HomeGlossary of Terms
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10BASE-T
The IEEE.802.3i standard specification for 10Mbps Ethernet transmission
over UTP wiring, using a star configuration with a hub at the centre.
100BASE-T
The IEEE.802.3u standard Ethernet specification for 100MBPS (Fast
Ethernet) using UTP cable.
A-law
A method of encoding audio signals. A-law is the most common within
Europe.
ATM (Asynchronous Transfer Mode)
LAN and WAN scaleable networking technology
Backbone
The part of the network that carries the heaviest traffic, normally LAN
to LAN
Bandwidth
The useable capacity of a network, normally measured in bits per second
(bps)
Bridge
A device that connects two networks or two segments of a network
together. Works at the Data Link layer. The equivalent of a two port
switch.
Broadcast
The transmission of a signal (audio and video) from one endpoint to
many.
Broadband
A network transmission technique that uses radio frequencies on a cable.
Bus topology
The physical layout of a network in which all systems connect to a main
cable in a linear fashion.
Cascading
A method of connecting two or more MCU's to increase the total number
of endpoints that can be included in a conference.
Centralised Multipoint Conference
A conference where all endpoints connect via an MCU.
Common Interface Format (CIF)
H.261 Standard video format (352 pixels x 288 lines) at a maximum of 30
frames per second.
Circuit Switched Network
A network that uses circuit switching techniques to establish a
dedicated network path between devices, for the duration of the
conference.
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Decentralised Multipoint Conference
A multipoint conference where the audio switching is managed by each
endpoint, without the use or necessity of an MCU.
E1
A digital circuit used in wide area networks. The maximum network speed
is 2.048Mbps however, this is often broken down in 30 distinct channels
of 64kbps
Ethernet
The underlying network technology, see 10BASE-T and 100BASE-T.
FDDI
Fibre Distributed Data Interface. Fibre optic standard with high
reliability, normally runs at 100Mbps
Firewall
A computer or computer software that connects to a LAN and lets only
certain types of information through.
Frame Relay
A high speed, low latency packet switching technology, used in WAN's
for LAN to LAN connectivity.
Full Duplex
Two way simultaneous transmission.
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Gatekeeper
An H.323 entity that provides address translation, access control and
bandwidth control.
Gateway
A network station that is used to interconnect two or more dissimilar
networks or devices. It may perform protocol conversation.
In strictly videoconferencing terms, it provides two way communication
between H.323 and H.320 endpoints.
H.245
The control protocol managing how H.323 endpoints send information
H.320
The ITU-T umbrella standard defining multimedia videoconferencing on a
WAN (typically ISDN)
H.323
The ITU-T umbrella standard defining multimedia videoconferencing on a
LAN.
Half Duplex
Two-way transmission, one at a time.
Hub
The central wiring concentrator in a star configured network.
IEEE
Institute of Electrical Engineers. The organisation that defines Token
Ring and Ethernet based standards
Integrated Services Digital Network (ISDN)
A public, circuit switched digital network.
International Standards Organisation (ISO)
A body that promotes standards. Developed the OSI model for network
communications.
Internet Protocol (IP)
The protocol that provides for transmitting data between devices using
fixed length addresses. The protocol has no mechanisms for ensuring
reliability, flow control and packet sequencing which are dealt by
other protocols operation within IP.
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kbps
Kilo Bits Per Second. Indicates a transmission speed of multiples of
1000 bits per second
Local Area Network (LAN)
A private communications network linking computers, printers and other
equipment in a limited geographic area or location.
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Mbps
Mega Bits Per Second. Indicates a transmission speed of multiples of
1000000 bits per second.
Multicast
The transmission of information from one to many endpoints.
Multipoint Conference
A conference with three or more participants
Multipoint Control Unit (MCU)
A device that combines audio, video and data streams originating from
different endpoints to all other endpoints taking part in the
conference.
An MCU generally consists of an MC and an MP
Multipoint Controller (MC)
Provides control of three or more endpoints in a multipoint conference.
Multipoint Processor (MP)
Provides mixing, switching and other processing in a multipoint
conference.
Network Interface Card
An adapter that connects a PC or other device to a Local Area Network.
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PSTN
Public Switched Telephone Network. The 'normal' analogue telephone
service. Also referred to as POTS (plain old telephone system)
Packet
Data, including information such as source and destination addresses
formatted for transmission.
Packet Analyser
A network diagnostic tool that hooks into a LAN and analyser its
traffic. Capable of capturing a packet examining it and breaking it
down into its component parts of destination, origin and protocol etc.
Protocol
Any defined set of procedures, conventions or methods that when adhered
to, allow devices to inter-operate.
Quality of Service
Refers to the ability of a network to deliver end to end services for
network applications with a defined and requested level of delay,
jitter, data loss and bandwidth.
Registration, Admission and Status (RAS)
Signalling used for communication between an endpoint and a Gatekeeper.
Repeater
A network device that regenerates and amplifies signals to extend the
length of a network.
Resource Reservation Protocol (RSVP)
A signalling protocol that allows applications to request specific
quality of service from the network.
Router
A network device that connects multiple networks together and directs
traffic between them. Operates at layer 3 of the OSI model.
Segment
A logical group of Endpoints running at the same network speed and
registered with the same Gatekeeper.
Shielded Twisted Pair (STP)
A thin diameter network wire, wrapped with a metal sheath for extra
protection against electrical interference.
Simple Network Management Protocol (SNMP)
A de-facto standard for managing network devices and for collecting
statistics, performance details and security.
Star Topology
A network cabling configuration that uses a central connection point
(hub) through which all communications pass.
Switch
A device that directs network traffic. A Layer 2 switch operates like a
bridge a Layer 3 switch like a router.
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T1
A digital circuit used in wide area applications. Circuit speed is
nominally 1.5044Mbps, however it is typically supplied preformatted to
28 general purpose channels operating at 64kbps. T1 is the US
equivalent of E1
T.120
The standard that defines data sharing within a conference.
Token Passing
A network transmission method that requires a node to have total
control of a token' before it can send messages.
Token Ring
IBM's implementation of token passing, governed by IEEE 802.5. Operates
at speeds up to 100Mbps.
Transcoding
The conversion of signals from one protocol to another e.g. H.323 to
H.320
Transmission Control Protocol (TCP)
A network protocol that provides communication paths over an IP network.
Twisted Pair
A popular and low cost LAN cabling method, also commonly used for
telephone wiring. Uses two wires twisted together to minimise
electrical interference.
Unshielded Twisted Pair (UTP)
A thin diameter network wire, popular in network cabling installations,
relatively cheap
User Datagram Protocol
A communication protocol that provides a generally unreliable, but
efficient communications path over an IP network.
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Wide Area Network (WAN)
A geographically dispersed network that connects two or more LAN's.
X.25
A WAN standard for protocols and message formats. Used to access public
packet switching networks.
Zone
An H.323 grouping of endpoints that are all associated with the same
Gatekeeper.