TERM

DEFINITION

Access Port

The physical gateway between a customer's local loop and the frame relay network.

ACD (Automatic Call Distribution)

A Central Office (C.O.) or premise-based system that answers and routes incoming calls sequentially and equally to agents, stations, or ports on another system.

ADSL (Asymmetric Digital Subscriber Line)

A new technology that allows more data to be sent over existing copper telephone lines. ADSL supports data rates of from 1.5 to 9 Mbps when receiving data (known as the downstream rate) and from 16 to 640 Kbps when sending data (known as the upstream rate).

AIN (Advanced Intelligent Network)

A software based telecommunications network services architecture, the goal of which is to allow services to be introduced, controlled, and managed efficiently by separating information about a call from the call itself, sending the information along a separate data path throughout the system.  Bellcore’s switching concept that centralizes a significant amount of intelligence rather than constantly placing more and more information in the central office switch. The AIN infrastructure makes possible a great number of long distance services, such as national 800-number service and Virtual Access to Private Networks. (See also IN).

ALI (Automatic Location Identification)

Provides the called party with the physical location from which a caller is dialing. It is part of the E911 system (operated by the RBOC), and is one reason accurate physical addresses are essential.

Alpha Test

The stage during new product research and development when a prototype is operated to ascertain that the system concept and design are functional and to identify areas that need further development and/or enhancement.

ALTS (Alternative Local Transport Service)

2.   Association for Local Telecommunications Services http://www.alts.org/, a CLEC industry association.

AMA (Automated Message Accounting)

Format in which a digital switch usually creates the usage data used for billing.

AMI (Alternate Mark Inversion)

Digital signaling method in which the signal carrying the binary value alternates between positive and negative polarities; zero and one values are represented by the signal amplitude at either polarity, while no-value “spaces” are at zero amplitude. Also called bipolar.

Amplifier

A device used to boost the strength of an electronic or optical signal, which is weakened (attenuated) as it passes through the transport network. Amplifiers add gain to the signal by an amount equal to the loss in the previous section of the network since last amplification.

ANI (Automatic Number Identification)

2.      A feature that sends a calling party’s telephone number over the network to the operator or called party.

ANSI (American National Standards Institute)

A standards-forming body affiliated with the International Organization for Standardization (ISO) that develops US standards for transmission codes, protocols, media and high-level languages, among other things.  See http://www.ansi.org

ATM (Asynchronous Transfer Mode)

A method of sending audio, visual and computer data at the same time over one high-speed digital line.

TERM

DEFINITION

Backhaul Capacity

Network capacity, typically on fiber optic cable systems, to transport traffic from one location where the traffic is introduced to the network to other locations where the traffic is needed or can be serviced; for example, metropolitan areas, switch sites, interconnection points, etc.

Backhaul Capacity

Capacity on terrestrial fiber optic cables from undersea cable landing stations to metropolitan areas.

Bandwidth

A measure of capacity of information-carrying capacity on a communications channel.

BGP (Border Gateway Protocol)

A routing protocol used in interdomain routing in large networks to maintain integrity of the network. It allows the routers to exchange only prespecified information with prespecified routers in other domains.

Bid

This is the process of sending a message that requests control of a circuit. Generally the station making the bid is requesting permission to take control of the circuit to send a message.

Bit
 

A binary unit of information that can have either of two values, 0 or 1. Contraction of binary digit.

BLSR (Bi-directional Line Switched Ring)

Commonly referred to as BLSR. It is a method of SONET transport in which half of the working network is sent counterclockwise over one fiber and the other half is sent clockwise over another fiber. BLSR offers bandwidth use advantages for distributed traffic in single-ring architectures.

Bridge

A data communications device that connects two or more network segments and forwards packets between them. It also amplifies the carrier signal, and accepts data packets, (perhaps buffering them during periods of network congestion) and forwards them.  The bridge can be directly connected to both LAN's or two bridges can be remotely connected using Wide Area Networks.

Broadband
 

A transmission channel usually carrying a tremendous amount of information at transmission speeds of 45 Mbps (45,000,000 bits per second) or greater. A communications channel with a bandwidth sufficiently large to carry voice, data and video on a signal channel. Any voice communications channel having a bandwidth greater than a voice grade channel.

Burst Mode

A way of doing data transmission, usually faster than normal transmission mode, in which a continuous block is transferred between main memory and an input/output device without interruption until the transfer has been completed. Characteristically, burst mode is sustainable for only limited periods of time under special conditions.

TERM

DEFINITION

Capacity

The information-carrying ability of a telecommunications system, as defined by its design (number of fibers, system length, and optoelectronic equipment) and its deployed equipment (amount of optoelectronics in the station) and measured in bits per second. Capacity is sold in discrete units, usually system interface levels such as DS-3's and STM-1's, that in the aggregate are the equivalent of total system capacity.

Carrier

A third party provider of communications services by wire, fiber or radio. Common Carrier: A private company offering facilities or services to the general public on a non-discriminatory basis and regulated as to market entry, practices, and rates by various Federal and State authorities. Private Carrier: Services provided for internal use and free of most common carrier regulations to allow discrimination in service provision or pricing.

Channelization

The process of subdividing the bandwidth of a circuit into smaller increments called channels. Typically, each channel carries an individual transmission, e.g., a voice conversation or a data conversation – a computer-to-computer session. This process is accomplished through a multiplexer, such as dense wavelength division multiplexers.

Circuit

This is the medium that conducts the message from the sender to the receiver. In communications systems the circuit is usually a telephone line. Other circuits include microwave systems, satellite links, fiber optic links, etc. The circuit can also be called the link or transmission path.

2.      The digital encoding of an analog signal and, conversely, decoding to an analog signal.

Compression

Algorithm that minimizes the redundancy in, and therefore the bandwidth required by, the signal to be transmitted.

Contention

The type of line discipline or protocol that allows the stations to bid or contend for control of the circuit. The winning station takes control of the circuit and sends its message.

Cryptography
 

The process of concealing the contents of a message from all except those who know the key. Cryptography is used to protect e-mail messages, credit card information, and corporate data. As the Internet and other forms of electronic communication become more prevalent, electronic security is also becoming increasingly important.

TERM

DEFINITION

Dark Wavelength
 

Refers to a virtual channel in a fiber optic system utilizing DWDM. Each virtual channel is supported through a specific wavelength of light, with many channels riding over the same fiber. Once the fiber system is deployed and the DWDM equipment is activated, some of the wavelengths may be activated immediately and others may be left dark for future needs. When the need arises, those dark wavelengths are lit up.  Also known as "windows" or "lambdas."

Digital

Describes a method of storing, processing and transmitting information through the use of distinct electronic or optic pulses representing the binary digits 0 and 1. In communications they will modify a carrier at a selected frequency. The precise signal transitions preclude any distortion such as graininess or snow in the case of video transmission or static or other background distortion in the case of audio transmission.

Digital Transmission

Method of storing, processing and transmitting information through the use of distinct electronic or optical pulses that represent the binary digits 0 and 1. Digital transmission and switching technologies employ a sequence of these pulses to represent information as opposed to a continuously variable analog signal. The precise digital numbers preclude any distortion such as graininess or snow in the case of video transmission, or static or other background distortion in the case of audio transmission.

Doped Fibers

Various impurities may be added to silica-based fiber optic strands as they are constructed to achieve specifically desired transmission or physical properties. Erbium-Doped Optical Fiber Amplifier (EDFA) optical amplifiers use a section of optical fiber doped with the rare earth erbium and optically pumped with a laser diode. It can amplify a range of wavelengths at the same time surrounding a base wavelength of 1550 nm. Praseodymium-doped fibers produce a signal gain of 30 dB in 1310 nm fibers.

Downstream

In a multipoint circuit with a designated master station, the remote stations are sometimes referred to as downstream or tributary stations.

DS-1 or T-1

The standard for digital transmission systems in North America is based on the ANSI T1 standards which were derived from the Western Electric Company standards. T1 is the lowest rate of transmission at 1.544 megabits per second. The T1 system carries 24 voice channels.

DSI

A digital transmission hierarchy supporting 1.544 million bits per second that may be used for "near-full motion" or compressed video, data or voice circuits (24, 48, or 96).

DWDM (Dense Wavelength Division Multiplexing)

A technique which employs more than one light source and detector operating at different wavelengths and simultaneously transmits optical signals through the same fiber while message integrity of each signal is preserved.

TERM

DEFINITION

E-1

E-1 is a standard European format for digital transmission systems based on the CEPT standards sometimes called the E Standards. E-1 is the lowest rate of CEPT transmission at 2.048 megabits per second. The E-1 system carries 32 channels at 64Kbps, versus the North American T-1, which carries signals at 1.544 Mbps (24 channels at 64Kbps).

Echo Canceller

EDFA (Erbium-Doped Fiber Amplifier)

A purely optical (as opposed to electronic) device used to boost an optical signal. It contains several meters of glass fiber doped with erbium ions. When the erbium ions are excited to a high energy state, the doped fiber changes from a passive medium to an active amplifying medium.

Email Address

Email Forwarding

Messages received at an email server for a specific email address or a range of addresses can be forwarded to any other email address by using the "email forwarding" function.

Email Header

The first part of an email message, including the To, From, Subject, Cc, Bcc, and Attachment fields. This allows the email's sender, receiver and subject to be easily identified.

Email Program

Also referred to as an "email client" or "mail client", this is the program on your computer used to send and receive email. Once you have configured your email program with the correct incoming and outgoing server settings, it will call up the correct servers to retrieve your incoming messages and send your outgoing messages. Some examples are Eudora, Microsoft Outlook, and Pegasus.

Email Server

This is where all of your incoming mail is held for you until you retrieve it, and where your outgoing mail is sorted and sent off to the correct locations.

TERM

DEFINITION

Fault Tolerance
 

The ability of a system to respond gracefully to an unexpected hardware or software failure. There are many levels of fault tolerance, the lowest being the ability to continue operation in the event of a power failure.

Fiber Kilometers

The number of route kilometers of cable sheath installed multiplied by the number of fiber strands installed in that sheath along the path.

Fiber Optics

FTP (File Transfer Protocol)

FTP programs, such as CuteFTP, Microsoft FrontPage, and FTP Voyager, can be used to upload (transfer) your website files to your website, so that when you type in your website address all of the website files that you have created will appear.

Full Duplex

This refers to a method of sending and receiving messages concurrently.  The simultaneous transmission of data in both directions, used when communicating between two computers. Full duplex is sometimes called "Echo On" by some communications programs.    It can be a reference to the physical network as in a full duplex circuit or it can refer to a full duplex protocol.

TERM

DEFINITION

Gbps (Gigabits per second)

A data rate of 1 Gbps corresponds to 1,000 million bits per second.

Gigabit

1 billion bits (1 Gb)

TERM

DEFINITION

Half Duplex

Refers to a method of transmission that is two way non- concurrent. It can be a reference to the physical network as in a half duplex circuit or it can refer to a half duplex protocol.

HDLC (High Level Data Link Control)
 

A generic link layer protocol standard for point-to-point and multi-point communications that is bit oriented and in which control codes differ according to their bit positions and patterns.

HIPPI (High Performance Parallel Interface)

HIPPI is used to network supercomputers, high-end workstations and peripherals using cross-bar type circuit switches. It provides for transfer rates of 800 megabits a second over 32 twisted pair copper wires (single HIPPI) and 1600 megabits a second over 64 pairs (double HIPPI).

TERM

DEFINITION

IMAP (Internet Messaging Access Protocol)

An upgrade of the standard POP3 email account, IMAP4 allows the user to archive messages into folders, store messages on the server, and read only the headers in a message without having to download the entire message.

IN (Intelligent Network)

Internet

A fabric of interconnected computer networks, originally known as the DARPA network (Defense Advanced Research Projects Agency) connecting government and academic sites. It currently links about 50 million people worldwide who use it for everything from scientific research to simple E-Mail.

Internet Protocol

The Internet Protocol (IP) provides the protocol and addressing that will move data across multiple networks.

Internet Protocol (IP) Address

An Internet address that is a unique number consisting of four parts separated by dots, sometimes called a "dotted quad." For example, 192.100.012.1.  Every Internet computer has an IP address and most computers also are assigned one or more domain names that are easier to remember than the dotted quad.

Internetworking

The ability to move information between computers on two or more different networks. When properly implemented, internetworking functions take care of networking transparently to the user's application program.

IOC (Independent Operating Company) 

A local exchange carrier that is not one of the Bell Operating Companies, typically operating in rural and small town areas.

IRU (Indefeasible Right of Use)

A measure of currency in the dark fiber and undersea cable business. The owner of an IRU has the right to use the capacity for the time and bandwidth to which the IRU applies.

In its simplest form (Basic Rate Interface), ISDN provides a means of transmitting two voice channels (each operating at 64 kbps) and one data channel (operating at 16 kbps) over a single pair of twisted copper conductors. Long distance providers, however, would use the Primary Rate Interface (PRI) ISDN, in which there are 23 “B” bearer channels operating at 64 kbps and one “D” data channel operating at 64 kbps (23B+D). This interface is commonly used to connect customer PBX systems directly to the long distance network, thereby bypassing the local exchange carrier and the access fees it would charge for long-distance calls.

ISDN (Integrated Services Digital Network)

The ISDN network is the next generation of telephone network where all signals are carried in digital format right into the subscribers home or office. The intent is that the new network can be used for more services such as high speed data or multimedia.

ISP (Internet Service Provider)

Your ISP is the company that allows you access to the internet by providing various ways to connect, such as through a modem, ISDN, or DSL, for a fixed monthly cost. Some of the most common ISPs are AOL, MSN, and At&T Worldnet. Most ISPs offer other services, such as email and website addresses, search engines, and informative sites based on various topics.

ITU (International Telecommunications Union)

The ITU is an intergovernmental agency of the United Nations within which the public and private sectors cooperate for the development of telecommunications. The ITU adopts international regulations governing the use of the radio spectrum and develops standards to facilitate the interconnection of telecommunications systems on a worldwide basis. It is headquartered in Geneva, Switzerland. In 1996, the ITU comprised 185 Member States and 363 members (scientific and industrial companies, public and private operators, broadcasters, regional and international organizations active in three sectors: Radio communications, Standardization and Development).

IXC or IEC (Interexchange Carrier) 

A telecommunications company that transmits information between LATAs, frequently simply called a long distance carrier.

TERM

DEFINITION

TERM

DEFINITION

Kilobit

1 thousand bits (1 Kb)

TERM

DEFINITION

Lambda
 

The 11th letter of the Greek alphabet. Lambda is used as the symbol for wavelength in lightwave systems. Fiber optic systems use multiple wavelengths of light through dense wavelength division multiplexing (DWDM). Each range of wavelength appears in a "window" roughly corresponding to a color in the visible light spectrum.

A local communications network connecting computer terminals or workstations, such as personal computers in an office or college campus. LANs are also used in the long distance network to connect off-switch processors, such as computers that provide billing, workforce management, voice recognition, and directory assistance databases.

LAN (Local Area Network)

A Local Area Network (or LAN) is a network that ties together devices in a department, building or campus. Generally the LAN can be a network that is entirely on a user's property and does not have any parts that are provided by outside LEC's or other carriers.

The geographic area that is the domain of the local exchange carrier.  Traditionally, calls within a LATA are handled by a local exchange carrier; calls from one LATA to another (known as interLATA calls) are carried by an interexchange carrier.

Latency
 

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.

The local telephone company, generally divided into Regional Bell Operating Companies and Independent Operating Companies. A number of large CAPs are now considered LECs.  See also ILEC and CLEC.

Line Discipline

This is the procedure that tells how information is to be sent over the circuit. The line discipline tells how a message is formatted to tell the beginning and end. It also describes how the correct receipt of the information shall be acknowledged.

Link Layer

In the ISO terminology, a link layer is where the local link protocol takes care of framing and error handling. In TCP/IP the link layer provides the local communications protocol and interface to the network. Examples of link layers can be Ethernet, PPP, HDLC or SLIP.

Local Loop

2.      The pair of wires that connect the telephone system to a home or office. Generally one pair of wires (or one loop) is one telephone line.

TERM

DEFINITION

Master Station

In a multipoint circuit the station that controls the line is called the "master." Usually the master station is the one that polls or selects the other stations. In some cases there can be a master station in point to point or contention protocols.

A capability of SONET fiber optic rings to ensure traffic can be rerouted around a failed site as opposed to a fiber cut.

Mbps (Megabit per second)

One Mbps corresponds to a data rate of 1,000,000 bits per second.

MGCP (Media Gateway Control protocol)

A proposed control and signal standard for the conversion of audio signals carried on telephone circuits to data packets carried over the Internet or other packet networks. Unlike regular phones, IP phones and devices are not fixed to a specific switch, so they must contain processors that enable them to function independently from a central switching location. MGCP eliminates the need for complex, processor-intense IP telephony devices, thus simplifying and lowering the cost of these terminals.

Megabit

1 million bits (1 Mb)

Official name for the 1982 Federal court ruling resulting in divestiture of the Bell Operating Companies from AT&T.

Morse Code

A transmission method whereby characters and symbols are represented by different combinations of dots and dashes. The Morse code was mainly used on telegraph (or radiotelegraph) systems where human operators read and transmitted the information.

Morse Telegraph

The early form of telegraph system invented by Samuel Morse. In this system the dots and dashes were printed on a strip of paper by the receiver. The operator removed the strip from the machine and transcribed the characters above the symbols.

Multicasting
 

The ability of one network node to send identical data to a number of end servers on the multicast backbone. For large amounts of data, IP multicasting is more efficient than normal Internet transmissions because the server can broadcast a message to multiple recipients simultaneously.

Multilink Point-to-Point Protocol or MP

MP allows multiple physical connections between two points to be combined into a single logical connection called a bundle. MP supports dynamic bandwidth allocation, which means that physical links can be added or removed from the bundle as needed.

Multimedia

The electronic conversation between two or more people or groups of people in different places using two or more types of digitally integrated communication for voice, sound, text, data, graphics, video, image or presence at the same time. Applications include conferencing, presentations, training, referencing, games, etc.

Multiplexing

An electronic or optical process that combines two or more lower bandwidth transmissions onto one higher bandwidth signal by splitting the total available bandwidth into narrower bands (frequency division) or by allotting a common channel to several transmitting sources one at a time in sequence (time division).

Multipoint
 

Pertaining or referring to a communications line to which three or more stations are connected. It implies that the line physically extends from one station to another until all are connected.

MultiProtocol Label Switching or MPLS

MPLS is a widely supported method of speeding up data communication over combined IP/ATM networks. This improves the speed of packet processing and enhances performance of the network.

TERM

DEFINITION

Network Layer

In communications protocols, the network layer is how computers communicate across multiple networks. The network layer knows the addresses and/or routes to other computers. The network layer in TCP/IP is the Internet Protocol (or IP) layer.

NPA (Numbering Plan Area) 

Another name for area code. The three-digit NPA makes up the first part of every phone number in the North American Numbering Plan (NANP).

Often referred to as the “prefix” or “exchange;” the second three numbers in telephone number, after area code, which identify the central office in the North American Numbering Plan (NANP).

TERM

DEFINITION

OC-192 (9,953.28 Mb/s – or commonly “10 Gb/s”)

Optical Fiber

Thin filaments of glass through which light beams are transmitted. Enormous capacity, low-cost, low-power consumption, small space, lightweight, insensitivity to electromagnetic interference characterizes this transport media.

A system that furnishes tools to provide network control, monitoring, and business functions from a centralized location. Nearly all pieces of network equipment or major network functions have an OS.

TERM

DEFINITION

Password

The word or code used to access an online account. It is recommended that a password be at least 6 characters long, with a combination of both letters and numbers and upper and lower case. Also, passwords should be changed periodically to improve security.

Customer premises version of a central office switch. Business customers may use dedicated access lines from a long distance carrier to connect PBX systems directly to the long distance switch, bypassing the local telephone company.

Point to Point

A circuit that connects only two points.

Polling

A method of calling stations and asking if they have traffic to send. Polling is usually controlled from a master station and mainly applies to multipoint circuits.

POP (Point Of Presence)

The physical location where a given carrier terminates lines before connecting to the local exchange company, another carrier, or directly to a customer.

POP3 (Post Office Protocol 3)

The standard type of mail server used in combination with an email program. With a POP3 email account, all email messages will be stored on the email servers until retrieved through an email client program. Once the email account is checked (downloaded) messages, they will no longer be on the server.

An ISDN trunk interface, operating at 1.544 Mb/s (DS-1) often used by long distance and internet carriers for dedicated access lines.  Also referred to “23 B+D” since the trunk is composed of 23 Bearer (message) channels and one Data channel.  See also ISDN.

Protocol

In early systems the terms line discipline and protocol were interchangeable. In modern data communications systems protocols refer to actions between systems and programs involved in the communications at higher levels. Line disciplines are the communications on the actual data circuits.

PTTs (Post, Telephone and Telegraph)

International telecommunications carriers which are generally under the control of the government in a country that has not yet privatized its telecommunication markets.

TERM

DEFINITION

RBOC (Regional Bell Operating Company) 

A term for the seven Regional Holding Companies created when AT&T divested the Bell Operating Companies required by the MFJ.

Receiver

In the communications model the receiver is the recipient of the message.

Reliable Transport

This is the methods and protocols that provide confirmation that data is sent correctly between two computers.

Requests for Comment (RFC)

Internet standards that have developed within the Internet community since 1969. They have grown to become a large series of numbered Internet informational documents and standards widely followed by commercial software and freeware in the Internet and Unix communities. Few RFCs are standards but all Internet standards are recorded in RFCs. Perhaps the single most influential RFC has been RFC 822, the Internet electronic-mail format standard. RFCs are unusual in that they are floated by technical experts acting on their own initiative and reviewed by the Internet at large, rather than formally promulgated through an institution such as ANSI (American National Standards Institute). For this reason, they remain known as RFCs even after they have been adopted as standards.

Route Kilometers

The number of route kilometers of a transmission installed on a given route.  This many be kilometers of cable, microwave radio or other media.

Router

A network device that connects two similar networks having the same network protocol. It also chooses the best path between two networks when there are multiple paths.   Routers provide internetworking by routing Network Layer traffic across various Link Layer interfaces.  Unlike bridges, which logically connect at OSI layer 2, routers provide logical paths at OSI layer 3. Like bridges, remote sites can be connected using routers over dedicated or switched lines to create WANs. Routers not only move the data between different networks but, they change the physical or link level protocols to match each part of the transmission network.

TERM

DEFINITION

SCE (Service Creation Environment) 

A set of software tools and activities required to create new services for AIN service subscribers.

SCP (Service Control Point) 

The centralized network element (typically a switch  or intelligent peripheral) in the Advanced Intelligent Network architecture that individual switches call on to obtain information and commands necessary for completing an AIN call.

SDH (Synchronous Digital Hierarchy)

Similar to SONET, it is a standard for synchronous digital transmission used outside of North America.

Sender

In the communications model the sender is the originator of the message.

Serial Line Internet Protocol or SLIP
 

An Internet protocol which is used to run IP over serial lines such as telephone circuits. It allows a packet to traverse multiple networks on the way to its final destination.

Service Layer

The Service Layer in TCP/IP provides a number of functions to transfer data across networks and simplify communications for application programs. As an example, the services layer in TCP/IP has built-in file transfer and electronic mail delivery programs which can be invoked by applications.

Signaling

The process that moves the information for call routing and network progress. Call routing would be the dialed number and other information. Network progress are the signals like dial tone, ringing and busy.

Simplex

This is the type of circuit that can send information in only one direction.

Sink

In the communications model the sink is the destination of the message (see receiver).

Slave Station

In a multipoint polling network the stations that are polled by the master are referred to as slaves. They can also be called downstream or tributary stations.

SMS (Service Management System)

The operations support system for Advanced Intelligent Networking. Provides the mechanism for downloading new features and monitoring the AIN network.

SMTP (Simple Mail Transfer Protocol)

SMTP protocol is used to send messages over the internet to various mail servers, such as POP3 and IMAP4, where the messages are held until retrieved by the recipient.

Family of optical transmission rates and interface standards allowing improved interworking of products from different vendors. The base optical line rate is 51.840 Mbps.  Higher rates are direct multiples. The most accepted standards are OC-3, OC-12, OC-48, and OC-192.  OC-768 is currently being tested in various lab environments.

Source

The origination point of messages in the basic communications model.

Spam

A common term used to describe sending large numbers of the same unsolicited message, usually an email advertisement, to random groups of people.

SS7 (Signaling System No. 7)

An out-of-band signaling system used to provide basic routing information, call set-up, and other call termination functions. Signaling is removed form the voice channel itself and put on a separate data network. Also known as Common Channel signaling No. 7 (CCS7).

SSP (Service Switching Point)

That node of the Intelligent Network normally associated with an end office switch.  An Intelligent Network entry point.

STM-1

The largest standard circuit unit of capacity, which consists of 155,500 kbps (equal to 155 Mbps). Thus, each Gbps contains enough capacity for 6.4 STM-1 circuits. While capacity is sold to the largest telecommunications companies in minimum investment units equal to one STM-1 unit, most telecommunications companies buy smaller units at a price higher than the equivalent STM-1 price.

STP (Signal Transfer Point)

A packet switch in the SS7 network that enables cost-effective routing of SS7 signals between other network elements.

STS (Synchronous Transport Signal) 

The electrical equivalent of the SONET-defined optical signals with a base rate of 51.840 Mbps.  STS-1 is the SONET equivalent of the asynchronous DS-3 in terms of capacity.

Switching

The process of connecting the telephone calls (circuits) and/or data packets across the network.

TERM

DEFINITION

TCP (Transport Control Protocol)

The Transport Control Protocol (or TCP) provides end-to-end reliable delivery of data. When two computers send information using TCP/IP, the TCP portion of the protocol suite will insure that all of the data is sent across the network and correctly received at the remote computer.

TCP/IP (Transport Control Protocol /Internet Protocol)

A pair of data communications protocols designed to simplify inter-network communications and insure fault tolerance between transmit and receive nodes.  See also TCP and IP.

Telegraph

The communications system based on the use of a manual code to enter the information. The practical telegraph was designed by Samuel Morse and transmitted information using dots and dashes to represent the alphabet, numbers and some special characters.

Terabit

1 trillion bits (1 Tb)

Time Division Multiplex or TDM

A technique for transmitting a number of separate data, voice and/or video signals simultaneously over one communications medium by quickly interleaving a piece of each signal one after another.

Transmission

Refers to the process of moving the signals across the telephone network. The measure of a good transmission system is that it will make the voice understandable enough so that the listener can hear the speaker without impairment or that a data signal arrive error free.

Transport Layer

In TCP/IP, the transport layer is where TCP resides. The transport layer provides the end-to-end reliable communications.

TERM

DEFINITION

URL (Uniform Resource Locator)

The address used to locate an website on the Internet. For example, http://www.whitehouse.gov is a URL. These addresses are typed into your web browser.

TERM

DEFINITION

VoIP (Voice over IP)

Voice communications converted to IP packet format and transmitted over an Internet communications path.

TERM

DEFINITION

WAN (Wide Area Network)

The Wide Area Network (or WAN) provides a network that connects one or more sites across public boundaries (or beyond a user's property). The examples would be a network that connects offices in different cities and/or different countries. The transmission circuits used in a WAN are usually rented from public service providers such as PTT's or Value Added Network services. In some cases a WAN can be built using microwave, fiber optics or other privately owned facilities.

WATS (Wide Area Telephone Service)

Discounted toll service offered on an inward or outward basis. Inward WATS is better known as 800 service.

Wavelength

The distance between two crests of a signal or a carrier and is measured in terms of meters, millimeters, nanometers, etc. In lightwave applications, because of the extremely high frequencies, wavelength is measured in nanometers (nm).

WDM (Wavelength Division Multiplexing)

A way of increasing the information-carrying capacity of an optical fiber by simultaneously operating at more than one wavelength. With WDM you can multiplex signals by transmitting them at different wavelengths through the same fiber.  See also DWDM.

TERM

DEFINITION

xDSL
 

A term referring to a variety of new Digital Subscriber Line technologies. Some of these varieties are asymmetric with different data rates in the downstream and upstream directions. Others are symmetric. Downstream speeds range from 384 kbps (or "SDSL") to 1.5-8 Mbps (or "ADSL").