VOIP Glossary of Terms Page 3 IP telephony (Internet Protocol telephony, also known as Voice over IP Telephony) A general term for the technologies that use the Internet Protocol's packet-switched connections to exchange voice, fax, and other forms of information that have traditionally been carried over the dedicated circuit-switched connections of the public switched telephone network (PSTN). The basic steps involved in originating an IP Telephony call are conversion of the analog voice signal to digital format and compression/translation of the signal into Internet protocol (IP) packets for transmission over the Internet or other packet-switched networks; the process is reversed at the receiving end. The terms IP Telephony and Internet Telephony are often used to mean the same; however, they are not 100 per cent interchangeable, since Internet is only a subcase of packet-switched networks. For users who have free or fixed-price Internet access, IP Telephony software essentially provides free telephone calls anywhere in the world. However, the challenge of IP Telephony is maintaining the quality of service expected by subscribers. Session border controllers resolve this issue by providing quality assurance comparable to legacy telephone systems. ITSP Internet Telephony Service Provider. ITU International Telecommunications Union—the international standards organization for all types of radio and telephony telecommunications. ITU-T International Telecommunications Union—Telecommunications sector. The part of the ITU responsible for both circuit-switched and packet-switched telecommunications. IVR Interactive Voice Response is a software application that accepts a combination of voice telephone input and touch-tone keypad selection and provides appropriate responses in the form of voice, fax, callback, e-mail and perhaps other media. IVR is usually part of a larger application that includes database access. Common IVR applications include: bank and stock account balances and transfers, surveys and polls, caller authorization centers (for example, the MCCP), etc. Latency (Also called Delay) The amount of time it takes a Packet to travel from source to destination. Together, Latency and Bandwidth define the speed and capacity of a network. Local Access and Transport Area (LATA) Defines that area, in a state served by a Bell telephone company, in which, under current federal Telecommunications Act rules, the company can provide service. Each Service Area may include one or more area codes or share a common area code. A connection between two local exchanges within the LATA is referred to as intraLATA. A connection between a carrier in one LATA to a carrier in another LATA is referred to as interLATA or 'long-distance' service. Long Distance Carrier A telephone company that provides connections between local exchanges in different geographic areas. Long-distance carriers provide interlocal access and transport area (interLATA) service as described in the Telecommunications Act of 1996. In the U.S., long distance carriers are called interexchange carriers (IXCs). Local Exchange Carrier (LEC) A public telephone company in the U.S. that provides ordinary local voice-grade telecommunications service under regulation within a specified service area. Some of the largest LECs are the Bell operating companies (BOCs) which were grouped into holding companies known collectively as the regional Bell operating companies (RBOCs) when the Bell System was broken up in 1983. In addition to the Bell companies, there are a number of independent LECs, such as GTE. Mean opinion score (MOS) A measurement of the subjective quality of human speech, represented as a rating index. MOS is derived by taking the average of numerical scores given by juries to rate quality and using it as a quantitative indicator of system performance. Megaco The IETF name for the ITU-T H.248 protocol standard recommendation for controlling a media gateway when connecting telephone calls between a LAN and the PSTN. It handles many telephony issues such as redundant MGC systems that MGCP does not address. The Megaco protocol is similar to the MGCP protocol but is not backward-compatible with it, meaning a system using Megaco will not interoperate with a system using MGCP. Media Gateway Control Protocol (MGCP) A protocol designed to control various devices that can handle different types of media, e.g., voice, video, data, etc. It is designed to allow a Media Gateway Controller (MGC) to control one or more unintelligent Media Gateway (MG) devices. Media Gateway Any device, such as a circuit-switched or IP gateway that converts data from the format required for one type of network to the format required for another. As defined in the Internet Engineering Task Force (IETF), a media gateway might terminate channels from a circuit-switched network as well as streaming media from a packet-switched network. Data input could be audio, video, or real-time multi-point communications, which the media gateway would handle simultaneously. The media gateway controller is sometimes called a softswitch. Media Gateway Controller A device that controls one or more media gateways and has enough intelligence to be able to control nearly all aspects of each media gateway, but does not have enough intelligence to control an entire call. Messaging In computer telephony, any means of message store and forward. This includes fax mail, voice mail and broadcast messaging. This horizontal application is the most popular of all other voice solutions. Messaging systems provide for the store and forward of "non-real time" communication. For example, a recorded voice message can be stored for later play back either locally or remotely, or a fax can be received and stored before it is re-transmitted to the ultimate recipient. Messages, then, can vary in content and media type - the distinction being that they are recorded or stored for pick up in the future. The time between original storage and retrieval of a message can be created and stored by a sales manager for later retrieval by multiple (worldwide) sales people. The sales staff can listen to the message at different times over an extended period. This is due to the nature if random retrieval by the recipients in their respective time zones. Messaging systems are a kind of "shared tenant" answering machine, because messages that were intended for as many as a thousand or more users can be stored and controlled by the same system. If a community of users agree on some basic ground rules, messages can be shared, forwarded, and distributed to multiple recipients in the same fashion as e-mail. PTT Network A term used to refer to the PSTN network of other countries. It comes from the abbreviation for Post, Telephone and Telegraph, which used to be the government-owned company within other countries that owned and managed the national postal, telephone and telegraph systems. Packet-switched A technique for routing data through a network by encapsulating the data in packets, labeling them with addresses and routing information (the packet header), and then routing the packets over various physical circuits (often times different for each packet) until they reach their intended destination. By breaking communication down into packets, packed-switched networks allow the same data path to be shared among many users in the network. Most traffic over the Internet uses packet switching. Post-dial delay (PDD) The time interval between when the caller presses the last digit of a number and when the phone on the other end begins to ring. It is the basic quantifier for routing speed as perceived by the user. POP Point of Presence, equivalent of a local phone company's central office. The place your long distance carrier terminates your long distance lines just before those lines are connected to your local phone company's lines, or to your own direct hookup. POTS Plain Old Telephone Service. The term refers to the standard telephone service that most homes use. The POTS network is also called the PSTN. Private Branch Exchange (PBX) A very small, specialized switch similar that permits attached telephones to call each other using shorter numbers, and requires the caller to select an 'outside line' in order to call through the PSTN. Public Switched Telephone Network (PSTN) The world's collection of interconnected voice-oriented public telephone networks, both commercial and government-owned. The PSTN is the aggregation of TDM circuit-switched telephone networks that has evolved from the days of Alexander Graham Bell. Today, it is almost entirely digital in technology except for the final link from the central (local) telephone office to the user. It is also referred to as the Plain Old Telephone Service (POTS) or the Switched Circuit Network (SCN).   <Prev Next>