Telcom Terminology & Industry Overviews

Industry Overviews PBX This diagram shows a private branch exchange (PBX) system. This diagram shows a PBX with telephone sets, voice mail system, and trunk connections to PSTN. The PBX switches calls between telephone sets and also provides them switched access to the PSTN. The voice mail depends on the PBX to switch all calls needing access to it along with the appropriate information to process the call.

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DSL This figure shows a simplified ADSL communication system that consists of a digital subscriber line access mulitplexer (DSLAM), local distribution lines that start from a main distribution frame (MDF) wire cabinet that brings the connection to the digital subscriber line (DSL) modem at the customer's location. Modems in the DSLAM convert the digital signals from the internet to high frequency signals that travel down the telephone line to the DSL modem. The DSL modem converts the RF signals back to its original digital form so it can be provided to the customer's computer. Most DSL technologies (such as ADSL shown in this example) transmit the data information on frequencies about the audio channel. This allows for the simultaneous transmission of analog and data signals on the same telephone line. The highest frequencies are used transmission from the DSLAM to the DSL modem and frequencies just above the audio band are used to transmit from the data from the customer to the DSLAM. Typical DSL technology allows up to 6 Mbps to be transmitted to the customer and up to 640 kbps can be received from the customer.

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ATM This figure shows that the Internet is the network of networks and it communicates using the universal protocol language TCP/IP. This diagram shows a user who is sending email through the Internet. In this diagram, the application is email. The data from the email is divided into packets and given sequence number by TCP protocol. The destination address is appended to each packet by the IP layer. The IP packets are then sent through an Ethernet LAN by encapsulating the IP datagram within the Ethernet data packet. When the data packet is extracted from the Ethernet, it is placed on the E1 transmission line. When the IP data packet reaches the ATM network, it is subdivided into very small 53 byte data packets that travel through the ATM network. When the ATM packets reach their destination in the ATM network, the original IP datagram is recreated and transferred via the T1 communication line. The T1 communication line interfaces to another Ethernet data network. This Ethernet data network encapsulates the IP datagram and forwards it on to the NIC of the receiving computer. The NIC of the receiving computer removes the IP address and reassembles the IP data packets to form the original email message.

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Quick Start- Some of the most popular terms and definitions: Asymetric Digital Subscriber Line 2 (ADSL2)-Asymmetric digital subscriber line 2 (ADSLs) is an evolved version of ADSL that uses a more advanced modulation technology over the 1.1 MHz of frequency bandwidth to increase the data transmission rate up to 12 Mbps (downstream). Asynchronous Transfer Mode (ATM)-Asynchronous transfer mode (ATM) is a packet data and switching technique that transfers information by using fixed length 53 byte cells. The ATM system uses high-speed transmission (155 Mbps) and is a connection-based system. When an ATM circuit is established, a patch through multiple switches is setup and remains in place until the connection is completed. ATM service was developed to allow one communication medium (high speed packet data) to provide for voice, data and video service. As of the 1990's, ATM has become a standard for high-speed digital backbone networks. ATM networks are widely used by large telecommunications service providers to interconnect their network parts (e.g. DSLAMs and Routers). ATM aggregators operate networks that consolidate data traffic from multiple feeders (such as DSL lines and ISP links) to transport different types of media (voice, data and video). Broadband-(1-data transfer) A term that is commonly associated with high-speed data transfer connections. When applied to consumer access networks, broadband often refers to data transmission rates of 1 Mbps or higher. When referred to LANs, MANs, or WANs, broadband data transmission rates are 45 Mbps or higher. (2-radio bandwidth) A frequency bandwidth that is much larger than the required bandwidth to transfer the information signal. For example, using a 1 MHz wide radio channel to transmit a 4 kHz limited audio signal. Calling Number Identification (CNI)-Calling number (and/or name) identification is a service that provides the number and/or name of the incoming to the telephone user prior to the user's answering of the call. This allows the customer to view the telephone number of the person who is calling before deciding to accept the call. CAMEL Application Part (CAP)-CAMEL application part is a set of call processing messages, originally defined for use with GSM, for the customization of setup and control of wireless calls in a GSM or WCDMA network. Cellular Telecommunications Industry Association (CTIA)-The Cellular Telecommunications Industry Association, a trade organization of cellular telephone operators. Competitive Local Exchange Carrier (CLEC)-A telephone service company that provides local telephone service that competes with the incumbent local exchange carrier (ILEC). Crossbar Switches (XBar)-Crossbar switches used mechanical arms to physically connect to wires (or busses) together. These mechanical arms ("Crossbars") connect horizontal and vertical bars together to connect input and output lines together. Magnets are used to open and close the crossbar switch contacts. Data Link Connection Identifier (DLCI)-A temporary channel identifier used in a communication system to identify a specific circuit along with its required communication parameters (such as peak data rates). The DLCI in a frame relay system is 10 bits. It is pronounced ("dill-see"). Digital Subscriber Line (DSL)-Digital subscriber line is the transmission of digital information, usually on a copper wire pair. Although the transmitted information is in digital form, the transmission medium is usually an analog carrier signal (or the combination of many analog carrier signals) that is modulated by the digital information signal. Dual Tone Multi-Frequency (DTMF)-DTMF signaling is a means of transferring information from a

user to the telephone network through the use of in-band audio tones. Each digit of information is assigned a simultaneous combination of one of a lower group of frequencies and one of a higher group of frequencies to represent each digit or character. There are 8 tones that are capable of producing 16 combinations; 0-9, *, #, A-D. The letters A-D are normally used for non-traditional systems (such as the military telephone systems). End Office (EO)-An end office is a switching system that interconnects calls between local customers and the telephone network. Each end office switch can usually supply service up to 10,000 customers. In larger areas (such as a city), established LECs may have several EO switches. The EO switches are interconnected using a higher level tandem switch. If is a significant amount of calls regularly processed between end offices, they may be directly connected via high-speed communication lines (trunks). Ethernet-Ethernet is a packet based transmission protocol that is primarily used in LANs. Ethernet is the common name for the IEEE 802.3 industry specification and it is often characterized by its data transmission rate and type of transmission medium (e.g., twisted pair is T and fiber is F). Ethernet systems in 1972 operated at 1 Mbps. In 1992, Ethernet progressed to 10 Mbps data transfer speed (called 10 Base T). In 2001, Ethernet data transfer rates included 100 Mbps (100 BaseT) and 1 Gbps (1000 Base T). In the year 2000, 10 Gigabit fiber Ethernet prototypes had been demonstrated. Ethernet can be provided on twisted pair, coaxial cable, wireless, or fiber cable. In 2001, the common wired connections for Ethernet was 10 Mbps or 100 Mbps. 100 Mbps Ethernet (100 BaseT) systems are also called "Fast Ethernet." Ethernet systems that can transmit at 1 Gbps (1 Gbps = 1 thousand Mbps) or more, are called "Gigabit Ethernet (GE)." Wireless Ethernet have data transmission rates that are usually limited from 2 Mbps to 11 Mbps. Originally created by an alliance between Digital Equipment Corporation, Intel and Xerox, Ethernet DIX, is slightly different than IEEE 802.3. In Ethernet the packet header includes a type field and the length of the packet is determined by detection. In IEEE 802.3, the packet header includes a length field and the packet type is encapsulated in an IEEE 802.2 header. Most modern day "Ethernet" devices are capable of using both protocol variation, however, older equipment was not able to do this. Fiber To The Home (FTTH)-A distribution system that uses fiber optic cable to connect telephone networks to nodes that are located in the homes of customers. The fiber optic transmission is used to provide broadband services beyond the central office, all the way through the drop wire to the optical node that is located in the customers home. Frame Relay-Frame relay is a packet-switching technology that provides dynamic bandwidth assignments. Frame relay systems are a simple bearer (transport only) technology and do not offer advanced error protection or retransmission. Frame relay were developed in the 1980s as a result of improved digital network transmission quality that reduced the need for error protection. Frame relay systems offer dynamic data transmission rates through the use of varying frame sizes. GR-303-A set of technical specifications that help define the next generation of digital loop carrier (DLC) interconnection. H.323-H.323 is an umbrella recommendation from the International Telecommunications Union (ITU) that sets standards for multimedia communications over Local Area Networks (LANs) that may not provide a guaranteed Quality of Service (QoS). H.323 specifies techniques for compressing and transmitting real-time voice, video, and data between a pair of videoconferencing workstations. It also describes signaling protocols for managing audio and video streams, as well as procedures for breaking data into packets and synchronizing transmissions across communications channels. High Bit Rate Digital Subscriber Line (HDSL)-An all digital transmission technology that is used on 2 or 3 pairs of copper wires that can deliver T1 or E1 data transmission speeds. HDSL is a symmetrical service. Integrated Services Digital Network (ISDN)-A structured all digital telephone network system that was developed to replace (upgrade) existing analog telephone networks. The ISDN network supports

for advanced telecommunications services and defined universal standard interfaces that are used in wireless and wired communications systems. ISDN provides several communication channels to customers via local loop lines through a standardized digital transmission line. ISDN is provided in two interface formats: a basic rate (primarily for consumers) and high-speed rate (primarily for businesses). The basic rate interface (BRI) is 144 kbps and is divided into three digital channels called 2B + D. The primary rate interface (PRI) is 1.54 Mbps and is divided into 23B + D for North America and 2.048 Mbps and is divided into 30B + 2D for the rest of the world. The digital channels for the BRI are carried over a single, unshielded, twisted pair, copper wire and the PRI is normally carried on (2) twisted pairs of copper wire. Interexchange Carrier (IXC)-Inter-exchange carriers (IXCs) interconnect local systems with each other. IXCs are also known as long distance carriers. In the US, from 1984 until 1997, IXC and LEC operating companies were legally required to refrain from engaging in directly competitive business operations with each other. Since 1997, one business entity can engage in both IXC and LEC business if it satisfies certain competitive legal rules. In Europe and throughout the rest of the world, the same PTT operators also usually provide inter-exchange service within their country. In any case, governments regulate how networks are allowed to interconnect to local and long distance networks. For inter-exchange connection, networks as a rule connect to long distance networks through a separate toll center (tandem switch). In the United States, this toll center is called a point of presence (POP) connection. International Telecommunication Union (ITU)-A specialized agency of the United Nations established to maintain and extend international cooperation for the maintenance, development, and efficient use of telecommunications. The union does this through standards and recommended regulations, and through technical and telecommunications studies. Based in Geneva, Switzerland, the ITLI is composed of two consultative committees: the International Radio Consultative Committee (CCIIR) and the Consultative Committee for International Telephony And Telegraphy (CCITT). Internet Protocol Centrex (IP Centrex)-IP Centrex is the providing of Centrex services to customers via Internet protocol (IP) connections. IP Centrex allows customer to have and use features that are typically associated with a private branch exchange (PBX) without the purchase of PBX switching systems. These features include 3 or 4 digit dialing, intercom features, distinctive line ringing for inside and outside lines, voice mail waiting indication and others. Internet Protocol Private Branch Exchange (IPBX) or (IP PBX)-A private local telephone system that uses Internet protocol (IP) to provide telephone service within a building or group of buildings in a small geographic area. IPBX systems are often local area network (LAN) systems that interconnect IP telephones. IPBX systems use a IP telephone server to provide for call processing functions and to control gateways access that allows the IPBX to communicate with the public switched telephone network and other IPBX's that are part of its network. IPBX systems can provide advanced call processing features such as speed dialing, call transfer, and voice mail along with integrating computer telephony applications. Some of the IPBX standards include H.323, MGCP, MEGACO, and SIP. IP PBX represents the evolution of enterprise telephony from circuit to packet. Traditional PBX systems are voice-based, whereas their successor is designed for converged applications. IP PBX supports both voice and data, and potentially a richer feature set. Current IP PBX offerings vary in their range of features and network configurations, but offer clear advantages over TDM-based PBX, mainly in terms of reduce Opex (operating expenses). Internet Protocol Telephony (IP Telephony)-IP telephone systems provide voice or multimedia communication services through the use Internet protocol (IP) networks. These IP networks initiate, process, and receive voice or multimedia communications using IP protocol. These IP systems may be public IP systems (e.g. the Internet), private data systems (e.g. LAN based), or a hybrid of public and

private systems. Internet Protocol Television (IPTV)-Internet protocol television (IPTV) is the process of providing television (video and/or audio) services through the use Internet protocol (IP) networks. These IP networks initiate, process, and receive voice or multimedia communications using IP protocol. These IP systems may be public IP systems (e.g. the Internet), private data systems (e.g. LAN based), or a hybrid of public and private systems. Internet Telephone (IP Telephone)-A telephone device that is specifically designed to communicate through the Internet without the need for a voice gateway. Internet telephones contain embedded software that allows them to initiate and receive calls through the Internet using standard protocols such as H.323 or SIP. Leased Line-Leased lines are telecommunication lines or links that have part or all of their transmission capacity dedicated (reserved) for the exclusive use of a single customer or company. Leased lines often come with a guaranteed level of performance for connections between two points. Light Energy Converter (LEC)-A photo-votalic semiconductor device that converts light energy into electrical energy. Local Area Network (LAN)-Local area networks (LANs) are private data communication networks that use high-speed digital communications channels for the interconnection of computers and related equipment in a limited geographic area. LANs can use fiber optic, coaxial, twisted-pair cables, or radio transceivers to transmit and receive data signals. LAN's are networks of computers, normally personal computers, connected together in close proximity (office setting) to each other in order to share information and resources. The two predominant LAN architectures are token ring and Ethernet. Other LAN technologies are ArcNet, AppleTalk, and fiber distributed data interface (FDDI). Local Loop-The local loop is the connection (wireless or wired) between a customer's telephone or data equipment and a local exchange company (LEC) or other telephone service provider. Traditionally, the local loop (also called "outside plant") has been composed of copper wires that extend from the end office (EO) switch. The EO is the last switching office in the telephone network that connects customers to the telephone network. Long Distance-Services charged at a toll rate, or services offered by interexchange companies for traffic that crosses LATAs (InterLATA). (See also: long-haul communications, toll.) Media Gateway (MG)-A network component which converts one media stream to another. In IP telephony this most commonly refers to a device which converts IP streams (such as audio) to the TDM or analog equivalent. A media gateway may interact with call controllers, proxies, and softswitches via proprietary or standard protocols such as MGCP, Megaco (H.248) , and SIP. There are two main types: Access gateways provide regular analog or primary rate (PRI) interfaces to a voice-over-packet (VoP) network. The inverse function is also available in VoB (voice over broadband) applications: calls are encoded digitally before entering the access network and are routed via conventional telephony once inside. Trunking gateways interface directly between the telephone network and a voice over packet (VoP) network in the core. Such gateways typically manage large numbers of digital virtual circuits. Media Gateway Control Protocol (MGCP)-MGCP is a control protocol that uses text or binary format messages to setup, manage, and terminate multimedia communication sessions in a centralized communications system. This differs from other multimedia control protocol systems (such as H.323 or SIP) that allow the end points in the network to control the communication session. MGCP is specified in RFC 2705 and it was first drafted in 1998. MGCP forms the basis of the PacketCable NCS protocol. Optical Network-Optical networks are a series of points that are interconnected by optical communications channels or systems. Optical networks are either common to all users or privately leased by a customer for some specific application. Optical Switching-Optical switching is the process of directly connecting optical signals between

multiple ports or time periods on an optical communication line without the need to convert the optical signals to electrical form. Plain Old Telephone Service (POTS)-Plain old telephone service is the providing of basic telephone service without any enhanced features. It is the common term for ordinary residential telephone service. The POTS system uses in-band signaling tones and currents to determine call status (e.g. call request). Because POTS allow for the transfer of audio signals below 3.3 kHz, POTS systems are also used for modems that allow data transmission (called dial up connection). Whenever a new service or feature is described, the author may refer to the previous available package of features and services as POTS, even when the previous package included several very sophisticated capabilities. Point Of Presence (POP)-A physical location that allows an interexchange carrier (IXC) to connect to a local exchange company (LEC) within a LATA. The point of presence (POP) equipment is usually located in a building that houses switching and/or transmission equipment for the LEC. Post, Telephone And Telegraph (PTT)-A term used for a government agency in many countries that supplies and maintains the infrastructure and provides basic telecommunication services. Private Automatic Branch Exchange (PABX)-A telephone switch that is generally located on a customer premise. Often referred to as a PBX, CBX, EPABX. This provides for the transmission of calls internally as well as to and from the public network. Private Branch Exchange (PBX)-PBX systems are private local telephone systems that are used to provide telephone service within a building or group of buildings in a small geographic area. PBX systems contain small switches and advanced call processing features such as speed dialing, call transfer, and voice mail. PBX systems connect local telephones ("stations") with each other and to the public switched telephone network (PSTN). Private Telephone System-Private telephone systems are independent telephone systems that are owned or leased by a company or individual. Private telephone networks include key telephone systems (KTS), private branch exchange (PBX) and computer telephone integration (CTI). Public Switched Telephone Network (PSTN)-Public switched telephone networks are communication systems that are available for public to allow users to interconnect communication devices. Public telephone networks within countries and regions are standard integrated systems of transmission and switching facilities, signaling processors, and associated operations support systems that allow communication devices to communicate with each other when they operate. Remote Digital Terminal (RDT)-The RDT provides an interface between a high speed digital transmission line (e.g. DS1) and the customer's access line. The RDT can dynamically assign time slots from a high speed line to customer access lines. Because customer access lines are not used at the same time, an RDT that interfaces to a DS1 line usually provides service to 96 customer access lines. The RDT is divided into three major parts; digital transmission facility interface, common system interface and line interface. The digital transmission interface terminates the high speed line and coordinates the signaling. The common system interface performs the multiplexing/de-multiplexing, signaling insertion and extraction. The line interface contains digital to analog conversions (if the access line is analog) or digital formatting (if the line is digital). Service Switching Point (SSP)-In an Intelligent Network (IN), a stored-program controlled switching system that has the functional capability to differentiate intelligent network calls and interact with service control points (SCPs). SCP databases are accessed by the SSP in providing database query oriented services such as the 800 Data Base Service and Alternate Billing Services. (See also: Intelligent Network). SSP is an IN term for the Class 4/5 Switch that have SS7 capabilities. The SSP has an open interface to the IN for switching signaling, control and handoff. Session Initiation Protocol (SIP)-SIP is an application layer protocol that uses text format messages to setup, manage, and terminate multimedia communication sessions. SIP is a simplified version of the ITU H.323 packet multimedia system. SIP is defined in RFC 2543. Signaling System 7 (SS7)-The signaling system #7 (SS7) is an international standard network

signaling protocol that allows common channel (independent) signaling for call-establishment, billing, routing, and information-exchange between nodes in the public switched telephone network (PSTN). SS7 system protocols are optimized for telephone system control connections and they are only directly accessible to telephone network operators. Common channel signaling (CCS) is a separate signaling system that separates content of telephone calls from the information used to set up the call (signaling information). When call-processing information is separated from the communication channel, it is called "out-of-band" signaling. This signaling method uses one of the channels on a multi-channel network for the control, accounting, and management of traffic on all of the channels of the network. An SS7 network is composed of service switching points (SSPs), signaling transfer points (STPs), and service control points (SCPs). The SSP gathers the analog signaling information from the local line in the network (end point) and converts the information into an SS7 message. These messages are transferred into the SS7 network to STPs that transfer the packet closer to its destination. When special processing of the message is required (such as rerouting a call to a call forwarding number), the STP routes the message to a SCP. The SCP is a database that can use the incoming message to determine other numbers and features that are associated with this particular call. In the SS7 protocol, an address, such as customer-dialed digits, does not contain explicit information to enable routing in a signaling network. It then will require the signaling connection control part (SCCP) translation function. This is a process in the SS7 system that uses a routing tables to convert an address (usually a telephone number) into the actual destination address (forwarding telephone number) or into the address of a service control point (database) that contains the customer data needed to process a call. Intelligence in the network can be distributed to databases and information processing points throughout the network because the network uses common channel signaling A set of service development tools has been developed to allow companies to offer advanced intelligent network (AIN) services Signaling Transfer Point (STP)-A signaling switch used in the SS7 common channel signaling network. These transfer points are used to route signaling messages (packets) to other signaling transfer points or network parts. Stream Control Transport Protocol (SCTP)-A protocol that is used to coordinate the sending of signaling information over real time communication sessions. SCTP is defined in RFC 2960. Switched Multimegabit Data Service (SMDS)-A high-speed data transmission service that is often used in metropolitan areas that allows for the dynamic creation and disconnection of virtual circuits through the network. It is based on the 802.6 standard and may use T1 and T3 circuits to provide Ethernet, Token Ring, and Fiber Distributed Data Interface (FDDI) interconnection services. Switching-Switching is the process of connecting two (or more) points together. Switching may involve a single physical connection (such as a light switch) or it may involve the setup of multiple connections within a network through several communication devices. Symmetrical Digital Subscriber Line (SDSL)-An all-digital transmission technology that is used on a single pair of copper wires that can deliver near T1 or E1 data transmission speeds. SDSL is a symmetrical service that ranges from 160 kbps to 2.3 Mbps and can reach to 18000 feet from the central switching office. Synchronous Digital Hierarchy (SDH)-Synchronous digital hierarchy is a digital transmission format that is used in optical (fiber) networks to transport high-speed data signals. SDH uses standard data transfer rates and defined frame structures formats in a synchronous (sequential) format. SDH is similar to SONET. Synchronous Optical Network (SONET)-Synchronous optical network is a digital transmission format that is used in optical (fiber) networks to transport high-speed data signals. SONET uses standard data transfer rates and defined frame structures formats in a synchronous (sequential) format.

Tandem-(1-general) The connection of the output terminals of one network, circuit, or link directly to the input terminals of another. (2-message network) A switching system that establishes trunk-trunk connections but has no subscriber lines connected to it. Tandem types include local tandems, LATA tandems, and access tandems. Telecommunication-The transmission and reception of audio, video, data, and other intelligence by wire, radio, light, and other electronic or electromagnetic system. Ultra Broadband-Ultra broadband is a term that is commonly associated with very high-speed data transfer connections. When applied to consumer access networks, ultra broadband often refers to data transmission rates of 10 Mbps or higher. Voice Mail (VM)-A service that provides a telephone customer with an electronic storage mailbox that can answer and store incoming voice messages. Voice mail systems use interactive voice response (IVR) technology to prompt callers and customers through the options available from voice mailbox systems. Voice mail systems offer advanced features not available from standard answering machines including message forwarding to other mailboxes, time of day recording and routing, special announcements and other features. Voice Over Internet Protocol (VoIP)-A process of sending voice telephone signals over the Internet or other data network. If the telephone signal is in analog form (voice or fax) the signal is first converted to a digital form. Packet routing information is then added to the digital voice signal so it can be routed through the Internet or data network. X.25-An international standard for communications with a packet data switching network. The X.25 standard specifies the protocol between the data device (such as a computer) and the network (such as a public packet data network). back to top