A

Access
1. The method, time, circuit, or facility used to enter the network.
2. The service provided by local exchange carriers or alternate access providers, that connects an InterExchange carrier with its customers.

There are two kinds of access services:
1. Switched access--Provides such service over the Public Switched Telephone Network
2. Special access--Provides dedicated access for private line services and sometimes at the closed end of switched services.

Access Line
The portion of a telephone line between the end user's location and the telephone company's central office. Also called local loop, subscriber loop or local line.

ADSL
See "Asymmetric Digital Subscriber Line"

Agent
A person or entity who acts on behalf of another person or entity with the principal's authorization.

Alternate Exchange Carrier Name (AECN)
A unique identifier for a CLEC.

Analog Transmission
The traditional telephone technology (for voice transmission) in which sound waves (or other data) are converted into electrical impulses of varying strength or amplitude.

Analog Two-Wire Loop
An analog facility between a RBOC central office and an end-user location.

ANI
See "Automatic Number Identification."

ARIN
ARIN provides services related to the technical coordination and management of Internet number resources (IP Addresses). The nature of these services is described in ARIN's mission statement:

Applying the principles of stewardship, ARIN, a nonprofit corporation, allocates Internet Protocol resources; develops consensus-based policies; and facilitates the advancement of the Internet through information and educational outreach.

These services are grouped in three areas: Registration, Organization, and Policy Development.

Area Code
Also known as a Numbering Plan Area (NPA). There are two general categories of NPAs: Geographic NPA--Associated with a defined geographic area; all telephone numbers bearing such an NPA are associated with services provided within that geographic area.

Asymmetric Digital Subscriber (ADSL)
A transmission technology that transmits an asymmetric digital signal using one of a variety of line codes as specified in the ANSI standard. ADSL technology enables data transmission over existing copper wiring at data rates several hundred times faster than analog modems, providing for simultaneous delivery of voice, video and data.

Asynchronous Transfer Mode (ATM)
A cell-switching technique using the cell relay method of transmission to provide high speed local and enterprise-wide WAN transport. ATM is asynchronous in the sense that it is not synchronized in time to establish ownership; rather, a header field is added to each data block to identify ownership.

ATM
See "Asynchronous Transfer Mode"

Automatic Number Identification (ANI)
The number transmitted through the network that identifies the calling party. Technically, a Common Channel Interoffice Signaling (CCIS) parameter that refers to the number transmitted on an out-of-band basis through the SS7 signaling network identifying the calling party's telephone number. Also known as Calling Party Number (CPN).

Autonomous System Number (ASN)
Autonomous System numbers (ASNs) are globally unique identifiers for Autonomous Systems. An Autonomous System (AS) is a group of IP networks having a single clearly defined routing policy, run by one or more network operators.

b

B Channel
See "Bearer Channel"

Backbone
High-capacity network infrastructure; the part that carries the heaviest traffic. The backbone is also that part of the network that joins LANs together - either inside a building or across a country. LANs are connected to the backbone by bridges and/or routers; the backbone serves as a communications highway for LAN-to-LAN traffic.

Bandwidth
The common measure of transmission capacity. For analog transmission, it is measured in cycles per second; for digital transmission, it is measured in bits per second.

Basic Rate ISDN (BRI)
A two-wire line-side local switching system port that uses the two-bit one-quaternary line code at a 160 kilobit per second rate to transport overhead and up to two B channels and one D channel.

Baud
A measure of the speed of transmission of data; the number of elements transmitted per second.

Bearer Channel (B Channel)
A 64 kilobits per second channel used for information transfer.

Beta Test
The stage at which a new product is tested under actual usage conditions. (Alpha testing is conducted in-house.)

BGP
See Border Gateway Protocol

Bit
The smallest unit of information in the binary system of notation.

Bit Rate
The speed at which digital signals are transmitted, usually expressed in bits per second (bps).

Border Gateway Protocol (BGP)
Protocol for communications between a router in one autonomous system and routers in another.

Bridge
A device that connects and passes data packets between two network segments.

Broadband
A data-transmission scheme in which multiple signals share the bandwidth of a medium such as fiber-optic cable. This allows the transmission of voice, data and video signals over a single medium; for example, cable television uses broadband to deliver dozens of channel signals over a single cable.

c

Cable Entrance Facility
The entrance area in a telephone central office building for all types of outside plant cables that carry subscriber lines and interoffice transmission facilities.

Central Office (CO)
RBOC building where end users' lines are joined to switching equipment that connects other end users to each other, both locally and via long distance carriers. The central office contains the associated inside plant network elements required to perform this function, such as distribution frames, interoffice facility termination points, and so on. Also known as End Office and Entity.

Central Office Code, CO Code, NXX, NXX Code
The three digit switch entity indicator which is defined by the "D", "E", and "F" digits of a 10-digit telephone number. Each NXX code contains 10,000 station numbers. Historically, entire NXX code blocks have been assigned to specific individual local exchange end office switches.

Central Office Prefix
The first three digits (NXX) of a seven-digit telephone number under which up to 10,000 telephone numbers are grouped; exchange area boundaries are associated with the central office code. Several central office codes may be served by a single central office switching system.

Central Office Switch (or Switch)
Often referred to as the switch, the telephone company facility that connects subscribers to each other, locally and long distance. CO switches include the following:

1. End Office Switches, Class 5 switches from which end-user Exchange Services are directly connected and offered
2. Tandem Office Switches, Class 4 switches that are used to connect and switch trunk circuits between and among central office switches

NOTE:Central office switches may be employed as combination end office switch/tandem office switches (combination Class 5/Class 4).

Centrex
A class of central office service that provides the equivalent of Private Branch Exchange (PBX) service from a telephone company switching system. Permits station-to-station dialing, direct inward dialing to a particular station, and station identification on outgoing calls.

Channel
An electrical or photonic (for fiber optic-based systems) communication path between two or more points of termination.

CIR
See "Committed Information Rate"

Circuit
A two-way communication path.

CLEC
See "Competitive Local Exchange Carrier"

CLLI Code
11-character code that identifies the wire center from which a call originated.

CO Code, Central Office Code, NXX, NXX Code
The three-digit switch entity indicator which is defined by the "D", "E", and "F" digits of a 10-digit telephone number within the North American Numbering Plan. Each NXX code contains 10,000 station numbers. Historically, entire NXX code blocks have been assigned to specific individual local exchange end office switches.

Coaxial Cable
A transmission line in which one conductor is a wire at the center of the cable; the other conductor surrounds the center wire with a layer of insulating material between them. Coaxial cable can transmit greater bandwidth than twisted pair wires.

Collapsed Backbone
A non-distributed backbone in which all network segments are interconnected via an internetworking device. A collapsed backbone may be a virtual network segment that exists in a device such as a hub, a router, or a switch.

Colocation (Collocation, Co-location)
An arrangement whereby the facilities of one party's (the Colocating Party) are terminated with the equipment necessary to provide interconnection or access to the network elements offered by the second Party. This equipment is installed and maintained at the premises of the second Party (the Housing Party). All such services and facilities used for Colocated Interconnection are for carriage of non-switched interstate traffic. For purposes of Colocation, the premises of a Housing Party are described as a Housing Party Wire Center, other mutually agreed-upon locations of the Housing Party, or any other location for which Colocation has been ordered by the FCC or the state Commission. RBOC provides Colocation housing under terms, rates, and conditions as described in tariffs filed with the FCC and Commissions.

Colocation may be physical or virtual. For physical colocation, the Colocating Party installs and maintains its own equipment in the Housing Party's premises. For virtual colocation, the Housing Party owns, installs, and maintains equipment that is purchased by the Colocating Party, located in the Housing Party's premises, and dedicated to use by the Colocating Party.

Committed Information Rate (CIR)
The specified transport speed that a frame relay network will maintain between service locations.

Competitive Local Exchange Carrier (CLEC)
Any company or person authorized to provide local exchange services in competition with an Incumbent Local Exchange Carrier. A CLEC provides similar or identical telecommunications services to the ILEC.

CPE
See "Customer Premise Equipment"

Cross Connection
A connection provided to a Colocator at the digital signal cross connect, main distribution frame or other frame or panel between the CLEC's equipment and equipment or facilities owned by the RBOC.

D

D Channel
The D channel is a packet-switched channel that carries signaling and control for B channels. In Basic Rate ISDN (BRI) applications, it can also support customer packet data traffic at speeds up to 9.6 kilobits per second.

Database (DB)
A collection of data organized in a structured manner so that information can be readily retrieved.

Dedicated Line
1. A communications circuit or channel provided for the exclusive use of a particular subscriber. Dedicated lines are used for computers when large amounts of data need to be moved between points. Also known as a private line.
2. A transmission circuit installed between two sites of a private network; it is "open," or available, at all times.

Default Route
Entry in a routing table that can redirect any frames for which the table has no definitive listing for the next hop.

DHCP
DHCP (Dynamic Host Configuration Protocol) is a communications protocol that lets network administrators centrally manage and automate the assignment of Internet Protocol (IP) addresses in an organization's network. Using the Internet Protocol, each machine that can connect to the Internet needs a unique IP address, which is assigned when an Internet connection is created for a specific computer. Without DHCP, the IP address must be entered manually at each computer in an organization and a new IP address must be entered each time a computer moves to a new location on the network. DHCP lets a network administrator supervise and distribute IP addresses from a central point and automatically sends a new IP address when a computer is plugged into a different place in the network.

Dial Up
A type of communication that is established by a switched-circuit connection using the telephone network.

Digital Signal 0 (DS-0)
A discontinuous signal that consists of discrete elements that represent specific information. The 64 Kilobits per second zero-level signal in the time-division multiplex hierarchy. The effective transport rate of a DS0 signal may be less than 64 Kilobits per second as a result of technology limitations. A DS0 provides the digital equivalent of an analog voice grade channel.

Digital Signal 1 (DS-1)
A discontinuous signal that consists of discrete elements that represent specific information. The 1.544 Megabits per second first-level signal in the time-division multiplex hierarchy. In the time-division multiplexing hierarchy of the telephone network, DS1 is the initial level of multiplexing. A DS1 typically provides twenty-four DS0 channels.

Digital Signal 3 (DS-3)
The telephony term describing High Capacity Digital Service-45 Megabit channel. The 44.736 Megabits per second third-level in the time-division multiplex hierarchy. In the time-division multiplexing hierarchy of the telephone network, DS3 is defined as the third-level of multiplexing. A DS3 traditionally provides twenty-eight DS1 channels.

Digital Subscriber Line (DSL)
A generic name for a group of enhanced speed digital services provided by telephone companies. DSL services run on twisted-pair wires; they carry both voice and data.

Digital Subscriber Line Access Multiplexer (DSLAM)
Technology that concentrates traffic in ADSL implementations. Located in the central office.

Digital Transmission
A mode of transmission in which all information is transmitted in digital form as a serial stream of pulses. Sound waves and other information are converted into binary computer code (a series of 0s and 1s) and transmitted to the end point. At the end point, binary code is converted back into the original format. Digital transmission provides sharper, clearer, faster transmission than analog transmission.

Disaster Recovery
The pre-defined use of alternative network circuits to re-establish communications channels in the event that primary channels are disconnected or malfunctioning.

DNS
The domain name system (DNS) is the way that Internet domain names are located and translated into Internet Protocol addresses. A domain name is a meaningful and easy-to-remember "handle" for an Internet address.

DS-0
See "Digital Signal 0"

DS-1
See "Digital Signal 1"

DS-3
See "Digital Signal 3"

DSLAM
See Digital Subscriber Line Access Multiplexer

Dual Homing (Multi-Homed)
Where a device is connected to the network via two independent access points (points of attachment). One access point is the primary connection; the other is a standby connection that is activated in the event the primary connection fails.

E

Email (or E-Mail)
An abbreviation for electronic mail, which is a network service that allows users to send and receive messages via computer. The Internet and common message protocols makes it possible to send and receive email messages worldwide.

End User
Any customer of a telecommunications service that is not a carrier, except for the following exceptions:

1. A carrier other than a telephone company is considered to be an "end user," when the carrier uses a telecommunications service for administrative purposes.
2. A person or entity that offers telecommunications services exclusively as a Reseller is considered to be an "end user" if all resale transmissions offered by the reseller originate on the premises of the reseller.

Enterprise Network
A geographically dispersed network under the auspices of one organization.

Entrance Facility
Point of interconnection between the local exchange carrier's Rate Demarcation Point and the external carrier's Point of Presence (POP).

Ethernet
A 100-Mbps technology based on the 10BASE-T Ethernet CSMA/CD network access method to accommodate the operation of local area networks (LANs).

Exchange
A unit generally smaller than a LATA, established by the Local Exchange Carrier for the administration of communications service in a specified area (usually a city, town, or village and its environs). An exchange consists of one or more central offices together with the associated facilities used to provide communications services within that area. One or more designated exchanges comprise a given LATA.

F

Facilities
Cables, poles, conduit, microwave, or carrier equipment, central office distributing frames, central office switching equipment, computers (both hardware and software), business machines, etc., used by a telephone to provide telecommunications services.

Facilities-Based Carriers
CLECs that own their own facilities. These facilities may be colocated in a telecommunications service provider's office. NOTE: CLECs may also lease facilities from service providers.

Fast Ethernet
A 100-Mbps technology based on the 10BASE-T Ethernet CSMA/CDNetwork access method for operating local area networks.

FCC
See "Federal Communications Commission"

Federal Communications Commission (FCC)
A federal government agency authorized by the Communications Act of 1934 to regulate interstate and international telecommunications originating in the United States. The FCC plays a role in implementing the Telecommunications Act of 1996.

Fiber Optics
Communications technology that uses thin filaments of glass or other transparent materials. Fiber optic technology offers extremely high transmission speeds, allowing for data-intensive services such as video on demand.

Field Technician
The RBOC employee responsible for installation, repair and maintenance of the outside RBOC network.

File Transfer Protocol (FTP)
A file sharing protocol used as follows:

1. In LAN technology for user authentication, file transfer, list directories of the foreign host, etc.
2. As an Internet tool for accessing file archives from around the world that are linked to the Internet.

Firm Order Confirmation Notice (FOC)
The notice issued in response to a firm order Access Service Request (ASR). An FOC signifies RBOC's good faith effort to provide the access service ordered.

FOC
See "Firm Order Confirmation Notice"

Frame Relay
High-performance interface or packet-switched networks. Considered more efficient than X.25 (which it is expected to replace). Frame relay technology can handle "bursty" communications that have rapidly changing bandwidth requirements.

FTP – File Transfer Protocol
File Transfer Protocol (FTP), a standard Internet protocol, is the simplest way to exchange files between computers on the Internet. Like the Hypertext Transfer Protocol (HTTP), which transfers displayable Web pages and related files, and the Simple Mail Transfer Protocol (SMTP), which transfers e-mail, FTP is an application protocol that uses the Internet's TCP/IP protocols. FTP is commonly used to transfer Web page files from their creator to the computer that acts as their server for everyone on the Internet. It's also commonly used to download programs and other files to your computer from other servers.

G

Gateway
The entrance and exit to a communications network or system; a device or set of functions that facilitate electronic access by users to remote services or systems and vice versa. In data networks, gateways are typically a network node that connects otherwise incompatible networks. Gateways are commonly used to connect computers on one network, say a token-ring network, with those on a long-distance network. A gateway may be used to interface between two incompatible electronic mail systems or for transferring files from one system to another.

h

High-Bit Rate Digital Subscriber Line (HDSL)
A transmission technology that transmits over two twisted cable pairs up to a DS1-level signal, using any one of the following line codes: Binary / 1 Quaternary (2B1Q) Carrierless AM/PM, Discrete Multitone ("DMT"), or Binary / 1 Octel ("3BO").

Hosting – Dedicated Server
In the Web hosting business, a dedicated server refers to the rental and exclusive use of a computer that includes a Web server, related software, and connection to the Internet, housed in the Web hosting company's premises. A dedicated server is usually needed for a Web site (or set of related company sites) that may develop a considerable amount of traffic - for example, a site that must handle up to 35 million hits a day. The server can usually be configured and operated remotely from the client company. Web hosting companies claim that the use of a dedicated server on their premises saves router, Internet connection, security system, and network administration costs.

Hosting – Shared
Shared hosting is Web hosting in which the service provider serves pages for multiple Web sites, each having its own Internet domain name, from a single Web server. Most Web hosting companies provide shared hosting. Although shared hosting is a less expensive way for businesses to create a Web presence, it is usually not sufficient for Web sites with high traffic. These sites need a dedicated Web server, either provided by a Web hosting service or maintained in-house.

i

ILEC
See "Incumbent Local Exchange Carrier"

Incumbent Local Exchange Carrier (ILEC)
In the Telecommunications Act of 1996 with respect to an area, the Incumbent Local Exchange Carrier is defined as the Local Exchange Carrier that, on the date of enactment of the Act, provided telephone exchange service in that area; for example, SBC is an ILEC.

Independent Telephone Company (ITC/ICO)
A Local Exchange Carrier other than a Regional Bell Operating Company.

Inside Wiring
Telephone wiring on the customer's side of the rate demarcation point, the point located on the subscriber's side of the telephone company's protector or other device serving the same purpose. For residences, the protector is usually located at the point where the telephone lines enter the house.

Integrated Digital Loop Carrier (IDLC)
A subscriber loop carrier system that integrates within the switch, generally at a DS1 level, twenty-four local link (loop) voice-grade equivalent transmission paths combined into a 1.544 megabits per second digital signal.

Integrated Services Digital Network (ISDN)
A widely available high bandwidth switched network service providing end-to-end digital connectivity over standard phone lines for simultaneous transmission of voice and data. There are two levels of service:

1. Basic Rate Interface-ISDN (BRI-ISDN)--provides for digital transmission of two 64 kbps bearer channels and one 16 kbps data and signaling channel (2B+D).
2. Primary Rate Interface-ISDN (PRI-ISDN)--provides for digital transmission of twenty three (23) 64 kbps bearer channels and one (1) 64 kbps data and signaling channel (23 B+D).

Interconnection
As described in the Telecommunications Act of 1996, Interconnection refers to the connection of separate pieces of equipment or transmission facilities within, between or among networks. For example, Interconnection includes Colocation arrangements, entrance facilities, Mid-Span Fiber Meet arrangements, etc.

Interconnection Facility
The physical connection of equipment, transmission facilities, etc., within, between and among networks, for transmission and routing of exchange service and exchange access.

Interconnection Point
The physical point on the network where two parties interconnect. The interconnection point is the demarcation point between ownership of the transmission facility and the outside network.

InterExchange Carrier (InterExchange Carrier or IC) or InterExchange Common Carrier (IXC):
A telecommunications service provider authorized by the FCC to provide interstate long distance communications services between LATAs; and authorized by the State to provide long distance communications services. An InterExchange Carrier provides, directly or indirectly, interLATA or intraLATA telephone toll services. May be an individual, partnership, association, joint-stock company, trust, governmental entity or corporation engaged for hire in interstate or foreign communication by wire or radio, between two or more exchanges. An InterExchange Carrier may be a customer of the RBOC.

Interface
A connection between two systems or devices. In routing terminology, a network connection; also, the boundary between adjacent layers of the OSI reference model. In telephony, a shared boundary defined by common physical interconnection characteristics, signal characteristics and meanings of interchanged signals.

InterLATA/LATA Service
As defined in the Telecommunications Act of 1996, InterLATA Service means telecommunications between a point located in a Local Access and Transport Area (LATA) and a point located outside such area. IntraLATA Service means telecommunications between two points located within the same LATA.

Internet
An international network of networks, originally started for military purposes, that connects millions of users instantaneously through commonly-used protocols such as TCP/IP, HTTP, FTP, Gopher, etc. The widely-used World Wide Web is available through the Internet.

Internet Access
The connection which allows you to get on the Internet through an Internet Service Provider (ISP) of your choice. The type of connection you choose is based on a number of different factors, including cost and the communications system you have.

Internet Address (IP Address)
Also called an IP (Internet Protocol) address; a 32-bit address assigned to hosts using TCP/IP. The address is written as four octets separated with periods (dotted decimal format) that are made up of a network section, an optional subnet section and a host section.

Internet Protocol (IP)
Part of the TCP/IP family of protocols that tracks the outgoing address of nodes, routes outgoing messages and recognizes incoming messages.

Internet Service Provider (ISP)
A vendor that provides direct access to the Internet, and services such as email. The user accesses the ISP by dialing up through a personal computer and modem, or through a dedicated line. Also known as an Internet Access Provider (IAP)

Interoperability
The ability to operate software and exchange information in a large network made up of different kinds of LANs.

Interstate Telecommunications
Telecommunications that originate and terminate in different states, subject to oversight by the FCC and state regulatory commissions.

IntraLATA/InterLATA Service
As defined in the Telecommunications Act of 1996, InterLATA Service means telecommunications between a point located in a Local Access and Transport Area (LATA) and a point located outside such area. IntraLATA Service means telecommunications between two points located within the same LATA.

Intrastate Communications
Telecommunications that originate and terminate in the same state, subject to oversight by a state regulatory commission as provided by the laws of the state involved.

Intrastate IntraLATA
Services between two points within the same LATA that are not used in connection with InterLATA channels.

IP:
1. Interconnection Point--The physical point on the network where two parties interconnect. The IP is the demarcation point between ownership of the transmission facility and the outside network.
2. Internet Protocol

IP Address
Internet Protocol address; a 32-bit address assigned to hosts using TCP/IP. The address is written as four octets separated with periods (dotted decimal format) that are made up of a network section, an optional subnet section and a host section. Also known as an Internet Address.

ISDN
See "Integrated Services Digital Network"

ISP
See "Internet Service Provider."

IT – Information Technology
IT (information technology) is a term that encompasses all forms of technology used to create, store, exchange, and use information in its various forms (business data, voice conversations, still images, motion pictures, multimedia presentations, and other forms, including those not yet conceived). It's a convenient term for including both telephony and computer technology in the same word. It is the technology that is driving what has often been called "the information revolution."

IVR – Interactive Voice Response
Interactive Voice Response (IVR) is a software application that accepts a combination of voice telephone input and touch-tone keypad selection and provides appropriate responses in the form of voice, fax, callback, e-mail and perhaps other media. IVR is usually part of a larger application that includes database access.

j

k

Kbps or Kbs
See "Kilobits per second."

Kilobit (K)
A measure, representing 1,000 bits, generally used to express the speed per second of telecommunications services and equipment. A bit is the smallest unit used to express digital information.

Kilobits per second (Kbps or Kbs)
A measurement for data transmission. One kilobit per second is one thousand bits per second.

l

LAN
See "Local Area Network."

Landline
A telephone circuit that travels over land-based circuits (as opposed to wireless).

LATA
See "Local Access and Transport Area."

LEC
See "Local Exchange Carrier."

LERG
See "Local Exchange Routing Guide."

LNP
See "Local Number Portability."

Local Access and Transport Area (LATA)
A geographic area within a telephone company's franchised territory which has been established in accordance with the Modification of Final Judgment (MFJ) for the purpose of defining the area within which a telephone company may offer services.

Local Area Network (LAN)
A short-distance data communications network. LANs are typically within a building or campus, and to link together computers and peripherals under a standard protocol. The network provides high-bandwidth communications over coaxial cable, twisted-pair, fiber, or microwave media. LANs are usually owned by the user.

Local Exchange
A local exchange is the local central office of a LEC. Lines from homes and businesses terminate at a local exchange. Local exchanges connect to other local exchanges within a LATA or to InterExchange Carriers, also known as long-distance carriers.

Local Exchange Carrier (LEC)
As defined in the Telecommunications Act of 1996, a company certified by the Federal Communications Commission to provide local exchange telecommunications service. A LEC can be either a Bell Operating Company or an independent company.

Local Exchange Routing Guide (LERG)
A document issued by Telcordia (formerly Bellcore) that is used to identify NPA-NXX routing and homing information, as well as network element and equipment designation. It contains a listing of local routing data such as destination codes, switching entities, rate centers and locality information by LATA. The LERG is an essential tool for network planning.

Local Loop (Last Mile)
The part of a communications circuit between the subscriber's equipment and the equipment in the local exchange. More formally, a transmission path that extends from the vertical side of a main distribution frame, DSX-panel, or functionally comparable piece of equipment in the subscriber's serving end office to the rate demarcation point (or Network Interface Device) in or at an end user's premises. Also known as the subscriber loop, local line and access line.

Local Number Portability (LNP)
The process by which an end user can retain the same telephone number regardless of which local service provider he/she chooses. The ability for phone numbers to be moved between local service providers is accomplished by shared access to a numbering database. Also known as Location Portability.

Loop Qualification
Categorizes certain physical characteristics of a loop prior to order placement.

m

Main Distribution Frame (MDF)
The primary point at which outside plant facilities terminate within a wire center for interconnection to other telecommunications facilities within the wire center.

MAN – Metropolitan Area Network
A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN). The term is applied to the interconnection of networks in a city into a single larger network (which may then also offer efficient connection to a wide area network). It is also used to mean the interconnection of several local area networks by bridging them with backbone lines. The latter usage is also sometimes referred to as a campus network.

Megabits (Mb)
A measure, representing 1,000,000 bits, generally used to express the speed per second of telecommunications services and equipment. See Kilobit. A bit is the smallest unit used to express digital information.

Megabits per second (Mbps)
A measurement of data transmission. One megabit per second equals one million bits per second.

Megabytes
A measure, representing 1,000,000 bytes generally used to express the storage capacity of digital components. A byte represents a single character, or group of eight bits.

MPLS
Multiprotocol Label Switching (MPLS) is a standards-approved technology for speeding up network traffic flow and making it easier to manage. MPLS involves setting up a specific path for a given sequence of packets, identified by a label put in each packet, thus saving the time needed for a router to look up the address to the next node to forward the packet to. MPLS is called multiprotocol because it works with the Internet Protocol (IP), Asynchronous Transport Mode (ATM), and frame relay network protocols. With reference to the standard model for a network (the Open Systems Interconnection, or OSI model), MPLS allows most packets to be forwarded at the layer 2 (switching) level rather than at the layer 3 (routing) level. In addition to moving traffic faster overall, MPLS makes it easy to manage a network for quality of service (QoS). For these reasons, the technique is expected to be readily adopted as networks begin to carry more and different mixtures of traffic.

Multiplexing
The process of combining a number of individual channels into a common frequency band or into a common bit stream for transmission.

n

NEBS (Network Equipment Building Systems)
A set of safety- and performance-related standards for telecommunications equipment installed in central offices.

Network Element
As defined in the Telecommunications Act of 1996, a facility or equipment used in provisioning a telecommunications service. The term may include the features, functions and capabilities of that facility or equipment.

NPA-Nxx
(see NPA and Nxx separately)

Numbering Plan Area (NPA)
An NPA is referred to as an area code. There are two general categories of NPAs:

1. Geographic NPA -- Associated with a defined geographic area; all telephone numbers bearing such an NPA are associated with services provided within that geographic area.
2. Non-Geographic NPA -- Associated with a specialized telecommunications service, which may be provided across multiple geographic NPA areas; for example 800, 900, 700, 500 and 888. Also known as a Service Access Code or SAC Code.

Number Portability
As defined in the Telecommunications Act of 1996, the ability of telecommunications service users to retain, at the same location, existing telephone numbers without impairment of quality, reliability, or convenience when switching from one telecommunications carrier to another.

NXX, NXX Code, Central Office Code, or CO Code
The three digit switch entity indicator which is defined by the "D", "E", and "F" digits of a 10-digit telephone number within the North American Numbering Plan. Each NXX code contains 10,000 station numbers. Historically, entire NXX code blocks have been assigned to specific individual local exchange end office switches.

o

OC-1
See "Optical Carrier Level."

OC-3
See "Optical Carrier Level."

Optical Carrier Level (OCx)
A SONET term. A range of bandwidths as specified in a Telcordia Technologies (formerly Bellcore) document and associated ANSI standards. For example: Optical Carrier Level 1 (OC-1)--The optical signal that results from an STS-1 signal conversion. Optical Carrier level 3 (OC-3)--An optical carrier with three 51.84M bps multiplexed OC-1 circuit streams on an underlying SONET/SDH circuit. Optical Carrier Level 3-c (OC-3c)--An OC-3 circuit with the three OC-1 lines concatenated into a 155.52M bps circuit; used in ATM transmission. See ATM and OQS (Open Query System).

Outside Plant
Includes facilities, equipment and other material connecting the RBOC central office building to the end user premise or another central office; for example, cable, poles, manholes, drop wires, etc.

p

Plain Old Telephone Service (POTS)
The basic single line switched access service offered by local exchange carriers to residential and business end users, using loop-start signaling.

Point of Presence (POP)
The physical place within a LATA where a long distance carrier or a cellular provider interfaces with the network of the local exchange carrier.

Primary Rate ISDN (PRI)
PRI is a 4-wire 1.544 megabits per second (DS1) local switching system port that uses the B8ZS line code and the ESF framing format. PRI is available in a twenty-three B channel plus one D channel (23B + D) configuration or a twenty-four B channel (24B) configuration.

Private Branch Exchange (PBX)
A private telephone switching system commonly located on the end user premises with an attendant console. The PBX is connected to a common group of lines from one or more central offices to provide service to a number of individual phones.

Public Switched Telephone Network (PSTN)
Usually used to refer to the worldwide voice telephone network.

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RADIUS
Remote Authentication Dial-In User Service (RADIUS) is a client/server protocol and software that enables remote access servers to communicate with a central server to authenticate dial-in users and authorize their access to the requested system or service. RADIUS allows a company to maintain user profiles in a central database that all remote servers can share. It provides better security, allowing a company to set up a policy that can be applied at a single administered network point. Having a central service also means that it's easier to track usage for billing and for keeping network statistics. Created by Livingston (now owned by Lucent), RADIUS is a de facto industry standard used by a number of network product companies and is a proposed IETF standard.

Rate Center
The specific geographic point and corresponding geographic area that are associated with one or more particular NPA/NXX codes that have been assigned to a local exchange carrier for its provision of Exchange Services. The geographic point is identified by a specific coordinate that is used to calculate distance-sensitive end user traffic to/from the particular NPA/NXX associated with the specific Rate Center.

RBOC
See "Regional Bell Operating Company"

Regional Bell Operating Company (RBOC)
The acronym for the local telephone companies created by the Modified Final Judgment in 1984 as part of the break-up of AT&T. The original seven RBOCs were Ameritech, Bell Atlantic, Bell South, Nynex, Pacific Telesis Group, Southwestern Bell, and US West.

Remote Terminal (RT)
A terminal connected to another terminal over a phone line.

Reseller
A business entity that purchases telecommunications services at wholesale and sells them to third parties; a service provider that does not own transmission facilities, but obtains communications services from a carrier for resale to the public for profit. Also known as a resale carrier.

Reseller Bill Period Account
For a Reseller, a bill period account carries the charges for every end user sub-account having that bill period, and itself has the same bill period.

Reseller Sub-Account
Each end user account converted from a RBOC account automatically becomes a Reseller Sub-Account. Each Reseller Sub-Account record contains the following identifiers: 1) Original end user's Billing Telephone Number (BTN) + new Customer Code; 2) Bill Period 3) Exchange Carrier Code; 4) Customer Identification Number (CIN).

Rights-of-Way Easements (ROE)
Right of access to land; used by telecommunications providers to place their facilities.

Router
An intelligent device near the edge of the network that forms data packets and selects the most expedient route for data to travel.

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Server
A networked computer that stores information and makes it available upon request to client programs that may be located on other computers. "Client-server" computing is the basis of virtually all local area networks and the World Wide Web.

Serving Wire Center
The first local exchange carrier wire center to which facilities are connected on the terminating path of a call proceeding from the customer premises to the terminating end office.

Shielded Twisted Pair (STP)
Two-pair wire medium used in the transmission of several different protocols. STP is capable of supporting CDDI for link distances of up to 100 meters. These wires have a layer of shielded insulation.

Signaling
The transmission of address and other switching information between end users and central offices, and between central offices.

SMTP
SMTP (Simple Mail Transfer Protocol) is a TCP/IP protocol used in sending and receiving e-mail. However, since it is limited in its ability to queue messages at the receiving end, it is usually used with one of two other protocols, POP3 or IMAP, that let the user save messages in a server mailbox and download them periodically from the server. In other words, users typically use a program that uses SMTP for sending e-mail and either POP3 or IMAP for receiving e-mail. On Unix-based systems, send mail is the most widely-used SMTP server for e-mail. A commercial package, Send mail, includes a POP3 server. Microsoft Exchange includes an SMTP server and can also be set up to include POP3 support.

SONET (Synchronous Optical Network)
An optical interface standard that allows different digital signals to be transported using a base transmission rate of 51.84 megabits per second OC-1 (Optical Carrier) STS-1 (Synchronous Transport Signal). Higher rates are direct multiples of the basic OC-1 building block.

Special Access Service
A transmission path directly connecting an InterExchange Carrier location in a LATA to an end user premise or another InterExchange Carrier location.

Spectrum
The range of electromagnetic radio frequencies used in the transmission of voice, data and television.

Subnet
A subnet (short for "subnetwork") is an identifiably separate part of an organization's network. Typically, a subnet may represent all the machines at one geographic location, in one building, or on the same local area network (LAN). Having an organization's network divided into subnets allows it to be connected to the Internet with a single shared network address. Without subnets, an organization could get multiple connections to the Internet, one for each of its physically separate subnetworks, but this would require an unnecessary use of the limited number of network numbers the Internet has to assign. It would also require that Internet routing tables on gateways outside the organization would need to know about and have to manage routing that could and should be handled within an organization.

Switched Access Service
A primary service offering under tariff. Switched Access Service provides for a two-way communications path capable of transmitting both voice and data services between an InterExchange Carrier location and the premises of its end-user customers. It includes access services that use the local exchange carrier's central office switches.

Synchronous
A form of communications where characters or bits are sent in a continuous stream, with the beginning of one signal continuous with the end of the preceding one; separation of one from the other requires the receiver to maintain a synchronization to a master timing signal.

Synchronous Optical Network (SONET)
An optical interface standard that allows different digital signals to be transported using a base transmission rate of 51.84 megabits per second OC-1 (Optical Carrier) / STS-1 (Synchronous Transport Signal). Higher rates are direct multiples of the basic OC-1 building block.

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T-1 Circuit
A digital circuit that uses the DS-1 signaling format to transmit information over the telephone network at 1.544 megabits per second. Can carry up to 24 uncompressed voice channels.

Tandem
The connection of networks or circuits in series; that is, the connection of the output of one circuit to the input of another. See Tandem Switch.

Tandem Switch
Tandem is a telephony term meaning "to connect in series." Thus, a tandem switch connects one trunk to another. A tandem switch is an intermediate switch or connection between an originating telephone call or location and the final destination of the call.

Tariff
A statement by a communications company filed with the FCC that sets forth services offered, and rates, terms, and conditions for those services.

TCP/IP
See "Transmission Control Protocol/Internet Protocol."

TDM – Time Division Multiplexing
Time-division multiplexing (TDM) is a method of putting multiple data streams in a single signal by separating the signal into many segments, each having a very short duration. Each individual data stream is reassembled at the receiving end based on the timing.

Telecommunications
As defined in the Telecommunications Act of 1996, transmission between or among points specified by the user, of information of the user's choosing, without change in the form or content of the information as sent and received. Any transmission, emission, or reception of signs, signals, writings, images, and sounds or intelligence by wire, radio, optical, or other electromagnetic systems.

Telecommunications Act of 1996
Public Law 104-104, enacted February 8, 1996, provided comprehensive reform of the 1934 Communications Act. The Act was designed to foster competition among local telephone, long distance telephone, cable and other communications companies.

Throughput
A measure of the overall efficiency, quality and performance of a communications link and its software/protocols.

Trunk
A communications path connecting two switching systems in a network, used to establish an end-to-end connection.

Trunk Group
A set of trunks that are traffic engineered as a unit in order to establish connections between switching systems in which all of the communications paths are interchangeable.

Tunneling
Tunneling is the transmission of data intended for use only within a private, usually corporate network through a public network in such a way that the routing nodes in the public network are unaware that the transmission is part of a private network. Tunneling is generally done by encapsulating the private network data and protocol information within the public network transmission units so that the private network protocol information appears to the public network as data. Tunneling allows the use of the Internet, which is a public network, to convey data on behalf of a private network.

Twisted Pair (TP)
Cable consisting of two 18 to 24 AWG (American Wire Gauge) solid copper strands twisted around each other. The twisting provides a measure of protection from electromagnetic and radio-frequency interference.

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Unbundled Loop (Unbundled Local Loop Element or UL)
A transmission path that extends from a Main Distribution Frame, DSX-panel, or functionally comparable piece of equipment in the customer's serving end office to the Rate Demarcation Point (or network interface device, if installed) in or at a customer's premises. The actual loop transmission facilities used to provide an ULL may utilize any of several technologies.

Unbundled Network Element (UNE)
Specific equipment and facilities that are "unbundled" from traditional end-to-end services (such as residential dial tone service) in order to allow other local exchange carriers to use components of an RBOC's network. An example of a network element would be a loop connected not to a RBOC switch, but to a competitor carrier's switch.

Unbundling
Term used to describe the access facilities that incumbent local exchange carriers must provide in order that other service providers may buy or lease portions of its network elements, such as interconnection loops to serve subscribers.

UNE
See "Unbundled Network Element"

Unshielded Twisted Pair (UTP)
Four-pair wire medium used in the transmission of many different telecommunications protocols such as Ethernet, 10BaseT, and CDDI

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VLAN
A virtual (or logical) LAN is a local area network with a definition that maps workstations on some other basis than geographic location (for example, by department, type of user, or primary application). The virtual LAN controller can change or add workstations and manage load balancing and bandwidth allocation more easily than with a physical picture of the LAN. Network management software keeps track of relating the virtual picture of the local area network with the actual physical picture.

VPN – Virtual Private Network
A virtual private network (VPN) is a network that uses a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network. A virtual private network can be contrasted with an expensive system of owned or leased lines that can only be used by one organization. The goal of a VPN is to provide the organization with the same capabilities, but at a much lower cost.

A VPN works by using the shared public infrastructure while maintaining privacy through security procedures and tunneling protocols such as the Layer Two Tunneling Protocol (L2TP). In effect, the protocols, by encrypting data at the sending end and decrypting it at the receiving end, send the data through a "tunnel" that cannot be "entered" by data that is not properly encrypted. An additional level of security involves encrypting not only the data, but also the originating and receiving network addresses.

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Webcasting
The use of the Web as a one-to-many medium to broadcast events or hold collaborative conferences among remote participants.

Wide Area Network (WAN)
A network that links multiple locations together. A WAN encompasses a much larger geographic area than that of a Local Area Network (LAN).

Wire Center
This term is often used interchangeably with the terms central office and switch. Technically, the wire center is the location where the local exchange carrier terminates subscriber local loops, along with the testing facilities necessary to maintain them. A wire center can be a building or space within a building that serves as an aggregation point on a local exchange carrier's network, where transmission facilities and circuits are connected or switched. "Wire center" can also denote a building in which one or more central offices, used for the provision of exchange services and access services, are located.

World Wide Web or WWW or Web
An area of the Internet that allows for graphical information retrieval via hypertext-based software, such as a web browser like Netscape Navigator or Microsoft Internet Explorer, in a point-and-click environment.

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