A

» Access Tandem Switch
» Advanced Intelligent Network (AIN)
» Application Server
» Asynchronous transfer mode (ATM)

B

» Backbone
» Bandwidth
» Broadband

C

» Carrier
» Circuit-Switched
» Class 4
» Class 5
» Competitive Local Exchange Carrier (CLEC)
» Core

E

» E1
» Edge Network

F

» Facility-based carrier

G

» Gatekeeper
» Gateway

H

» H.323

I

» Incumbent Local Exchange Carrier (ILEC)
» Interexchange Carrier (IXC or IEC)
» Interconnection
» IETF
» Intelligent Network
» Internet Protocol (IP)
» IP Network
» Interoperability
» Integrated Services Digital Network (ISDN)
» ITU
» ITU-T

L

» Last-mile technology
» Least cost routing
» Local Access and Transport Area (LATA)
» Long Distance Carrier
» Local Exchange Carrier (LEC)

M

» Megaco
» Media Gateway Control Protocol (MGCP)
» Media Gateway
» Media Gateway Controller

O

» Operational Support System (OSS)
» Open Network Architecture (ONA)

P

» PTT Network
» Packet-switched
» Platform
» Point to Point
» Port
» Private Branch Exchange (PBX)
» Protocol
» Public Switched Telephone Network (PSTN)


Q

» Quality of Service


R

» Reliability
» Regional Bell Operating Company (RBOC)
» Reseller
» Router

S

» Session Initiation Protocol (SIP)
» Scalability
» Signaling
» Signaling System 7 (SS7)

T

» T1
» Tandem Switch
» Time Division Multiplexing (TDM)


V

» VoIP



Access Tandem Switch
A switch that interconnects with CO switches and other access tandem switches to form the PSTN network. It is often called a “class 4” switch, a reference to the original AT&T hierarchal network structure.





Advanced Intelligent Network (AIN)
A telephone network architecture that separates service logic from switching equipment, allowing new services to be added without having to redesign switches to support new services. A later version of Intelligent Network, AIN uses a "service-independent" architecture in which a given part of a telephone number can be interpreted differently by different services depending on factors such as time of day, caller identity, and type of call. AIN is recognized as an industry standard in North America because it makes it easier for a provider to add services, it offers customers more service choices and it encourages competition among service providers.





Application Server
A computer that implements applications, such as prepaid calling, “class 5” services, automated operator services, etc., and interfaces with a softswitch in order to permit interactions with a caller.





Asynchronous transfer mode (ATM)
A high-speed dedicated-connection switching technology that organizes digital data into 53-byte cell units to support multiple types of traffic. ATM is designed to be easily implemented by hardware (rather than software) to enable faster processing and switching speeds. ATM, specified in international standards, is asynchronous in the sense that cells carrying user data need not be periodic.





Backbone
The high-traffic-density connectivity portion of any communications network. At the local level, a backbone is a line or set of lines that local area networks connect to for a wide area network connection or within a local area network to span distances efficiently (for example, between buildings). On the Internet or other wide area network, a backbone is a set of paths that local or regional networks connect to for long-distance interconnection. In packet-switched networks, a backbone consists primarily of switches and interswitch trunks.





Bandwidth
A term used to describe the capacity of a physical circuit or piece of equipment to transport or switch information and is often expressed in terms of bits per second. Common abbreviations are Kbits, Mbits, and Gbits for kilobits (thousands of bits), megabits (millions of bits), and gigabits (billions of bits), respectively.





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 sent on many different frequencies or channels within the 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). Broadband offers consumers integrated access to voice, high-speed data service, video-demand services, and interactive delivery services.





Carrier
A long distance company which uses primarily its own transmission facilities, as opposed to resellers which lease or buy most or all transmission facilities from carriers. Many people refer to any type of long distance company, whether it has its own network or not, as a carrier, so the term is not as restrictive as it used to be.





Circuit-Switched
A type of network in which a physical path is obtained for and dedicated to a single connection between two end-points in the network for the duration of the connection. Ordinary voice phone service is circuit-switched. The telephone company reserves a specific physical path to the number you are calling for the duration of your call. During that time, no one else can use the physical lines involved.





Class 4
AT&T's name for the type of switch used in a telephone tandem office. In the past, Class 4 switches dealt only with high-speed, four-wire T1, T3 and OC-3 connections in contrast to two-wire local lines on Class 5 switches. Today, all switches support four-wire lines. See Access Tandem Switch





Class 5
AT&T's name for the type of switch used in a local telephone end office. It provides customer services such as call waiting and call forwarding. In the past, a Class 5 switch implied two-wire ports from the customer and four-wire ports out the back end. Today, all switches support four-wire lines.





Competitive Local Exchange Carrier (CLEC)
A U.S. telephone company that competes with the already established local telephone business by providing its own network and switching. The term distinguishes new or potential competitors from established local exchange carriers (LEC) that were providing local service when the Telecommunications Act of 1996 was enacted.





Core
The heart, or central part, of something. The core of a communications network is the high-traffic-density connectivity portion.





E1
E1 is a European digital transmission format named by the Conference of European Postal and Telecommunication Administration (CEPT). It's the equivalent of the North American T1 or T-carrier system format.





Edge Network
A network located on the periphery of a centralized network. The edge network feeds the central, or core, network.





Facility-based carrier
A long-distance service provider that owns its own physical facilities. The bulk of the long-distance companies are resellers.





Gatekeeper
A device or computer that controls one or more gateways within a “zone”. Gatekeepers are responsible for routing all calls to/from the gateways in a non-point-to-point situation. Gatekeepers can communicate with other gatekeepers, but usually only between those of the same manufacturer.





Gateway
A communication network element that interconnects two otherwise incompatible network elements by performing a protocol conversion operation across a wide spectrum of communications functions.





H.323
An ITU-T standard for handling video, data and voice call information. This standard was originally proposed for the PictureTel system, which allowed video/voice calls, but has been enlarged to encompass many types of media devices. This “protocol” is actually a umbrella for multiple protocols, each responsible for different items such as packet format and transmission, video codecs, voice codecs, call signaling, conferencing, etc. Version 1 was formally approved in 1996 and the latest, version 4, was approved in November 2000.





Incumbent Local Exchange Carrier (ILEC)
A U.S. telephone company that was providing local service when the Telecommunications Act of 1996 was enacted. ILECs include the regional Bell operating companies. A "local exchange" is a carrier’s local "central office", where residential and business lines terminate. Local exchanges connect to other local exchanges within a local access and transport area or to interexchange carriers such as long-distance carriers like AT&T and Sprint.





Interexchange Carrier (IXC or IEC)
Synonymous in common usage with "long-distance carrier", an interexchange carrier (IXC) is a telephone company that provides connections between local exchanges in different geographic areas. Under the federal Telecommunications Act, an IXC carries communications traffic across LATA boundaries. BOCs, at this time, are only permitted to carry communications within LATA boundaries.





Interconnection
The connection of one telecommunication carrier's network to another or the connection of a piece of telephone equipment to the nationwide telephone network.





IETF
The Internet Engineering Task Force is the organization responsible for defining standards that affect or use the IP network.





Intelligent Network
A name given to a telephone network architecture that separates service logic for a call from the switching facilities in order to allow services to be added or changed without having to redesign switching equipment.





Internet Protocol (IP)
The method by which data is sent from one computer to another on the Internet.





IP Network
A packet-oriented network designed to transport packets of data between systems. Systems are assigned IP addresses that identify them to the IP network.





Interoperability
The ability of a piece of equipment to interoperate with like equipment from other manufacturer’s.





Integrated Services Digital Network (ISDN)
A point-to-point signaling protocol designed to interface PBX equipment with central office switches.





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.





Last-mile technology
The infrastructure that carries signals from the broad telecommunication along the relatively short distance to and from the home or business. In many communities, last-mile technology represents a major remaining challenge to high-bandwidth applications such as on-demand television, fast Internet access, and Web pages full of multimedia effects.





Least cost routing
A feature of a telephone system that automatically connects an outgoing telephone call with the telephone service that costs the least to that location at that time of day. Depending on how it is programmed, least cost routing will either drop down to the second most-efficient service if the first is not available, or it will give the caller a busy signal.





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.





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.





Operational Support System (OSS)
A set of programs that help a communications service provider monitor, control, analyze, and manage problems with a telephone or computer network. As the voice and data networks converge, more sophisticated systems are needed for such activities as ordering and keeping track of network components, such as tracking usage, billing, and reporting.





Open Network Architecture (ONA)
An overall design of a regulated common carrier's basic network facilities and basic services that permits all vendors of basic or enhanced services (including the common carrier itself) to procure specific basic network functions and interfaces on an unbundled equal-access basis.





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.





Platform
The underlying computer system on which application programs can run. A platform consists of an operating system and the hardware that performs logic operations and manages data movement in the computer.





Point to Point
A communications circuit between two terminations which does not connect with a public telephone system.





Port
In a communications network, a point at which signals can enter or leave the network en route to or from another network.





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.





Protocol
A formal set of rules governing the interaction of communicating end points in a telecommunication connection. Protocols exist at several levels in a telecommunication connection and may govern portions of a network, types of service, or administrative procedures. There are hardware telephone protocols. There are protocols between each of several functional layers and the corresponding layers at the other end of a communication. Both end points must recognize and observe a protocol. Protocols are often described in an industry or international standard.





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).





Quality of Service
A subjective rating of telephone communications quality in which listeners judge transmissions by qualifiers, such as excellent, good, fair, poor, or unsatisfactory.





Reliability
An attribute of a network or network component that consistently performs according to its specifications. Reliability has long been considered a critical attributes that must be considered when making, buying or using any hardware, software or network component.





Regional Bell Operating Company (RBOC)
A term describing one of the U.S. regional telephone companies (or their successors) that were created as a result of 1984 breakup of the Bell System which comprised the arm of AT&T providing local telephone services. Each company was given the right to provide local phone service while AT&T was allowed to retain its long-distance service. RBOCs are part of the class of local exchange carriers (LECs).





Reseller
A long distance company that purchases large amounts of transmission capacity or calls from other carriers and resells it to smaller users.





Router
A hardware and software system that directs data packets entering the router toward their intended destinations. Routers have various physical interfaces such as 100baseT Ethernet, T1, E1, DS3, OC-3, etc. Routing is based upon the destination address contained within the header of the IP data packet.





Session Initiation Protocol (SIP)
A protocol designed to allow personal computers to place telephone calls on the Internet. It is often used by devices on the Internet and is currently used for telephone calls, most often “SIP-enabled” telephones.





Scalability
An attribute of a network or network component that enables it to continue to function well as it is changed in size or volume. Typically, when a network component is scalable, it not only has the ability to function well in a rescaled situation, but it has the ability to actually take full advantage of the new situation in terms of performance.





Signaling
In a telecommunications network, the information exchange concerning the establishment and control of a connection and the management of the network, in contrast to user information transfer.





Signaling System 7 (SS7)
The international data network and signaling protocols that control the PSTN voice circuits and calls, ensuring that calls are set up securely and efficiently. Although SS7 is an international telecommunications standard, it has country-by-country variations.





T1
The T-carrier system, introduced in the U.S. in the 1960s, was the first successful system that supported digitized voice transmission. The original transmission rate (1.544 Mbps) in the T1 carrier is the most commonly used digital line in the United States, Canada, and Japan. T1 lines use copper wire and span distances within and between major metropolitan areas. A T1 Outstate System has been developed for longer distances between cities. Another level, the T-3 line, which provides 44.736 Mbps, is also commonly used by Internet service providers.





Tandem Switch
See Access Tandem Switch.





Time Division Multiplexing (TDM)
The technique by which circuit-switched networks (PSTN) carry multiple voice calls over a single physical circuit.





VoIP
VoIP (voice over IP - that is, voice delivered using the Internet Protocol) is a term used in IP telephony that refers to any means of converting voice calls into voice data packets that are transmitted over an IP network, either public or private. By sending voice information in digital form in discrete packets rather than in the traditional circuit-switched protocols of the public switched telephone network (PSTN), VoIP traffic avoids the tolls charged by ordinary telephone service.