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Glossary of VoIP Terms

ANI—Automatic Number Identification — A service that tells the recipient of a phone call the phone number of the person making the call. This number can be passed to computer equipment to automatically retrieve associated information about the caller, i.e. account status, billing records, etc.

Asynchronous Communication — A data communications method in which bits are sent without using a clock signal for synchronization. Instead, each character is transmitted surrounded by a start and stop bit that designates the beginning and ending points of the information. This as opposed to synchronous communication where blocks of data are transmitted using a synchronizing clock.

Analog Telephone Adapter (ATA) — A device – typically measuring 5 x 7 inches -- that plugs into a broadband Internet connection and regular phone, enabling traditional home or office phones to make VoIP phone calls using the Internet.

Audio Menu — A verbal choice provided by a recording over the phone. The recording asks the caller for caller input. Audio menus can instruct you to speak commands or press keys on a touch-tone keypad as commands.

Broadband — In general, broadband refers to telecommunication in which a wide band of frequencies is available to transmit information. Because a wide band of frequencies is available, information can be multiplexed (separated) and sent on many different frequencies or channels within one band concurrently, allowing more information to be transmitted in a given amount of time (much as more lanes on a highway allow more cars to travel on it at the same time).

Cable Modem — A device that you attach to the “coaxial cable” that the cable company installs in your home/office to provide you with broadband Internet access. The cable modem typically also has a port (opening) on it so that you can connect another network cable between it and your PC, enabling your PC to access the Internet. If your cable company supports such access, it is typically at 1.5-3.0Mbps, about 50-100 times faster than a 56K modem typically used for direct phone (“dial up”) access to the Internet.

Call Detail Record (CDR) — a data record typically used in a telephony system to record usage information on a per-call basis. This information might include the number called from, number called to, start-time, call duration, etc.

Call Duration — The time interval between when the phone is taken off the hook for a phone call and when it is put back on the hook, thereby ending the phone call.

Call Hunting — A calling feature for inbound phone calls that will “roll past” a busy signal or try multiple numbers until the phone call reaches a number where it is answered.

Call Setup Time — The length of time, measured in seconds, required to establish a traditional circuit-switched phone call between users.

Clipping — The loss of speech-signal components, resulting in the dropping of the initial or end parts of a word or words.

Codec — Voice encoding/decoding mechanism. Codecs are used to compress the voice signal into data packets. Each codec has different bandwidth requirements. The most popular codecs are: G.729, G.729A, G.723.1, G711mU-Law.

CALEA (Communications Assistance for Law Enforcement Act): A 1994 act that requires telecommunications services to provide wiretapping access. The Act specifically excludes information services, so the question is whether VoIP is a telecommunications service, thus covered by the Act, or an information service, thus exempted. VoIP providers are receiving pressure to comply with the Act.

Circuit-switched — Communication system that dedicates a channel for each transmission. The copper-wire telephone system (referred to as “POTS”, or Plan Old Telephone Service) uses circuit switching, as do PBX systems. Dedicated channels means strong reliability and low latency/delay, but the downside is that only one type of communication can use the channel at any given time.

Competitive Local Exchange Carrier (CLEC) — A telephone company that competes with the larger incumbent phone carriers (ILECS) through leasing and reselling the ILEC service and/or creating services that use the ILEC’s infrastructure. The Regional Bell Operating Companies are ILECs; local phone companies are frequently CLECs. Depending on the type of authority granted to a particular CLEC by the FCC and/or a State Public Service Commission, CLECs may build their own networks consisting of local communications “loops” in the community, (wired, or wireless). CLECs include PCS providers, Cable Providers (CATV), Competitive Access Providers (CAPs), Local Multipoint Distribution System Operators (LMDS), and power utilities.

Compression — VoIP uses various compression ratios, the highest approximately 12:1. Compression varies according to available bandwidth.

Conference Bridge — A device used to connect multiple parties over the phone. A proctor or operator can monitor conference bridges. There are standalone conference bridges and conference bridge functions built in to some PBXs (Private Branch Exchange)/ “switchboards.” These systems have circuitry for summing and balancing the energy (noise) on each channel so everyone can hear each other. More sophisticated conference bridges have the ability to “idle”/hold the transmitting side of channels of non-speaking parties.

Dynamic Host Configuration Protocol (DHCP) — A protocol that provides a means to dynamically allocate IP addresses to computers on a local area network.

Dial-tone delay — The time interval, measured in milliseconds, between when a phone is taken off the hook and when a dial tone sounds.

Dialed Number Identification Service (DNIS) — A telephone function that sends the dialed phone number to the answering service.

DSPs (Digital Signal Processors) — All digital systems use DSP technology in order to differentiate between signal and noise. In telephone communications, too, much noise creates problems in maintaining connections, and in VoIP systems the DSP component provides features such as tone generation, echo cancellation, and buffering.

Digital Subscriber Line (DSL) — A method for moving data over regular phone lines. A DSL circuit is much faster than a regular phone connection, and the wires coming into the subscriber's premises are the same (copper) wires used for regular phone service. The phone service is connected to your PC to provide broadband Internet access, and the DSL service shares the line with your regular or VoIP telephone calls.

Dual-tone Multifrequency (DTMF) — This is basically the technology behind touch-tone dialing. The system used by touch-tone telephones, DTMF assigns a specific frequency (made up of two separate tones) to each key so that it can easily be identified by a microprocessor

E911 (Enhanced 911) — Technology allowing 911 calls from cellular phones to be routed to the geographically correct emergency stations (a.k.a. PSAP/Public Safety Access Points) mandated by the FCC. VoIP users currently have limited access to 911 services, because VoIP is not geographically based.

Emergency Calling Service — Lingo’s Emergency Calling Service dialing routes your call from the Lingo network to the Public Safety Answering Point (PSAP) in your area, in collaboration with a leading 911 third party vendor. It is important to note that your call will be routed to the local police station/PSAP for the address you have on file in your account profile, not your temporary location.

Fax Server — A computer based fax machine. Fax servers are “shared use devices,” typically installed on a Local Area Network. Clients on the LAN can use the fax server from their PCs in much the same way they share the use of a printer connected to the network.

Federal Communications Commission (FCC) — The regulator of telephone and telecommunications services in the United States. The full extent to which the FCC will regulate VoIP communications is not yet known. Part of the complication lies with determining the regulation of communications that begin or end on an FCC-regulated system, such as the standard phone service.

Find-me/Follow-me — A feature that allows calls to find you wherever you are, ringing multiple phones (such as your cell phone, home phone, and work phone) all at once. Lingo has a “Simultaneous Ring” feature that allows the phone call to be transmitted to up to 10 different phone numbers.

Firewall — Security software or appliance that sits between the Internet and your individual PC or networked device. Firewalls can intercept traffic before it reaches network routers and switches, or between router/switch and PC, or both. Because the job of firewalls is to prevent access from specific packets over specific network ports, some firewalls must be specially configured to allow VoIP traffic to pass through.

Frame Relay — In data communications, Frame Relay is a packet switching method that uses available bandwidth only when it is needed. This fast packet switching method is efficient enough to transmit voice and data communications with the proper network management.

File Transfer Protocol (FTP) — A communications protocol governing the transfer of files from one computer to another over a network.

FoIP (Fax over Internet Protocol) — The fax counterpart to VoIP, available from some providers either free or at additional cost.

Gateway — A gateway is basically a protocol converter, i.e. a network point that connects networks using different protocols (tech languages) so that data can be exchanged seamlessly between endpoints. For example, a POTS (or “Plain Old Telephone Service”)-to-VoIP Gateway connects the public phone network and packet-switched networks, translating the voice/data into IP packets.

H.323 — The global industry standard for real-time voice, video and data communication over packet-based networks such as the Internet. H.323 addresses problems inherent to packet-switched networks such as packet delay and packet loss on a Local Area Network, corporate intranets, and the Internet. The oldest of the VoIP protocols. (See SIP and MGCP)

Interactive Voice Response (IVR) — IVR is an application that allows a caller to access computer-based information over the phone by using a telephone instead of a computer. For example: “Please enter your account number using the touch-tones on your phone.” The data you request is then “fetched” by the IVR platform from the host computer.

International Universal Numbers/Virtual Numbers — A Lingo feature that allows the customer to add a phone number from another country code to their Lingo service. This phone number can then be used by someone in that country (say a relative) who places a local phone call to reach the customer on his/her Lingo service. Universal Numbers allow callers to avoid the high cost of international phone calls.

Internet — The Internet consists of the world’s combined public IP-based packet-switched networks. The Internet is an outgrowth and combination of a variety of university and government sponsored computer networks. Federal and private sector subsidies supported the DARPA-NET, NSFnet (National Science Foundation) and thousands of other subnetworks, which were used to do interagency research and communication. Today, the Internet is made up of millions upon millions of computers and subnetworks—almost entirely supported by commercial funds except in countries where deregulation has not occurred. The Internet is the chief communications backbone for the worldwide web (WWW).

Internet Telephony — Internet telephony is transport of phone calls over the Internet, no matter whether traditional telephony devices, multimedia PCs or dedicated terminals take part in the calls and no matter whether the calls are entirely or only partially transmitted over the Internet.

IP (Internet Protocol) — The “language” used to exchange data over the Internet

IP Address — Every computer or device on the Internet has what is known as an IP address, which uniquely defines that device and enables devices to find each other on the Internet. The IP address format is a string of four numbers, each from 0 to 255, separated by periods, for example, 192.168.15.1.

IP PBX — IP PBX is a phone system on the customer’s site that manages telephones in the enterprise and acts as the “gateway” to external networks (the “switchboard”). Unlike a conventional PBX that requires two separate networks, one each for data and voice, an IP PBX is based on both and can be used with IP phones, softphones and traditional phones connected to Ethernet adapters (an ATA/”Lingo Box”) or PCs.

Internet Service Provider (ISP) — A business that provides subscriber-based access to the Internet. Subscribers can be individuals or businesses.

Latency — The time it takes for a packet to travel from its point of origin to its point of destination. In telephony, the lower the latency, the better the communication. Latency has always been an issue with telephone communication taking place over exceptionally long distances (the United States to Europe, for example). With VoIP, however, latency takes on a new form because of the splitting of the message into packets (see packet-switched) and network delay in general.

Media Access Control Address (MAC Address) — An address—typically made up of numbers and letters-- assigned to your hardware that uniquely identifies it’s place on the network. If you need your MAC address during the Lingo installation process, it can be found on the back of the “Lingo box.”

MGCP (Media Gateway Control Protocol) — Another protocol competing with H.323 and SIP, MGCP handles the traffic between media gateways and their controllers. Especially useful in multimedia applications. Designed to take the workload away from IP telephones themselves and thereby make phones less complex and expensive.

Modem — A modem (modulator/demodulator) is equipment that converts digital signals to analog signals and vice-versa. Modems are used to send data signals (digital) over the telephone network, which is usually analog.

Narrowband — Generally, narrowband describes telecommunication that carries voice information in a narrow band of frequencies. More specifically, the term has been used to describe a specific frequency range set aside by the U.S. FCC for mobile or radio services, including paging systems, from 50 cps to 64 Kbps. The term is usually contrasted with wideband or broadband.

Network Access Translation (NAT) — A hardware device currently being developed and used to extend the Internet addresses already in use.

Packet — A logically grouped unit of data. Packets contain a “payload” (the information to be transmitted), originator, destination, and synchronization information. The idea with packets is to transmit them over a network so each individual packet can be sent along the most optimal route to its destination. Packets are de-constructed on one end of the communication and re-constructed on the receiving end based on the header addressing information at the front of each packet. Routers in the network will store and forward packets based on network delays, errors, and re-transmittal requests from the receiving end.

Packet-switched — Communication system that chops messages into small packets before sending them. All packets are addressed and coded so they can be recompiled at their destination. Each packet can follow its own path and therefore can work around problematic transmission segments.

PBX (Private Branch eXchange) — in-house telephone switching system that interconnects telephone extensions to each other.

Post-dial delay — 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 call routing speed as perceived by the user.

Point of Presence (PoP) — The equivalent of a local phone company’s central office (CO). The place where 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.

Post Office Protocol (POP) — An Internet standard for storage and retrieval of email messages.

POTS (Plain Old Telephone Service) — Nothing more than a standard telephone line, the kind Ma Bell and then AT&T handled exclusively before the deregulation of the telephone industry. Upgrade your POTS to DSL, and you have broadband; add VoIP, and you have a system that uses POTS, the PSTN, and the Internet in (ideally) seamless system.

PSAP (Public Safety Answering Point) — A physical location or dispatch center where 911 emergency phone calls are received and then routed to the proper emergency services in a given community (fire, police, ambulance, etc.).

Public Switched Telephone Network (PSTN) — The network of wires, signals, and switches that lets one phone connect to another anywhere in the world. Some VoIP services provide a gateway from the Internet to the PSTN and vice versa.

VoIP (Voice over Internet Protocol) — The technology behind Internet phones. VoIP works by digitizing voice signals and sending them as packets through the same networking channels as your data.

Quality of Service (QoS) — Measure of performance for a transmission system that reflects its transmission quality and service availability.

SIP (Session Initiation Protocol) — An ASCII-based protocol that provides telephony services similar to H.323, but is less complex and uses less resources. It creates, modifies, and terminates sessions with one or more participants. Such sessions include Internet telephony and multimedia conferences. SIP is a request-response protocol, dealing with requests from clients and responses from servers.

Softswitch(Also referred to as media gateway controller or call agent). The generic name for a new approach to telephony switching that has evolved to enable transporting voice traffic over packet-switched networks. At the most basic level, a softswitch is defined as media gateway controller software that provides call control and resource management for a media gateway. Call control relates to the setup and termination of phone calls, including call routing. A softswitch also provides call authentication and authorization, and accounting services by accessing information available in an existing Signaling System 7 (SS7) network.

Softphone — An IP telephone in software. It can be installed on a personal computer and function as an IP phone. Soft phones require appropriate audio hardware to be present on the personal computer they run. This can either be a sound card with speakers or headset/earphones and a microphone, or, alternatively a USB phone set. Soft phones are generally inferior to hard phones but cheaper to obtain, many are available as a free download.

Telephony — Taken from the Greek root words meaning “far sound,” telephony means the process of converting or transmitting voice or other signals over a distance, and then re-converting them to an audible sound at the far end.

T-1 — North American digital standard for high capacity transmission of telephony and data communications. In telephone T-1 provides a 1.544 Mbps link which is divided into 24 discrete, 64 kpbs voice-grade channels. In data communications, T-1 links are used to directly connect CPE (Customer Premises Equipment) routers to the Internet and for Private Data Network or VPN circuits.

T-3 — North American standard for DS-3. Operates at a signaling rate of 44.736 Mbps, or the equivalent of 28 T-1s.

Transmission Control Protocol (TCP) — The transport layer protocol developed for the ARPAnet which comprises layers 4 and 5 of the OSI model. By combining TCP and IP --“TCP/IP” – a connection between two hosts (callers) is made to send messages back and forth.

UNIX — A multi-user, multi-tasking operating system originally developed in 1969 by Ken Thompson of AT&T Bell Laboratories. UNIX is used in telephone company and mission-critical applications.

Universal Service — The availability of affordable telecommunications technology for all Americans, part of the 1966 Telecommunications Act, and regulated by the FCC. Current discussions revolve around the applicability of VoIP to universal service and whether or not VoIP providers should be taxed accordingly.

Voice over Internet Protocol (VoIP) — Functionally, VoIP delivers voice information as data packets using the Internet. It is the capability to carry normal telephony style voice over an IP-based network with the functionality, reliability, and voice quality provided by traditional phone service. VoIP enables a network router to carry voice traffic (for example, telephone calls and faxes) over an IP network. In VoIP, the voice signal is segmented into frames, which then are coupled in groups of two and stored in voice packets. These voice packets are transported using IP protocol in compliance with international networking specifications – “H.323,” “SIP,” or “MGCP.”

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4/18/05