Here are some of the terms you will come across whilst in the world of VoIP. This list is no way complete and if you should find a term missing post below and it will be added to the main Glossary once validated.

What is VoIP?
Lets start right at the beginning. VoIP is short for Voice Over Internet Protocol - Internet Protocol is shortened to IP in everyday terms. You may have heard of an IP address? When used in speech VoIP is often called Voice over IP.

VoIP is a method of sending voice information over networks used IP networks rather than the traditional circuit switched networks of the public switched telephone networks (PSTN). It can be just around a commercial network before breaking out to Plain Old Telephone System (POTS) or it can span the world traveling over the internet before reaching its destination, having never left IP networks.

A

ADSL Asymmetric digital subscriber line. A form of data communications technology that enables faster data transmission over copper telephone lines. Used for internet access. Download bandwidth is usually much higher than upload bandwidth.

Audio Menu A spoken menu provided to callers to prompt them to press a button or speak.

Audio Response Unit A system which can simply play a message to users or react to an input, be that a spoken command or a button press.

B

Bandwidth Bandwidth is the amount of data which can be transfered in a given time frame. This is usually expressed as bps or bits per second.

Broadband High speed internet access usually provided via DSL or via cable. Broadband uses different frequencies to dialup internet access and does not affect telephone usage.

C

Circuit switched They use a dedicated point-to-point connection for each call. This reduces their utility because no network traffic can move across the switches that are being used to transmit a call.

Client (Software) A client is the application used to communicate with another piece of software. In VoIP the client is usually a softphone used to make phone calls.

CodecCodec is a term that arises from the Compressor-Decompressor process. It is used for software or hardware devices that can convert or transform a data stream. For instance, at the transmitting end codecs can encode a data stream or data signal for easy transmission, storage or encryption. At the receiving end, they can decode the signal in the appropriate form for use.

Compression Compression is the act of metaphorically squeezing data in a format that takes less space to store or less bandwidth to transmit. It is very useful in handling large graphics, audio and video files.

D

DSL Digital Subscriber Line. This has become the marketing name for ADSL but is infact the DSL family include many kinds of service.

E

E999 Enhanced 999 is the ability for the 999 operator to locate the caller from the location registered against the number.

F

Full Duplex In networking terms this means both ends of the route will be able to send and receive data at full speed without degrading the quality of the content.

G

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H

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I

IP IP or Internet Protocol, defines the way data packets should be moved between the destination and the source.

IP address An IP address is the machine number used to identify all devices that are connected to the net. Each device has its own unique number which it uses to communicate. This number is fixed in the case of those computing devices that have a fixed IP address. The rest are allotted a dynamic IP address, which is valid for the period they are connected to the net. The numbers range from 0.0.0.0 to 255.255.255.255.

IVR (Interactive Voice Response) This is an interface between computer data and the caller. Specific information or routing is generated using the response to a prompt from the IVR, for example banks sometimes use an IVR to retrieve bank details in relation to an account number the caller gives.

J

Jitter Jitter is a momentary fluctuation in the transmission signal. This happens in computing when a data packet arrives either ahead or behind a standard clock cycle. In telecommunication, it may result from an abrupt variation in signal characteristics, such as the interval between successive pulses.

K

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L

Latency Latency is the time that elapses between the initiation of a request for data and the start of the actual data transfer. This delay may be in nanoseconds but it is still used to judge the efficiency of networks.

M

Modem A modem (modulator / demodulator) is a piece of equipment used to convert digital signal to analog signal and then reverse this at the other end.

N

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O

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P

Packet A unit of data which can be sent separate to the other packets which make up the whole communication. The idea being that individual packets can be routed in the best possible way and reconstructed when received.

Packet Switching Packet switching is the practice of sending each packet over the best possible route. In contrast circuit switching is opening a full circuit between two points and that is the only path data will flow. Plus with packet switching routes can carry packets from multiple sources where a circuit switched network can only carry one signal down a circuit at one point. The internet is packet switched where as the POTS is circuit switched for the most part.

Packet loss Packet loss is the term used to indicate the loss of data packets during transmission over a computer network. This may happen on account of high network latency or on account of overloading of switches or routers that are unable to process or route all the incoming data.

Protocol A protocol a convention or standard that defines the procedures to be adopted regarding the transmission of data between two computing end points. These procedures include the way the sending device should sign off a message or how the receiving device should indicate the receipt of a message. Similarly, the protocols also lay down guidelines for error checking, data compression, and other relevant operational details.

PBX (Private Branch eXchange) PBXs make connections among the internal telephones of a private organisation and also connects them to the public switched telephone network (PSTN).

PSTN (Public Switched Telephone Networks) The worlds combined public circuit switched telephone network. The PSTN used to be entirely analog but now it tends to be mostly digital.

Q

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R

RJ11 An RJ11 is a 6 position jack. Often found when connecting modems to PSTN lines.

RJ45 An 8 postion jack used commonly in data communications. Often seen connecting computers to a switch.

Router A router is a network device that that handles message transfer between computers that form part of the Internet. The messages, which are in the form of data packets, are forwarded to their respective IP destinations by the router.

S

SIPSIP is Session Initiation Protocol. SIP is a signaling protocol, widely used for controlling multimedia communication sessions such as voice and video calls over IP.

T

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U

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V

VoIP Voice over internet protocol. The name given to the many ways of transmitting (mainly) spoken noise over networks. This can be over a LAN, WAN or even over the internet.

Voicemail Voicemail or VM is a telephone messaging system that digitizes the analog voice signals and stores them on disk or flash memory in a central location. These messages can then be retrieved by users at a later date.

W

WAN Wide Area Network. A private network spread over a large geographical area. A WAN can connect to the internet or even use the internet to transmit its data (for example using VPNs or MPLS infrastructure).

X

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Y

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Z

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This is a working list so please feel free to suggest any additions!