Glossary of Terms
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.
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.
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
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.
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.
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.
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.
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.
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info@centralcommunications.co.uk