1. Interrogating-Call Session Control Function,
2. Intermediate-Call Session Control Function.

Abbreviation for interface.

Abbreviation for input/output.

Synonym input-output controller.

Abbreviation for Internet second generation. A proposed high-speed Internet for use exclusively by government researchers and academic institutions.

"i3" refers to the NG9-1-1 system architecture defined by NENA, which standardizes the structure and design of Functional Elements making up the set of software services, databases, network elements and interfaces needed to process multi-media emergency calls and data for NG89-1-1.

The 4-wire (2-pair) bidirectional primary rate interface point on the network side of the termination equipment (i.e., NT1, NT2), including the equipment connecting cord, or equivalent, on the user side of the interface cable. [After T1.217-1991] [After T1.408-1990]

Initial Address Message

Abbreviation for Internet Assigned Numbers Authority. An organization directed by the Internet Architecture Board (IAB) and which assigns IP numbers and protocol parameters such as port, protocol, and enterprise numbers, and options, codes, and types.

The 4-wire (2-pair) bidirectional primary rate (PR) interface point on the user side of the termination equipment (i.e., NT1 and NT2), including the equipment connecting cord or equivalent on the network side of the interface cable. [T1.408-1990]

Interconnect Border Control Function

Abbreviation for integrated circuit.

Abbreviation for International Communications Association.

Internet Content Adaptation Protocol

ITU Carrier Code

Information and Context Exchange

Abbreviation for incoming call identification.

Abbreviation for Internet Control Message Protocol. An Internet protocol that reports datagram delivery errors.
Note 1: ICMP is a key part of the TCP/IP protocol suite.
Note 2: The packet internet gopher (ping) application is based on ICMP.

In computer systems, a small, pictorial representation of an application software package, idea, or concept used in a window or a menu to represent commands, files, or options.

Intercarrier Communication Process

Information and Communication Technology

Abbreviation for interrupted continuous wave.

Identifier

Intelligent Transportation System Data Bus

Integrated Development Environment

Developed in Switzerland and licensed for non-commercial use in PGP. IDEA uses a 128 bit user supplied key to perform a series of nonlinear mathematical transformations on a 64 bit data block. Compare the length of this key with the 56 bits in DES or the 80 bits in Clipper.

[The] process an information system (IS) uses to recognize an entity. [INFOSEC-99]

The discrete identification, friend or foe code assigned to a particular aircraft, ship, or other vehicle for identification by electronic means. [JP1]

A form of notification information that consists of the documentation of the actual sequence of intermediate networks traversed by a signaling message. The documentation of the sequence of networks traversed may also include the origination and destination networks. The documentation that the message traversed a given network is performed by that network itself. Intermediate networks that are not ISNI-capable are… (Read More →)

A system using electromagnetic transmissions to which equipment carried by friendly forces automatically responds, for example, by emitting pulses, thereby distinguishing themselves from enemy forces. [JP 1-02]
Note: The secondary surveillance radar (SSR) system used in modern air traffic control systems is an outgrowth of the military IFF system used during World War II. The IFF equipment carried by modern… (Read More →)

1. In telecommunications and data processing systems, one or more characters used to identify, name, or characterize the nature, properties, or contents of a set of data elements.
2. A string of bits or characters that names an entity, such as a program, device, or system, in order that other entities can call that entity.
3. In programming languages, a… (Read More →)

A unique piece of information which is recognized as denoting a particular entity within a security domain. The identity information is only unique within the domain [ECMA138].

The performance of tests to enable a data processing system to recognize entities.
Note: An example of identity authentication is the checking of a password or identity token. [2382-pt.8]

1. A device, such as a metal key or smart card, used for identity authentication. [After 2382-pt.8]
2. [A] Smart card, metal key, or other physical object used to authenticate identity. [INFOSEC-99]

Tests enabling an information system to authenticate users or resources. [INFOSEC-99]

A security policy based on the identities and/or attributes of users, a group of users, or entities acting on behalf of the users and the resources/objects being accessed [7498-2]

Abbreviation for intermediate distribution frame.

1. Interface Definition Language,
2. Interactive Data Language.

Integrated Digital Loop Carrier

A control character that is transmitted when no useful information is being transmitted. [From Weik '89]

A special sequence that indicates that no data are being sent on the channelized side. [T1.509-1995]

The telecommunications service condition that exists whenever user messages are not being transmitted but the service is immediately available for use.

A period during which a system, circuit, or component is not in use, but is available.

Noise that is present in a communications channel when no signals are applied.
Note: The channel conditions and terminations must be stated for idle-channel noise measurements to be meaningful.

A switch-controlled electrical network that maintains a desired impedance at a trunk or line terminal that is in the idle state.

Identity Management

Abbreviation for integrated digital network.

Identity Provider

Abbreviation for improved-definition television.

Institute of Electrical and Electronics Engineers

International Emergency Preference Scheme

Internet Engineering Task Force

Abbreviation for intermediate frequency.

See heterodyne repeater.

An interface suitable for star concentration. [T1.201-1987] [T1.204-1988]

An interface suitable for communication between a network element (NE) location and operations systems (OSs) over packet switched networks, dedicated lines, or circuit switched connections. [T1.201-1987] [T1.204-1988]

An interface suitable for multipoint concentration by polling. [T1.201-1987] [T1.204-1988]

An interface between a network element (NE) to one or more network elements (NEs) in other locations using star configuration embedded operations channel (EOCs) or conventional communications services. [T1.204-1992]

Abbreviation for identification, friend or foe.

Abbreviation for International Frequency Registration Board.

Abbreviation for ionospheric forward scatter. See ionospheric scatter.

Internet Gateway Device

Internet Group Management Protocol

Interior Gateway Routing Protocol

Intelligent Grouping and Resource Sharing

IPTV Interoperability Forum

Incumbent Internet Service Provider

Internet Key Exchange

Abbreviation for injection laser diode.

Abbreviation for incumbent local exchange carrier. The incumbent or existing franchised local exchange carrier in any given area. [After FCC]

A character, or a combination of bits, that is not valid in a given system according to specified criteria, such as with respect to a specified alphabet, a particular pattern of bits, a rule of formation, or a check code. [From Weik '89] Synonyms false character, forbidden character, improper character, unallowable character, unused character.

Abbreviation for instrument landing system.

1. Itensity modulation,
2. Element Management Layer,
3. Instant Messaging,
4. IP Multimedia,
5. Intermodulation.

IM-Home Serving System

In the field of image processing, a two-dimensional representation of a scene. Synonym picture.

A hypothetical mirror-image, i.e., virtual-image, of an antenna, i.e., antenna element, considered to extend as far below ground, i.e., the ground plane, as the actual antenna is above the ground plane.
Note 1: The image antenna is helpful in calculating electric field vectors, magnetic field vectors, and electromagnetic fields emanating from the real antenna, particularly in the vicinity of the… (Read More →)

The transducing of the information in a real image into the photographic or electronic medium.
Note: Normally in motion-reproducing systems, synchronous audio information is simultaneously transduced. [After SMPTE]

1. Application of an appropriate transfer function to an image signal so as to limit dynamic range.
2. Application of bandwidth limiting or bit-rate reduction to an image signal in order to bring it within the limitations of a lower capacity channel. [After SMPTE]

In video technology, a technique used to improve contrast and picture clarity by flattening the camera response to 400 lines (by aperture correction) and applying an additional correction to increase the depth of modulation in the range of 250 to 300 lines (in an NTSC system), both vertically and horizontally.
Note: Image enhancement produces a correction signal with symmetrical overshoots… (Read More →)

The formalization of a multidisciplinary agreement—regarding digital image characteristics, such as the structure of digital image files, the organization of the image data itself, and the definition of fully flexible, interoperable, scalable, and extensible systems—which agreement facilitates the exchange of such files across various technology interfaces.

A block of data that (a) may contain, in standardized format, data concerning production, ownership, access, previous processing, etc. , relevant to the basic interpretation of the data, and (b) enhances the utility of the main data for the user.

A compact label for image files, created using a universally accepted algorithm, that (a) identifies the encoding standard, (b) specifies the length of the file, (c) indicates whether a readable descriptor is included, (d) permits random interception of data stream, and (d) offers optional error protection.

The defining file format for exchange of digital motion-picture information on a variety of media between computer-based systems.
Note: This flexible file format describes pixel-based (raster) images with attributes defined in the binary file descriptor—which identifies (a) generic file information, image information, data format, and image orientation information; (b) motion-picture and television industry-specific information; and (c) user defined information. The… (Read More →)

A recommended practice intended to provide a method of coding video index information in which various picture- and program-related source data can be carried in conjunction with the video signal.
Note: There are three classes of video index data based on type and use of the data. Class 1 contains information that is required to know how to use the… (Read More →)

In radio reception using heterodyning in the tuning process, an undesired input frequency that is capable of producing the same intermediate frequency (IF) that the desired input frequency produces.
Note: The term image arises from the mirror-like symmetry of signal and image frequencies about the beating-oscillator frequency.

Synonym image rejection ratio.

The creation of an image from an image concept.
Note: The image can be created with computer-graphics software or photography, for example.

A Web page feature in which hyperlinks are assigned ("mapped") to different portions of a graphic image, thereby allowing users to access links by clicking with a mouse on the mapped areas.
Note: Image map requests are processed by CGI scripts on the server.

In reception using heterodyning in the tuning process, the ratio of (a) the intermediate-frequency (IF) signal level produced by the desired input frequency to (b) that produced by the image frequency.
Note 1: The image rejection ratio is usually expressed in dB.
Note 2: When the image rejection ratio is measured, the input signal levels of the desired and image… (Read More →)

Collectively, the representations of objects reproduced electronically or by optical means on film, electronic display devices, or other media. [JP1]

Abbreviation for intermodulation distortion.

See communications deception.

The bound on performance allowed for a circuit or connection that is in service. When any parameter value exceeds the IAL, the circuit or connection is considered defective and corrective action is necessary. [T1-506-1989]

In cryptology, a condition of readiness associated with a key having no effective date.
Note: A key is immediately activated (a) by the receiver when the RSM is sent in response to the KSM that carried that key, and (b) by the sender when the RSM is received in response to the KSM that carried the key. [After X9.17]

A category of precedence reserved for messages relating to situations that gravely affect the security of national/allied forces or populace and that require immediate delivery to the addressee(s). [JP 1-02]

The ability of an assembly, equipment, or a system to perform without degradation in the presence of an electromagnetic disturbance. [T1.308-1996]

Abbreviation for interface message processor.

Is where an individual circuit exceeds the transmission limits or where the quality of service is diminished. A circuit is also impaired if its signaling functions (e.g., seizure, disconnect, ANI) is experiencing intermittent failures.

The total passive opposition offered to the flow of electric current.
Note 1: Impedance is determined by the particular combination of resistance, inductive reactance, and capacitive reactance in a given circuit.
Note 2: Impedance is a function of frequency, except in the case of purely resistive networks.

The connection of an additional impedance to an existing one in order to accomplish a specific effect, such as to balance a circuit or to reduce reflection in a transmission line.

[A] form of spoofing. [INFOSEC-99]

[In security, an] electronic device or electronic equipment modification designed to gain unauthorized interception of information-bearing emanations. [INFOSEC-99]

A phase of the Development Process wherein the detailed specification of a Target of Evaluation is translated into actual hardware and software [ITSEC].

A scheme under which user terminals first detect a possible congestion condition by means other than explicit congestion messages, and then take appropriate action to reduce their throughput. [T1.615-1992]

Services that a platform provides without a direct request [POSIX.0].

Synonym illegal character.

Television transmitters and receivers that (a) are built to satisfy performance requirements over and above those required by the NTSC standard and (b) remain within the general parameters of NTSC standard emissions.
Note 1: IDTV improvements may be made at the TV transmitter or the receiver.
Note 2: Examples of improvements include enhancements in encoding, digital filtering, scan interpolation, interlaced… (Read More →)

See FM improvement threshold.

Instant Messaging and Presence Services

A short surge of electrical, magnetic, or electromagnetic energy. Synonym yysurge.

The production of oscillation in a circuit or device by impressing a stimulus (signal) for a period that is extremely short compared to the duration of the oscillation that it produces. Synonym shock excitation.

Noise consisting of random occurrences of energy spikes having random amplitude and spectral content.
Note: Impulse noise in a data channel can be a definitive cause of data transmission errors.

1. Of a device, the mathematical function that describes the output waveform that results when the input is excited by a unit impulse.
2. The waveform that results at the output of a device when the input is excited by a unit impulse.

IP Multimedia Subsystem

Abbreviation for intelligent network.

A UPT (Universal Personal Telecommunications) call type which permits a UPT user to have calls to his/her UPT number routed to the terminal specified by the user. [After T
1. Rpt41-1995]

A feature by which incoming calls are presented at the terminal address registered previously by in-call registration. This feature is invoked when originating parties or others call the UPT (Universal Personal Telecommunications service) user. [T1.701-1994]

A code or block for which local routing information has been input to the LERG Routing Guide and the carrier has begun to activate and assign numbers within the NXX code or NXX-X block to end users (FCC 00-104, ¶240).

Using or involving the information digit time slots of a DS1 frame; i.e., bit assignments of a frame exclusive of the framing bit. [T1 Gloss ‘90] [T1.403-1989]

Control effected by sending control information over the same channel as the one used to send data.

For multichannel equipment, the ratio of (a) the mean noise power measured in any channel, with all channels loaded with white noise, to (b) the mean noise power measured in the same channel, with all channels but the measured channel loaded with white noise.

Signaling that uses frequencies or time slots within the bandwidth or data stream occupied by the information channel.

A feature that enables the UPT (Universal Personal Telecommunications service) user to register from the current terminal address for incoming calls to be presented to that terminal address. When registered, all incoming calls to the UPT number of the UPT user will be presented to the registered terminal address, for the duration specified by the UPT user (duration may also… (Read More →)

Signaling performed in the associated channel time slot.

A signaling link that has been deactivated and cannot therefore carry signaling traffic. [T1.110-1987]

1. Industry Numbering Committee,
2. International Carrier.

1. In information systems (IS), [an] assessed occurrence having actual or potentially adverse effects on an IS. [INFOSEC-99]
2. In COMSEC, the occurrence that potentially jeopardizes the security of COMSEC material or the secure electrical transmission of national security information or information governed by 10 U. S. C. Section
231
5. [INFOSEC-99]

A device that radiates radio frequency energy during the course of its operation although the device is not intentionally designed to generate radio frequency energy. [NTIA]

The angle determined by the plane containing the orbit and the plane of the Earth's equator. [NTIA] [RR]

Any nonequatorial orbit of a satellite.
Note: Inclined orbits may be circular or elliptical, synchronous or asynchronous, and direct or retrograde.

A foreign object present within, for example, an optical fiber or a crystal.

In optics, characterized by a degree of coherence significantly less than
0. 88.

The ability of a user to terminate data calls via an ISDN. [T1.615-1992]

A switching system feature that allows an attendant to identify visually the type of service or trunk group associated with a call directed to the attendant's position.

An implementation-defined relation between the values of MAC labels or Information Labels. Two labels are incomparable if neither label dominates the other, that is the two labels are disjoint [POSIX.6].

A block successfully delivered to the intended destination user, but having one or more incorrect bits, additions, or deletions, in the delivered block.

Data compaction accomplished by specifying only the initial value and all subsequent changes.
Note: An example of incremental compaction is the storing or transmitting of a line voltage followed only by the deviations from the initial value. Thus, instead of transmitting the values 102, 104, 105, 103, 100, 104 and 106, only the values 102, +2, +1, -2, -3, +4,… (Read More →)

In spread-spectrum systems, phase modulation in which one binary code sequence is shifted with respect to another, usually to conduct a synchronizing search, i.e., a search to discover if the two sequences are the same, and perhaps thereby enabling two data streams to be synchronized. [From Weik '89]

1. A call sign that represents a group of facilities, commands, authorities, activities, or units rather than one of these.
2. In radio communications, a call sign that does not identify a station and that is used in the call-up signal or in a message that has the station call sign encrypted in the text. [From Weik '89]

In communication network timing subsystems, free-running precision clocks used, for synchronization purposes, at the nodes.
Note: Variable storage buffers, installed to accommodate variations in transmission delay between nodes, are made large enough to accommodate small time (phase) departures among the nodal clocks that control transmission. Traffic may occasionally be interrupted to allow the buffers to be emptied of some or… (Read More →)

Two security domains are independent if and only if: - they are administered by different administrations, and - no dependency relationship exists between the security domains [ECMA138].

Double-sideband transmission in which the information carried by each sideband is different.
Note: The carrier may be suppressed.

In an optical fiber, an undesired decrease in the refractive index at the center of the core.
Note: An index dip is an artifact of certain manufacturing processes. Synonym profile dip.

1. In facsimile, the product of the total line length and the number of lines per unit length, divided by .
2. For rotating devices, the product of the drum diameter and the number of lines per unit length. Synonyms: diametral index of cooperation, international index of cooperation.

Synonym refractive index.

Synonym refractive index profile.

Synonym gel.

A substance, usually a liquid, cement (adhesive), or gel, which has an index of refraction that closely approximates that of an optical fiber, and is used to reduce Fresnel reflection at the fiber endface. (FAA)
Note 1: An index-matching material may be used in conjunction with pairs of mated connectors, with mechanical splices, or at the ends of fibers.
Note… (Read More →)

See interaction crosstalk.

In digital data transmission, the use of a clock rate of 2n times the modulation rate, where n is an integer greater than one.

A wave, such as a radio wave or sound wave, that arrives at a given point by reflection or scattering from surrounding objects, rather than directly from the source. [From Weik '89]

A line that connects a single user to a switching center.

The reception of emissions from a space station in the broadcasting-satellite service by simple domestic installations and in particular those possessing small antennae. [NTIA] [RR]

The transfer of energy from one circuit to another by virtue of the mutual inductance between the circuits.
Note 1: Inductive coupling may be deliberate and desired (as in an antenna coupler) or may be undesired (as in power line inductive coupling into telephone lines).
Note 2: Capacitive coupling favors transfer of higher frequency components, whereas inductive coupling favors transfer… (Read More →)

Operation of equipment or appliances designed to generate and use locally radio-frequency energy for industrial, scientific, medical, domestic or similar purposes, excluding applications in the field of telecommunications. [NTIA] [RR]

A standing committee of the Alliance for Telecommunications Industry Solutions (ATIS) that provides an open forum to address and resolve industry-wide issues associated with planning, administration, allocation, assignment and use of the North American Numbering Plan (NANP) numbering resources within the NANP area.

A voluntary, industry-developed document that establishes requirements for products, practices, or operations.

Indirect access to information, without access to the data which represents it [CESG].

A slang term for The Internet or NII. See National Information Infrastructure.

Synonym droid.

1. Facts, data, or instructions in any medium or form. [JP 1-02]
2. The meaning that a human assigns to data by means of the known conventions used in their representation. [JP 1-02]
3. The meaning assigned to data by means of the convention and context used in its representation [CESG].
Note: Information is represented by data and is not… (Read More →)

Information operations (IO) that protect and defend information and information systems (IS) by ensuring their availability, integrity, authentication, confidentiality, and nonrepudiation. This includes providing for restoration of information systems by incorporating protection, detection, and reaction capabilities. [INFOSEC-99]

See user information bit.

A single-digit data element in the 7-digit format that is outpulsed by the network to indicate the numbering plan digit (NPD) and CESID (caller's emergency service ID) display status. In the 10-digit format, two information digits used to indicate the CESID display status. The information digit or digits can also indicate a maintenance test call. [T1.414-1998]

The return of received data to the source, usually for the purpose of checking the accuracy of transmission by comparison with the original data.

In data transmission, a field assigned to contain user information.
Note: The contents of the information field are not interpreted at the link level.

See Covert Channel [CESG].

[In COMSEC, a] procedure to ensure that information transfers within an information system (IS) are not made from a higher security level object to an object of a lower security level. [INFOSEC-99]

In a frame-relaying network, the condition when all frames relayed by the network satisfy the frame check sequence check. [After T1.606-1990]

The item visible at the POSIX.6/D13.1 interface that is used for associating labeling information with object data. This information is not related to mandatory access control [POSIX.6].

The operation whereby one information label is combined with another information label. The specific algorithm used to define the result of a combination of two labels is implementation defined [POSIX.6].

The implementation-defined policy that determines to what degree information labels associated with data are automatically adjusted as data flows through the system [POSIX.6].

A formal representation of entities including their properties, relationships and the operations that can be performed on them. The entities can be either real or intangible.

Equipment used to input into or receive output from the telecommunications network. [47 CFR Pt.36-A]

Synonym data processing.

A facility staffed and equipped for processing and distributing information.
Note: An IPC may be geographically distributed.

An entity that collects information and makes it available to Internet users.
Note: The information can be provided directly to users, or provided via an Internet access provider or a content provider. [After 2382-pt.35]

For a frame relay logical connection, the average number of end user bits transferred per second, in one direction, across a user-network interface as measured over an interval of duration 't'. The measurement interval 't' is network dependent. [T1.615-1992]

The protection of information against unauthorized disclosure, transfer, modification, or destruction, whether accidental or intentional.

Synonym source user.

Synonym National Information Infrastructure.

1. A system, whether automated or manual, that comprises people, machines, and/or methods organized to collect, process, transmit, and disseminate data that represent user information.
2. Any telecommunications and/or computer related equipment or interconnected system or subsystems of equipment that is used in the acquisition, storage, manipulation, management, movement, control, display, switching, interchange, transmission, or reception of voice and/or data,… (Read More →)

[The] protection of information systems against unauthorized access to or modification of information, whether in storage, processing or transit, and against the denial of service to authorized users, including those measures necessary to detect, document, and counter such threats. [INFOSEC]

The branch of technology devoted to (a) the study and application of data and the processing thereof; i.e., the automatic acquisition, storage, manipulation (including transformation), management, movement, control, display, switching, interchange, transmission or reception of data, and (b) the development and use of the hardware, software, firmware, and procedures associated with this processing.

The European ITSEC represent the harmonized evaluation criteria for secure products and systems for use within the European Community (EC). These criteria encompass both functionality and assurance ("correctness" and "effectiveness") aspects of IT security and form the basic standards against which UK evaluations and certifications are carried out within the UK IT Security Evaluation and Certification Scheme [CESG].

Synonymous with EIP Systems (qv) [CESG].

The process of moving messages containing user information from a source to a sink.
Note: The information transfer rate may or may not be equal to the transmission modulation rate.

The capability associated with the transfer of different types of information through the ISDN. It can be used to characterize a telecommunication service or connection. Values associated with this attribute are unrestricted digital, speech,
3. 1-kHz audio, 7- kHz audio, 15-kHz audio, and video. [T1.603-1990] [T1.604-1990]

Establishment of a communication (signaling) path and any required bearer path between the RPT/RT and the radio port. For example, in TDMA and FDMA, time slots and frequencies are identified, and in CDMA, sequence codes are identified. [T
1. Rpt34-1994]

The operational mode for transferring (transportation and switching) user information through the ISDN. It can be used to characterize a telecommunication service or a connection in the network. Values associated with the attribute are circuit mode and packet mode. [T1.603-1990] [T1.604-1990]

The transfer of digital information between two access points or reference points. Values associated with this attribute are appropriate bit rate (in circuit mode) and throughput rate (in packet mode). [T1.603-1990] [T1.604-1990]

1. A channel capable of transmitting all the information required for communication, such as user data, synchronizing sequences, and control signals.
Note: The information-bearer channel may operate at a higher data rate than that required for user data alone.
2. A basic communications channel with the necessary bandwidth but without enhanced or value-added services.

In an information-transfer transaction, the phase during which user information blocks are transferred from the source user to a destination user.

A coordinated sequence of user and telecommunications system actions that cause information present at a source user to become present at a destination user.
Note: An information-transfer transaction usually consists of three consecutive phases called the access phase, the information-transfer phase, and the disengagement phase.

Acronym for information systems security.

The region of the electromagnetic spectrum bounded by the long-wavelength extreme of the visible spectrum (approximately
0. 7 m) and the shortest microwaves (approximately
0. 1 mm). See electromagnetic spectrum.

Preemptive or reactive risk-management techniques designed to increase confidence that disruption of a system will be minimized if its critical infrastructure is attacked.

Preemptive or reactive risk-management techniques designed to prevent disruption of a system after its critical infrastructure is attacked.

A signal that prevents the occurrence of an event.
Note: An inhibiting signal may be used, for example, to disable an AND gate, thus preventing any signals from passing through it as long as the inhibiting signal is present. [From Weik '89]

A procedure used to qualify a signaling link for carriage of signaling traffic, either for the first time or after failure has occurred. [T1.226-1992]

An initial block or “footprint” block is the first NXX-X block that a service provider receives in a rate center where the SP has no other assigned resources (FCC 00-104, ¶ 86 and 191).

The first geographic NXX code assigned to a Service Provider for each rate center in which it provides service.

A preliminary statement of the basic security-relevant facts about a system [CESG].
Note: An initial System Security Policy constitutes the basis for the Departmental Security Officer's risk assessment and Security requirement.

In cryptography, a 64-bit binary sector that may be attached to the beginning of a message. [After X9.23]

Initialization is a consumer device setup and initial configuration phase that is either performed at manufacturing time or manually entered by the user. This stage is outside the scope of the ATIS IIF. However, the date elements, such as identity and authentication credentials and their default values, are in scope for the ATIS IIF.

In encryption, a nonsecret binary vector used as the initializing input algorithm for the encryption of a plaintext block sequence to increase security by introducing additional cryptographic variance and to synchronize cryptographic equipment. [After X9.52]

Setting the state of a cryptographic logic prior to key generation, encryption, or other operating mode. [INFOSEC-99]

The mobile switching center (MSC) (switch) that obtains routing information (i.e., LRN). [T1.708-1998]

An entity (e.g., human user or computer based entity) that attempts to access other entities [10181-3].

ADI associated with the initiator [10181-3].

Access control information relating to the initiator [10181-3].

Synonym launching fiber.

A laser that uses a forward-biased semiconductor junction as the active medium.
Note: Stimulated emission of coherent light occurs at a p-n junction where electrons and holes are driven into the junction. Synonyms diode laser, laser diode, semiconductor laser. See figure on following page.

Recording in which vaporized ink particles are deposited directly upon the record medium.

An image on a web page that is displayed directly to the viewer rather than being made available only as a hot link.

Is where an individual circuit will not function in service (e.g., open, shorted) or cannot transmit address signaling in either direction

1. In a device, process, or channel, a point that accepts data.
2. A state, or a sequence of states, of a point that accepts data.
3. A stimulus, such as a signal or interference, that enters a functional unit, such as a telecommunications system, a computer, or a computer program.

1. Data being received or to be received by a device or a computer program.
2. Data to be processed.

The attribute of a user interface component, such as a window, that enables it to receive input from a particular input device, such as the keyboard. [T1.232-1996]

For analog input channels, protection against overvoltages that may be applied between any two input connectors or between any input connector and ground.

For a computer, a device that handles the transfer of data between internal memory and peripheral equipment.

A functional unit that controls one or more input-output channels. Synonym I/O controller.

A device that introduces data into or extracts data from a system.

The gain resulting from the insertion of a device in a transmission line, expressed as the ratio of the signal power delivered to that part of the line following the device to the signal power delivered to that same part before insertion.
Note 1: If the resulting number is less than unity, an "insertion loss" is indicated.
Note 2: Insertion… (Read More →)

1. The loss resulting from the insertion of a device in a transmission line, expressed as the reciprocal of the ratio of the signal power delivered to that part of the line following the device to the signal power delivered to that same part before insertion.
Note: Insertion loss is usually expressed in dB.
2. In an optical fiber system,… (Read More →)

Of a system or device, a plot of the amplitude as a function of frequency.
Note: The insertion-loss-vs. -frequency characteristic may be expressed as absolute gain or loss, or it may be normalized with respect to gain or loss at a specified reference frequency.

Synonym internal call.

1. All the cabling and equipment installed in a telecommunications facility, including the main distribution frame (MDF) and all the equipment extending inward therefrom, such as PABX or central office equipment, MDF protectors, and grounding systems.
2. In radio and radar systems, all communications-electronics (C-E) equipment that is installed in buildings.

See on-premises wiring.

A collection of produced units from which a statistically valid sample is to be drawn and inspected to determine conformance with acceptability criteria.
Note: The inspection lot may differ from a collection of units designated as a lot for other purposes, such as for production, storage, packaging, and shipment.

the process of creating a managed object according to a managed object class definition. [T1.260-1998]

In a programming language, an expression that specifies one operation and identifies its operands, if any.

A fixed station operated by an educational organization and used primarily for the transmission of visual and aural instructional, cultural, and other types of educational material to one or more fixed receiving locations. [47 CFR
7
4. 901]

1. A radio-navigation system which provides aircraft with horizontal and vertical guidance just before and during landing and, at certain fixed points, indicates the distance to the reference point of landing. [NTIA] [RR]
2. A system of radio navigation intended to assist aircraft in landing which provides lateral and vertical guidance, which may include indications of distance from the optimum… (Read More →)

A system of vertical guidance embodied in the instrument landing system which indicates the vertical deviation of the aircraft from its optimum path of descent. [NTIA] [RR]

A system of horizontal guidance embodied in the instrument landing system which indicates the horizontal deviation of the aircraft from its optimum path of descent along the axis of the runway. [NTIA] [RR]

Telecommunications plant containing from one to six paired conductors, and possibly a shield. Wire may be found in either aerial or buried installations. [T1.316-1997]

An electronic circuit that consists of many individual circuit elements, such as transistors, diodes, resistors, capacitors, inductors, and other active and passive semiconductor devices, formed on a single chip of semiconducting material and mounted on a single piece of substrate material. Synonyms yychip, microcircuit. [From Weik '89]

A network that uses both digital transmission and digital switching.

A set of interconnected frames that is intentionally grounded via multiple connections to a ground reference. Multiple connections are intended to keep voltage drops (due to power faults in the ac or dc power systems or from lightning) to acceptable levels. The following are examples of an integrated ground plane: building steel, water pipes, ground rod systems, counterpoises, vertical and… (Read More →)

A circuit, or group of interconnected circuits, consisting of miniature solid-state optical components on semiconductor or dielectric substrates.
Note: IOC components include light sources, optical filters, photodetectors, and thin-film optical waveguides.

An integrated digital network in which the same time-division switches and digital transmission paths are used to establish connections for different services.
Note 1: ISDN services include telephone, data, electronic mail, and facsimile.
Note 2: The method used to accomplish a connection is often specified: for example, switched connection, nonswitched connection, exchange connection, ISDN connection.

A terminal device in which a telephone and one or more other devices, such as a video display unit, keyboard, or printer, are integrated and used over a single circuit.

A telecommunication system that transfers analog and digital traffic over the same switched network.

See integrated station.

A network (circuit) that produces an output waveform that is the time integral of the input waveform.
Note: Integrating networks are used in signal processing, such as for producing sawtooth waves from square waves.

1. [In INFOSEC, the] quality of an information system (IS) reflecting the logical correctness and reliability of the operating system; the logical completeness of the hardware and software implementing the protection mechanisms; and the consistency of the data structures and occurrence of the stored data. Note that, in a formal security mode, integrity is interpreted more narrowly to mean protection… (Read More →)

[A] checksum capable of detecting modification of an information system (IS). [INFOSEC-99]

Synonym droid.

1. A network that allows functionality to be distributed flexibly at a variety of nodes on and off the network and allows the architecture to be modified to control the services.
2. In North America, an advanced network concept that is envisioned to offer such things as (a) distributed call-processing capabilities across multiple network modules, (b) real-time authorization code verification,… (Read More →)

A service provided using the capabilities of the intelligent network. [T1.667-1999]

A protocol for intelligent network applications contained in Layer 7 (the Application Layer of the OSI model). [T1.667-1999]

1. A functional component that may be used most efficiently when accessed locally.
2. An intelligent-network feature that provides specialized telecommunication capabilities required by IN/2 service logic programs.

For voice communications, the capability of being understood.
Note: Intelligibility does not imply the recognition of a particular voice.

Crosstalk from which information can be derived.

Abbreviation for International Telecommunications Satellite Organization. [47 CFR
0. 453]

The square of the electric field strength of an electromagnetic wave.
Note: Intensity is proportional to irradiance and may be used in place of the term "irradiance" when only relative values are important.

In optical communications, a form of modulation in which the optical power output of a source is varied in accordance with some characteristic of the modulating signal.
Note: In intensity modulation, there are no discrete upper and lower sidebands in the usually understood sense of these terms, because present optical sources lack sufficient coherence to produce them. The envelope of… (Read More →)

1. Between local access and transport areas (LATAs).
2. Services, revenues, and functions associated with telecommunications that originate in one LATA and that terminate in another one or that terminate outside of that LATA.

A radiocommunication service providing links between artificial Earth satellites. [NTIA] [RR] [47CFR]

Crosstalk caused by coupling between carrier and noncarrier circuits.
Note: If the interaction crosstalk is, in turn, coupled to another carrier circuit, that crosstalk is called "indexing. "

Pertaining to a communications environment in which more than one party is equipped and ready to participate actively in a session or a protocol. [After X9.42]
Note: Common usage of the term refers to a session where at least one of the parties is human and another of the parties is a software application.

A unidirectional message, transmitted via a data channel, that requires a response in order for work to proceed logically.

See Electronic Program Guide.

In an integrated services digital network (ISDN), a telecommunications service that facilitates a bidirectional exchange of information among users or among users and hosts.
Note: Interactive services are grouped into conversational services, messaging services, and retrieval services.

On a data recording medium, an area used to indicate the end of a block or physical record.
Note: Examples of interblock gaps are the gaps between blocks on magnetic tape and disks.

1. To stop a telephone call directed to an improper, disconnected, or restricted telephone number, and to redirect that call to an operator or a recording.
2. To gain possession of communications intended for others without their consent, and, ordinarily, without delaying or preventing the transmission.
Note: An intercept may be an authorized or unauthorized action.
3. The acquisition of… (Read More →)

An operator services call request initiated by the network because of the service condition of the line of the called party (e.g., line out of service, etc. ). [T1.661-1997]

Mutual acceptance and exchange of messages between entities. [After X9.24]

A circuit that facilitates the exchange of data and signaling information between data terminal equipment (DTE) and data circuit-terminating equipment (DCE).
Note: An interchange circuit can carry many types of signals and provide many types of service features, such as control signals, timing signals, and common return functions.

1. The ability to exchange hardware components having the same form, fit, and function, across platforms, without affecting the functionality of the system. [JP 1-02]
2. A condition which exists when two or more items possess such functional and physical characteristics as to be equivalent in performance and durability, and are capable of being exchanged one for the other without… (Read More →)

Connectors that share common installation geometry and have the same transmission performance.

In asynchronous transmission, the time interval between the end of the stop signal of one character and the beginning of the start signal of the next character.
Note: The intercharacter interval may be of any duration. The signal sense of the intercharacter interval is always the same as the sense of the stop element, i.e., "1" or "mark. "

1. A telephone apparatus by means of which personnel can talk to each other within an aircraft, tank, ship, or activity. [JP 1-02]
2. A dedicated voice service within a specified user environment.

In a communications network, one or more communications links that (a) are used to provide local area communications service among several locations and (b) collectively form a node in the network.
Note 1: An interconnect facility may include network control and administrative circuits as well as the primary traffic circuits.
Note 2: An interconnect facility may use any medium available… (Read More →)

An entity that provides interconnected VoIP service, as that term is defined in 47 U. S. C. § 153(25) (47 CFR §
5
2. 5 (b)). Interconnected VoIP providers are providers of a service that (1) enables real-time, two-way voice communications, (2) requires a broadband connection from the user’s location, (3) requires Internet protocol-compatible customer premises equipment, and (4) permits… (Read More →)

Two or more networks connected for purposes of call processing. [T1.207-1998]

1. The linking together of interoperable systems. [JP 1-02]
2. The linkage used to join two or more communications units, such as systems, networks, links, nodes, equipment, circuits, and devices.

See interconnection.

A multifrequency (MF) and dual tone multifrequency (DTMF) signal timing interval that is equal to the sum of the fall time, signal-off time, and rise time. The interdigit interval starts when the MF or DTMF signal duration ends. The interdigit interval ends when the next MF or DTMF signal duration begins. [T1.414-1998]

an authority recognized by two or more Security Administrations as a trusted source of security information used between the respective Security Domains [ECMA138].

A gathering or category of network users who have a similar interest in a particular topic and who share their opinions with each other via email or an internet forum.

A unique three-character alphabetic code that identifies customers receiving services from exchange carriers.

1. (or IC):
1. A communications common carrier authorized to provide interexchange telecommunications services within world zone 1 using the North American numbering plan. [After T1.104-1988]
2. A telecommunications common carrier authorized to provide telecommunications services between LATAs. [After T1.502-1988] [T1.508-1998]
Note: The term "interexchange carrier" is also used to refer to any other entity that connects to the exchange… (Read More →)

A circuit which is included in the interexchange transmission equipment. [47 CFR Pt.36-A]

The combination of (a) interexchange cable and wire facilities, (b) interexchange circuit equipment and, (c) associated land and buildings. [47 CFR Pt.36-A]

1. In a system , a shared boundary, i.e., the boundary between two subsystems or two devices.
2. A shared boundary between two functional units, defined by specific attributes, such as functional characteristics, common physical interconnection characteristics, and signal characteristics.
3. A point of communication between two or more processes, persons, or other physical entities.
4. A point of interconnection… (Read More →)

The parameter within a primitive that is the unit of information transferred to/from the upper layer or sublayer in a single interaction. [T1.629-1999]

In telephony, the characteristic of interfaces that allows them to support transmission, switching, and signaling functions identical to those used in the enhanced services provided by the carrier.
Note: As part of its comparably efficient interconnection (CEI) offering, the carrier must make available standardized hardware and software interfaces that are able to support transmission, switching, and signaling functions identical to… (Read More →)

A processor-controlled switch used in packet-switched networks to route packets to their proper destination.

In integrated services digital networks (ISDN), the part of the bit stream through a framed interface used for telecommunications services and signaling.

Synonym point of interface.

The gross bit rate of the signal at the boundary between the physical layer and the physical medium. [T1.107-1988]

A standard that describes one or more functional characteristics (such as code conversion, line assignments, or protocol compliance) or physical characteristics (such as electrical, mechanical, or optical characteristics) necessary to allow the exchange of information between two or more (usually different) systems or equipment.
Note 1: An interface standard may include operational characteristics and acceptable levels of performance.
Note 2:… (Read More →)

1. In a system, a shared boundary, i.e., the boundary between two subsystems or two devices.
2. A shared boundary between two functional units, defined by specific attributes, such as functional characteristics, common physical interconnection characteristics, and signal characteristics.
3. A point of communication between two or more processes, persons, or other physical entities.
4. A point of interconnection between… (Read More →)

1. In general, extraneous energy, from natural or man-made sources, that impedes the reception of desired signals.
2. A coherent emission having a relatively narrow spectral content, e.g., a radio emission from another transmitter at approximately the same frequency, or having a harmonic frequency approximately the same as, another emission of interest to a given recipient, and which impedes reception… (Read More →)

Emission that results in an electrical signal's being propagated into, and interfering with the proper operation of, electronic or electrical equipment.
Note: The frequency range of interference emissions may include the entire electromagnetic spectrum.

An optical filter that reflects one or more spectral bands or lines and transmits others, while maintaining a nearly zero coefficient of absorption for all wavelengths of interest.
Note 1: An interference filter may be high-pass, low-pass, bandpass, or band-rejection.
Note 2: An interference filter consists of multiple thin layers of dielectric material having different refractive indices. There also may… (Read More →)

The locus of points surrounding a transmitter where the predicted median field strength of the signal from that transmitter is the maximum field strength that is not considered to cause interference at the service contour of another transmitter. [47CFR]

An instrument that uses the principle of interference of electromagnetic waves for purposes of measurement.
Note: Interferometers may be used to measure a variety of physical variables, such as displacement (distance), temperature, pressure, and strain.

The branch of science devoted to the study and measurement of the interaction of waves, such as electromagnetic waves and acoustic waves.
Note 1: The interaction of the waves can produce various spatial-, time-, and frequency-domain energy distribution patterns. [After 2196]
Note 2: Interferometric techniques are used to measure refractive index profiles, e.g., those of the preforms from which optical… (Read More →)

In digital data transmission, a sequence of bits transmitted between consecutive frames.
Note: Interframe time fill does not include bits stuffed within a frame.

In raster-scanned video displays, a scanning technique in which all odd-numbered scanning lines are first traced in succession, followed by the tracing of the even-numbered scanning lines in succession, each of which is traced between a pair of odd-numbered scanning lines.
Note 1: The pattern created by tracing the odd-numbered scanning lines is called the odd field, and the pattern… (Read More →)

Synonym interlaced scanning.

The transmission of pulses from two or more digital sources in time-division sequence over a single path.

A circuit between two local central office units, either manual or dial. Interlocal trunks may be used for either exchange or toll traffic or both. [47 CFR Pt.36-A]

In cryptology, certificates in a certificate chain other than the first or end certificate.

In a central office or customer premises, a frame that (a) cross-connects the user cable media to individual user line circuits and (b) may serve as a distribution point for multipair cables from the main distribution frame (MDF) or combined distribution frame (CDF) to individual cables connected to equipment in areas remote from these frames.

In a network, a line-unit-line termination (LULT) or a line-unit-network termination (LUNT).

Synonym intermediate-field region.

A frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception.

In computer programming, a target language into which all or part of a single statement or a source program--in a source language--is translated before it is further translated or interpreted.
Note: For a subsequent translation, an intermediate language may serve as a source language.

Any interconnecting network(s) between the originating network and terminating network.

Intermediate numbers are numbers that are made available for use by another telecommunications carrier or non-carrier entity for the purpose of providing telecommunications service to an end user or customer. Numbers ported for the purpose of transferring an established customer’s service to another service provider shall not be classified as intermediate numbers (47 CFR §
5
2. 15 (f) (1)… (Read More →)

In some operating system (OS) architectures, the OS functions that may be implemented through a central element and one or more remote elements that may do such work as area resource control or area reports. [After T1.201-1987] [After T1.204-1988]

A system that provides an Open Systems Interconnection--Reference Model (OSI--RM) Network Layer relay function in which data received from one corresponding network entity are forwarded to another corresponding network entity.

A translation signaling point (TSP) that translates the global title (as received or after changing to another global title) to identify the next TSP in succession to which the switched control center system (SCCP) message is then routed. The next TSP may be another ITSP or a final TSP (FTSP). [T1.226-1992]

A channel mapping designation that ranges between 1 and 216 and relates the digital circuit multiplication equipment (DCME) transmission trunk to an internal numbering designation used within the DCME for conveying trunk-channel-to-bearer-channel connectivity via the DCME assignment channel. [T1.309-1990]

Synonym intermediate-field region.

For an antenna, the transition region--lying between the near-field region and the far-field region--in which the field strength of an electromagnetic wave is dependent upon the inverse distance, inverse square of the distance, and the inverse cube of the distance from the antenna.
Note: For an antenna that is small compared to the wavelength in question, the intermediate-field region is… (Read More →)

In computer, communications, and data processing systems, a programming language that (a) is less machine-oriented than a machine language, (b) is not so machine-independent as a common language, such as Ada®, COBOL, or Fortran, (c) contains macros that are less powerful than common-language macros, and (d) usually is the object language of a root compiler. Examples of intermediate-level languages include… (Read More →)

The area receiving service from the groundwave of a broadcast station but beyond the primary service area and subject to some interference and fading. [47 CFR
7
3. 14]

Synonym multimode distortion.

Incorrect synonym for multimode distortion.

Synonym multimode distortion.

The production, in a nonlinear element of a system, of frequencies corresponding to the sum and difference frequencies of the fundamentals and harmonics thereof that are transmitted through the element.

Nonlinear distortion characterized by the appearance, in the output of a device, of frequencies that are linear combinations of the fundamental frequencies and all harmonics present in the input signals.
Note: Harmonic components themselves are not usually considered to characterize intermodulation distortion. When the harmonics are included as part of the distortion, a statement to that effect should be made.

In a transmission path or device, noise, generated during modulation and demodulation, that results from nonlinear characteristics in the path or device.

In the output of a nonlinear system, a frequency produced by intermodulation of harmonics of the frequencies present in the input signal.

In a start-stop teletypewriter receiving mechanism, bias generated locally by the mechanism, and which has the same effect on the operating margin as bias external to the receiver, i.e., applied bias.
Note: Internal bias may be a marking bias or a spacing bias.

A call placed within a private branch exchange (PBX) or local switchboard, i.e., not through a central office in a public switched network. Synonym inside call. [From Weik '89]

In a computer, all of the storage spaces that are accessible by a processor without the use of the computer input-output channels.
Note: Internal memory usually includes several types of storage, such as main storage, cache memory, and special registers, all of which can be directly accessed by the processor. Synonym internal storage.

A photoconductive or photovoltaic effect.

Synonym internal memory.

The time scale established by the Bureau International des Poids et Mesures (BIPM--International Bureau of Weights and Measures in Sevres, France) on the basis of atomic clock data supplied by cooperating institutions.

A carrier authorized to provide telecommunications services outside World Zone 1 using the international dialing plan; however, the carrier has the option of providing service to World Zone 1 points outside the forty-eight contiguous states of the United States. [T1.104-1991]

The direct dialing of an international call from a customer in the NANP area to a customer outside the NANP area. The dialing format for an IDDD call is an international prefix followed by the international (E.164) number, which typically consists of a country code and a national number.

A fixed service carried on for the purpose of communicating between transmitting stations, receiving stations, message centers or control points in the international fixed public radiocommunication service. [47CFR]

A fixed service, the stations of which are open to public correspondence and which, in general, is intended to provide radiocommunication between any one of the contiguous 48 states (including the District of Columbia) and the state of Alaska, or the State of Hawaii, or any U. S. possession or any foreign point; or between any U. S. possession and… (Read More →)

See Radio Regulations Board.

Synonym index of cooperation.

See ISO.

An international organization that (a) consists of member bodies that are the national standards bodies of most of the countries of the world, (b) is responsible for the development and publication of international standards in various technical fields, after developing a suitable consensus, (c) is affiliated with the United Nations, and (d) has its headquarters at 1, rue de Varembé,… (Read More →)

The combination of digits to be dialed by a calling subscriber making a call to a subscriber in another country to obtain access to the automatic outgoing international equipment. [T
1. Rpt30-1994]

See ITU-R.

See ASCII.

A 3-digit code within the North American numbering plan, beginning with 1, that classifies international calls as requiring either regular or special handling. [T1.104-1988]

The modern form of the metric system, which has been adopted by the United States and most other nations.
Note: The SI is constructed from seven base units for independent physical quantities. Tables showing these values are included below and are current as of Fall
199
5. SI Prefixes. The common metric prefixes are: Multiplication FactorPrefix NamePrefix Symbol1 000 000… (Read More →)

A civil international organization established to promote standardized telecommunications on a worldwide basis.
Note: The ITU-R and ITU-T are committees under the ITU. The ITU headquarters is located in Geneva, Switzerland. While older than the United Nations, it is recognized by the U. N. as the specialized agency for telecommunications.

The Radiocommunications Sector of the International Telecommunication Union (ITU); responsible for studying technical issues related to radiocommunications, and having some regulatory powers.
Note: A predecessor organization was the CCIR.

The Telecommunication Standardization Sector of the International Telecommunication Union (ITU).
Note 1: ITU-T is responsible for studying technical, operating, and tariff Questions and issuing Recommendations on them, with the goal of standardizing telecommunications worldwide.
Note 2: In principle, the ITU-T combines the standards-setting activities of the predecessor organizations formerly called the International Telegraph and Telephone Consultative Committee (CCITT) and the… (Read More →)

An alphabet in which (a) 128 unique 7-bit strings are used to encode upper- and lower-case letters, 10 decimal numerals, special signs and symbols, diacritical marks, data delimiters, and transmission control characters, (b) 12 of the 7-bit strings are not assigned to any letter, numeral, or control character, and (c) the unassigned bit strings are open for use in a… (Read More →)

See ITU-T.

See International Atomic Time.

The process of designing and developing a product with a set of features, functions, and options intended to facilitate the adaption of the product to satisfy a variety of cultural environments [POSIX.0].

Slang term for a user of the Internet. Synonym cybernaut.

Any interconnection among or between private, industrial or governmental computer (digital communication) networks.
Note: The term internet (spelled with a lower case "i") is distinguished from the Internet (spelled with the "I" capitalized). "The Internet" refers to a specific, historic, ubiquitous worldwide digital communications network. See Internet [the].

In The Internet protocol, the decimal-numeric, fixed-length address that identifies the hosts of data sources, and, specifically, a communication port.
Note: A single Internet address can have multiple URLs. Synonyms IP address, Internet protocol address.

Synonym thin client.

The technical body that oversees the development of the Internet suite of protocols (commonly referred to as "TCP/IP"), and that has two task forces (the Internet Research Task Force and the Internet Engineering Task Force), each charged with investigating a particular field.

An organization, directed by the Internet Architecture Board, that assigns IP numbers and protocol parameters such as port, protocol, and enterprise numbers, and opinions, codes, and types.

Commercial software, written in HTML, that combines the functions of a file-conversion tool and a Web browser.

Synonym thin client.

See ICMP.

One of the task forces (with more than 40 working groups) of the Internet Architecture Board, responsible for solving short-term engineering needs of the Internet.

IGMP v2, as defined in RFC 2236, is an enhancement to the original version of the IGMP protocol that adds “leave” messaging in conjunction with existing “join” messaging. IGMPv2 does not support SSM since the join and leave messages only define the group address and not the source address.

IGMPv3, as defined in RFC 3376, adds support for SSM along with join-leave signaling in a single notification message. IGMPv3 is backwards compatible with IGMPv2 and can support ASM.

See InterNIC.

Synonym message transfer agent.

Synonym cybermall.

See InterNIC.

A combination of software and hardware that allows a user to approximate a telephone conversation over an Internet connection instead of using a traditional telephone system.
Note 1: The required hardware generally consists of a microphone and headphones.
Note 2: The sound quality of current Internet-phone systems is much less than that of traditional telephone systems. Synonym Web phone.

See IPP.

A DOD standard protocol designed for use in interconnected systems of packet-switched computer communication networks.
Note: The internet protocol provides for transmitting blocks of data called datagrams from sources to destinations, where sources and destinations are hosts identified by fixed-length addresses. The internet protocol also provides for fragmentation and reassembly of long datagrams, if necessary, for transmission through small-packet networks.

1. The creation of IP packets with counterfeit (spoofed) IP source addresses.
2. A method of attack used by network intruders to defeat network security measures such as authentication based on IP addresses.
Note 1: An attack using IP spoofing may lead to unauthorized user access, and possibly root access, on the targeted system.
Note 2: A packet-filtering-router firewall may… (Read More →)

Synonym Internet address. See IP address.

See IRC.

See IRTF.

Within the Internet, an accessible facility or entity that contains information or provides data-processing capabilities.
Note: An example of an Internet resource is a Web server. [After 2382-pt.35]

Synonym droid.

See ISP.

A company or organization that provides connections to the Internet to companies or individuals via dial-up, ISDN, yyT1, or other connection.

See ISOC.

See Internet phone.

See Internet phone.

1. A worldwide interconnection of individual networks a) with an agreement on how to talk to each other, and b) operated by government, industry, academia, and private parties.
Note: The Internet originally served to interconnect laboratories engaged in government research, and has now been expanded to serve millions of users and a multitude of purposes, such as interpersonal messaging, computer… (Read More →)

See I2.

Synonym internet.

See gateway.

The point of demarcation between networks when service is provided across multiple networks. [T1.503-1989] [T1.507-1996]

See IPX.

The process of interconnecting two or more individual networks to facilitate communications among their respective nodes.
Note: The interconnected networks may be different types. Each network is distinct, with its own addresses, internal protocols, access methods, and administration.

Contraction of Internet Network Information Center. The association of providers of domain-name registration, information, and database services to the Internet.

A single direct transmission channel, e.g., voice-frequency circuit, between central offices.

1. The ability of systems, units or forces to provide services to and accept services from other systems, units, or forces and to use the services so exchanged to enable them to operate effectively together. [JP 1-02]
2. The condition achieved among communications-electronics systems or items of communications-electronics equipment when information or services can be exchanged directly and satisfactorily between… (Read More →)

A document that establishes engineering and technical requirements that are necessary to be employed in the design of systems, units, or forces and to use the services so exchanged to enable them to operate effectively together.

The use of interoperable systems, units, or forces. [JP 1-02]

The input trunk channel multiplication ratio that is achieved through DSI. The interpolation gain is the ratio of the number of input transmission trunks to the number of DCME bearer channels where the same signal encoding rate is used for both trunk and bearer channels. [T1.309-1990]

1. A single direct transmission channel, e.g., voice-frequency circuit, between two positions of a large switchboard to facilitate the interconnection of other circuits appearing at the respective switchboard positions.
2. Within a technical control facility, a single direct transmission circuit, between positions in a testboard or patch bay, which circuit facilitates testing or patching between the respective positions.

To translate and to execute each source language statement of a computer program before translating and executing the next statement.

1. The transmission of a signal or combination of signals intended to trigger a response.
2. The process whereby a station or device requests another station or device to identify itself or to give its status.

A suspension of a process, such as the execution of a computer program, caused by an event external to that process, and performed in such a way that the process can be resumed. Synonym interruption.

Modulation in which there is on-off keying of a continuous wave.

Synonym isochronous burst transmission.

Synonym interrupt.

A system that monitors a pilot for interruptions on frequency division multiplexing (FDM) systems and that transmits an indication to the switching equipment. [T1.110-1987]

A single direct transmission channel, e.g., voice-frequency circuit, between switching nodes.

1. In a digital transmission system, distortion of the received signal, which distortion is manifested in the temporal spreading and consequent overlap of individual pulses to the degree that the receiver cannot reliably distinguish between changes of state, i.e., between individual signal elements.
Note 1: At a certain threshold, intersymbol interference will compromise the integrity of the received data.
Note… (Read More →)

Circuits between toll centers and circuits between a toll center and a tandem system in a different toll center area. [47 CFR Pt.36-A]

A single direct transmission channel, e.g., voice-frequency circuit, between two toll offices.

Mechanisms that mask differences in physical, link, and network technologies by converting (or mapping) states and protocols into consistent network and user services. [After T
1. Rpt34-1994]

Within the boundaries of a local access and transport area (LATA).

An intra-service provider block port allows an SP to port a thousands-block of numbers from one switch to another serving the same rate center using a port type of “pool” in the NPAC. This can be used in an area where pooling has or has not been established. An ISP block port may be denoted in BIRRDS with a thousands-block… (Read More →)

An intra-service provider port allows an SP to retain unavailable TNs in contaminated thousands-blocks that are being donated to an industry inventory pool.  Specifically, numbers assigned to customers from donated thousands-blocks that are contaminated will be ported back to the donating carrier to enable it to continue to provide service to those customers.  An intra-service provider port can also be… (Read More →)

In an optical fiber, distortion caused by dispersion, such as material or profile dispersion, of a given propagating mode. [After 2196]

Any private network that uses some or all of the protocols of The Internet.
Note: In an intranet, nodes interact in a client-server relationship, nodes are identified by using Internet protocol (IP) addresses, and files are identified by universal resource locators (URLs). The data being exchanged are typically formatted using the HTML language, and is controlled and displayed using a… (Read More →)

A single direct transmission channel, e.g., voice-frequency circuit, within a given switching center.

Of nonidentical optical fibers joined by a splice or a mated pair of connectors, the power loss attributable to manufacturing variations, in such parameters as physical dimensions, differences in refractive index (including profile parameter), numerical aperture, and mode field diameter.

In a transmission path or device, that noise inherent to the path or device and not contingent upon modulation.

Measurements that require that the facility be taken out of service and made unavailable to the user. [T
1. Rpt25-1993]

A frame for which one or more of the following conditions apply: the frame is not properly bounded by flags; the frame does not consist of an integral number of octets prior to zero-bit insertion or following zero-bit extraction; the frame contains a frame-check sequence error (note that this condition is not recorded in the protocol abnormality log); the frame… (Read More →)

The term “inventory“ refers to all telephone numbers distributed, assigned or allocated: to a service provider, or to a pooling administrator for the purpose of establishing or maintaining a thousands-block number pool (CFR §
5
2. 7 (j))

In the encoder and the feedback path of the decoder, the process that maps the core bits into a quantized difference signal. In the feed-forward path of the decoder, the process that maps the core bits and the received enhancement bits into a quantized difference signal. [T1.310-1991]

A functional unit capable of accessing and combining two or more low-speed circuits into a virtual broadband circuit, up to and including an aggregate equal to a T1 rate.

The physical law stating that irradiance, i.e., the power per unit area in the direction of propagation, of a spherical wavefront varies inversely as the square of the distance from the source, assuming there are no losses caused by absorption or scattering.
Note: For example, the power radiated from a point source, e.g., an omnidirectional isotropic antenna, or from any… (Read More →)

In frequency-division multiplexing, a position of a translated channel in which an increasing signal frequency in the untranslated channel causes a decreasing signal frequency in the translated channel.

1. In electrical engineering, a device for converting direct current into alternating current. [JP 1-02]
2. In computers, a device or circuit that inverts the polarity of a signal or pulse. Deprecated synonym negation circuit.

See eight-hundred (800) service.

Acronym for Inward Wide-Area Telephone Service. See eight-hundred (800) service.

Abbreviation for input-output controller, integrated optical circuit.

Abbreviation for Internal Organization of the Network Layer. The OSI standard for the detailed architecture of the Network Layer.
Note: Basically, it partitions the Network layer into subnetworks interconnected by convergence protocols (equivalent to internetworking protocols), creating what is called a catenet or internet.

That part of the atmosphere, extending from about 70 to 500 kilometers, in which ions and free electrons exist in sufficient quantities to reflect and/or refract electromagnetic waves. [After JP1]

A device that transmits signals for the purpose of determining ionospheric conditions. [NTIA] [RR]

Absorption occurring as a result of interaction between an electromagnetic wave and free electrons in the ionosphere.

An increase in the ionization of the ionosphere, caused by solar activity, which results in greatly increased radio wave absorption.

Synonym ionospheric scatter.

Of electromagnetic waves propagating in the ionosphere, a redirection, i.e., bending--by a complex processing involving reflection and refraction--of the waves back toward the Earth.
Note: The amount of bending depends on the extent of penetration (which is a function of frequency), the angle of incidence, polarization of the wave, and ionospheric conditions, such as the ionization density.

The propagation of radio waves by scattering as a result of irregularities or discontinuities in the ionization of the ionosphere. [NTIA] [RR] Synonym forward propagation ionospheric scatter.

A technique that provides real-time data on high-frequency ionospheric-dependent radio propagation, using a basic system consisting of a synchronized transmitter and receiver.
Note: The time delay between transmission and reception is translated into effective ionospheric layer altitude. Vertical incident sounding uses a collocated transmitter and receiver and involves directing a range of frequencies vertically to the ionosphere and measuring the… (Read More →)

Ongoing disturbances of the ionosphere that scatter incident electromagnetic waves.
Note: Ionospheric turbulence results in irregularities in the composition of the ionosphere that change with time. This causes changes in reflection properties. These, in turn, cause changes in skip distance, fading, local intensification, and distortion of the incident waves. [From Weik '89]

1. Intelligent Peripheral,
2. Internet Protocol.

A device's or resource's numerical address as expressed in the format specified in the Internet Protocol.
Note 1: In the current addressing format, IP version 4 (IPv4), an IP address is a 32-bit sequence divided into four groups of decimal numbers separated by periods ("dots"), commonly referred to as "dotted decimals. " The IP address of a device is made… (Read More →)

The fundamental unit of information passed across any network utilizing Internet protocol.
Note: An IP datagram contains source and destination addresses along with data and a number of fields that define such things as the length of the datagram, the header checksum, and flags that indicate whether the datagram can be (or has been) fragmented.

Nonpermanent access, by means of a switched network (e.g., the public switched telephone network), to any network utilizing The Internet Protocol, especially The Internet.
Note: Two well-known protocols for dialup access are PPP (point-to-point) and SLIP (serial line internet protocol). [After 2382-pt.35]

A technique that allows packets to be simultaneously transmitted over the Mbone (multicast backbone on The Internet) to a selected set of destinations.
Note: Standard Internet traffic requires a separate set of packets for each destination. IP multicast allows for one set of packets to be sent to multiple destinations.

Synonym IP address.

1. A technique used by hackers to access computer systems by modifying packet headers to make them appear to have originated from a trusted port.
2. The practice of falsifying an e-mail header to make it appear as though it originated from a different address.

A method of routing developed to use asynchronous transfer mode (ATM) hardware to route packets through networks more rapidly.

IP Connectivity Access Networks

Abbreviation for information processing center.

Internet Protocol Control Protocol

1. Internet Protocol Data Record,
2. Internet Protocol Detail Record.

IP Flow Information Export

IP (Internet Protocol) Gateway

Abbreviation for IP next generation, IP version 6.

Abbreviation for Internet presence provider. An organization or commercial enterprise that provides storage space for the Web resources of an individual or other entity and enables those resources to be accessed by Internet users.
Note: An IPP may not offer basic Internet connections as an ISP usually does.

IP Security

Internet Protocol for Smart Objects

Abbreviation for Infrastructure Protection Task Force.

Internet Protocol Television

A term used to denote either an IPTV Subscriber or an IPTV User. See also Consumer.

A role that is played by a person or an organization (associated with the "IPTV Account" entity) that is involved in an implicit or explicit commercial agreement for the purchase of IPTV Products, IPTV Services, or IPTV resources from an IPTV SP. This entity is liable for payment of the incurred charges. An IPTV Customer is associated with one or… (Read More →)

The IIF enables the interoperability, interconnection, and implementation of IPTV systems/services by developing ATIS standards and facilitating related technical activities. This forum will place an emphasis on North American and ATIS Member Company needs in coordination with other regional and international standards development organizations.

IPTV Terminal Function (ITF) (as defined in the IPTV Architecture Requirements, ATIS-0800002), represents the functionality within the consumer network that is responsible for terminating the IP signal and converting the content into a renderable format (e.g., a STB).

A role that is played by business or organization that has commercial agreement with IPTV Customers and provides IPTV Products and IPTV Services to IPTV Subscribers and IPTV Users associated with these IPTV Customers. The IPTV SP may integrate the services of NP(s) in order to deliver a total IPTV Service. See also Service Provider.

A role that is played by a person or an organization (associated with one or more IPTV users) that is engaged in an implicit or explicit agreement for the right to use IPTV Products, IPTV Services, or IPTV resources from an IPTV SP. The IPTV Subscriber is allowed to subscribe and unsubscribe IPTV Services, to register an IPTV User, or… (Read More →)

The ITF represents the functionality within the consumer network that is responsible for terminating the IP signal and converting the content into a renderable format -- e.g., a STB.

A role that is played by a person that employs one or more IPTV Products, IPTV Resources, and/or IPTV Services provided by an IPTV SP. The IPTV User entity is associated with an IPTV Customer. A single IPTV User has access to one or more IPTV Devices. See also User.

Internet Protocol version 4

Internet Protocol version 6

Abbreviation for Internetwork Packet Exchange. A proprietary (LAN) protocol.

Abbreviation for infrared.

Abbreviation for Internet relay chat. A service for conducting a chat on the Internet, i.e., an application that allows a number of individual users to exchange text messages simultaneously in real time over The Internet.

Radiant power incident per unit area upon a surface.
Note: Irradiance is usually expressed in watts per square meter, but may also be expressed in joules per square meter. Deprecated synonym power density.

The product of irradiance and time, i.e., the time integral of irradiance.
Note: For example, an irradiation of 100 J/m2 (joules per square meter) is obtained when an irradiance of 25 W/m2 (watts per square meter) is continuously incident for 4 seconds.

Encryption that produces ciphertext from which the original data cannot be reproduced.
Note: Irreversible encryption is useful in authentication. For example, a password might be irreversibly encrypted and the resulting ciphertext stored. A password presented later would be irreversibly encrypted identically and the two strings of ciphertext compared. If they are identical, the presented password is correct. Synonyms irreversible encipherment,… (Read More →)

Abbreviation for Internet Research Task Force. A task force of the Internet Architecture Board (IAB), and which is responsible for research and development of the Internet protocol suite.

Intra-Site Automatic Tunnel Addressing Protocol

Abbreviation for independent sideband. See independent-sideband transmission.

IMS Service Control

Integrated Services Digital Network

The functional part of the Signaling System No.7 (SS7) protocol, i.e., the part that specifies the interexchange signaling procedures for the set up and tear down of trunk calls between networks. The ISDN User Part is one of the specified users of the Message Transfer Part (MTP) transport capability of the SS7 interconnections. The user part identification is encoded in… (Read More →)

1. IP Multimedia Services Identity Module,
2. IMS Identity Module.

Abbreviation for industrial, scientific, and medical applications (of radio frequency energy).

A Web page feature in which hyperlinks are assigned or "mapped" to different portions of a graphic image.
Note: Users access links by using a mouse to click on mapped areas. ISMAP requests are processed by common gateway interface (CGI) scripts on the server.

International Organization for Standardization

Abbreviation for Internet Society. A nongovernmental, international organization for global cooperation and coordination for The Internet and its internetworking technologies and applications.

A line on a map or chart joining points associated with a constant time difference from the transmitter to receiver of electromagnetic waves, such as radio waves, at all points along the line. [From Weik '89]

1. Of a periodic signal, pertaining to transmission in which the time interval separating any two corresponding transitions is equal to the unit interval or to a multiple of the unit interval.
2. Pertaining to data transmission in which corresponding significant instants of two or more sequential signals have a constant phase relationship.
Note: "Isochronous" and "anisochronous" are characteristics, while… (Read More →)

In a data network where the information-bearer channel rate is higher than the input data signaling rate, transmission performed by interrupting, at controlled intervals, the data stream being transmitted.
Note 1: Isochronous burst transmission enables communication between data terminal equipment (DTE) and data networks that operate at dissimilar data signaling rates, such as when the information-bearer channel rate is higher… (Read More →)

Demodulation in which the time interval separating any two significant instants is equal to the unit interval or a multiple of the unit interval.

The difference between the measured modulation rate and the theoretical modulation rate in a digital system.

Modulation in which the time interval separating any two significant instants is equal to the unit interval or a multiple of the unit interval.

A signal in which the time interval separating any two significant instants is equal to the unit interval or a multiple of the unit interval.
Note 1: Variations in the time intervals are constrained within specified limits.
Note 2: "Isochronous" is a characteristic, while "synchronous" indicates a relationship.

To restrict communication in both directions with a participant of the conference. [T1.647-1995]

Synonym isolated ground plane.

A set of interconnected frames that is intentionally grounded via only one connection to a ground reference; this plane, taken as a conductive unit with all of its metallic surfaces and grounding (earthing) wires bonded together, is insulated from contact with any other grounded metalwork in the building. Synonym isolated bonding network. [T1.313-1997]

A single bit period of logical value "1" with adjacent bit periods of logical value "0". [T1.106-1988]

A pulse free from the effects of the other pulses in the same signal. (A suitable testing signal is a repetitive pattern of one "one" and seven "zeros". ) [T1.408-1990]

Any bit period of logical value "
1. " [T1.106-1988]

See optical isolator.

1. Pertaining to a material with properties, such as density, electrical conductivity, electric permittivity, magnetic permeability, or refractive index that do not vary with distance or direction.
2. Pertaining to a material with magnetic, electrical, or electromagnetic properties that do not vary with the direction of static or propagating magnetic, electrical, or electromagnetic fields within the material.

A hypothetical antenna that radiates or receives equally in all directions.
Note: Isotropic antennas do not exist physically but represent convenient reference antennas for expressing directional properties of physical antennas.

Synonym absolute gain.

Internet Service Provider

IPTV Security Solution/Authentication

Information Systems Security Architecture

Information System Security Assurance Architecture

Integrated Services (Digital Network) User Part

Information Technology

ITAR are the regulations covering the exporting of weapons and weapons related technology from the United States. For some strange reason, the government claims that data encryption is a weapon and comes under the ITAR regulations. There is presently a move in Congress to relax the section of ITAR dealing with cryptographic technology.

In electrical circuits, for a four-terminal network, the impedance that, if connected across one pair of terminals, will match the impedance across the other pair of terminals.
Note: The iterative impedance of a uniform line is the same as its characteristic impedance.

IPTV Terminal Function

CPU processing power and other HW resources as well as SW functionality (e.g., QoS management and NAT/media relay) available with an ITF.

Independent Testing Laboratories

International Telecommunication Union

International Telecommunication Union - Telecommunication Development Sector

International Telecommunication Union - Radio

International Telecommunication Union - Telecommunications Standardization Sector

Interactive Television

Abbreviation for integrated voice data terminal. See integrated station.

Interactive Voice Response

Internet Exchange

Interexchange Carrier