of a transmitted signal in time or phase that can cause
errors or loss of synchronism.
JPEG
JPEG (the common name for the raster image format defined by the Joint Photographic
Experts Group) is the most common way to compress photographic and rendered images. Because of the
overhead involved, it doesn't work well for small images or line art.
Kbpbs
A modem's speed is measured in the number of data
'bits' per second. The fastest analog modem shifts 56 000 bits per second
(56 kbps or 56k).
Local Area Network (LAN)
A computer network that spans a
relatively small area. Most LANs are confined to a single building or
group of buildings. However, one LAN can be connected to other LANs over
any distance via telephone lines and radio waves. A system of LANs
connected in this way is called a wide-area network (WAN).
LAN Segment
A part of a LAN that is separated from the rest by one or more bridges.
LANE
LAN Emulation
LAT (Local Area Transport)
A protocol unique to DEC products, for virtual terminal
access across an Ethernet network.
LATA (Local Access and Transport Area)
An U.S. geographical subdivision used to
define local (as opposed too long-distance) telephone service.
Latency
The time between initiating a request for data and the beginning of the
actual data transfer.
Layer
In the OSI reference model, one of seven basic layers, referring to a
collection of related network processing functions; one level of a hierarchy of functions.
Leased Line
A private communications channel, leased from a common carrier in a
point-to-point or multi-point configuration. Also called a private line.
Line Modulation
The means by which a carrier is varied to represent a signal
carrying information.
Link
A communications circuit or transmission path connecting two points.
Link Layer
Layer Two of the OSI reference model; also known as the Data-Link Layer.
LLC (Logical Link Control)
A protocol developed by the IEEE 802 committee for
data-link-layer transmission control.
Local Bridge
A bridge that links two local LANs; in the same building, for example.
Local Bus
A type of bus with a very short signal path between main processor and
I/O processor(s).
LocalTalk
A LAN access method from Apple that uses twisted-pair wires and transmits
at 230.4Kbps.
Loopback
A diagnostic test that returns the transmitted signal back to the sending
device after it had passed through a network or across a particular link. The returned signal
can then be compared to the transmitted one. The discrepancies between the two help trace the
fault. When trying to locate a faulty piece of equipment, loopbacks will
be repeated, eliminating satisfactory machines until the problem is found.
Log on/Log in
This is the term that is used to describe the
process of connecting your computer to a computer network. You log on/log
in to the Interne
A series of 32-bit PCs from Apple introduced in 1984 that use the
Motorola 68000 CPU family and an operating system that simulates a user’s desktop on screen.
MAC (Media Access Control layer)
The protocol that controls access to the physical
transmission medium on a LAN.
Mbps
Megabits per second (bps).
Meltdown
Term for an Ethernet problem in which the network becomes over-saturated
with misdirected packets and slows to a crawl.
MIB (Management Information Base)
The set of variables or database that a gateway
running CMOT, SNMP, or CMIP network management protocols maintains. It defines variables needed
by the SNMP protocol to monitor and control components in a network. Managers fetch or store
into these variables. MIB-II refers to an extended SNMP management database that contains
variables not shared by both CMOT and SNMP. The CMIP and SNMP MIB formats differ in structure
and complexity.
Microsoft LAN Manager
A network operating system developed by Microsoft and 3Com.
MIME (Multimedia Internet Message Exchange)
Extensions to the SMTP format that
enable it to carry multiple types of data (binary, audio, video, etc.).
Mirroring
A complete, redundant duplicate of a device including its programming and
data. Kept active, current, and on-line as a fault-tolerant backup system.
Mirror site
A host which duplicates the contents of another
host in the same or another network.
Modem (MOdulator-DEModulator)
A device that adapts a terminal or computer to a
telephone line converting the computer’s digital pulses into audio frequencies (analogue) for
the telephone system and converts the frequencies back into digital pulses at the receiving side.
Multicast Address
An address that refers to multiple network devices. Synonymous
with group address.
Multicast Bit
A bit found in the Ethernet addressing scheme that indicates that the
massage is to be sent to all stations.
Multilink PPP
(ML-PPP) A varient of PPP that addresses the additional features of
compression and channel aggregation. MP-PPP is outlined in IETF RFC 1717.
Multiplexer
A device that can send several signals over a single line. They are
then separated by a similar device at the other end of the link. This can be done in a variety
of ways; time division multiplexing, frequency division multiplexing and statistical multiplexing
. Multiplexers are also becoming increasingly efficient in terms of data
compression, error correction, transmission speed and multi-drop capabilities.
Network Access Point (NAP)
(1) Point at which the dedicated
Internet backbone lines are reached.
(2) A point at which ISPs connect
with one another. NAPs serve as data interchange points for backbone
service providers. NAPs and Metropolitan Area Exchanges (MAEs) are
generally spoken of at the beginning of 1999 as public Internet exchange
points (IXPs).
NetBEUI (NetBios Extended User Interface)
A network device driver or transport
protocol that is the transport driver supplied with LAN Manager. It can bind with as many as
eight media access control drivers.
NetBios (Network Basic Input/Output System)
Software developed by IBM that provides
the interface between the PC operating system, the i/o bus, and the network. Since its design,
NetBios has become a de facto standard.
Netscape
A web browser for Windows, Macintosh and X Windows from Netscape
Communication Corporations.
NetWare
LAN Network Operating System and related products developed by Novell.
Network
An interconnection of computer systems, terminals, or data-communications
facilities.
Network Address
The part of an IP address that specifies the network.
Network Access Control: Circuits that dictate when individual workstations may transmit messages
within a LAN.
Network Adapter or Network Interface Card (NIC)
A printed circuit board that plugs
into both the client workstations and the servers, providing control over the exchange of data
between them.
Network Administrator
The person responsible for maintaining the corporate network.
Network Analyser
A device for testing and troubleshooting networks by monitoring the
actual network data traffic.
Network Architecture
The communication equipment, protocols and transmission links
that constitute a network, and the methods by which they are arranged.
Network Cloud
A cloud-like symbol in a network diagram used to reduce an entire
communications network into points of entry and exit.
Network Device Driver
A program that enables the operating system software to
communicate the network adapter cards. Also a software module running on a host or workstation
that is responsible for the communications between the computer and the network or a device
attached to the network.
Network Driver Interface
A software interface between the transport protocol and
the data-link protocol.
Network Interface Card/Controller (NIC)
Circuitry connecting a node to a network,
usually in the form of a card in a PC expansion slot. In conjunction with NOS and PC operating
system it helps transmit and receive messages on the network.
Network Layer
Level Three in the OSI stack, it is responsible for the necessary
routing and relaying through one or more networks in multiple link or wide area environments.
Network Operating System (NOS)
An operating system that manages multiple requests
concurrently and provides the security necessary in a multi-user environment.
Network Topology
The physical and logical arrangement of the links and nodes within
a network.
Network Utilities
Programs that handle routine procedures such as troubleshooting.
NFS (Network File System)
A distributed file system from SunSoft that enable data
to be shared across a network regardless of machine. Operating system, network architecture or
protocol.
Newsgroups
Internet-based message areas or discussion groups,
organised by subject hierarchies. Collectively known as Usenet.
Node
A network junction or connection point. Node is often used instead of
workstation.
Noise
Random electrical signals, generated by circuit components or by natural
disturbances that corrupt the data transmissions by introducing errors.
NT1 (Network Terminator)
A device that terminates an ISDN line at the customer’s
premises.
NT2 (Network Termination, type 2)
Devices that handle on-premises switching,
multiplexing, or ISDN concentration.
NuBus
A high-speed bus used in the Macintosh family of computers.
NUI (Network User Identification)
A combi- nation of a packet-switched network
user’s address and the corresponding password.
Off-line
The condition in which a user, terminal, or other device is not connected
to a computer or isn’t actively transmitting via a network.
Off-line Browser
Software that downloads e-mail and selected data from an online
service, allowing the user to browse the captured material after disconnecting.
OLE, OLE2 (Object Linking Embedding)
A Microsoft specification for implementing
object-oriented software developments. An improved form of DDE, it adopts a layered approach and
allows a file or program to be embedded as an object in another file. OLE2 (the most recent
version) and ODBC drivers can be altered without affecting core software, enabling software
applications from different vendors to be accessed seamlessly. More and more organisations are
adopting this set-up.
On-Line
The condition in which a user, terminal or other device is actively
connected with the facilities of a communications network or computer.
Online Service Provider (OSP)
A company that provides
customer-only content to subscribers of their service. Most OSPs now offer
Internet access, but their main feature is the privately maintained
network that is only accessible to their customers. This network is not
part of the Internet, although some OSPs are currently making some content
available on the Web.
Online Service and Software Companies
Companies which operate
Internet sites whose principal function is to provide services in
electronic form, including transactions with third parties, sales and
support for its products and software which can be down loaded by end
users for a fee or without charge.
Optical Fibre
Any filament or fiber, made of electrical materials, that is used to
transmit laser or LED-generated signals.
OSI (Open System Interconnection)
An architectural model developed by the
International Standards Organisation (ISO) for the design of open systems networks. All
communication functions are divided into seven standardised layers; Physical, Data Link, Network,
Transport, Session, Presentation and Application.
Out-of-Band
Taking place on a channel distinct from the one that carries normal data
traffic.
Overhead
All information, such as control, routing and error-checking characters,
that is in addition to user-transmitted data.
PABX (Private Branch Exchange)
An in-house telephone switching system that
interconnects telephone extensions to each other, as well as to the outside telephone network.
Packet: A collection of bits, including the address, data and control that are switched and
transmitted together. The terms frame and packet are often used synonymously.
Packet
An information block identified by a label at layer 3
of the OSI reference model.
Packet Header
In packet-switched networks, the first three octets of an X.25 packet.
Packet Overhead
Refers to the time it takes to transmit data on a packet-
switched network.
Packet-Switched Network
A networking technology used in wide area networks (WANs)
that break up a message into smaller packets for transmission and switches them to their required
destination.
Packet-Switching
The function of handling, routing,
supervising and controlling user packet data, as required, by an
exchange.
Packet Type Identifier
The third octet in a packet header, which identifies the
packet’s function.
PAP (Password Authentication Protocol)
An authentication protocol used to verify a
user’s name and password for PPP Internet connections.
Passive Hub
A central connecting device in a network that joins wires form several
stations in a star configuration.
Patch Cord, Patch Cable
A short cable used to make a connection between two nearby
components.
Patch Panel
A group of sockets that function as a manual switching centre between
incoming and outgoing lines in a communications, electronic, or electrical system.
PBX (Private Branch Exchange)
Privately owned telephone systems that serve a
particular location such as an office, providing connections from one extendion to another,
as well as a set of external connections to the external public telephone network.
PCI (Peripheral Component Interconnect) Bus
PCI Local Bus is a high-performance bus
that provides a processor-independent data path between the CPU and high-speed peripherals. PCI
is a robust interconnect mechanism designed specifically to accommodate multiple high-
performance peripherals for graphics, full-motion video, SCSI, and LANs.
PCMCIA (Personal Computer Memory Card International Association)
A non-profit trade
association founded in 1989 to standardise a method for connecting peripherals to PCs. PCMCIA
created a 16-bit socket, that is “plug-and-play” compatible and can be automatically configured
by a software driver called PCMCIA card services.
PC Card
The name for an accessory card for PCs that follows the standards set by
PCMCIA.
PDN (Packet Data Network)
A network established and operated by a common carrier or
private operating company for the specific purpose of providing data-communications service to
the public.
Peering
The exchange of routing announcements between two
Internet Service Providers for the purpose of ensuring that traffic from
the first can reach customers of the second, and vice-versa. Peering takes
place predominantly at IXPs and usually is offered either without charge
or subject to mutually agreed commercial arrangements.
Peer-to-Peer
Communications in which both sides have equal responsibility for
initiating, maintaining, and terminating the session.
Peer-to-Peer Network
A communications network that enables all workstations and
computers in the network to act as servers to all other users on the network. Sometimes referred
to as a workgroup.
Physical Layer
Within the Open System Interconnection model, the lowest layer
concerned with the electrical, mechanical, and handshaking procedures over the device interface
that connects to a transmission medium.
PING (Packet InterNet Groper)
A utility used to determine what devices are available
and responsive on a network or at an Internet site.
Pinout
The description and purpose of each pin in a multiline connector.
Plug and Play
Also known as PnP, it’s an Intel standard for the design of PC
expansion boards that the IRQ and DMA settings and I/O and memory addresses self-configuration
on start-up.
PNG
PNG (pronounced "ping") is a new graphics format to replace GIF with a superior,
patent-free compression method, better colour capabilities and an alpha channel. PNG supports
bi-directional interlacing, colour depths of up to 48 bits, grayscale depths of up to 16 bits, a
full 8-bit alpha channel, gamma correction for cross platform "brightness" control, and file-
corruption checking, all while remaining open and extensible into the future.
Point of Presence (PoP)
A Point of Presence is a node
offering users dial-up access to the Internet via a specific telephone
number. The greater the number of Points of Presence, the higher the
likelihood that they users can connect using a local telephone call.
Point-to-Point Line
A communications network that provides a path from one location
to another (point A to point B).
Polling
The computer determines when a terminal is ready to send data, continually
interrogating all of its attached terminals in a round-robin sequence.
POP3
Post Office Protocol version 3. Most popular and
flexible system for Internet email. Some free ISPs don't currently offer
this, giving you Web-based email instead.
Port
A computer interface capable of attachment to another device, such as a modem
for communicating with a remote terminal or, if the port is within a hub, to a workstation.
Portable Document Format (PDF)
Adobe's PDF is a page-description file format based
on PostScript that gives designers precise control over the look and feel of pages. Because it is
largely a vector format, PDF is resolution independent, or scalable. You can zoom into a PDF page
in any increment, up to 800%, or view it at smaller than actual size, with excellent design
fidelity. PDF is a fixed output format, embeds fonts and prints beautifully.
Portal
Although an evolving concept, the term portal commonly
refers to the starting point, or a gateway through which users navigate
the Web gaining access to a wide range of resources and services, such as
e-mail, forums, search engines, and shopping malls.
Port Concentrator/Concentration
A device that enables several terminals to share a
single computer port; it performs communications and demultiplexing for the host system.
PostScript
PostScript is a page-description language that offers total graphical
control of fixed-size pages.
POTS (Plain Old Telephone Service)
The basic analogue service provided by the
public telephone network, without any added facilities.
Power Adapter
A transformer that converts AC power from a wall outlet into the DC
power required by an electronic device.
PPP (Point-to-Point Protocol)
A data-link protocol that provides dialup access over
serial lines by encapsulating protocols in specialised Network Control Protocol packets. These
packets can be used to replace a network adapter driver which allows remote users can log on
to the network as if they were in-house.
Presentation Layer
In the OSI model, the layer of processing that provides services
to the Application Layer, so it can interpret the data exchanged, and to structure data messages
for transmission in a specific display and control format.
PRI (Primary Rate Interface)
An ISDN service that provides 23 B channels and one
64-Kbps D channels (23B+D), which is equivalent to the 24 channels of a T1 line. In Europe,P.R.I
includes 30 B channels and one D channel, equivalent to an E1 line.
Primary Domain Controller
The server at which the master copy of a domain’s user
accounts database is maintained. The primary domain controller also validates logon requests.
A LAN Manager term.
Private Line
A term for a dedicated voice or data circuit, usually leased from a
Common Carrier, such as BT in the UK.
Proprietary
Describes non-standard technology owned and controlled by a single
entity and available from a single source.
Protocol
A set of rules governing the information flow within a communications
infrastructure, often known as “data link control”. Protocols control format, timing, error
correction and running order. They are essential for a device to be able to interpret incoming
Public Network
A network operated by common carriers or telecommunications
administrations for the provision of circuit-switched, packet-switched, and leaseed-lin
circuits to the publlic.
Public Switched Network
Any switching communications system such as Telex,
Teletypewriter Exchange Service, or public telephone networks, that provides circuit switching
to many customers.
Punch-down Block
Telephony term describing the connector arrangements for
distibuting and connecting UTP/STP wiring inside a building. Typically found in phone wiring
closets.
Push and Pull media
Terms which describe alternative modes of
operation between Internet Content Providers and Internet users. For pull
media, a user typically "pulls down" data from a website, for instance
using http. For push media, a Internet Content Provider typically "pushes"
data to pre-subscribed users at regular intervals, for instance by
e-mail.
QoS
Quality of Service.
Quad Fibre Cable
A cable onsiting of four single optical fibre cables placed
inside a polyvinyl chloride jacket.
Query
A message sent by a search engine or database to find a
particular file, Website, record, or set of records in a database.
Rackmount
Components that are built to fit in a metal frame which can be installed
in a cabinet, usually 19” wide.
Reconfiguration
The process of physically altering the location or functionality of
network or system elements. Automatic configuration describes the way sophisticated networks can
readjust themselves in the event of a link or device failing, enabling the network to continue
operation.
Redirect
A packet switching function that routes calls to an alternative network
address if the link to the original address is not working. It is carried out by end point
switches.
Repeater
1. A communications device that amplifies or regenerates the data signal
in order to extend the transmission distance.
2. A device used to tie two LANs of the same
type together.
Ring
1. A network topology in which stations are connected to one another in a
closed logical circle, with access to the medium passing sequentially from one station to the
next by means of polling from a master station, or by passing an access token from one station
to another.
2. Signal sent to a phone in the form of an audible ringing tone.
RJ-11
A wiring designation with 4- or 6-wire modular connectors; commonly used for
standard telephone lines.
RJ-12
The designation for 6-wire modular connectors.
RJ-14
A jack which looks identical to a RJ-11 except two phone lines are supported.
RJ-45
A wiring designation with 8-wire modular connectors.
RMON (Remote Monitoring)
SNMP specification for mulitvendor statistics-gathering by
a standards-based (de facto SNMP) management station from de facto standard (RMON)-compliant
devices.
Router
Specialised computers that take incoming packets and
compare their destination addresses to internal routing tables and,
depending on routing policy, send the packets out to the appropriate
interface. This process may be repeated many times until the packets reach
their intended destination.
Routing
The process of delivering a message across one or more networks via the most
appropriate path.
RIP (Routing Information Protocol)
The protocol used by Berkeley 4BSD Unix systems
to exchange routing information among a small group of computers. Implemented by the Unix
program “routed”, RIP is derived from an earlier protocol of the same name developed at Xerox.
RSVP
Resource Reservation Protocol.
Secure Electronic Transaction (SET)
SET (Secure Electronic
Transaction) is a protocol used to ensure the security of financial
transactions on the Internet. It is supported by Mastercard, Visa, IBM,
Microsoft, Netscape, and others. With SET, a user is given an electronic
wallet (digital certificate) and a transaction is conducted and verified
using a combination of digital certificates and digital signatures among
the purchaser, a merchant, and the purchaser's bank in a way that ensures
privacy and confidentiality.
Secure Sockets Layer (SSL)
SSL (Secure Sockets Layer) is a
programme layer created by Netscape for managing the security of message
transmissions in a network. SSL uses a public-and-private key encryption
system, which also includes the use of a digital certificate.
Segment
A bus LAN term meaning an electrically continuous piece of the bus. Segments
can be joined together using repeaters or bridges.
Server
1)A host computer on a network that sends stored
information in response to requests or queries.
(2) The term server is
also used to refer to the software that makes the process of serving
information possible.
Session
A logical connection between two nodes on a network for the exchange of data
; alternatively, any live link between any two data devices, such as a minicomputer and a dumb
terminal. A session is also used simply to describe connection time.
Session Layer
Layer 5 of the OSI model that provides protocols for assembling
physical messages into logical messages.
Shared Access
An access method that enables many stations to use the same, (shared),
transmission medium in a LAN.
Simplex Transmission
A communications system or link which can only carry a signal
in one direction.
Single-Mode Fibre
An optical fibre that supports only one mode of light propagation
above the cut off wavelength. The core diameters are usually between 5 and 10 microns.
Smart Hub
A twisted-pair concentrator with built-in network management facilities
for use in Ethernet and ARCNET networks.
SNMP (Simple Network Management Protocol)
SNMP is used to monitor IP gateways and
their networks. It defines a set of variables that the gateway must keep and specifies that all
operations on the gateway are a side effect of fetching or storing to data variables. It consists
of three parts; structure of management information (SMI), Management Information Base (MIB) and
the protocol itself. The SMI and MIB define and store the set of managed entities; SNMP itself
conveys information to and from these entities.
SMTP (Simple Mail Transfer Protocol)
The TCP/IP standard protocol for transferring
electronic mail messages from one machine to another. SMTP specifies how two mail systems
interact and the format of control messages they exchange to transfer mail.
Spanning Tree Algorithm
An IEEE standard algorithm that enables loops to be
configured in a bridged network to provide alternate data paths. This algorithm ensures that only
one path connects any pair of stations, selecting one bridge as the ‘root’ bridge, with the
highest priority one identifier, from which all paths should radiate.
SPID (Service Profile Identifier)
A number assigned to an ISDN line by the ISDN
service provider that identifies certain characteristics of the line.
Spike
A burst of extra voltage in a power line, lasting only a fraction of a second.
Splitter
A device that multiplies one input into a number of identical ports.
Spoofing: A method of fooling network end stations into believing that keep-alive signals have
come from and return to the host. These responses are sent to the host polling device to maintain
an active session. The result is a non-time critical network with a minimum of keep-alive
traffic between deterministic end stations, while retaining the opportunity to send flags should
an end station alter its state.
Star Topology
A network layout or design in which each station is connected to a
central station by a point-to-point link, and communicates with all other stations through the
central station.
Start-Stop Transmission
An asynchronous transmission where a group of signals
representing a character is preceded by a start bit and followed by a stop bit.
S/T Interface
A four-wire ISDN BRI interface presented to the customer by the PTTs
in non-North American markets.
STM (Synchronous Transfer Mode)
A B-ISDN communications method that transmits multiple
streams of synchronised data to a single reference clock.
Store and Forward
A buffering technique in which messages or packets are received
in their entirety by an intermediary, even if the ultimate recipient is not presently able to
receive. This is used exclusively in the context of electronic mail across wide area networks,
and occasionally for terminal I/0.
STP (Shielded Twisted Pair)
Cabling that is a twisted-pair cable with a foil and/or
braided shield to minimise EMI/RFI.
Straight-Through Pinning
Cable configuration that has connectors wired, pin for pin
(Pin 1 to Pin1, Pin 2 to Pin2, etc.).
Streaming
1.Transmitting data continuously.
2.An error condition in which a
device continuously transmits random data.
Stream RoutingLatency-minimising method found in ATM by using the information contained
in the first cell for routing.
Subnetwork
One of the networks linked by a bridge or a router.
Switch
Equipment used to connect and distribute communications between a trunk line
or backbone and individual nodes.
Switched Ethernet
An Ethernet hub with integrated MAC-layer bridging or switching
capability.
T1
A digital carrier facility used to transmit a DS-1 formatted digital signal at
1.544 Mbps that can be divided into 24 separate DSO channels at either 56 or 64-Kbps.
T3
A US standard for high-speed data transmission at 44.736Mbit/s, providing the
equivalent bandwidth of 28 T1 circuits. Also called a DS3.
TCP/IP (Transmission Control Protocol/Internet Protocol)
A set of layered protocols
that enables shared applications among PCs, hosts, or workstations in a high-speed
communications environment.
Telecommunications Facility Provider
An entity that supplies
underlying transmission capacity for sale or lease and either uses it to
provide services or offers it to others to provide services.
Teletrade
Tele-trade or teleporting refers to business use of
private telecommunications networks and increasingly the Internet to
re-deploy both high-skill and clerical/accounting jobs to developing
countries.
TELNET
A terminal-emulation protocol commonly used on the command-line level of the
Internet. It allows a user at one site to transparently interact with, or pass through to, a
remote network or timesharing system at another site, while appearing as a local terminal.
Terminal Adapter (Interface Adapter)
ISDN basic rate interface device for
circuit-switched voice and data communications access that’s installed at the customer’s site.
Terminal Emulation
Software that allows a PC to mimic the attributes of a dumb
terminal normally attached to a mainframe or mini-computer, giving the user with access to
function keys and control sequences which the host applications normally use when communicating with one of their own dumb terminals.
Terminal Server
A device that enables one or more terminals to connect to an
Ethernet LAN.
Termination
1. Placement of a connector on a cable or distribution panel.
2. The presence of an electrical load at the end of a circuit equal to the characteristic line
impedance of the physical medium being used to eliminate standing waves reflections during a
transmission signal.
Terminator
A device that provides termination for a signal line, or several lines,
at the end of a cable.
TFTP (Trivial File Transfer Protocol)
The TCP/IP standard protocol for file transfer
with minimal capability and minimal overhead. TFTP depends on the connectionless datagram
delivery service, UDP.
Thick Ethernet, Thicknet
Standard 10BASE5 Ethernet. Refers to the coax backbone.
Thin Ethernet
An 802.3 LAN that uses smaller than normal diameter coaxial cable;
often used to link PCs together. It runs at the same frequency as Ethernet but at smaller
distances. Also known as Cheapernet or ThinNet.
Throughput
The effective transmission rate through the
network from one end point to another. A measurement of throughput will
necessarily be impacted by the slowest link in the path of transmission as
well as current traffic volumes on each of these links on the path from
start to the end.
Throughput Delay
The length of time required to re-transmit a received signal.
TNC
A commonly used connector for coaxial cable. After inserting the plug, the
threaded outer ring is turned, tightening the pins in the socket.
Token
Unique information in a packet header which acknowledges that control of the
network is to be relinquished upon receipt of the packet. The token packet passes round the LAN
continuously and, as it goes by, gives each workstation the all-clear to transmit data.
Token Ring
A network-access mechanism and ring topology in which a supervisory frame
or token is passed from station to station as a poll for network transmission (IEEE 802.5
standard).
Topology
The logical or physical arrangement of network stations, in relation to
each another.
Transceiver
A hardware device that links a node with a baseband network backbone,
enabling transmitting and receiving capabilities.
Transmission Control Protocol/Internet Protocol (TCP/IP)
The
suite of protocols that defines the Internet and enables information to be
transmitted from one network to another.
Transport Layer
Layer 4 of the OSI model that defines the transport protocol and
transport services, including the lower-level data-link protocol that moves packets from one node
to another.
Tree
A network topology that recognises only one route between two nodes. The map
resembles a tree or the letter T.
Twinaxial Cable
A coaxial cable with twin centre conductors.
Twisted Pair
Two insulated copper wires twisted together with the twists or lays
varied in length to reduce potential signal interference between the two pairs. The most common
medium for connecting phones, computers and terminals to PABXs.
Type A Coax
In IBM 3270 Systems, a serial transmission protocol operating at
2.35Mbps.
Type B Coax
A type of RG59 coaxial cable used in pre-1977 IBM 3270 systems.
U Interface
A two-wire interface presented to the customer by the telco in the U.S.
market. The customer is responsible for converting this signal to the four-wire S/T interface to
make a connection.
UPS (Uninterruptible Power Supply)
A battery, attached to a piece of hardware, for
example a server, that provides backup power for conducting an orderly shutdown if the server’s
normal power supply fails.
UTP (Unshielded Twisted Pair)
The standard cabling used for telephone lines. A cable
with two conductors twisted as a pair and bundled within the same outer PVC covering.
Uniform Resource Locator ("URL")
The standard way to give the
address or domain name of any Internet site that is part of the World Wide
Web (WWW). The URL indicates both the application protocol and the
Internet address e.g.,: http://www.itu.int
VAN (Value-Added Network)
A communications network that provides services beyond
normal transmission, such as automatic error detection and correction, protocol conversion,
and message storing and forwarding.
Virtual LAN (VLAN)
A logical rather than a physical LAN comprising workgroups drawn
together for business reasons or for a particular project irrespective of each member’s actual
location. Members are likely to belong to several such LANs as their job function dictates.
VN3/VN4
The French national ISDN standards.
VPN (Virtual Private Network)
The provision of private voice and data networking
from the public switched network through advanced public switches. The network connection
appears to the user as an end-to-end, nailed-up circuit without actually involving a permanent
physical connection, as in the case of a leased line. VPNs retain the advantages of private
networks but add benefits like capacity on demand.
WAN (Wide Area Network)
A network which covers a larger geographical area than a
LAN and where telecommunications links are implemented.
Warm Boot
To cause an operating system to completely reload software. Also known as
a soft boot. Web-based Email
A type of service that lets you collect your
email messages from a website, rather than from your ISP.
Webcasting
A group of emerging services that use the Internet
to deliver content to users in ways that sometimes closely resemble other
traditional communication services such as broadcasting.
Website / Webpage
A website (also known as an Internet site)
generally refers to the entire collection of HTML files that are
accessible through a domain name. Within a website, a webpage refers to a
single HTML file, which when viewed by a browser on the World Wide Web
could be several screen dimensions long. A "home page" is the webpage
located at the root of an organisations URL.
Wireless LAN
A LAN in which data flows by radio or infrared transmissions, rather
than over wires.
Wiring Closet
A central location for termination and routing of premise wiring
systems.
Whole Circuit
A circuit that connects points in different
countries where a single entity owns the circuit in its entirety or owns,
leases or operates two half-circuits in combination.
World Wide Web (WWW)
(1) Technically refers to the hypertext
servers (HTTP servers) which are the servers that allow text, graphics,
and sound files to be mixed together.
(2) Loosely refers to all types
of resources that can be accessed including: HTTP, Gopher, FTP, Telnet,
USENET, and WAIS.
Zero-Slot LAN
Refers to transmitting between computers over a serial or parallel
port, which frees up an expansion slot normally used by LAN cards (NICs).
Zone
1. A logical sub-network in an AppleTalk network.
2. A series of specified areas, beyond the based-rate
service area of an exchange furnished in zones at
rates or tolls in addition to base-rate service charges.
LIST OF ABBREVIATIONS AND ACRONYMS
AOL America Online
APNIC Asia-Pacific Network Information Centre
ARIN American Registry for Internet Numbers
ARP Address Resolution Protocol
ARPAnet Advanced Research Projects Agency Network
ASCII American Standards Committee for Information Interchange
ATM Asynchronous Transfer Mode
AUI Attachment unit interface
BER Bit error rate/ratio
BISDN Broadband ISDN
BRI Basic rate interface
CCITT International Telegraph and Telephone Consultative Committee
( now ITU-T)
CAGR Compound Annual Growth Rate
CD-ROM Compact Disk - Read-Only Memory
CERN European Laboratory for Particle Physics
CLNAP Connectionless Network access protocol
CLNIP Connectionless Network interface protocol
CLNS Connectionless Network service
CMIP Common Management Information Protocol
CSMA Carrier Sense Multiple Access
CSMA/CA CSMA with collision avoidance
CSMA/CD CSMA with collision detection
CSPDN Circuit switched PDN
DAP Directory Acccess Protocol
DARPA (US) Defense Advanced Research Projects Agency
DCE Data circuit terminating equipment
DLC Data Link Control
DLCI Data Link Connection Identifier
DNS Domain Name System
DTE Data terminal equipment
DTP Distributed Transaction Processing
EDI Electronic Data Interchange
EGP Exterior Gateway Protocol
EIA Electrical Industries Association
E-Mail Electronic Mail
ETSI European Telecommunications Standards
EU European Union
FCS Frame Check Sequence
FDDI Fiber Distributed Data Interface
FDM Frequency-division multiplexing
FDMA Frequency division multiple access
FEP Front end processor
FIFO First-in, first-out
FTP File Transfer Protocol
GNP Gross National Product
gTLDs Generic Top Level Domains
HDLC High-level data link control
http Hypertext Transport Protocol
IAHC International Ad Hoc Committee
IANA Internet Assigned Numbers Authority
ICANN Internet Corporation for Assigned Names and Numbers
ICMP Internet control message protocol
IEEE Institute of Electrical and Electronics Engineers
IETF Internet Engineering Task Force
IGP Interior Gateway Protocol
IP Internet Protocol
IS Intermediate System
ISDN Integrated Services Digital Network
ISO International Standardisation Organisation
ISP Internet Service Provider
ITU International Telecommunication Union
ITU-T ITU - Telecommunications (Sector)
IXP Internet Exchange Point
LAN Local Area Network
LAPB Link access procedure, balanced
LCN Logical Channel Number
LED Light emitting diode
LLC Logical link control
MAC Media/Medium access control
MAN Metropolitan area network
MIB Management information base
MOTIS Message-oriented text interchange standard
MUX Multiplexer
NAK Negative acknowledgement
NAP Network Access Provider
NEXT Near end crosstalk
NMS Network Management System
NRM (Unbalanced) normal response mode
NRZ Non-return to zero
NRZI Non-return to zero inverted
NS Network service
NSF National Science Foundation
NT Network termination
OECD Organisation for Economic Co-operation and Development
OOK On-off keying
OSI Open Standards Interconnection
OSPF Open shortest path first
PABX Private automatic branch exchange
PAD Packet assembler-disassembler
PAM Pulse amplitude modulated
PBX Private branch exchange
PC Personal Computer
PDH Plesiochronous digital hierarchy
PDN Partial distinguished name/Public data network
PDU Protocol data unit
PICS Platform for Internet Content Selection
PING Packet internet groper
PISO Parallel in, serial out
PIXEL Picture element
PLP Packet layer protocol
PoP Point of Presence
POP3 Post Office Protocol ver 3
PPDU Packet PDU
PPDU Presentation PDU
PPP Point-to-point protocol
PRI Primary rate interface
PSAP Presentation service access point
PSDN Packet switched data network
PSE Packet switching exchange
PSK Phase-shift keying
PSTN Public Switched Telephone Network
PTO Public Telecommunication Operator
PTT Post, Telegragh, and Telephone (authority)
PVC Permanent virtual connection/circuit
QoS Quality of service
RARP Reverse ARP
RF Radio frequency
RI Ring indication
RIP Routing information control
RIPE Reseaux IP Europeens
ROM Read only memory
RPC Remote Procedure Call
RSVP Resource Reservation Setup Protocol
RTP Real Time Protocol
RTS Request to send
RVCI Ring virtual channel identifier
SA Source address
SAP Service access point
SAPI Service access point identifier
SD Start delimiter
SDH Synchronous digital hierarchy
SDLC Synchronous data link control
SET Secure Electronic Transaction
SFD Start-of-frame delimiter
SIPO Serial in, parallel out
SLIP Serial line interface protocol
SMDS Switched multi-megabit data service
SMTP Simple Mail Transfer protocol
SNA Systems Network Architecture (IBM)
SNMP Simple network management protocol
SONET Synchronous optical network
SPF Shortest-path path
SSL Secure Sockets Layer
STM Synchronous transport mode
STP Shielded twisted pair
SVC Switched virtual connection
TA Terminal adapter
TCP/IP Transmission Control Protocol / Internet Protocol
TCU Trunk coupliing unit
TDM Time division multiplexing
TDMA Time-division multiple access
TFTP Trivial file transfer protocol
TSAP Transport service access point
TTL Transistor transistor logic
UA User agent
UART Universal asynchronous receiver transmitter
UDP User Datagram Protocol
USRT Universal synchronous receiver transmitter
VC Virtual connection
VCC Virtual channel connection
VCI Virtual channel identifier
VPN Virtual Private Network
VT Virtual terminal
WAN Wide area network
WHO World Health Organisation
WIPO World Intellectual Property Organisation
WTO World Trade Organisation
WWW World Wide Web
Some of these terms were taken from the ITU Publication,"Internet for Development: CHALLENGES
TO THE NETWORK". Others are from different Internetworking sources.
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