VoIP Glossary

As with any technology, VoIP has it's fair share of buzz words. Check out the latest terminology and their meanings below.

Use the following links to quickly find the more common terms:

|  VoIP  |  ATA  |  FXO  |  FXS  |  PSTN  |  QoS  |  SIP  |  Soft Phone  |  RFC  |  VSP  |  






802.1p - An IEEE standard for providing QoS using three bits (defined in 802.1q) to allow switches to reorder packets based on priority level.

802.1q - An IEEE standard for providing virtual LAN (VLAN) identification and QoS levels. Three bits are used to allow eight priority levels, and 12 bits are used to identify up to 4,096 VLANs.

ADSL - Asymmetric Digital Subscriber Line is a technology for bringing high-bandwidth information to homes and small businesses over ordinary copper telephone lines.

ANI - Automatic Number Identification. A telephone function that transmits the billing number of the incoming call (Caller ID, for example).

AP - Access Point. A Wireless Acces Point is used to connect wireless devices to the network.

Asterisk - An Open Source "Do it all" PC based software PBX. You can set up your own highly flexible voip or analog PBX using PC hardware for very little cost. For more information, refer to www.asterisk.org.

ATA - Analog Terminal Adapter - The Analog Terminal Adapter is a hardware device that converts the signals from a standard analogue telephone into the digital signals that a VOIP device needs to communicate over the internet.

ATM - Asynchronous Transfer Mode is an International Telecommunication Union-Telecommunications Standards Section (ITU-T) standard for cell relay wherein information for multiple service types, such as voice, video, or data, is conveyed in small, fixed-size cells.

Bandwidth - The maximum data carrying capacity of a transmission link. For networks, bandwidth is usually expressed in bits per second (bps), kilo bits per second, (Kbps) mega bits per second (Mbps) or giga bits per second (Gbps).

BLI - Busy Lamp Indicator. A light or LED on a telephone that shows which line is in use.

Broadband - Broadband comes from the words "broad bandwidth" and is used to describe a high-capacity, two-way link between an end user and access network suppliers capable of supporting full-motion, interactive video applications. Broadband includes cable and ADSL internet connections. VoIP needs broadband to operate at a minimal Quality of Service that is acceptable to most people.

CID - Caller Identification This is where the identity (number) of an incoming telephone caller is displayed on a compatable telephone handset . If the receiver of the telephone call knows the caller and has the caller's phone number programmed into their compatible handset, the name of the caller can also be displayed on the handset.

Codec - Abbreviation of coder/decoder. Converts audio signals into a digital format. Compression can be used during the conversion process to make the data "smaller" and easier to transmit. With a residential voip service compression is often used to allow the Voip data that's transmitted over your broadband link to be "small" enough to make a quality call without dropouts. Too much compression can make it sound like you're talking into a tin can. The most popular codecs in VoIP are G.729 (AB) and G.711 (u/A).

CRM - Customer Relationship Management - maximizing the value of customer relationships with different strategies.

Data Rate - The speed for sending or receiving data packets. Data rates for typical user services are measured in kilobits per second (kbps) or megabits per second (Mbps).

downstream data rate For an end user, the data rate for receiving information from a network (e.g. what you hear from the other person).

upstream data rate For an end user, the data rate for sending information to a network (e.g. what the other person hears from you).

Example: A “512/128 ADSL service” refers to a data service using Asymmetric Digital Subscriber Line technology that has a downstream rate of 512kbps and an upstream rate of 128kbps.

DHCP - The Dynamic Host Configuration Protocol (DHCP) is an internet protocol that automates the allocation of ip addresses for computers that use TCP/IP.

DID - Direct Inward Dialing (VoIP speak for phone number). This is a telephone number that you can give to other people to phone you. Not all VSPs will give you a DID. All DIDs in Australia are registered with Telstra, and Telstra charges VSPs $5.00 per month for each DID. The VSP will then charge you $5.00 if you want a DID. Not everyone that uses VoIP will need a DID (ie if you keep your normal PSTN phone number and only use VoIP for outgoing calls)

Diff-Serv - Differentiated Services. The Diff-Serv model divides traffic into a small number of classes to provide quality of service (QoS).

DNIS - Dialed Number Identification Service. A telephone function that sends the dialed telephone number to the answering service.

DSL - Digital subscriber line is a technology for bringing high-bandwidth information to homes and small businesses over ordinary copper telephone lines.

DTMF - Dual-Tone Multifrequency. The type of audio signals generated when you press the buttons on a touch-tone telephone

E1 - The European counterpart to T1 which transmits at 2.048 Mbps

ENUM - Telephone Electronic Number Mapping is a system where anyone that has a PSTN phone or a DID can register their phone number on an international database of VoIP users. Whenever someone with a VoIP telephone service (from a participating VSP) calls a phone number using their VoIP service, their participating VSP first checks the ENUM database.

Ethernet - is one of the most widely implemented LAN standards. Ethernet is a local-area network (LAN) architecture developed by Xerox Corporation in cooperation with DEC and Intel in 1976. Ethernet uses a bus or star topology and supports data transfer rates of 1 Gbps.

Firewall - A firewall protects your computer network from the internet by preventing network traffic communicating between each other. That's great to prevent malicious attacks however it can cause havoc if you are trying to get your ip telephone to work. All routers have a firewall built in. Information about routers is available on this site on the routers page.

FXO - Foreign Exchange Office. Receives voltage and ring signal from external source such as the phone company. A good example of this would be your standard analog phone.

FXS - Foreign Exchange Station. Provides power and ring signal to external locations. for example, your phone company provides you with an FXS interface.

G.711 - An ITU-T PCM half-duplex codec that uses either A-law or µ-law compression (64 kbps, high quality, minimum processor load).

G.723.1 - An ITU-T double rate CELP codec (6.4/5.3 kbps, medium quality, high processor load).

G.726 - An ITU-T ADPCM wave form codec (16/24/32/40 kbps, good quality, low processor load).

G.728 - An ITU-T low delay CELP codec (16 kbps, medium quality, very high processor load).

G.729 - ITU-T ACELP codec (8 kbps, medium quality, high processor load).

G.7xx - A family of ITU standards for audio compression.

H.323 - A popular ITU (International Telephone Union) Voip and videoconferencing protocol that is widely in use today.

Hard Phone - A real desktop phone. Ranges in quality and price. Better than a soft phone by a long shot.

IAX - Inter Asterisk Exchange. A proprietary Asterisk Protocol that is firewall resistant and easier to use than SIP.

IP - Internet Protocol - IP specifies the format of packets, also called datagrams, and the addressing scheme. Most networks combine IP with a higher-level protocol called Transmission Control Protocol (TCP), which establishes a virtual connection between a destination and a source. IP by itself is something like the postal system. It allows you to address a package and drop it in the system, but there is no direct link between you and the recipient.

IP Address The Internet Protocol Address is a unique number that is used to identify a hardware device on a network (NB The biggest network in the world is the Internet itself). An IP address takes the form ###.###.###.### where # = any integer. IP Addresses are allocated by routers so that the router knows what hardware devices are connected to it.

ISP - Internet Service Provider. A company (ie like BigPond, Optusnet) that provides internet service to a subscriber (ie you). An ISP physically connects to the internet by paying for a connection to one or more internet service providers. The ISP then allows you to connect to their network and in doing so connects you to the internet.

IVR - Interactive Voice Response. A recored message that offers you a menu of choices and responds accordingly. (ie "Press 1 for sales, 2 for support...")

LCR - Least Cost Routing (or Least Cost Calling) is a method where the cheapest route for calling a particular number is used. In VoIP, it commonly refers to using a VSP that provides the best rates based on the destination number.

MAC Address - a 12 digit HEX number that uniquely identifies computer hardware that connects to the internet.

MER - A Multi Extension Ring Group. This term is mainly used when dealing with an Epygi Quadro IP PBX. It means a number of extensions have been set up to ring at the same time. The call can be answered by any of the extensions that are ringing.

MGCP - Media Gateway Control Protocol. Signaling Protocol for Voip.

MPEG-2 - MPEG-2 is a widely used format for the transmission of digital television signals that are broadcast by terrestrial (over-the-air), cable, and satellite Television systems

PBX - Private Branch eXchange. An in-house telephone switching system that interconnects telephone extensions to each other as well as to the outside telephone network.

POTS - Plain Old Telephone Service. The same service that your parents grew up with and with which we are all familiar.

PRI - Primary Rate Interface. An ISDN service that provides 23 64-Kbps B (Bearer) channels and one 64-Kbps D (Data) channel (23 B and D).

PSTN - Public Switched Telephone Network is the international telephone system based on copper wires carrying analog voice data. See also: POTS.

QoS (Quality of Service) - An overall measure of service performance. Quality of Service is a software inclusion in many routers that allows the user to prioritise the upstream bandwidth for a particular device. In this way, you can give a device such as an ATA priority over other internet traffic so that the quality of the VoIP call is maintained. This is important because most broadband connections have a smaller upstream bandwidth than the downstream bandwith. A low QoS measure can mean an unusable service.

RFC - The Internet's Request for Comments documents series: The RFCs are working notes of the Internet research and development community. A document in this series may be on essentially any topic related to computer communication, and may be anything from a meeting report to the specification of a standard.

ROI - Return on Investment = funds raised as a percentage of fund raising expenses.

Router - A router is effectively a 'powerboard' for the internet. You can connect more than one internet device to your single internet connection. Almost certainly if you have started with broadband internet, and then decided to add VoIP to your suite of internet services, you will need to buy a router.

RTP - Real Time Protocol

SHDSL - Symmetric High-Bitrate Digital Subscriber Loop.

SIP - Session Initation Protocol. An IETF (Internet Engineering Task Force) application-layer protocol used for establishing and tearing down unicast and multicast multimedia sessions. Currently the most useful and popular protocol for Voip. See this Wiki for all of the gory details.

Skinny - Also called SCCP. Proprietary Cisco protocol used in cisco voip products.

Skype - Skype is a PC based VoIP service that uses a propriatry protocol. This means that Skype users can only phone other Skype users, and they cannot make calls to the PSTN network. For more information go to http://www.skype.com/

SLA - Service Level Agreement is a contract between a network service provider and a customer that specifies, usually in measurable terms, what services the network service provider will furnish. Many Internet service providers ISPs provide their customers with an SLA.

Soft Phone - A Voip Phone completely implemented in software designed to be used from a computer with a headset or a microphone and speaker. Often because of ambient noise or poor quality microphones and sound cards yields poor results.

STD - Subscriber Trunk Dialing is the technical term for what is commonly referred to as National or Long Distance phone calls. The term came about because prior to this Long distance calls were only possible with the intervention of a Telephone Operator.

STUN - Simple Traversal of UDP through NAT. Different routers handle NAT differently. Which method your router uses will have an impact on how your ATA needs to operate. Some ATAs have a STUN client built in. Therefore your ATA can send a message to a STUN server and get a response back. This process called Stunning will tell the ATA what the public IP address of the ATA is, and how the Router is passing packets between the ATA and the internet.

T1 - A 1.544-Mbps point-to-point dedicated digital circuit provided by the telephone companies consisting of 24 channels.

TAPI - Telephony API. A programming interface that allows Windows client applications to access voice services on a server.

TDM - Time Division Multiplexing

TOS - Type of Service. A method of setting precedence for a particular type of traffic for QoS.

TR-069 - (short for Technical Report 069) is DSL Forum technical specification entitled Customer Premise Equipment (CPE) WAN Management Protocol (CWMP). It defines a method for remote management of end-user devices. See this link for more details.

Trunk - A communications channel between two points, typically referring to large-bandwidth telephone channels between switching centers that handle many simultaneous voice and data signals.

UPS - Uninterruptible Power Supply. A battery powered device that will allow your computer to run when AC power is turned off. These are also essential for a reliable VoIP service as you can also plug in your Broadband and VoIP devices.

VCI/VPI - Virtual Channel Identifier (VCI) / Virtual Path Identifier (VPI). The VCI/VPI pair uniquely identifies a user-to-user information flow and is carried in each ATM cell header. These figure are used to specify the Transmission channels for asynchronous transfer mode (ATM) links.

VoIP - Voice over Internet Protocol is a protocol which allows you to make telephone calls using a computer network, over a data network like the Internet.

A means of transmitting voice over an IP network. This is done by breaking up the voice signal into blocks of data (known as packets), transmitting it over the network(s) and reassembling the signal at the end.

VoIP gateway - A VoIP Gateway is a device which connects between your telephone system and your Ethernet network

VSP - VoIP Service Provider. Also called ITSP.

If you haven't found the term you are looking for, then why not enter it into the Google Definition search below.

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