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Telecom Dictionary - Definitions of terms

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N

NA - Abbreviation for numerical aperture. 1. The sine of the vertex angle of the largest cone of meridional rays that can enter or leave an optical system or element, multiplied by the refractive index of the medium in which the vertex of the cone is located. Note: The NA is generally measured with respect to an object or image point and will vary as that point is moved. 2. For an optical fiber in which the refractive index decreases monotonically from n 1 on the axis to n 2 in the cladding, an expression of the extent of the fiber's ability to accept, in its bound modes, non-normal incident rays, given by NA = ( n 1 2 - n 2 2 ) ½ . Note: In multimode fibers, the term equilibrium numerical aperture is sometimes used. This refers to the numerical aperture with respect to the extreme exit angle of a ray emerging from a fiber in which equilibrium mode distribution has been established. 3. Loosely, the sine of the radiation or acceptance angle of an optical fiber, multiplied by the refractive index of the material in contact with the exit or entrance face. Note: This usage is approximate and imprecise, but is often encountered.

Nailed-Up Circuit - Deprecated term. See dedicated circuit, permanent virtual circuit. A circuit designated for exclusive use by specified users. Note: DOD normally considers a dedicated circuit to be between two users only. A virtual circuit used to establish a long-term connection between data terminal equipments (DTE). Note 1: In a PVC, the long-term association is identical to the data transfer phase of a virtual call. Note 2: Permanent virtual circuits eliminate the need for repeated call set-up and clearing.

NAK - Acronym for negative-acknowledge character . A transmission control character sent by a station as a negative response to the station with which the connection has been set up. Note 1: In binary synchronous communication protocol , the NAK is used to indicate that an error was detected in the previously received block and that the receiver is ready to accept retransmission of that block. Note 2: In multipoint systems, the NAK is used as the not-ready reply to a poll.

NAK Attack - In communications security systems, a security penetration technique that makes use of the negative-acknowledge transmission - control character and capitalizes on a potential weakness in a system that handles asynchronous transmission interruption in such a manner that the system is in an unprotected state against unauthorized access during certain periods.

Naming Authority - With respect to Internet addressing, an entity responsible for the allocation of names. Note: Such naming is typically hierarchical, so that the authority to allocate domain names is restricted to a particular level within a domain, such as ".com", ".net", or ".gov".

NAP - See Network Access Point. A centralized point where Internet traffic is exchanged or shared.

Narrative Traffic - Traffic consisting of plain or encrypted messages written in a natural language and transmitted in accordance with standard formats and procedures. Note: Examples of narrative traffic include (a) messages that are placed on paper tape and transmitted via a teletypewriter ( TTY ), and on reception, are converted back to a printed page on another teletypewriter or teleprinter and (b) messages printed on a sheet of paper, transmitted via optical character recognition ( OCR ) equipment, and on reception, converted back to a printed page on a printer.

Narrowband Modem - A modem whose modulated output signal has an essential frequency spectrum that is limited to that which can be wholly contained within, and faithfully transmitted through, a voice channel with a nominal 4- kHz bandwidth . Note: High frequency (HF) modems are limited to operation over a voice channel with a nominal 3-kHz bandwidth.

Narrowband Radio Voice Frequency (NBRVF) - In narrowband radio, the nominal 3- kHz bandwidth allocated for single channel radio that provides a transmission path for analog and quasi-analog signals.

Narrowband Signal - Any analog signal or analog representation of a digital signal whose essential spectral content is limited to that which can be contained within a voice channel of nominal 4- kHz bandwidth. Note: Narrowband radio uses a voice channel with a nominal 3-kHz bandwidth.

n-ary code - A code that has n significant conditions, where n is a positive integer greater than 1. Note 1: The integer substituted for n indicates the specific number of significant conditions, i.e., quantization states, in the code. For example, an 8-ary code has eight significant conditions and can convey three bits per code symbol. Note 2: A prefix that indicates an integer, e.g., "bi," "tern," or "quater," may be used in lieu of a numeral, to produce "binary," "ternary," or "quaternary" (2, 3, and 4 states respectively).

n-ary signaling - See n-ary code.

NATA - Abbreviation for North American Telecommunications Association.

National Communications System (NCS) -1. The organization established by Section 1(a) of Executive Order No. 12472 to assist the President, the National Security Council, the Director of the Office of Science and Technology Policy, and the Director of the Office of Management and Budget, in the discharge of their national security emergency preparedness telecommunications functions. The NCS consists of both the telecommunications assets of the entities represented on the NCS Committee of Principals and an administrative structure consisting of the Executive Agent, the NCS Committee of Principals, and the Manager. 2. The telecommunications system that results from the technical and operational integration of the separate telecommunications systems of the several executive branch departments and agencies having a significant telecommunications capability.

National Coordinating Center (NCC) for Telecommunications - The joint telecommunications industry/Federal Government operation established by the National Communications System to assist in the initiation, coordination, restoration, and reconstitution of National Security or Emergency Preparedness (NS/EP) telecommunications services or facilities.

National Electric Code® (NEC) - A standard that governs the use of electrical wire, cable, and fixtures, and electrical and optical communications cable installed in buildings. Note: The NEC was developed by the NEC Committee of the American National Standards Institute ( ANSI ), was sponsored by the National Fire Protection Association (NFPA), and is identified by the description ANSI/NFPA 70-XXXX, the last four digits representing the year of the NEC revision.

National Information Infrastructure (NII) - A proposed, advanced, seamless web of public and private communications networks, interactive services, interoperable hardware and software, computers, databases, and consumer electronics to put vast amounts of information at users' fingertips. Note: NII includes more than just the physical facilities (more than the cameras, scanners, keyboards, telephones, fax machines, computers, switches, compact disks, video and audio tape, cable, wire, satellites, optical fiber transmission lines, microwave nets , switches, televisions, monitors, and printers) used to transmit, store, process, and display voice, data, and images; it encompasses a wide range of interactive functions, user -tailored services, and multimedia databases that are interconnected in a technology-neutral manner that will favor no one industry over any other. Synonym information superhighway.

National Number - The number identifying a calling user line within an area designated by a country code.

National Prefix - A digit or combination of digits to be dialed by a calling subscriber, making a call to a subscriber in his own country but outside his own numbering area. It provides access to the automatic outgoing trunk equipment.

National Security Information (NSI) - Information that has been determined, pursuant to Executive Order 12958 or any predecessor order, to require protection against unauthorized disclosure.

National Security System - Any telecommunications or information system operated by the United States Government, the function, operation, or use of which: (a) involves intelligence activities; (b) involves cryptologic activities related to national security; (c) involves command and control of military forces; (d) involves equipment that is an integral part of a weapon or weapon system; or (e) is critical to the direct fulfillment of military or intelligence missions and does not include a system that is to be used for routine administrative and business applications (including payroll, finance, logistics, and personnel management applications). 40 U.S.C. Section 1452, Information Technology Management Reform Act of 1996.

National Security or Emergency Preparedness telecommunications - See NS/EP telecommunications.

National Television Standards Committee Standard - See NTSC standard. The North American standard (525-line interlaced raster -scanned video ) for the generation, transmission, and reception of television signals. Note 1: In the NTSC standard, picture information is transmitted in vestigial- sideband AM and sound information is transmitted in FM. Note 2: In addition to North America, the NTSC standard is used in Central America, a number of South American countries, and some Asian countries, including Japan.

Natural Frequency - The natural frequency of an antenna is the lowest frequency at which the antenna resonates without the addition of any inductance or capacitance.

Nautical Mile (nmi) - A unit of distance used in navigation and based on the length of one minute of arc taken along a great circle. Note 1: Because the Earth is not a perfect sphere, various values have been assigned to the nautical mile. The value 1852 meters (6076.1 ft.) has been adopted internationally. Note 2: The nautical mile is frequently confused with the geographical mile, which is equal to 1 min of arc on the Earth's equator (6087.15 ft.).

Navigate - To move around (a) within a series of Web pages, or (b) among different Web pages, by following hyperlinked paths within each document. Synonyms browsing, surfing.

Navigation Assistant - Synonym droid. 1. In the Internet, an intelligent search tool that automatically seeks out relevant online information based on the user 's specifications. Synonyms agent, bot, crawler, hotbot, infobot, information agent, intelligent agent, Internet search engine, knowbot, knowledge robot, personal agent, robotic librarian, search robot, spider, Web crawler, Web spider, wizard. 2. In artificial intelligence, an entity with the ability to sense its environment and to act in such a way or to affect that environment; typically knowledge-based entities that can communicate with each other through some message -passing scheme.

Navigator - Synonym droid. 1. In the Internet, a navigator is an intelligent search tool that automatically seeks out relevant online information based on the user 's specifications. Synonyms agent, bot, crawler, hotbot, infobot, information agent, intelligent agent, Internet search engine, knowbot, knowledge robot, personal agent, robotic librarian, search robot, spider, Web crawler, Web spider, wizard. 2. In artificial intelligence, a navigator is an entity with the ability to sense its environment and to act in such a way or to affect that environment; typically knowledge-based entities that can communicate with each other through some message -passing scheme.

NBH - Abbreviation for network busy hour. See busy hour. In a communications system, NBH is the sliding 60-minute period during which occurs the maximum total traffic load in a given 24-hour period. Note 1: The busy hour is determined by fitting a horizontal line segment equivalent to one hour under the traffic load curve about the peak load point. Note 2: If the service time interval is less than 60 minutes, the busy hour is the 60-minute interval that contains the service timer interval. Note 3: In cases where more than one busy hour occurs in a 24-hour period, i.e., when saturation occurs, the busy hour or hours most applicable to the particular situation are used.

NBRVF - Abbreviation for narrowband radio voice frequency. In narrowband radio, the nominal 3- kHz bandwidth allocated for single channel radio that provides a transmission path for analog and quasi-analog signals.

NCC - Abbreviation for National Coordinating Center for Telecommunications. The NCC is the joint telecommunications industry/Federal Government operation established by the National Communications System to assist in the initiation, coordination, restoration, and reconstitution of National Security or Emergency Preparedness (NS/EP) telecommunications services or facilities.

NC Code - Abbreviation for network channel (NC) code . NC Code is a code used to identify both switched and nonswitched channel services. Included in this code set are customer options associated with individual channel services, or feature groups and other switched services.

NCI Code - Abbreviation for network channel interface code . An encoded representation used to identify 5 interface elements located at a point of termination ( POT ) at central office or customer location. The interface elements are: total conductors, protocol, impedance, protocol options, and transmission level points.

NC (no circuit) - A call disposition category for a call attempt that does not find an available outgoing trunk.

NCS - Abbreviation for National Communications System, net control station. 1. The organization established by Section 1(a) of Executive Order No. 12472 to assist the President, the National Security Council, the Director of the Office of Science and Technology Policy, and the Director of the Office of Management and Budget, in the discharge of their national security emergency preparedness telecommunications functions. The NCS consists of both the telecommunications assets of the entities represented on the NCS Committee of Principals and an administrative structure consisting of the Executive Agent, the NCS Committee of Principals, and the Manager. 2. The telecommunications system that results from the technical and operational integration of the separate telecommunications systems of the several executive branch departments and agencies having a significant telecommunications capability.

NDUB (network-determined user busy) - A condition of an interface, as determined by the network, based on the network's capability to terminate another call to that interface. The interface is said to be NDUB if any of the following conditions exist: (a) if the maximum number of information channels available has been reached and the network does not support the offering of additional calls beyond this number; (b) if the limit of additional offering had been reached; (c) if the maximum number of total calls supported for User B has been reached.

Near Absolute Immunity - Near Absolute Immunity is a central office or similar facility 's ability to maintain continuity of operations without any operationally significant interruption of service from either hardware or software failures in the presence of one or more HEMP ( high-altitude electromagnetic pulse ) events.

Near-End Crosstalk - Near-End Crosstalk is Crosstalk that is propagated in a disturbed channel in the direction opposite to the direction of propagation of a signal in the disturbing channel. Note: The terminals of the disturbed channel, at which the near-end crosstalk is present, and the energized terminal of the disturbing channel, are usually near each other.

Near Field - Synonym near-field region. Near Field is defined as 1. The close-in region of an antenna wherein the angular field distribution is dependent upon distance from the antenna. Synonym near zone. 2. In optical fiber communications, the region close to a source or aperture. Note: The diffraction pattern in this region typically differs significantly from that observed at infinity and varies with distance from the source.

Near-Field Diffraction Pattern - A Near-Field Diffraction Pattern is the diffraction pattern of an electromagnetic wave, which pattern is observed close to a source or aperture, as distinguished from a far- field diffraction pattern. Note: The pattern in the output plane is called the near-field radiation pattern. Synonym Fresnel diffraction pattern.

Near-Field Region - A Near-Field Region is defined as 1. The close-in region of an antenna wherein the angular field distribution is dependent upon distance from the antenna. Synonyms near field , near zone . 2. In optical fiber communications , the region close to a source or aperture . Note: The diffraction pattern in this region typically differs significantly from that observed at infinity and varies with distance from the source.

Near-Field Scanning - Near-Field Scanning is a technique for measuring the refractive- index profile of an optical fiber by using an extended source to illuminate an endface and measuring the point-by-point radiance at the exit face.

Near Real Time - Near Real Time is defined as 1. Pertaining to the delay introduced, by automated data processing, between the occurrence of an event and the use of the processed data, e.g., for display or feedback and control purposes. Note 1: For example, a near-real- time display depicts an event or situation as it existed at the current time less the processing time. Note 2: The distinction between near real time and real time is somewhat nebulous and must be defined for the situation at hand. 2. Pertaining to the timeliness of data or information which has been delayed by the time required for electronic communication and automatic data processing. This implies that there are no significant delays.

Near-Vertical-Incidence Skywave - In radio propagation , Near-Vertical-Incidence Skywave is a wave that is reflected from the ionosphere at a nearly vertical angle and that is used in short-range communications to reduce the area of the skip zone and thereby improve reception beyond the limits of the ground wave.

Near Zone - Synonym near-field region. Near Zone is defined as 1. The close-in region of an antenna wherein the angular field distribution is dependent upon distance from the antenna. Synonym near field. 2. In optical fiber communications, the region close to a source or aperture . Note: The diffraction pattern in this region typically differs significantly from that observed at infinity and varies with distance from the source.

NEC - Abbreviation for National Electric Code ® - NEC is a standard that governs the use of electrical wire, cable, and fixtures, and electrical and optical communications cable installed in buildings. Note: The NEC was developed by the NEC Committee of the American National Standards Institute ( ANSI ), was sponsored by the National Fire Protection Association (NFPA), and is identified by the description ANSI/NFPA 70-XXXX, the last four digits representing the year of the NEC revision.

Necessary Bandwidth -1. For a given class of emission, the width of the frequency band which is just sufficient to ensure the transmission of information at the rate and with the quality required under specified conditions. Note: Emissions useful for the adequate functioning of the receiving equipment, e.g., the emission corresponding to the carrier of reduced carrier systems, must be included in the necessary bandwidth. ( See Annex J of NTIA Manual of Regulations and Procedures for Federal Radio Frequency Management for formulas used to calculate necessary bandwidth.) 2. The calculated spectral width of an emission. Calculations are made using procedures set forth in part 2 of this chapter [of 47CFR ]. The bandwidth so calculated is considered to be the minimum necessary to convey information at the desired rate with the desired accuracy.

Need To Know -Need to Know is 1. The legitimate requirement of a person or organization to know, access, or possess sensitive or classified information that is critical to the performance of an authorized, assigned mission. 2. The necessity for access to, or knowledge or possession of, specific information required to carry out official duties.

Negation Circuit - Deprecated synonym for inverter. 1. In electrical engineering, a negation circuit is a device for converting direct current into alternating current. 2. In computers, a negation circuit is a device or circuit that inverts the polarity of a signal or pulse.

Negative-Acknowledge Character (NAK) - A Negative-Acknowledge Character is a transmission control character sent by a station as a negative response to the station with which the connection has been set up. Note 1: In binary synchronous communication protocol , the NAK is used to indicate that an error was detected in the previously received block and that the receiver is ready to accept retransmission of that block. Note 2: In multipoint systems, the NAK is used as the not-ready reply to a poll.

Negative Feedback - See feedback. If the feedback is degenerative (subtractive), it is called " negative feedback ," which reduces the gain and distortion, and increases linearity and stability. Note 1: Feedback may occur inadvertently, and be detrimental. 2. Information returned as a response to an originating source.

Negative Justification - Synonym de-stuffing. Negative justification is the controlled deletion of stuffing bits from a stuffed digital signal, to recover the original signal.

Negative Pulse Stuffing - Synonym de-stuffing. Negative Pulse Stuffing is the controlled deletion of stuffing bits from a stuffed digital signal, to recover the original signal.

N-Entity - An active element in the n -th layer of the Open Systems Interconnection--Reference Model ( OSI -RM) that (a) interacts directly with elements, i.e. , entities, of the layer immediately above or below the n -th layer, (b) is defined by a unique set of rules, i.e. , syntax, and information formats, including data and control formats, and (c) performs a defined set of functions. Note 1: The n refers to any one of the 7 layers of the OSI-RM. Note 2: In an existing layered open system, the n may refer to any given layer in the system. Note 3: Layers are conventionally numbered from the lowest, i.e., the physical layer, to the highest, so that the n + 1 layer is above the n -th layer and the n - 1 layer is below.

NEP - Abbreviation for noise equivalent power. At a given data - signaling rate or modulation frequency , operating wavelength, and effective noise bandwidth, the radiant power that produces a signal-to-noise ratio of unity at the output of a given optical detector. Note 1: Some manufacturers and authors define NEP as the minimum detectable power per square root bandwidth. When defined this way, NEP has the units of watts per ( hertz ) 1/2 . Therefore, the term is a misnomer, because the units of power are watts. Note 2: Some manufacturers define NEP as the radiant power that produces a signal-to-dark-current noise ratio of unity. The NEP measurement is valid only if the dark-current noise dominates the noise level.

Neper (Np) - A neper is a unit used to express ratios, such as gain, loss, and relative values. Note 1: The neper is analogous to the decibel, except that the Naperian base 2.718281828. . . is used in computing the ratio in nepers. Note 2: The value in nepers, Np , is given by Np = ln( x 1 / x 2 ), where x 1 and x 2 are the values of interest, and ln is the natural logarithm, i.e., logarithm to the base e. Note 3: One neper (Np) = 8.686 dB, where 8.686 = 20/(ln 10). Note 4: The neper is often used to express voltage and current ratios, whereas the decibel is usually used to express power ratios. Note 5: Like the dB, the Np is a dimensionless unit. Note 6: The ITU recognizes both units.

Nested Command Menu - A command menu within another command menu. See command menu.

Net - Synonym communications net. - An organization of stations capable of direct communication on a common channel or frequency.

Net Browser - Abbreviation for network browser. A computer program for browsing hyperlinked documents (especially on the Web ). Note 1: A network browser formats and displays information so obtained in a form useful to the viewer. Note 2: A network browser may function in a graphical mode or in a text-only mode.

Net Control Station (NCS) -1. A radio station that performs net control functions, such as controlling traffic and enforcing operational discipline. 2. A terminal in a secure telecommunications net responsible for distributing key in electronic form to the members of the net.

Net Gain - Net Gain is the overall gain of a transmission circuit. Note 1: Net gain is measured by applying a test signal at an appropriate power level (see Note 5) at the input port of a circuit and measuring the power delivered at the output port. The net gain in dB is calculated by taking 10 times the logarithm of the ratio of the output power to the input power. Note 2: The net gain expressed in dB may be positive or negative. Note 3: If the net gain expressed in dB is negative, it is also called the " net loss." Note 4: If the net gain is expressed as a ratio, and the ratio is less than unity, a net loss is indicated. Note 5: The test signal must be chosen so that its power level is within the usual operating range of the circuit being tested.

Netiquette - [Slang] A contraction of network etiquette. The written or unwritten rules of etiquette that govern online interaction between users on the Internet. Note: Some typical rules are a ban on profane or offensive language, a requirement to respect other users, and a ban on floods of unsolicited advertisements. Netiquette rules may be enforced by a moderator or may be self-policed by other users.

Net Loss - The overall loss of a transmission circuit.

Net Loss Variation - The maximum change in net loss occurring in a specified portion of a communication system during a specified period.

Net Operation - The operation of an organization of stations capable of direct communication on a common channel or frequency. Note: Net operations (a) allow participants to conduct ordered conferences among participants who usually have common information needs or related functions to perform, (b) are characterized by adherence to standard formats and procedures, and (c) are responsive to a common supervisory station, called the " net control station," which permits access to the net and maintains net operational discipline.

Net Radio Interface (NRI) - An interface between a single- channel radio station (usually in a radio net ) and switched communications systems.

NETS - Abbreviation for Nationwide Emergency Telecommunications Service. See Government Emergency Telecommunications Service.

Network - A network is the total infrastructure for transmitting phone and/or Internet messages. 1. An interconnection of three or more communicating entities. 2. An interconnection of usually passive electronic components that performs a specific function (which is usually limited in scope), e.g., to simulate a transmission line or to perform a mathematical function such as integration or differentiation. Note: A network may be part of a larger circuit.

Network Access Point (NAP) - A centralized point where Internet traffic is exchanged or shared.

Network Address - The signaling point code, containing for U.S. national networks, the network identification, network cluster, and network cluster member fields (24 bits).

Network Administration - A group of network management functions that (a) provide support services, (b) ensure that the network is used efficiently, and (c) ensure prescribed service -quality objectives are met. Note: Network administration may include activities such as network address assignment, assignment of routing protocols and routing table configuration, and directory service configuration.

Network Architecture - 1. The design principles, physical configuration, functional organization, operational procedures, and data formats used as the bases for the design, construction, modification, and operation of a communications network. 2. The structure of an existing communications network, including the physical configuration, facilities, operational structure, operational procedures, and the data formats in use.

Network Availability - The probability a network can perform its required functions.

Network Browser - A computer program for browsing hyperlinked documents (especially on the Web ). Note 1: A network browser formats and displays information so obtained in a form useful to the viewer. Note 2: A network browser may function in a graphical mode or in a text-only mode.

Network Busy Hour (NBH) - See busy hour. In a communications system, the sliding 60-minute period during which occurs the maximum total traffic load in a given 24-hour period. Note 1: The busy hour is determined by fitting a horizontal line segment equivalent to one hour under the traffic load curve about the peak load point. Note 2: If the service time interval is less than 60 minutes, the busy hour is the 60-minute interval that contains the service timer interval. Note 3: In cases where more than one busy hour occurs in a 24-hour period, i.e., when saturation occurs, the busy hour or hours most applicable to the particular situation are used.

Network Cluster - The field in the U.S. signaling point code structure that identifies groups of signaling points and individual STPs (signaling transfer points) of a signaling network.

Network Computer -1. Synonym thin client. 2. Any computer connected to a network.

Network Connectivity - The topological description of a network that specifies, in terms of circuit termination locations and quantities, the interconnection of the transmission nodes.

Network Control Program (NCP) - In a switch or network node , software designed to store and forward frames between nodes. Note: An NCP may be used in local area networks or larger networks.

Network Data - Data that are specific to the functionality of the network.

Network Element Function Block - A functional block that communicates with a telecommunications management network (TMN) for the purpose of being monitored, or controlled, or both.

Network Element Location (NE location) - A building (such as a central office ) or nonbuilding location housing NEs. Communication within an NE location may be accomplished with minimal attention to such factors as noise, lightning protection, or the cost of bandwidth; communication outside an NE location uses suitable modems and uses conventional communications services or an EOC ( embedded operations channel ).

Network Element (NE) - In integrated services digital networks, a piece of telecommunications equipment that provides support or services to the user.

Network Engineering -1. In telephony, the discipline concerned with (a) determining internetworking service requirements for switched networks, and (b) developing and implementing hardware and software to meet them. 2. In computer science, the discipline of hardware and software engineering to accomplish the design goals of a computer network. 3. In radio communications, the discipline concerned with developing network topologies.

Network Etiquette (netiquette): See netiquette. The written or unwritten rules of etiquette that govern online interaction between users on the Internet. Note: Some typical rules are a ban on profane or offensive language, a requirement to respect other users, and a ban on floods of unsolicited advertisements. Netiquette rules may be enforced by a moderator or may be self-policed by other users.

Network Facility - The connection between the radio port controller and the PCS (personal communications services) switching center.

Network Failure - A complete or partial failure of a component or components of a network because of malfunction or natural or human-caused disasters. Partial failures include degradation (and graceful degradation).

Network Failure Triple - A combination of the network 's unservability (U), duration (D), and extent (E) parameters that exceeds a threshold.

Network File System (NFS) - See NFS. 1. A file system that is distributed over a computer network. 2. A file system, on a single computer, that contains the low- level networking files for an entire network.

Network Identification - The field in the U.S. signaling point code structure that identifies signaling networks.

Network Indicator (NI) - Information within the service information octet of the message signal unit that permits discrimination between national and international messages.

Network Information Center (NIC) - See NIC. An entity that provides information management, technical support, and administrative services to users of a given network. Note: NICs can form a hierarchy. A specific NIC, designated at the " Internetwork information center" or " InterNIC," has been the authority that assigns the network numbers to the subnetworks that it connects to the Internet.

Network Integrity - See network survivability. The (a) ability of a network to maintain or restore an acceptable level of performance during network failures by applying various restoration techniques, and (b) mitigation or prevention of service outages from network failures by applying preventive techniques.

Network Interface - 1. The point of interconnection between a user terminal and a private or public network. 2. The point of interconnection between the public switched network and a privately owned terminal. Note: Code of Federal Regulations, Title 47, part 68, stipulates the interface parameters. 3. The point of interconnection between one network and another network. 4. The point of demarcation between the carrier's facilities and the customer installation, which establishes the technical interface and division of operational responsibility. In this definition, the term "customer" refers to the end-user.

Network Interface Card (NIC) - See NIC. A network interface device ( NID ) in the form of a circuit card that is installed in an expansion slot of a computer to provide network access. Note: Examples of NICs are cards that interface a computer with an Ethernet LAN and cards that interface a computer with an FDDI ring network.

Network Interface Device (NID) - 1. A device that performs interface functions, such as code conversion, protocol conversion, and buffering, required for communications to and from a network. 2. A device used primarily within a local area network (LAN) to allow a number of independent devices, with varying protocols, to communicate with each other. Note 1: An NID converts each device protocol into a common transmission protocol. Note 2: The transmission protocol may be chosen to accommodate directly a number of the devices used within the network without the need for protocol conversion for those devices by the NID. Synonym network interface unit.

Network Interface Unit (NIU) - Synonym network interface device.

Network Interworking - Cooperation among networks in the processing, management, and creation of services that span multiple networks.

Network Inward Dialing (NID) - Synonym direct inward dialing. A service feature that allows inward-directed calls to a PBX to reach a specific PBX extension without human intervention.

Network-Launched Application - In a computer networking environment, an application ( program ) that is centrally stored, e.g. , on a server, and copies of which may be accessed on demand by a client and used temporarily ( i.e. , for a single session) by the client ( e.g. , a desktop computer). Note: Multiple clients may make simultaneous use of a given network -launched application.

Network Layer - Layer 3. This layer responds to service requests from the Transport Layer and issues service requests to the Data Link Layer. The Network Layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks while maintaining the quality of service requested by the Transport Layer. The Network Layer performs network routing, flow control, segmentation/desegmentation, and error control functions. See Open Systems Interconnection--Reference Model.

Network Layer Relay - A function within the network layer by means of which one correspondent network entity forwards data to another correspondent network entity.

Network Loss - Loss added to the network to control echo.

Network Management - The execution of the set of functions required for controlling, planning, allocating, deploying, coordinating, and monitoring the resources of a telecommunications network, including performing functions such as initial network planning, frequency allocation, predetermined traffic routing to support load balancing, cryptographic key distribution authorization , configuration management, fault management, security management, performance management, and accounting management. Note: Network management does not include user terminal equipment.

Network Manager - In network management, the entity that initiates requests for management information from managed systems or receives spontaneous management-related notifications from managed systems.

Network Node (NN) - A grouping of one or more network elements (at one or more sites) which provides network related functions, and is administered as a single entity. A single site may contain more than one network node. For the purpose of this glossary, a network node is considered synonymous with a network element, and is usually at a single site. This restriction simplifies the definition of the network node interface (NNI) and INI, which would not apply between network elements.

Network Number - An identification number, within a computer network or set of interconnected networks, that uniquely identifies a computer. Note: Under the Internet protocol system, the network number forms a part of the IP address of each computer in the network.

Network Operating System (NOS) - Software that (a) controls a network and its message (e.g., packet) traffic, and queues, (b) controls access by multiple users to network resources such as files, and (c) provides for certain administrative functions, including security. Note 1: A network operating system is most frequently used with local area networks and wide area networks, but could also have application to larger network systems. Note 2: The upper 5 layers of the OSI--Reference Model provide the foundation upon which many network operating systems are based.

Network Operation Center (NOC) - A round-the-clock operation where Network engineers monitor and troubleshoot technical equipment and connections.

Network Operator - The operator responsible for the development, provision and maintenance of real- time networking services and for operating the corresponding networks.

Network Outpulsing State - A call state in which the network transmits the caller's emergency service ID (CESID) to the public service answering point (PSAP) customer installation (CI).

Network Outward Dialing (NOD) - Synonym direct outward dialing. An automated PBX service feature that provides for outgoing calls to be dialed directly from the user terminal.

Network Performance - The qualitative level at which a network fulfills its function.

Network Provided Number (NPN) - An ISDN number, supplied by the calling user 's or the redirecting user's network , which is associated with the calling user or the redirecting user. It is possible that the NPN may have the same value as the user provided number (UPN) especially in cases where delivery of two calling party numbers is supported. The NPN may also be accompanied by a subaddress.

Network Provider - The organization that maintains and operates the network components required for intelligent network (IN) functionality. A network provider may also take more than one role, e.g., also acting as service provider.

Network Reliability - See network survivability. The (a) ability of a network to maintain or restore an acceptable level of performance during network failures by applying various restoration techniques, and (b) mitigation or prevention of service outages from network failures by applying preventive techniques.

Network Restoration - Automatic or manual methods to return a network to its normal function in response to a network failure.

Network Section - The network components that provide a virtual connection between two circuit sections. A network section may be either an access network section or a transit network section.

Network Security: Protection of networks and their services from unauthorized modification, destruction, or disclosure. It provides assurance the network performs its critical functions correctly and there are no harmful side-effects.

Network Security Architecture - A subset of network architecture specifically addressing security -relevant issues.

Network Service Part - The combination of the MTP ( message transfer part ) and the SCCP ( signaling connection control part ).

Network Site -1. A collection of functional units that provide network services and that belong to one management domain and are considered as a whole. [2382-pt.35] 2. A specific location that houses telecommunications equipment entities and/or facility terminations at that location, or a specific location that houses administrative operations . A location is usually designated as a network site when it houses one or more network applications.

Network Surveillance - A process concerned with surveillance of the network as a whole. It includes activities for coordination and assigning priorities to maintenance actions. The information necessary to support this process comes from alarms, measurements, and indicators of operational (including congestion ) status.

Network Side - The side of the network interface or the network functions as seen from the interface.

Network Survivability - The (a) ability of a network to maintain or restore an acceptable level of performance during network failures by applying various restoration techniques, and (b) mitigation or prevention of service outages from network failures by applying preventive techniques.

Network Survivability Model - The analytical processes for estimating how well network services will be affected and restored with transparencies to the users as a result of a failure.

Network Terminal Number (NTN) - In the ITU-T International X.121 format, the sets of digits that comprise the complete address of the data terminal end point. Note: For an NTN that is not part of a national integrated numbering format, the NTN is the 10 digits of the ITU-T X.25 14- digit address that follow the Data Network Identification Code (DNIC). When part of a national integrated numbering format, the NTN is the 11 digits of the ITU-T X.25 14-digit address that follow the DNIC.

Network Terminating Interface (NTI) - Synonym for demarcation point. That point at which operational control or ownership of communications facilities changes from one organizational entity to another. Note: The demarcation point is usually the interface point between customer-premises equipment and external network service provider equipment.

Network Termination - Network equipment that provides functions necessary for network operation of ISDN access protocols. Note: Network termination provides functions essential for transmission services.

Network Termination 1 (NT1) - In Integrated Services Digital Networks ( ISDN ), a functional grouping of customer-premises equipment that includes functions that may be regarded as belonging to OSI Layer 1, i.e., functions associated with ISDN electrical and physical terminations on the user premises. Note: The NT1 forms a boundary to the network and may be controlled by the provider of the ISDN services.

Network Termination 2 (NT2) - In Integrated Services Digital Networks ( ISDN ), an intelligent device that may include functionality for OSI Layers 1 through 3 (dependent on individual systems requirements).

Network Topology - The specific physical, i.e., real, or logical, i.e., virtual, arrangement of the elements of a network. Note 1: Two networks have the same topology if the connection configuration is the same, although the networks may differ in physical interconnections, distances between nodes, transmission rates, and/or signal types. Note 2: The common types of network topology are illustrated [refer to the figure on this page] and defined in alphabetical order below:


Network Trusted Computing Base (NTCB) - The totality of protection mechanisms within a network, including hardware, firmware, and software, the combination of which is responsible for enforcing a security policy.

Network Utility - An internetwork administrative signaling mechanism in the call control procedure between packet switching public data networks.

Network Weaving -1. In computer security, a penetration technique in which different communication networks are used to gain access to a data processing system to avoid detection and trace-back. 2. A penetration technique in which different communication networks are linked to access an information system (IS) to avoid detection and trace-back.

Neutral -1. In ac power distribution, the conductor that (a) is intentionally grounded on the supply side of the service disconnect and (b) provides a current return path for ac power currents. 2. In three- phase ac "Y," i.e., wye, power distribution, the low-potential fourth wire that conducts only that current required to achieve electrical balance, i.e., to provide a return path for any current imbalance among the three phases.

Neutral Direct-Current Telegraph System - A telegraph system in which (a) current flows during marking intervals and no current flows during spacing intervals for the transmission of signals over a line, and (b) the direction of current flow is immaterial. Synonyms single-current system, single-current transmission system, single-Morse system.

Neutral Ground - An intentional ground applied to the neutral conductor or neutral point of a circuit, transformer, machine, apparatus, or system.

Neutral Operation - A method of teletypewriter operation in which marking signals are formed by current pulses of one polarity, either positive or negative, and spacing signals are formed by reducing the current to zero or nearly zero.

Neutral Relay - A relay in which the direction of movement of the armature does not depend upon the direction of the current in the circuit controlling the armature.

New Customer Premises Equipment - All customer premises equipment not in service or in the inventory of a regulated telephone utility as of December 31, 1982.

News Client - Synonym newsreader. A local software application ( client program ) that provides access by means of which a user may view one or more forums or newsgroups from one or more news servers. Note: Most newsreaders format and display information from the server in a form suitable to the user.

Newsfeed - Information distributed by a computer , e.g., one operated by an Internet service provider that maintains current articles within selected groups.

Newsgroup - A discussion group in which you can leave messages for others to read on UseNet.

Newsreader - A local software application ( client program ) that provides access by means of which a user may view one or more forums or newsgroups from one or more news servers. Note: Most newsreaders format and display information from the server in a form suitable to the user.Synonym news client.

News Server - A server on a network that stores, organizes, and distributes messages for selected newsgroups.

NF - Abbreviation for noise figure. Of an active device, over the bandwidth of interest, the contribution by the device itself to thermal noise at its output. The noise figure is usually expressed in decibels ( dB ), and is with respect to thermal noise power at the system impedance, at a standard noise temperature (usually 20 o C, 293 K) over the bandwidth of interest. It is determined by (a) measuring (determining) the ratio, usually expressed in dB, of the thermal noise power at the output, to that at the input, and (b) subtracting from that result, the gain, in dB, of the system. Typical noise figures range from 0.5 dB for very low noise devices, to 4 to 8 dB. In some systems, e.g., heterodyne systems, total output noise power includes noise from other than thermal sources, such as spurious contributions from image - frequency transformation, but noise from these sources is not considered in determining the noise figure. In this example, the noise figure is determined only with respect to that noise that appears in the output via the principal frequency transformation of the system, and excludes noise that appears via the image frequency transformation.

NFS - Abbreviation for network file system. 1. A file system that is distributed over a computer network . 2. A file system, on a single computer, that contains the low- level networking files for an entire network.

n -function - A defined action performed by an n -entity. Note: An n -function may be (a) a single action, i.e., a primitive function, or (b) a set of actions.

950 + WXXX - A carrier access code for obtaining switched access to interchange carriers where (a) the calling customer accesses the IC and passes the address information, if any, in two distinct operations; (b) the calling customer usually uses in-band signals to pass the address, if any, to the IC; and (c) the EC does not repeat the address information. Note: The X digits in WXXX are the carrier identification code for the IC, and W is 0 or 1.

Nibble - Part of a byte, usually half of a byte.

NIC -1. Abbreviation for network interface card. A network interface device ( NID ) in the form of a circuit card that is installed in an expansion slot of a computer to provide network access. Note: Examples of NICs are cards that interface a computer with an Ethernet LAN and cards that interface a computer with an FDDI ring network. 2. Abbreviation for network information center. An entity that provides information management, technical support, and administrative services to users of a given network. Note: NICs can form a hierarchy. A specific NIC, designated at the " Internetwork information center" or " InterNIC," has been the authority that assigns the network numbers to the subnetworks that it connects to the Internet.

NID - Network Interface Device - A device used within a local area network, which allows a number of independent devices (computers, modems, etc.) to communicate with one another. Also, a device usually mounted on the outside of the customer's home that connects the customer's inside wiring to the telephone company's wiring and protects the customer's phone equipment from lightning and any large rise or fall in electricity.

NII (National Information Infrastructure) - A proposed, advanced, seamless web of public and private communications networks, interactive services, interoperable hardware and software, computers, databases, and consumer electronics to put vast amounts of information at users' fingertips. Note: NII includes more than just the physical facilities (more than the cameras, scanners, keyboards, telephones, fax machines, computers, switches, compact disks, video and audio tape, cable, wire, satellites, optical fiber transmission lines, microwave nets, switches, televisions, monitors, and printers) used to transmit, store, process, and display voice, data, and images; it encompasses a wide range of interactive functions, user-tailored services, and multimedia databases that are interconnected in a technology-neutral manner that will favor no one industry over any other. Synonym information superhighway.

Nine-Hundred (900) Service - A telephone service via which the caller may access information on a charge-per- call or charge-per- time basis.

NIU - Abbreviation for network interface unit. See network interface device. 1. A device that performs interface functions, such as code conversion, protocol conversion, and buffering, required for communications to and from a network. 2. A device used primarily within a local area network ( LAN ) to allow a number of independent devices, with varying protocols, to communicate with each other. Note 1: An NID converts each device protocol into a common transmission protocol. Note 2: The transmission protocol may be chosen to accommodate directly a number of the devices used within the network without the need for protocol conversion for those devices by the NID.

Nmap - A security -violating, network - scanning tool that can scan a network using a variety of protocols, can operate in stealth mode, and can automatically identify remote operating systems.

NMI - Abbreviation for nautical mile. A unit of distance used in navigation and based on the length of one minute of arc taken along a great circle. Note 1: Because the Earth is not a perfect sphere, various values have been assigned to the nautical mile. The value 1852 meters (6076.1 ft.) has been adopted internationally. Note 2: The nautical mile is frequently confused with the geographical mile, which is equal to 1 min of arc on the Earth's equator (6087.15 ft.).

NNTP - Abbreviation for network news transfer protocol. An application protocol that provides the means to transfer files for computer conferences.

NOC - See Network Operation Center A centralized organization responsible for the operation and maintenance of its network.

No Circuit Double Prime (NC") - An SIT ( special information tone ) classification for call attempts that fail to find an available long distance service provider outgoing trunk.

No Circuit (NC) - A call -disposition category for a call attempt that does not find an available outgoing trunk.

No Circuit Prime (NC') - An SIT ( special information tone ) classification for call attempts that fail to find an available Local Service Provider outgoing trunk.

NOD - Acronym for network outward dialing. An automated PBX service feature that provides for outgoing calls to be dialed directly from the user terminal.

Nodal Clock - The principal clock or alternate clock located at a particular node that provides the timing reference for all major functions at that node.

Nodal Point - Synonym node.

Node - 1. In network topology, a terminal of any branch of a network or an interconnection common to two or more branches of a network. Synonyms junction point, nodal point. 2. In a switched network, one of the switches forming the network backbone. Note: A node may also include patching and control facilities. 3. A technical control facility (TCF). 4. A point in a standing or stationary wave at which the amplitude is a minimum. In this sense, synonym null.

Noise - 1. An undesired disturbance within the frequency band of interest; the summation of unwanted or disturbing energy introduced into a communications system from man-made and natural sources. 2. A disturbance that affects a signal and that may distort the information carried by the signal. 3. Random variations of one or more characteristics of any entity such as voltage, current, or data. 4. A random signal of known statistical properties of amplitude, distribution, and spectral density. 5. Loosely, any disturbance tending to interfere with the normal operation of a device or system.

Noise Current -1. Interfering and unwanted electrical currents in a device or system. 2. In optical communications, the rms component of the optical detector output electrical current with no incoming signal present.

Noise Equivalent Power (NEP) - At a given data - signaling rate or modulation frequency, operating wavelength, and effective noise bandwidth, the radiant power that produces a signal-to-noise ratio of unity at the output of a given optical detector. Note 1: Some manufacturers and authors define NEP as the minimum detectable power per square root bandwidth. When defined this way, NEP has the units of watts per ( hertz ) 1/2 . Therefore, the term is a misnomer, because the units of power are watts. Note 2: Some manufacturers define NEP as the radiant power that produces a signal-to-dark-current noise ratio of unity. The NEP measurement is valid only if the dark-current noise dominates the noise level.

Noise Factor - Synonym noise figure. Of an active device, over the bandwidth of interest, the contribution by the device itself to thermal noise at its output. The noise figure is usually expressed in decibels ( dB ), and is with respect to thermal noise power at the system impedance, at a standard noise temperature (usually 20 o C, 293 K) over the bandwidth of interest. It is determined by (a) measuring (determining) the ratio, usually expressed in dB, of the thermal noise power at the output, to that at the input, and (b) subtracting from that result, the gain, in dB, of the system. Typical noise figures range from 0.5 dB for very low noise devices, to 4 to 8 dB. In some systems, e.g., heterodyne systems, total output noise power includes noise from other than thermal sources, such as spurious contributions from image - frequency transformation, but noise from these sources is not considered in determining the noise figure. In this example, the noise figure is determined only with respect to that noise that appears in the output via the principal frequency transformation of the system, and excludes noise that appears via the image frequency transformation.

Noise Field - An indication of the level of background noise that the terminating end-point may play out in the absence of packets.

Noise Figure (NF) - Of an active device, over the bandwidth of interest, the contribution by the device itself to thermal noise at its output. The noise figure is usually expressed in decibels ( dB ), and is with respect to thermal noise power at the system impedance, at a standard noise temperature (usually 20 o C, 293 K) over the bandwidth of interest. It is determined by (a) measuring (determining) the ratio, usually expressed in dB, of the thermal noise power at the output, to that at the input, and (b) subtracting from that result, the gain, in dB, of the system. Typical noise figures range from 0.5 dB for very low noise devices, to 4 to 8 dB. In some systems, e.g., heterodyne systems, total output noise power includes noise from other than thermal sources, such as spurious contributions from image - frequency transformation, but noise from these sources is not considered in deter