Internet Firewall-iXXX

Internet Firewall

See Firewall.

Internet Freedom and Broadband Deployment Act

A proposed 2002 act of the House of Representatives also called the Tauzin-Dingell Bill. The bill pushes the Regional Bell Operating Companies (RBOCs) to offer broadband Internet services over long-distance lines without opening up their local phone service monopolies to outside competition. The Tauzin-Dingell bill, or more formally H.R. 1542, the Internet Freedom and Broadband Deployment Act, is legislation written by Representatives John D. Dingell (D-MA) and Billy Tauzin (R-LA).

Internet Gateway

Internet gateways are devices which typically sit on a local area network and handle all the translations between IPX traffic on your LAN (IPX is the NetWare protocol) and the TCP/IP traffic on the Internet. TCP/IP is the protocol used on the Internet. See also Internet Servers and other definitions beginning with Internet.

Internet Group Name

In Microsoft networking, a name registered by the domain controller that contains a list of the specific addresses of computers that have registered the name. The name has a 16th character ending in 0x1C.

Internet Imposters

A term created by Gretchen Morgenson of the New York Times for overheated stocks posing as growth companies.

Internet Integrator

A fancy name for a consulting firm which specializes in helping its clients do stuff with the Internet, including transaction processing; supply chain infrastructure integration; wireless integration; business to business (B2B) and application monitoring/management.

Internet Intellectual Infrastructure Fund

A fund created in 1995 to offset government funding for the preservation and enhancement of the intellectual infrastructure of the Internet. The fund was funded by 30% of the Internet domain registration fee, which was set at $50 per year at that time. On March 16, 1998, the funding for the Intellectual Infrastructure was completed, and the InterNIC ceased to collect that portion of the annual fee, thereby reducing it to $35 for new registrations. Proceeds of the fund are to be used to build Internet2, which will be a separate Internet for institutions of higher learning. See also CORE , DNS and InterNIC.

Internet Key Exchange

See IKE.

Internet Mail Consortium

IMC. A technical trade association which pursues cooperative promotion and enhancement of electronic mail and messaging on the Internet. Activities cover promotion of Internet mail and the products and services which serve to implement it. IMC is involved in formative efforts for IETF (Internet Engineering Task Force) mail standards, with a focus on implementation guidelines.

Internet Message Access Protocol


Internet MIB Subtree

A tree-shaped data structure in which network devices on a local area network and their attributes can be identified within the confines of a network management scheme. The name of an object or attribute is derived from its location on this tree.

For example, an object in MIB-I might be named the first 1 indicates the object is on the Internet. The 2 denotes that it falls within the Management category. The second 1 shows the object is part of the first fully defined MIB, known as MIB-I. The third 1 indicates which of the eight object groups is being referenced. And the fourth 1 is a textual description of the network component. The O indicates there is only one object instance. An object instance links a particular object to a specific node on the network. The numbering system is infinitely extendible to accommodate additions to this base identification scheme. This common naming structure permits equipment from a variety of vendors to be managed by a single management station that uses SNMP. The four main categories of the tree are Directory, Management, Experimental and Private/Enterprises.

Internet Number

The dotted -quad address used to specify a certain system. The Internet number for is A resolver is used to translate between hostnames and their numeric Internet addresses. See gTLD and Internet.

Internet Numbers Registry

IR. The officially designated organization responsible for the assignment of IP addresses, the IR assigns unique URLs (Uniform Resource Locators), which are translated into IP addresses through a resolver. IR is a responsibility of the IANA (Internet Assigned Numbers Authority), a function assigned to the Information Sciences Institute (ISI) of the University of Southern California. In accordance with its discretionary authority, ISI initially delegated that responsibility to SRI International and, subsequently, to Network Solutions Inc. (NSI). Beginning March 1998, NSI shares that responsibility with CORE and Emergent Corporation, which administers the Shared Numbers Registry (SRS). See also CORE, IANA, SRS, and URL.

Internet Offloading

Internet offloading is a term used to describe Internet data traffic from a carrier's telephone voice switch and process it on a separate data switch or other equipment, in order to get rid of the Internet-bound traffic and handle that data more cheaply. Here's the logic: A normal central office telephone switch is designed to handle voice phone calls, each averaging three minutes. Pricing is done to accommodate this pattern. After the Internet became very popular, the manager of my local phone company complained to me that his average phone call had now risen to one hour (from three minutes) and this was "killing him." He had been forced to put in more capacity, even though he wasn't getting paid any more money.

Internet Open Trading Protocol

IOTP. An interoperable framework for Internet commerce, IOTP was developed by the Open Trading Protocol Consortium, and has been accepted by the Internet Engineering Task Force (IETF) for standards development. IOTP is intended to be independent of any underlying electronic payment systems, such as SET (Secure Electronic Transaction), Mondex, CyberCash, and DigiCash. According to the IETF, a "fundamental ideal of the IOTP effort is to produce a definition of these trading events in such a way that no matter where produced, two unfamiliar parties using electronic commerce capabilities to buy and sell that conform to the IOTP specifications will be able to complete the business safely and successfully."

Internet Packet Exchange

IPX. Novell NetWare's native LAN communications protocol, used to move data between server and/or workstation programs running on different network nodes.

Internet Peering

See Peering.

Internet Plumbers

Internet plumbers are the companies who make the equipment that makes up the Internet's infrastructure, such as the routers and the servers. They include Cisco, IBM, Lucent and Sun.

Internet Print Server

An Internet print server allows anyone to print a document on any printer on the Internet with the same ease as printing on a printer attached to the PC. Internet Printing is just like e-mail, Internet faxing, Internet Telephone and Video. It is a new method of data streaming through the Internet, that will further open up the Internet for new applications. Black Ice Software, was the first company to announce an Internet print server,

Internet Protocol

IP. Part of the TCP/IP family of protocols describing software that tracks the Internet address of nodes, routes outgoing messages, and recognizes incoming messages. Used in gateways to connect networks at OSI network Level 3 and above. See Internet, Internet Protocol Address and TCP/IP.

Internet Protocol Data Record


Internet Protocol Address

Also called IP Address. It's a unique, 32-bit number for a specific TCP/IP host on the Internet. IP addresses are normally printed in dotted decimal form, such as Once your domain is assigned a group of numbers by the Internet's central registry, it can house one or several domains and/or hosts, i.e. and People looking for those domains will be pointed to that server where they will find all information in the domain ” perhaps a home page, or a place to leave e-mail, etc. There are three classes of IP address A, B, and C ” the most common of which is a class "C" address block. A class "C" address block can address about 256 hosts (e.g., 128.10.10.*). a class "B" address block can contain about 256*256 (e.g., 128.10.*.*) hosts . Some ip addresses are reserved for broadcasts in respective domains. See Domain and Internet.

Internet Protocol Datagram

The fundamental unit of information passed across the Internet. Contains source and destination addresses along with data and a number of fields which define such things as the length of the datagram, the header checksum, and flags to say whether the datagram can be (or has been) fragmented , This is a self-contained packet, independent of other packets.

Internet Protocol Suite

The TCP/IP suite of network protocols which were mandated for use in the Internet in 1983. The suite includes the following protocols (and the Layer at which each functions in the context of the OSI Reference Model): IP, or Internet Protocol (Layer 3); TCP, or Transmission Control Protocol (Layer 4); UDP, or User Datagram Protocol (Layer 7); FTP, or File Transfer Protocol (Layer 7); TELNET, or TELecommunications NETwork (Layer 7); SMTP, or Simple Mail Transfer Protocol (Layer 7); and SNMP, or Simple Network Management Protocol (Layer 7). See the definitions of these terms for much more detail.

Internet Radio

As I write this, I am wearing headphones plugged into my laptop listening to Klassik Radio from Hamburg, Germany. Find it and others at The music is wonderful. The clarity is perfect. How does this work? The "radio station" simply sets up a web server attached to the Internet. Instead of putting up text and pictures like other web sites do, it puts up its "radio station." That radio station may be programming its broadcasting over the air in Hamburg, or it may be programming by just specially putting the material up on he web site. That station might also give you its program. How do I listen to Internet radio broadcasts? Most internet radio broadcasts are easily accessible using your web browser and either RealPlayer (from or Windows Media Player, which comes with Microsoft's browser Internet Explorer. Both of these softwares come with preloaded addresses for interesting Internet radio stations . But you can find thousands more by searching on Web for "Internet Radio." There are four neat things about Internet radio: The quality is perfectly fine on a dial connection; there's a huge variety of available radio stations (at least several thousand), enough to satisfy anyone's taste; it's all free and fourth, when you log onto many of the stations, a screen may pop up giving you the Radio's program guide. Internet Radio is one of the Internet's enormous benefits.

Internet Registry

Activities involved in the administration of generic Top Level Domains (gTLDs) in the CORE (Council or REgistrars) Domain System. Such activities comprise all the services needed for assignment and maintenance of Internet domain names . As many as 90 registrars will be authorized by CORE as registrars to administer and maintain the new gTLDs: .arts, .firm, . info , . nom, .rec, .shop and .web. InterNIC historically has been primarily responsible for the assignment, administration and maintenance of a subset of the traditional gTLDs, specifically , .com, .edu and .org. Future responsibility for those traditional gTLDs is uncertain . See also CORE, DNS, gTLD and InterNIC.

Internet Relay Chat

IRC. Sort of like CB radio, but run on the Internet, and far more confusing than CB radio. See IRC for a real definition.

Internet Research Task Force

IRTF. An Internet organization that creates long- and short-term research groups concentrating on protocols, architecture, and technology issues. For more information on IRTF, see

Internet Router

see Router.

Internet Security

Information traveling on the Internet usually takes a circuitous route through several intermediary computers to reach any destination computer. The actual route your information takes to reach its destination is not under your control. As your information travels on Internet computers, any intermediary computer has the potential to eavesdrop and make copies. An intermediary computer could even deceive you and exchange information with you by misrepresenting itself as your intended destination. These possibilities make the transfer of confidential information such as passwords or credit card numbers susceptible to abuse. This is where Internet security comes in and why it has become a rapidly growing concern for all who use the Internet. See the Internet and Secure Channel.

Internet Server

  1. An Internet server is a device which users on the Internet access to get services. Such services might be electronic mail, news, a Web page, etc. A company will have one or more Internet servers attached to the Internet when it wants to deliver services to people on the Internet. Such Internet servers could be called e-mail servers, FTP servers, News servers and World Wide Web servers. Internet servers most commonly run on Unix. But Microsoft Windows NT is increasingly gaining popularity.

  2. A Sun Microsystems term, Part of Solaris' Server Suite. Provides secure, scalable workgroup-based Internet computing.

Internet Server API


Internet Service Provider

ISP. A vendor who provides access for customers (companies and private individuals) to the Internet and the World Wide Web. The ISP also typically provides a core group of internet utilities and services like E-mail, News Group Readers and sometimes weather reports and local restaurant reviews. The user typically reaches his ISP by either dialing-up with their own computer, modem and phone line, or over a dedicated line installed by a telephone company. An ISP is also called a TSP, for Telecommunications Service Provider, and a ITSP, for Internet Telephony Service Provider.

Internet Small Computer Systems Interface

See iSCSI.

Internet Society


Internet Telephony

In the very beginning, Internet telephony simply meant the technology and the techniques to let you make voice phone calls ” local, long distance and international ” over the Internet using your PC. To make these calls, both people on the phone need appropriate hardware and software. The hardware is typically a sound card or voice modem in a PC. There are almost as many ways of making phone calls on the Internet as there are software packages. The key is to figure a way that your PC can dial and reach someone else's distant PC ” which must be turned on, plugged in and connected to some place that my PC can find you at. In short, making voice phone calls was the first definition of Internet telephony. But then people started thinking of other things Internet telephony could become. For example, Internet telephony could let you talk to someone while the two of you worked on making perfect a document that was on both your screens. If the Internet could send email, people started thinking of sending fax, voice, video and imaging mail/messages. And maybe, as you cruise the Internet and find a product you'd like to buy, you might see a button that says "I'd like to know more. Have an operator call me." So you click the button, and 15 seconds later your phone rings. The operator is calling, wanting to know how he can help? In short, the definition of Internet telephony is broadening day by day to include all forms of media (voice, video, image), all forms of messaging and all variations of speed from real-time to time-delayed. See Gold, Packet Switching, Tier 1 and, for the best explanation, TAPI 3.0.

Internet Terminal

A sub-$500 machine specially designed for Internet browsing and first proposed in the late Fall of 1995 by Larry Ellison, head of database software company Oracle. Part of its appeal to people outside Microsoft and Intel is that the Internet Appliance would not have to be based on standard PC technology. It need have an Intel chip and need not run Windows. This device is also called an Internet Terminal, a Network Computer or an IPC, an Interpersonal computer. The original description of the Internet Appliance was that it would come with 4mb of RAM, 4mb of flash memory, processor, monitor, keyboard and mouse ” all for under $500. Also called a NC, or Network Computer.

Internet Time

This term came into the English language around 1994 and became canonical during the late 1990s. It was used to describe the accelerated pace at which, in an Internet/Web enabled world, all business was supposedly going to be conducted . Internet time and its cousins, Web Time and Warp Speed, did well as titles of books, which didn't sell well, but little else. See also New Economy.

Internet Worm

This software program caused a major part of the Internet network to crash by replicating and generating spurious data.


Internet2 is a high-speed network created by a consortium of U.S. universities called the University Corporation for Advanced Internet Development (UCAID). It transmits high-quality audio and video with almost no delay 34 U.S. universities announced the formation of Internet2 in October 1996 Subsequently, the central goals of the project were adopted as part of the Clinton administration's Next Generation Initiative (NGI). This second version of the Internet is a collaboration of the National Science Foundation (NSF), the U.S. Department of Energy, over 110 research universities, and a small number of private businesses. Each participating university has committed at least $500,000 to fund the project. Intended to serve as a private Internet for the exclusive use of its member organizations, it will be separate from the traditional Internet. The network eventually will operate over fiber optic transmission facilities at speeds of up to 2.4 Gbps (SONET OC-48). Internet2 will connect through gigiPOPs, switches with throughput in the range of billions of packets per second, and will run the IPv6 protocol. See also IPv6 and the Internet.


See Internetworking.

Internetwork Management

A generic term used to describe the actions that help maintain, a complex network.

Internetwork Operating System

IOS. Cisco's massive operating system that runs most routers on the Internet.

Internetwork Packet Exchange

IPX. A network layer protocol developed by Novell and used in NetWare implementations . See IPX.

Internetwork Router

In local area networking technology, an internetwork router is a device used for communications between networks. Messages for the connected network are addressed to the internetwork router, which chooses the best path to the selected destination via dynamic routing. Internetwork routers function at the network layer of the Open Systems Interconnection (OSI) model. Also known as a network router or simply as a router.


  1. Communication between two networks or two types of networks or end equipment. This may or may not involve a difference in signaling or protocol elements supported. And, in the narrower sense ” to join local area networks together. This way users can get access to other files, databases and applications. Bridges and routers are the devices which typically accomplish the task of joining LANs. Internetworking may be done with cables ” joining LANs together in the same building, for example. Or it may be done with telecommunications circuits ” joining LANs together across the globe.


Internet Network Information Center. The InterNIC registry is where you always used to go to register your domain name. Registration was free until 1995; then it changed to $50 a year; now it's $35 a year for domain names with anniversary dates on or after April 1, 1998. The InterNIC Registration Services Host computer contains information on Internet Networks, ASNs, Domains, and POCs (Points of Contact, the person or persons identified in a record). The InterNIC was established in January 1993 as a collaborative project between AT&T, General Atomics (no longer involved) and Network Solutions, Inc., and was supported through a 5-year cooperative agreement with the NSF (National Science Foundation). InterNIC participates in Internet forums to promote Internet services, explore new tools and technologies, and contribute to the Internet community. InterNIC currently is operated by Network Solutions Inc., a subsidiary of SAIC (Science Applications International Corporation), the private company which also has acquired Bellcore. On December 22, 1997, responsibility for assignment of IP numbers was shifted to ARIN (American Registry of Internet Numbers) for the geographic areas of North American, South America, the Caribbean and sub-Saharan Africa. About the same time, the decision was made to shift responsibility for domain name registration to the Council of Registrars (CORE). CORE is empowered to authorize as many as 90 independent registrars, including InterNIC, to register domain names, or URLs (Uniform Resource Locators). See also ARIN, CORE, Domain, Domain Name and POC.


Communication paths which originate in one node and terminate in another.

Internode Link

A data line for high-bandwidth connections between PBXs.


Between two telephone company switching offices.

Interoffice Channel

A portion of a communications circuit between central offices of a common carrier which serves customers located in different central office areas. When associated with foreign exchange service, the term denotes the channel which interconnects a primary wire center to a different wire center.

Interoffice Trunk

A trunk circuit connecting two local telephone company central offices.


The ability of equipment from several vendors to work together using a common set of protocols. We're not talking about identical products, but ones that conform to the same protocol and theoretically can talk to each other. For example, two lap- tops from different manufacturers should be able to talk to each other using infra-red communications because both conform (theoretically at least to the same infra-red communications protocol. Interoperability is not Yes or No. There are levels of it. See Interoperability Testing.


See Interoperate.

Interoperability Testing

In our industry there are several levels of testing of new products and services. Clearly, the manufacturer does one level of testing. His job is to ensure that his product meets the claims that he promotes for it. Then there is a inter- operability testing. This is testing to ensure that his product works with other products that allegedly conform to the same standard/s. Clearly it is one thing for a bunch of engineers to create a new standard on paper. And it is another thing to have engineers build product to that standard and have their products communicate with other products from other manufacturers who also allegedly conform to the standard. The most public example of inter- operability testing in the telecom industry is that which occurred so successfully in the ATM Forum. That organization was established by manufacturers who make ATM products. Their objective was not to establish new standards (they already existed), but to make sure that their products worked successfully with each other without hardware modification. Plug the equipment together. Configure the software. Bingo it would work. See Interoperate.


Modular hardware or software that implements part of the OSI model and can work with components implementing the other parts of the model.

Interpacket Gap

IPG. A delay or time gap between CSMA/CD packets intended to provide interface recovery time for other CSMA/CD sublayers and for the Physical Medium. For 10Base-T, the IPG is 9.6 us (96 bit times). For 100Base-T, the IPG is 0.96 us (96 bit times).


Calls coming into one PBX can be transferred to extensions on another PBX using direct tie lines between the two PBXs.

Interpersonal Message

IPM. The term used in the 1984 X.400 recommendations to refer to a message in the Interpersonal Messaging System. The 1988 X.400 recommendations use the term "interpersonal message" (IPM).

Interpersonal Message (IPM) User Agent

A class of cooperating user Agents capable of processing Interpersonal (IP) messages. An x.400 term.

Interpersonal Messaging

IPM. Electronic exchange of information between two or more persons.


  1. The process of estimating values of (a function) between two known values.

  2. A video technique used in motion compensation where a current frame of video is reconstructed by using the differences between it and past and future frames . This technique is also known as forward and backward prediction. Intel (originator of Indeo Video) defines interpolation slightly differently, namely: The process of averaging pixel information when scaling an image. When the size of an image is reduced, pixels are averaged to create a single new pixel; when an image is scaled up in size , additional pixels are created by averaging pixels of the smaller image.

Interposition Calling

One operator in a multi-position system calling another.

Interposition Transfer

Transfer of a call from one operator to another.

Interposition Trunk

  1. A connection between two positions of a large switchboard so that a line on one position can be connected to a line on another position.

  2. Connections terminated at test positions for testing and patching between testboards and patch bays within a technical control facility.


An equipment configuration in which carrier-provided terminal equipment accesses exchange carrier facilities through customer-provided terminal equipment. An old term.


Interpret means that the computer will translate a stored program expressed in pseudocode into machine language and will perform the indicated operations as they are translated. See Interpreter for a longer explanation.


Much like a compiler, an interpreter translates source code written by a programmer into machine code the computer can understand. For example, a compiler takes instructions written in a "higher" level language such as BASIC, COBOL or ALGOL and converts them into machine language that can be read and acted upon by a computer. The translated code is in the form of an executable program, which can be run on the target computer without additional translation software. Compilers convert large sections of code at one time, usually translating the code so that it can be run at a later time on the target computer. Interpreters translate commands one line at a time while the application is running. Therefore, the machine running the application must also be running the interpreter. Interpreters are useful in the testing of new or modified code, and for teaching programming. See also Bytecode and Compiler.

Interprocess Communications

The ability of programs to share information. At the most basic level, it consists of cutting and pasting information between two programs. Above that ranks the "live" paste, in which information shared between two documents is updated whenever one of the documents is modified. This is referred to as Dynamic Data Exchange (DDE). In advanced DDE, programs can send messages as well as data to other programs running locally or remotely. Beyond DDE is Object Linking and Embedding (OLE), which lets one program borrow the specialized capabilities of another program loaded on the machine (say, advanced chart creation) rather than having to implement that capability redundantly.

InterRepeater Link

IRL. A networking term. A mechanism for connecting two and only two repeater sets.


To determine the state of a device or unit.


See RFID reader.


A temporary suspension of a process caused by an event outside of that process. More specifically, an interrupt is a signal or call to a specific routine. An interrupt setting allows the hardware in a file server, router, workstation or PC to send an interrupt signal to the processor. The interrupt signal temporarily suspends the other station tasks while the processor performs the task requested by the interrupting device. After the routine is completed, the processor then continues with the original tasks. Each piece of hardware (serial and parallel ports and network boards ) installed in the same computer needs a unique interrupt. Interrupts are divided into two general types, hardware and software. A hardware interrupt is caused by a signal from a hardware device, such as a printer. A software interrupt is created by instructions from within a software program.

TIP: When you slide a new card into one of the empty slots on your PC and things go awry, check that the new card's interrupt is not the same as one of the other cards in your bus. An interrupt is also called a hardware interrupt or an InterRupt reQuest (IRQ). For a listing of normal IRQs see IRQs. See also Interrupt Requests and Polling.

Interrupt Driven

Someone who moves through a workday responding to interruptions rather than the work goals as originally set.

Interrupt Flag

In a PC, there is a configuration control (addressed as bit IF of the processor flag register). This control process manages the CPU's ability to receive and process interrupt requests. The flag is often set to zero (which means interrupts disabled) by device drivers or other I/O privilege-level code that needs exclusive access to the CPU during critical operations. See also Interrupt, Interrupt Handling Routine and UART.

Interrupt Handling Routine

This program, which is often part of a device driver, handles all requests from a particular interrupt line. Interrupt-handling routines are defined in the CPU's Interrupt Descriptor Table (IDT). When the CPU (the Central Processing Unit of your PC) receives an interrupt request, it looks up the matching interrupt-handling routine in the IDT, then transfers control to the routine until it (the CPU) gives an interrupt return call (IRET), indicating the task is complete.

Interrupt Latency

The delay in servicing an interrupt request is known as interrupt latency. It is not a problem with devices that are not sensitive to timing inconsistencies (such as hard-disk controllers or video boards). But it is a problem with high-speed, asynchronous communications (9,600 bps and above), which are highly time-sensitive operations.

Interrupt Overhead

The cumulative demand on your computer's central microprocessor by peripheral devices that generate interrupt requests is referred to as interrupt overhead. Such devices include hard-disk controllers, network interface cards, parallel and serial ports.

Interrupt Request

IRQ. This is the communications channel through which devices issue interrupts to the interrupt handler of an IBM PC or IBM compatible PC's microprocessor. It's the channel through which these devices get the microprocessor's attention. Different IRQs are assigned to different devices. This assignment pattern differs from PC to PC. Many LAN interface cards use an IRQ to get to the microprocessor. You must be sure that your LAN interface card is not trying to use the IRQ assigned to another peripheral, like the hard disk controller or EGA card. See also IRQ for a different and longer explanation.

Interrupt Request Lines

Hardware lines over which devices can send signals to get the attention of the processor when the device is ready to accept or send information. Typically, each device connected to the computer uses a separate IRQ.


An automatically operated electromechanical device used to turn lights, bells or other signals on and off in timed sequences. An interrupter makes lights wink on and off on a key system. Or did, when everything was electromechanical. It was used on 1A key telephone systems.

Interrupting Equipment

Motor-driven mechanical devices used to break the ringing generator's output into ringing and silent periods, creating the busy and ringback tone pulses .

Intersatellite Link

A message transmission circuit between two communication satellites , as opposed to a circuit between a single satellite and the earth.


The full name is InterSpan Frame Relay and it's AT&T's new frame relay data communications service, announced in the late fall of 1991.


A Russian satellite system similar in concept to the West's Intelsat, except that it's set up by Russia and the Eastern bloc countries . Two US carriers , AT&T and IDB Communications, once used Intersputnik to alleviate their shortage of US-Russia circuits. See INTELSTAT.


Literally, between states (crossing a state line). Services, traffic or facilities that originate in one state, crossing over and terminating in another.

Interstate Highway System

When the U.S. Interstate Highway System was begun during the Einsenhower era, it was required that one mile in every five must be straight. These straight sections would be usable as airstrips in times of war or other emergencies.


In cable construction, the spaces, valleys or voids between or around the cable's components.

Interswitch Trunk

A circuit between two switching machines.

Intersymbol Interference

ISI. Intersymbol interference is a source of noise in baseband signaling that occurs when the signal pulses or symbols spread into adjacent pulses or symbols. This spreading effect occurs when the signal varies with frequency or when portions of the signal are delayed due to multipath fading. See also Baseband and Multipath Fading.

Intertandem Trunk Groups

A category of trunk groups that interconnects tandems.

Intertoll Trunks

Trunks connecting Class 4 and higher switching machines in the AT&T long distance network.


Time. Pulse interval, for example, means the time from the start of one pulse to the start of the next.


The ability to seamless communicate between devices supporting dissimilar protocols, such as frame relay and ATM, by translating between the protocols, not through encapsulation. Many carriers are planning to implement the necessary equipment and conversion algorithms to allow the network itself to transparently convert from frame relay to ATM, and vice versa.




Intra means inside. Intrastate means inside the state. Interstate means between states.

Intra-Area Cell Transfer

A cellular radio term. A cell transfer between two cells that are controlled by the same serving Mobile Data Intermediate System (MD-IS).

Intrabuilding Backbone

Telecommunications cable(s) that are part of the building subsystem that connect one closet to another.


This is an outside plant term. Intracalling refers to the ability of a remote line concentrator to interconnect users served by the same concentrator without providing two trunks directly back to the central office.

Intraday Distribution

A call center term. A historical pattern consisting of factors for each intra-day period of the week that define the typical distribution of call arrival or average handle time throughout each day. Each factor measures how far call volume or average handle time in that half hour or quarter hour deviates from the average half-hourly or quarter-hourly figure for that day. This information enables the program to forecast intraday call volumes and staffing requirements.

IntraEnterprise Communications

Communications that are exchanged within a single organization (including multiple sites of the organization).


Any traffic or service within an exchange area or serving area.


This is an automatic call distribution term. It refers to the ability to select a second or subsequent group of agents to backup the primary agent group. This is designed to allow the caller to be serviced more efficiently and less expensively.

Intraframe Coding

A way of video compression that compresses information within a single frame. Compare to Interframe Coding.


Telecommunications services that originate and terminate in the same Local Access and Transport Area. See also Local Access and Transport Area. This can be either Interstate or Intrastate service, traffic or facilities.

Intramodal Distortion

In an optical fiber, the distortion resulting from dispersion of group velocity of a propagating mode. It is the only form of multi mode distortion occurring in single-mode fibers.


A private network that uses Internet software and Internet standards. In essence, an Intranet is a private Internet reserved for use by people who have been given the authority and passwords necessary to use that network. Those people are typically employees and often customers of a company. An Intranet might use circuits also used by the Internet or it might not. Companies are increasingly using Intranets ” internal Web servers ” to give their employees easy access to corporate information.

According to my friends at Strategic Networks Consulting, Boiled down to its simplest, an Intranet is: a private network environment built around Internet technologies and standards ” predominantly the World Wide Web. The primary user interface, called a Web browser, accesses Web servers located locally, remotely or on the Internet. The Web server is the heart of an Intranet, making selection of Web server software a crucial decision, even though much fanfare has focused on browsers (Netscape's Navigator vs. Microsoft's Explorer).

At its core, a Web server handles two arcane languages (HTML and CGI) that are the meat and potatoes of generating Web pages dynamically, making connections and responding to user requests. But in the rush to dominate the potentially lucrative Intranet market, these simple Web functions are being bundled into operating systems and vendors are now touting pricey "Intranet suites" which encompass everything from database and application interfaces, to e-mail and newsgroups, to the kitchen sink.

Most medium- or larger- sized companies will need more than just a handful of simple Web servers to deploy a reasonably robust Intranet. To help a company post current job openings, or make up-to-date product specs and available inventory accessible by traveling sales reps, an Intranet needs the following capabilities:

  • Database access. Getting at critical data housed in corporate databases can be accomplished via generic, universal ODBC linking or based on "native" links directly to Sybase, Oracle et al. allowing use of all the database's features.

  • Application hooks. Used by developers, a standard programming interface (API) allows outside applications like Lotus Notes to interact with Web data and vice versa. In addition, proprietary APIs exist ” most notably Microsoft's ISAPI (for "Internet Server API") which lets developers link directly to Microsoft applications.

  • User publishing. In addition to dialogues via chat/newsgroup/bulletin board features, users will want to post their own content on Web servers without having to attain Webmaster status.

  • Search vehicles. How does an engineer find the current specs on Project #686-2 among thousands of pages spread across a bunch of Web servers? The answer: an indexing and search engine that creates an internal Yahoo! for your own Web sites.

  • Admin/management. A catch-all for loads of important, but still ill-conceived features for managing access, users, content and the servers themselves . Intranet administrators are currently fascinated with analyzing Web server logs which contain data of some sort, including user connections and page activity. According to a white paper released by Sun Microsystems in the summer of 1996, the basic infrastructure for an intranet consists of an internal TCP/IP network connecting servers and desktops, which may or may not be connected to the Internet through a firewall. The intranet provides services to desktops via standard open Internet protocols. In addition to TCP/IP for basic network communication, these also include protocols for:

    File Service


    Mail Service


    Naming Service


    Directory Services


    Booting Services


    Network Administration


    Object Services


See also Extranet and Intranet.

Intranodal Service

A feature of "intelligent remotes" (i.e., intelligent remote switching nodes), intranodal service refers to the ability of the node to continue to switch calls within its own geographic domain, even if the signaling and control link to the CO (Central Office) fails. This capability usually is limited to the basic switching of voice calls. More complicated processes, such as the support of custom calling services or other complex features, are interrupted until such time as the signaling and control link can be restored to the CO, where the majority of programmed logic and memory reside.


Communications path which originates and terminates in the same node. See Intranodal Service for a fuller explanation.

Intraoffice Call

A call involving only one switching system.

Intraoffice Trunk

A telephone channel between two pieces of equipment within the same central office.


An entrepreneur who works inside a big company. Hence, intra, as in inside. It's hard to imagine it actually happening. But the word has became popular as a way for large companies to motivate their employees to take personal career risks and introduce new products.


Services, traffic or facilities that originate and terminate within the same state. Therefore, if related to telephone, falling under the jurisdiction of that state's telephone regulatory procedures.


A term coined by "Data Communications" and referring to the software, hardware, and Internet services underlying a corporate Intranet.

Intrinsic Joint Loss

That loss in optical power transmission, intrinsic to the optical fiber, caused by fiber parameters, e.g., dimensions, profile parameter, mode field diameter, mismatches when two non identical fibers are joined.


Intrinsics are a component of many windows toolkits. The windows toolkit intrinsics definition has been developed by the MIT X Consortium. The intrinsics define the function of specific graphical user interface and window objects. They do not define any particular look or feel, just the function. Example: A pull down menu intrinsic would define the function of a pull down menu within a toolkit but not the appearance of it.

Intrusion Detection

A technology that gathers and analyzes information across gateways, servers, and desktops to identify possible security breaches that can occur from within or outside an organization. A related area of intrusion detection is vulnerability assessment, which uses scanning technology to determine misconfigurations or other security vulnerabilities contained within a computer system or network.

Intrusive Scan

See Port Services.

Intrusive Test

Breaking a circuit in order to test its functionality. Testing intrusively will drop service on the circuit.


Internet Services. IETF's model to transport audio, video, real-time and traditional data within a single architecture.


International Telecommunications Users Group.


The cognition (i.e., knowledge) or understanding of something without evident rational thought or inference. User interfaces to devices, systems and software applications often are touted as being "highly intuitive." That means that the manufacturer claims that anyone of normal intelligence can operate the thing without having to read the manual. Such claims are always inflated, to put it politely. See also Cockpit Problem, Help Desk, Idiot-Proof, and RTFM.

Intumescent Firestop

A firestopping material that expands under the influence of heat.

Invar Shadow Mask

A special type of shadow mask that is made out of Invar, an alloy that is able to withstand the high temperature generated by an electron beam. An Invar shadow mask allows the CRT to generate a brighter image than a conventional shadow mask. An Advanced Invar Shadow Mask improves brightness by 40% over a standard shadow mask.

Inventory Workdown

In 1999 and 2000, the telecom industry shipped too much equipment. When demand dropped off, a lot of it languished in warehouses and factories. As demand picked up, inventories sitting around began to drop. That phenomenon became known as inventory workdown. The theory was when the inventory was worked down to a normal level (whatever that is), factory shipments would pick up. It sort of started to happen at the end of 2001.

Inverse ARPA

See Reverse DNS.

Inverse Fourier Transform

Inversion of Fourier transform to convert frequency representation of signal to time representation.

Inverse Multiplexer

I-Mux. An inverse multiplexer performs the inverse function of a multiplexer. "Multiplexer" translates to "many fold." For example, a TDM Mux (Time Division Multiplexing Multiplexer) accepts many (typically 24) low-capacity inputs in the form of information streams, and folds them together through a process know as byte interleaving in order to send them over a single, high-capacity, shared digital circuit. In this example, each of the 24 voice-grade channels supports a transmission of 64 Kbps; the total capacity of the T-1 circuit is 1.536 Mbps. The advantage of this approach is that of economy of scale ” a single, high-capacity T-1 circuit is far less expensive that are 24 individual voice-grade circuits. An inverse multiplexer does just the inverse. In other words, it accepts a single, high-capacity information stream and splits it up into multiple information streams, each of which is sent over a separate and lower-capacity circuit; the process is reversed on the receiving end. Videoconferencing, for example, may make use of inverse multiplexers. A full-motion videoconference requires a full T-1. While a user organization may have multiple T-1s at a given site, a full T-1 may not be available at the moment it is required. Therefore, an inverse mux might split that video datastream into four data streams of 384 Kbps, and send each over six channels of four separate T-1s. At the receiving end of the video datastream, the four data streams are received, demultiplexed and resynchronized in order to reconstitute the original datastream. Resynchronization is critical, as each of the four circuits may impose different levels of propagation delay on the signal due to reasons such as differing route lengths. Synchronization prevents your head (which traveled over T-1 #1) from appearing at your knees (which traveled over T-1 #3) on the receiving TV monitor. Inverse Multiplexing over ATM (IMA) is an access specification approved in 1997 by the ATM Forum. This User-Network Interface (UNI) standard allows a single ATM cell stream to be split across multiple access circuits from the user site to the edge of the carrier's ATM network. In an ATM LAN application, for instance, the ATM switch deployed in the enterprise backbone typically operates at 155 Mbps or 622 Mbps. In this example, ATM traffic from the enterprise to the public ATM carrier-based network, requires 6 Mbps-well more than the level supported by a T-1, but less than a full T-3. Rather than subscribing to a T-3, which requires a fiber optic access circuit and which is very expensive, IMA is used. Thereby, the ATM data stream is split across four T-1 circuits by an access concentrator which possesses IMA capability. The IMA process works in a round- robin fashion, with cell #1 traveling over T-1 #1, cell #2 traveling over T-1 #2, and so on. Each of the four T-1 circuits is relatively inexpensive, can be provisioned over twisted-pair, and is readily available. At the edge of the carrier network, the ATM switch receives each of the four separate data streams, and reverses the IMA process in order to reconstitute the original datastream, which then is switched and transported through the network to the far edge. At that far edge, the IMA process may take place again, from the edge of the carrier network, over four T-1s, and to the IMA-capable ATM concentrator on the user premises. See also ATM and TDM.

Inverse Multiplexing

The process of splitting a single high-speed channel into multiple signals, transmitting each of the multiple signals over a separate facility operating at a lower rate than the original signal, and then recombining the separately-transmitted portions into the original signal at the original rate. See Inverse Multiplexer for a full description of the process. Inverse multiplexing is also called loop bonding. See Loop Bonding.

Inverted Backbone

A network architecture in which the wiring hub and routers become the center of the network; all the network segments attach to this hub.

Inverted Rotary Converter

A motor driven device that produced dial tones, busy tones, ringing signals, etc. and was used in conjunction with 701 type step-by-step electromechanical switches.


  1. A device which converts direct current electricity to alternating current electricity, often used to power AC devices in a car.

  2. See Analog Inverter and Digital Inverter.

Invitation To Send

A character or sequence of characters which calls for a station to begin transmission. Usually this is part of a polling arrangement.

Inward Operator Trunk Group

A trunk group used to provide distant operators with the means of obtaining an inward operator's assistance for the completion of calls. A typical application commonly employs a tandem to cord switchboard type trunk group.

Inward Restriction

A Centrex service feature which stops Centrex lines from receiving certain incoming calls.

Inward Trunk

Used only for incoming calls, these trunks cannot dial out. "800" lines, for example, can only be used to receive calls.


INward Wide Area Telephone Service. A service of interexchange carriers (e.g., AT&T, MCI, and Sprint), local exchange carriers, the Bell operating companies and the independent phone companies and long distance resellers in North America which allows subscribers to receive calls from specified areas (depending on the rate band chosen ) with no charge to the person who's calling. Rather, the charges are billed to the called party. See 800 Service for a much bigger explanation.


See Interim Operating Authority.


  1. Inter-Office Channel.

  2. Independent Operating Carrier.


Identified Outward Dialing. See also AIOD and Call Accounting System.


Input/Output Engine. The part of the Novell SFT III operating system that handles physical processes, such as network and disk I/O, hardware interrupts, device drivers, timing, and routing. SFT III is split into two parts: the IOEngine and the MSEngine (Mirrored Server Engine). The IOEngine routes packets between the network and the MSEngine. To network workstations (i.e. PCs on the LAN), the IOEngine appears as a standard NetWare router or bridge. The primary server and the secondary server each have an IOEngine, but they share the same MSEngine. Because the IOEngines are not mirrored, NetWare Loadable Modules (NLMs) and applications that directly interface with hardware, such as backup NLMs may be installed in the IOEngines on both the primary and the secondary server. See MSENGINE.


Inter Office Facility.

Ion Exchange Technique

A method of fabricating a graded-index optical fiber by an ion exchange process.


The process of breaking up molecules into positively and negatively charged carriers of electricity called ions.


A type of energy, in the upper end of the electromagnetic spectrum, that has the ability to strip electrons from molecules, thus forming a new, distinct ion or compound.


Internal Organization of the Network Layer. The OSI standard for the detailed architecture of the Network layer. Basically, it partitions the Network layer into subnetworks interconnected by convergence protocols (equivalent to internet working protocols), creating what the Internet community calls a catenet or internet.


That part of the atmosphere in which reflection and/or refraction of electromagnetic waves occurs. It extends from about 70 to 500 kilometers. At that point, ions and free electrons exist in sufficient quantities to reflect electromagnetic waves.

Ionospheric Absorption

Attenuation of the energy in a radio wave due to the interaction between it and gas molecules. Deviative absorption describes the appreciable bending that occurs in an ionospheric layer at close to critical frequency. Non-deviative absorption describes the condition where little or no bending occurs as the wave passes through an ionized layer. See Ionosphere.

Ionospheric Cross Modulation

Nonlinearities within the medium can produce nonlinear absorption. This can lead to the modulation on a strong signal being transferred to a weaker carrier. Sometimes described as the Luxembourg effect.

Ionospheric Disturbance

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

Ionospheric Focusing

A variation in the curvature of the ionospheric layers can give rise to a focusing/defocusing effect at a receiving antenna. This may produce either an enhancement or attenuation in the received field strength due to signal phase variations.

Ionospheric Refraction

The change in the propagation speed of a signal as it passes through the ionosphere.


  1. Input/Output Processor.

  2. Interoperability: The ability of equipment from different manufacturers (or different implementations) to operate together.


Internet OPerators Group. On May 20, 1997 Nine of the nation's major Internet service providers announced the formation of IOPS.ORG, a group of Internet service providers (ISPs) dedicated to making the commercial Internet more robust and reliable. IOPS.ORG will focus primarily on resolving and preventing network integrity problems, addressing issues that require technical coordination and technical information-sharing across and among ISPs. These issues include joint problem resolution, technology assessment, and global Internet scaling and integrity. IOPS.ORG will provide a point-of-contact for these industry-wide technical issues.

The founding members of IOPS.ORG are ANS Communications, AT&T, BBN Corporation, EarthLink Network, GTE, MCI, NETCOM, PSINet, and UUNET, and it is expected that additional national and international Internet operators will join. IOPS.ORG will work with other Internet organizations, with Internet equipment vendors, and with businesses that rely on the Internet. IOPS.ORG members individually will continue to support other Internet organizations such as the Internet Engineering Task Force (IETF), the North American Network Operators Group (NANOG), and the Internet Society.

The Corporation for National Research Initiatives (CNRI), a Reston, VA-based not-for- profit organization which works with industry, academia, and government on national-level initiatives in information technology, will host the initial operations of IOPS.ORG. "IOPS.ORG will play a key role in the healthy technical and operational evolution of the Internet as an increasingly important component of the economy," said CNRI President Robert Kahn.


Index of Refraction. The ratio of light velocity in a vacuum to its velocity in a given transmission medium, such as an optical fiber.


  1. Internetwork Operating System from Cisco. This operating system runs the vast majority of routers now deployed in the core of the Internet. See also Junos Code.

  2. See ISO.


Iota, written as i or sometimes j in electrical engineering is the square root of -1. The concept of iota was introduced by Leonhard Euler, Swiss Mathematician. The important property of i (or j) is that it maps any kind of differential, whether application in differential amplifier of differential dense wave multiplexing or differential time division multiplexing. To understand i (or j) more deeply, one has to attempt a conjecture of number theory.......or simply apply intuition.


See Internet Open Trading Protocol.


  1. The Internet Protocol. IP is the most important of the protocols on which the Internet is based. The IP Protocol is a standard describing software that keeps track of the Internet's addresses for different nodes, routes outgoing messages, and recognizes incoming messages. It allows a packet to traverse multiple networks on the way to its final destination. Originally developed by the Department of Defense to support interworking of dissimilar computers across a network. While its roots are in the ARPAnet development, IP was first standardized in RFC 791, published in 1981, and updated in RFC 1349. This protocol works in conjunction with TCP and is usually identified as TCP/IP. It is a connectionless protocol that operates at the network layer (layer 3) of the OSI model. See IP Address, IPv4, IPv5, IPv6, the Internet, and TAPI 3.0.

  2. Intelligent Peripheral. A device in an IN (Intelligent Network) or AIN (Advanced IN) that provides capabilities such as voice announcements, voice recognition, voice printing and help guidance. By way of example, MCI's 1-800-COLLECT makes use of IPs, which are specialized voice processing systems. The IP prompts the caller to enter the target telephone number and speak his or her name. The system then instructs the network to connect the call. Based on a spoken acceptance of the call by the called party, the system authorizes call completion.

  3. Information Provider. A customer that offers recorded information on its listed numbers.

  4. Intellectual Property. A legal term that refers to original creative work (a book, a movie, software code, etc.) manifested in a tangible form that can be legally protected, for example, by a patent, trademark, or copyright.

  5. Illustrative Paragraph. See Stupid.

IP Address

See Internet Address.

IP Address Confirmation

Also called IP Confirmation. Here's how it works. In order to send electronic mail over the Internet, you need what's called a SMTP (Simple Mail Transfer Protocol) server, a specialized computer to send your mail. If you have your own domain name, like, then it's easy to set up your own mail server. Most of us, however, don't. We need to use someone else's. In the good old days you could pretty well anyone's SMTP server. Simply tell your email client. These days many owners of SMTP mail servers got unhappy with people using their servers to spam (i.e. send zillions of unwanted email). So they set up a system to check the IP address from where you were coming before they allowed your email through. If your IP Address was one of the company's addresses, e.g. one you'd been assigned temporarily while you were on line, then they let your email through. If it wasn't, your email would be stopped . This process is called IP Address Confirmation.

IP Address Mask

Internet Protocol address mask. A range of IP addresses defined so that only machines with IP addresses within the range are allowed access to an Internet service. To mask a portion of the IP address, replace it with the asterisk wild card character (*), For example, 192.44.*.* represents every computer on the Internet with an IP address beginning with 192.44. See IP Addressing.

IP Addressing

A networking term. IP (Internet Protocol) addressing is a system for assigning numbers to network subdivisions, domains, and nodes in TCP/IP networks. IP addresses are figured as 32-bit (four-byte) numbers. The high bytes constitute the "Class A" and "Class B" portions of the address, which denote network and subnetwork. The low bytes ("Class C" address segments) identify unique nodes ” individual machines or (in the case of multi-addressing) individual node processes. The Class C address segment (two bytes) can represent 65,536 unique values ” enough so that in most conventional TCP/IP LANs, sufficient values are available to afford each machine its own "fixed" IP address. In public internet-access, however, the number of fixed addresses available to a provider may not be sufficient to provide each dialup client with a permanent IP address. In such scenarios, available Class C addresses can be assigned dynamically, as machines log into network access ports ” on the presumption that no more than N clients will attempt to log on, simultaneously (where N denotes the number of absolute addresses in the pool). Thus:

"Fixed" or "Static" IP address: a four-byte TCP/IP network address permanently assigned to an individual machine or account.

"Dynamically-assigned" IP address: a four-byte TCP/IP network address assigned to a machine or account for the duration of a single session.

IP Confirmation

Also called IP Address Confirmation. See IP Address Confirmation.

IP Datagram

The fundamental unit of information passed across the Internet. Contains source and destination addresses along with data and a number of fields which define such things as the length of the datagram, the header checksum, and flags to say whether the datagram can be (or has been) fragmented.

IP Device Control

IPDC. See Simple Gateway Control Protocol.

IP Edge Concentrator

An IP Edge Concentrator as defined by Seranoa Networks, is a subscriber aggregation device attached to an edge router at the POP of an IP service provider. It provides a high-capacity, cost-effective alternative to vendor-specific WAN line cards installed in edge routers. It operates as a layer 2 switch to forward low- speed subscriber access circuits (e.g. T-1) onto a high speed trunk (e.g., GigE) to the edge router. It may include a network processsor to offload various IP services from the edge router such PPP, Multilink PPP, IP DiffServ QOS, and traffic policing and rate limiting. This edge architecture enables IP service providers to reduce the cost of adding additional subscribers by 75%, increase edge capacity, improve performance and availability, enable auto recovery through router redundancy, and offer support for valuable multi-link services, according to Seranoa.

IP Masquerade

Also known as MASQ. A LINUX networking function similar to the NAT (Network Address Translation) function found in many network routers and firewalls. IP Masquerade allows multiple client computers internal to a premises-based network to share a single connection to the Internet or other IP-based network through a centralized LINUX MASQ server. The individual computers (e.g., client workstations) typically are attached to the server via a LAN (typically Ethernet), and may or or may not be running the TCP/IP protocol suite. As a workstation connects to the Internet through the MASQ server, the server translates the internal network address it uses into a registered IP address, which is required for access to the public Internet. As the destination computer responds to the public IP address, the server re-translates that address to the internal network address in order to deliver the data packets to the device that originated the data session. See also LINUX and NAT.

IP Multicasting

IP multicasting is a form of networking where one computer sends information out to a group of other computers at the same time. The originator achieves this by sending packets through a special multicast address, which delivers to a group of hosts, rather than a single (unicast) host. The number of receivers in a multicast session is not limited to bandwidth of the originator (as in the case of unicast). The technology has proven to be more efficient than sending a copy of the stream to all nodes since not all may want it and users are limited to a particular subnet (as in the case of broadcast). For IP multicast only one copy of the stream will pass over any link in the network ” thereby conserving bandwidth.


Internet Protocol PBX. An IP PBX connects its phones via an Ethernet LAN and sends its voice conversations in IP packets. There are pros and cons to IP PBXs. Moves and changes with the phones are easier. Wiring is easy. Voice quality and management controls vary between systems. The IP PBX is an evolving animal. See IP Telephony and TCP/IP.

IP Router

A computer connected to a multiple physical TCP/IP networks that can route or deliver IP packets between networks. See also Gateway.

IP Security

See IPsec.

IP Service Edge Switch

A IP switch platform for network services, such as secure Internet access, private intranets and extranets with quality of service, and managed network firewalls. This type of switch allows network operators to add services quickly through a graphical application set which is synchronized with the switch's command line interface. See IP Switching.

IP Spoofing

The use of a forged IP source address to circumvent a network firewall. The illicit packet seeking to gain access appears to have come from inside the protected network and to be eligible for forwarding into the network. In short, IP spoofing is an attack whereby a system attempts to illicitly impersonate another system by using its IP network address. See Firewall, IP, IP Address and IP Router.

IP Subnet

All devices which share the same network address. Routers are boundaries between subnets so each connection to a router has a different network address.

IP Switching

A term coined by Ipsilon Networks to describe a new class of switch it developed, combining intelligent IP routing with high-speed ATM switching hardware in a single, scalable platform. The IP switch implements the IP protocol stack on ATM hardware, allowing the device to dynamically shift between store-and-forward and cut-through switching based on the flow requirements of the traffic as defined in the packet header. Data flows of long duration can be optimized by cut-through switching, with the balance of the traffic afforded the default ATM treatment, which is hop-by-hop , store-and-forward routing. Ipsilon suggests that first-generation IP Switches can achieve rates of up to 5.3 million PPS (packets per second) by avoiding ATM cell segmentation and reassembly, ATM overhead, and ATM switch processing of each cell header. One of the advantages of IP Switching is the use of IP (Internet Protocol), which protocol is mature, well- understood , and widely deployed across a wide range of networks. Contrast with Tag Switching. See IP Service Edge Switch.

IP Telephony

Here is Microsoft's definition, excerpted from their white paper on TAPI 3.0: IP Telephony is an emerging set of technologies that enables voice, data, and video collaboration over existing IP-based LANs, WANs, and the Internet. Specifically, IP Telephony uses open IETF and ITU standards to move multimedia traffic over any network that uses IP (the Internet Protocol). This offers users both flexibility in physical media (for example, POTS lines, ADSL, ISDN, leased lines, coaxial cable, satellite, and twisted pair) and flexibility of physical location. As a result, the same ubiquitous networks that carry Web, e-mail and data traffic can be used to connect to individuals, businesses, schools and governments worldwide.

What are the benefits of IP Telephony? IP Telephony allows organizations and individuals to lower the costs of existing services, such as voice and broadcast video, while at the same time broadening their means of communication to include modern video conferencing, application sharing, and whiteboarding tools. In the past, organizations have deployed separate networks to handle traditional voice, data, and video traffic. Each with different transport requirements, these networks were expensive to install, maintain, and reconfigure. Furthermore, since these networks were physically distinct, integration was difficult if not impossible , limiting their potential usefulness .

IP Telephony blends voice, video and data by specifying a common transport, IP, for each, effectively collapsing three networks into one. The result is increased manageability, lower support costs, a new breed of collaboration tools, and increased productivity. Possible applications for IP Telephony include telecommuting , real-time document collaboration, distance learning, employee training, video conferencing, video mail, and video on demand. See the Internet, IP Telephony Algorithms, TAPI, TAPI 3.0 and TCP/IP.

IP Telephony Algorithms

The major IP Telephony Algorithms in the market today (fall of 1997), according to a white paper, called "IP Telephony powered by Fusion" from Natural MicroSystems (, include:

  • MS-GSM: This algorithm, marketed by Microsoft, runs at 13kbps and is a derivative of the ITU (International Telecommunications Union) standard GSM work. GSM is used in 85 countries around the world as the standard for digital cellular communications. Microsoft's implementation varies from the standard in several ways including how the encoded data is represented and what aspects of the encoder are supported. Natural MicroSystems provides an MS-GSM encoder that is compatible with Microsoft's Win95/WinNT embedded product.

  • ITU G.723.1: This algorithm runs at 6.3 or 5.4 kbps and uses linear predictive coding and dictionaries which help provide smoothing. The smoothing process is CPU- intensive , however (30Mips on an Intel Pentium), so don't expect a PC-based implementation to work well for lots of real-time activity.

  • VoxWare: This is a proprietary encoder that has been bundled by Netscape with their Browser. It delivers 53:1 compression and very low jitter. VoxWare presents very low network bandwidth requirements; however, it also has lower speech quality.

Most speech encoder algorithms have a set of rules concerning packet delivery and disposition management. This is often called jitter buffer management. "Jitter" in this case refers to when the signal is put into frames. The decoding algorithm must decompress and sequence data and make "smoothing" decisions (when to discard packets versus waiting for an out-of-sequence packet to arrive ). Given the real-time nature of a live connection, jitter buffer management policies have a large affect on voice quality. Actual sound losses range from a syllable to a word, depending on how much data is in a given packet. The first buffer size is often a quarter-second, large enough to be a piece of a word or a short word ” similar to drop-outs on a cellular connection in a poor coverage area.

IP Telephony Gateway

ITG. Also called a Voice over IP (VoIP) Gateway. A bridge between traditional circuit-switched telephony and the Internet that extends the advantages of IP telephony to the standard telephone by digitizing the standard telephone signal (if it isn't already digital), significantly compressing it, packetizing it for the Internet using Internet Protocol (IP), and routing it to a destination over the Internet.

IP Tunneling

IP Tunneling means carrying a foreign protocol with a TCP/IP packet. For example, IPX can be encapsulated and transmitted via TCP/IP.


Internet Protocol Virtual Private Network. An IP VPN is a private network connecting any number of end points using private circuits and a shared core. It carries IP traffic - voice, video and data traffic.


Intellectual Property Attorney.


Installation Package.


The International Passenger Airline Reservation System. An IBM-originated term.


An alliance of ISPs (Internet Service Providers) and IAPs (Internet Access Providers) to provide roaming capabilities for travelers. Based on proprietary standards, roamers are authenticated before being afforded Internet access. Usage is cross-billed through the I-PASS clearinghouse, with fees being set by each ISP for use of its facilities by roamers. I-PASS includes over 100 member ISPs in approximately 150 countries, and includes over 1,000 POPs (Points of Presence). I-PASS competes with GRIC (Global Reach Internet Connection). The IETF's Roamops working group is developing a standard for roaming, as well. See also GRIC and ROAMOPS.


  1. Interprocess Communications. A system that lets threads and processes transfer data and messages among themselves; used to offer services to and receive services from other programs. Supported IPC mechanisms under MS OS/2 are semaphores, signals, pipes, queues, shared memory, and dynamic data exchange.

  2. Interprocessor Communication. See InfiniBand.


Initial Paging CHannel is the channel number used by your cellular provider to "page" the phones on the system. The term "paging" refers to notifying a particular phone that it has an incoming call. All idle, turned-on phones on a system monitor the data stream on the IPCH. Non-wireline cellular carriers use channel 0333 as the IPCH, while wireline providers (those operated by a telephone company use channel 0334).


See Integrated Personal Computer Interface.


A utility program used to list various Internet Protocol configuration information, including host address, subnet mask, and gateway addresses.


IP Control Protocol; protocol for transporting IP traffic over a PPP connection.


Internet Protocol Device Control. See MGCP and Simple Gateway Control Protocol.


Internet Protocol Data Record. A developing standard for an open billing method for IP (Internet Protocol) traffic. IPDR is intended to specify a common format for billing records and billing procedures in order that IP-based carriers can exchange billing information easily and, thereby, to enable the internetwork provisioning and billing of a wide variety of value-added IP-based services and applications. IPDR is an initiative of


Intelligent Printer Data Stream. It's IBM's host-to-printer page description protocol for printing. You can now buy kits which let you use your present printer to emulate an IBM printer.


Intelligent Peripheral Equipment. Northern Telecom's term for being able to extend all the features of its PBX over distances longer than a normal extension in a building. See Fiber Remote.


International Portable Equipment Identities. A wireless term.


If the Product Ever Materalizes.


IntraLATA Primary Interexchange Carrier.


Initial Program Load.


International Private Leased or Line Circuit.


Interruptions Per Minute or Impulses Per Minute.


Integrated Public Number Database.


IPng. IP Next Generation. Collective term used to describe the efforts of the Internet Engineering Task force to define the next generation of the Internet Protocol (IP) which includes security measures, as well as larger IP addresses to cope with the explosive growth of the Internet. The were three candidate protocols for IPng (CATNIP, TUBA and SIPP), were blended into IPv6, which is in trial stages at the time of this writing. See IPv6.


International Private Network Service. It actually international private line service and it's typically a circuit from 9.6 Kbit/sec up to T-1 or E-1. Domestically you would simply call it "Private line data service."


IPP is the Internet Print Protocol, a collection of IETF standards developed through the Printer Work Group,, that will make it as easy to print over the Internet as it is to print from your PC. IPP uses the HTTP protocols to "POST" a supported MIME Page Description Language file to a printer. Printers are given Internet addresses such as,, so they can be located on the Internet. IPP has the support of all the major printer companies including, Xerox, HP, Lexmark, IBM as well as Novell and Microsoft. Since fax, at a sufficient level of abstraction, is "remote printing," work is under way to create a Fax Profile for IPP as well, so that IPP can duplicate the legal as well as common practices of fax transmissions. Richard Shockey. contributed this definition. Thank you.


Initial Public Offering. Start a company. Some years later, take it public. Come out at $12. A week later, your stock is at $24. You're a success, and rich. IPOs are critical in saying "Thank You" to all your hardworking employees. See also Initial Public Offering.


IP (Internet Protocol) Phone over Data. There tend to be two variations ” emulation and driving. The emulation iPOD connects directly to digital station ports on a PBX and emulates a digital PBX feature phone. The emulation iPOD also enables the new PC IP PBX vendors to interoperate with enterprise PBXs. The driving iPOD drives digital PBX phones in the same fashion as if the phone were connected directly to a PBX station circuit card. The driving iPOD can enable the new PC PBX vendors to use existing desk sets in the enterprise. Both versions of the iPOD provide a TCP/IP interface for the purpose of transporting the voice and call control signaling associated with a PBX digital station call over a packet network. Protocols, DSP algorithms, densities and different form factors all constitute possible platform variations.


Intellectual Property Rights.


Internet Protocol Routing Service. Defined by Bell Atlantic as "a low-cost access service for ISPs. This service supports basic dial, ISDN, and dedicated requirements for transparent connectivity from the end-user to the ISP."


  1. Internet Protocol Suite. See also IPS7.

  2. Inches Per Second. A measurement of the speed of tape movement. Industry standards are as follows : 15132 ips, 15116 ips, 1-718 ips, 3-314 ips, 7-112 ips, 15 ips.

  3. Intrusion Protection System. See NIP.


Internet Protocol Signaling 7. A Nortel initiative for a standardized signaling and control protocol between PSTN networks and multimedia IP-based networks. SS7 (Signaling System 7) is the international standard for signaling and control in the circuit- switched PSTN (Public Switched Telephone Network). There is no standard protocol for VoIP (Voice over Internet Protocol), and no standard protocol for the interexchange of signaling and control messages between VoIP networks and the PSTNs. Such interexchange is required in order that support for CLASS (Custom Local Access Signaling Services) services (e.g., Call Forwarding, Call Waiting, and Calling Line ID) can be supported seamlessly across the PSTN and VoIP networks. A standard, open architecture for IPS7 has been submitted by Nortel to the IETF (Internet Engineering Task Force) for its consideration. See also IP, PSTN, SS7, and VoIP.


A collection of IP security measures that comprise an optional tunneling protocol for IPv6. IPsec supports authentication through an "authentication header" which is used to verify the validity of the originating address in the header of every packet of a packet stream. An "encapsulating security payload" header encrypts the entire datagram, based on the encryption algorithm chosen by the implementer. See also Authentication, Encryption, IPv6, and Tunneling.


IP Telephony.

IPT Gateway

IP Telephony Gateway. Imagine you and I work for a company which has a PBX ” a telephone system. You dial 234 to reach Harry. You dial 9 and a long distance number to dial your biggest client in Los Angeles. Now imagine you want to call your the company's branch office in London. You dial 22. You hear a dial tone. You then punch in 689. You hear another dial tone. Then you punch 123. Bingo, the boss of the London office answers. Here's what all those numbers mean. Dialing 22 dials you into a PC called the IP Telephony Gateway, which, on the one side, is connected to your PBX and on the other side is connected to a data line your company has between your office and your London office. Dialing 689 is you telling the IPT Gateway that you want to speak to the PBX in your London office. Dialing 123 tells the London PBX to dial extension 123.

That connection between your PBX and your London office's PBX might be anything from a dedicated private data line (e.g. part of your company's Intranet), to a virtual circuit on a Virtual Private Network (VPN) or it might be the public Internet. The IPT Gateway's major function is to convert the analog voice coming out of your PBX into VoIP (voice over Internet Protocol) and then send it on a packet switched data circuit which conforms to the IP. In short, an IPT Gateway allows users to use the Internet (or most likely an Intranet or Virtual Private Network) to talk with remote sites using (Voice over Internet Protocol).


On April 30, 1998, Ericsson Inc. released a press release which contained, inter alia, "Ericsson Inc. has developed a new IP telephony platform called Internet Telephony Solution for Carriers (IPTC) that raises the standard for IP telephony systems. IPTC offers phone-to-phone , fax-to-fax and PC-to-phone services over a TCP/IP network. It provides a superior operations and management (O&M) facility that moves IP telephony to a true carrier-class communications system. IPTC works by taking phone and fax calls that originate in the public switched telephony network (PSTN) and passing them to the IPTC platform, which carries them over the TCP/IP network to their destination where they are fed back to the PSTN network. PC-to-phone calls are taken directly from the TCP/IP network and carried to their destination in the same way...IPTC software runs on industry standard platforms that are based on Intel Pentium processors and Microsoft Windows NT...IPTC uses a Web-based management program to update and control multiple gateways. No longer is it necessary to change the parameters in individual gateways when IPTC can update all gateways within a network through one "netkeeper" applications program. The call and traffic control for individual gateways in a network is handled by sitekeepers. The sitekeepers connect to the netkeeper, which acts as a single point of control for the O&M functions of the whole IPTC platform. The netkeeper is not involved in the processing of calls but stores the platform topology information, routing configuration and alarm information. Other features included in the IPTC platform are least-cost routing, dynamic route allocation, multiple IP networks support, and the ability to handle validated and un- validated traffic. Real- time billing with fraud prevention and call duration advice with integrated voice response software is also provided."


Internet Protocol television. IPTV is a Microsoft project. The technology is designed to let telecommunications and cable companies offer new subscriber services that use their two-way broadband networks. Planned features for Microsoft IPTV include instant channel changing, interactive programming guides with integrated video and multiple picture-in-picture capability on standard TV sets. Microsoft said the technology will support high-definition television, "next-generation" (whatever that is) digital video recording and video-on- demand.


Intelligent Processing Unit. Another way of saying CPU. See CPU. Also Intelligent Peripheral Unit, the hardware associated with an intelligent peripheral. Also Alcatel's parlance for an actual workstation that's associated mostly with one of Alcatel's applications called the local applications platform or LAP and a software applications package called the monitor reset controller-2 or MRC-2. In short, everyone is using IPU to mean whatever cool thing they want it to mean. Certainly sounds cool.


Internet Protocol Version 4. The current version of the Internet Protocol, which is the fundamental protocol on which the Internet is based. Although its roots are in the initial development work for ARPAnet, IPv4 was first formalized as a standard in 1981. Since that time, it has been widely deployed in all variety of data networks, including LANs and LAN internetworks. While IPv4 served its purpose for some 25 years, it has lately proved to be inadequate, largely in terms of security and limitations of the address field. The address field is limited to 32 bits; although 2 to the 32nd power is a very large number, we are running out of IP addresses just as we have run out of 800 numbers and traditional area codes. Hence, the development of IPv6. See IP.


Internet Protocol Version 5. IPv5 is not exactly a missing link, although it might appear so. Rather, IPv5 was assigned to ST2, Internet Stream Protocol Version 2, which is documented in RFC 1819. ST2 is an experimental protocol developed as an adjunct to IP for support of real-time transport of multimedia data. See IP and IPv6.


Internet Protocol Version 6. The new proposed Internet Protocol designed to replace and enhance the present protocol which is called TCP/IP, or officially IPv4. IPv6 has 128- bit addressing, auto configuration, new security features and supports real-time communications and multicasting. IPv6 is described in RFC 1752, The Recommendation for IP Next Generation Protocol, including the strengths and weaknesses of each of the proposed protocols which were blended to form the final proposed solution. At the time of this writing, IPv6 is standardized, but not widely deployed. It requires upgrades that are expensive. They will be fork-lift upgrades in many cases. Therefore, IPv6 is being deployed pretty much only in the NextGen carrier networks, which are being built from the ground up. IPv6 offers 128-bit addressing, auto configuration, new security features and supports real-time communications and multicasting. The 128-bit addressing scheme will relieve pressure on the current 32-bit scheme, which is nearly exhausted due to the widespread use of IP in the Internet and a wide variety of LAN, MAN and WAN networks. Clearly, 2 to the 128th power is a huge number, yielding a staggering number of IP addresses. According to Mark Miller of Diginet Corporation, it equates to approximately 1,500 addresses per square angstrom, with an angstrom being one ten-millionth of a millimeter. Another way of looking at this is that IPv6 yields about 32 addresses per square inch of dry land on the earth's surface ” in other words, we are not likely to run out of IPv6 addresses. (Don't be surprised to see your telephone assigned an IP address in the future.)

Autoconfiguration Protocol, an intrinsic part of IPv6, allows a device to assign itself a unique IP address without the intervention of a server. The self-assigned address is based in part on the unique LAN MAC (Media Access Control) address of the device, which might be in the form of laptop computer. This feature allows the user the same full IPv6 capability when on the road as he might enjoy in the office when the laptop is inserted into a LAN-attached docking station. IPv6 security is provided in several ways. Data integrity and user authentication are provided by any of a number of authentication schemes. Second, the Encapsulating Security Payload feature provides for confidentiality of data through encryption algorithms such as DES (Data Encryption Standard). Several different types of IPv6 addresses support various types of communications. Unicast supports point-to-point transmission, Anycast allows communications with the closest member of a device group, and Multicast supports communications with multiple members of a device group.


Internet Packet eXchange. Novell NetWare's native LAN communications protocol, used to move data between server and/or workstation programs running on different network nodes. IPX packets are encapsulated and carried by the packets used in Ethernet and the similar frames used in Token-Ring networks. IPX supports packet sizes up to 64 bytes. Novell's NCP and SPX both use IPX. See also IPX.COM.

IPX Autodiscovery

The ability of a network manager to discover the node address and functionality of network devices.


The Novell IPX/SPX (Internetwork Packet eXchange/Sequenced Packet eXchange) communication protocol that creates, maintains, and terminates connections between network devices (workstations, file servers, routers, etc.). IPX.COM uses a LAN driver routine to control the station's network board and address and to route outgoing data packets for delivery on the network. IPX/SPX reads the assigned addresses of returning data and directs the data to the proper area within a workstation's shell or the file server's operating system. See also Netware.


Internetwork Packet Exchange/Sequenced Packet Exchange. Two network protocols. IPX is NetWare protocol for moving information across the network; SPX works on top of IPX and adds extra commands. In the OSI model, IPX conforms to the network layer and SPX is the transport layer.


IPX Control Protocol; protocol for transporting IPX traffic over a PPP connection.


A Novell specification describing the protocol to be used for exchanging router- to-router information to enable the transmission of Novell IPX data traffic across WAN (Wide Area Network) links.


  1. Infrared. The band of electromagnetic wavelengths between the extreme of the visible part of the spectrum (about 0.75 um) and the shortest microwaves (about 100 um). See Infrared and Infrared Technology.

  2. Internet Registry. See also Internet Assigned Numbers Authority.

  3. Investor Relations. That part of the company which handles investors ” private or institutions.

  4. Intermediate Reach. The distance specification for optical systems that operate effectively from 3 to 20 km (1.8 to 12.5 mi).


International Radiocommunications Advisory Committee. A committee established to provide advice to the Australian Communications Authority regarding international radio- communications matters.


Intelligent RAM. The idea is to put a microprocessor into a memory chip ” a move that dramatically improve computer performance.


  1. International Record (i.e. non-voice) Carrier. One of a group of common carriers that, until a few years ago, exclusively carried data and text traffic from gateway cities in the U.S. to other countries. The distinction between international companies providing "record" and data has eroded and now both types of companies provide voice and data services internationally.

  2. Internet Relay Chat. IRC is another Internet-based technology, like FTP, Telnet, Gopher, and the Web. Described in RFC 1459, IRC is live text communication between two or groups of people that uses special IRC software and ASCII commands. Each IRC is delegated to a single channel and each channel is dedicated to a different area of interest. Users enter the IRC channel on the basis of a "nick" (nickname). IRC requires special software, use of complicated ASCII-based commands and it doesn't have a graphical interface, so people more generally use World Wide Web-based chat rooms instead. See also Internet.

  3. Interference Rejection Combining. A cellular term.


Integrated Receiver/Descrambler. A receiver for satellite signals that also decodes encrypted or scrambled signals. Especially used in the cable TV business.


  1. A suite of protocols for infrared (IR) exchange of data between two devices, up to one meter apart (20 to 30 cm for low-power devices). IrDA devices typically have throughput of up to either 115.2 Kbps or 4 Mbps. IrDA protocols are implemented in some cell phones, PDAs, printers and laptop computers. Specific standards have been set for Serial Infrared Link (SIR), Infrared Link Access Protocol (IrLAP), and Infrared Link Management Protocol (IrLMP). IrLAP explains how link initialization, device address discovery, connection start-up (including link data rate negotiation), information exchange, disconnection, link shutdown, and device address conflict resolution occur on an IR connection. IrLAP implements the high-level data-link control (HDLC) communications protocol for infrared environments; the rules for discovery and address-conflict resolution are IrLAP's most significant departure from HDLC. Transmission speeds included in the specifications range from 1.152 Mbps to 4.0 Mbps. Imagine that you're carrying around a small portable laptop, PDA or other device and you want to exchange data with your desktop, you simply aim the device at your desktop PC and transmit information back and forth. IrDA works like a charm . I've used it many times. I simply aim the back of my laptop at the back of another laptop. All of a sudden, one laptop's taskbar will pop up with a message "I smell another IrDA port. Want to transfer something." It pops up a screen asking you which file you want to send or receive....It couldn't be easier. frankly, I was surprised. It's a great tool for casual file transfer ” like the time I had given a PowerPoint presentation to some students at MIT and one asked for a copy of the presentation. I simply aimed my laptop at his...and bingo, my file was his. See also Infrared, IrLAP and IrLMP.

  2. InfraRed Data Association. A not-for-profit organization formed in 1993 to set and support hardware and software standards for infrared data transmission, IrDA membership now exceeds 160 corporations worldwide. Standards activities are across hardware, software, systems, components, peripherals, communications, and consumer markets.


Institute of Radio Engineers.


The Interrupt Request signal between a PCMCIA Card and a socket when the I/O interface is active.


The name for Motorola's original and incredibly ambitious satellite project "to bring personal communications to every square inch of the earth." The idea was that you could use an Iridium phone pretty well anywhere ” so long as you were outside (you had to be outside) and could "see" one of the Iridium satellites. According to Motorola, "for the first time, anyone, anywhere , at any time can communicate via voice, fax, or data." Iridium used the 1610 to 1626.5 MHz band. Motorola originally estimated the service costing $3 a minute. The idea is that we all carry an Iridium handset ” a device larger than today's cellular phone ” and that we talk directly from the phone to one of 66 (or so) Iridium LEO satellites circling the Earth at 480 miles up and then down to the satellite closest to the called person, then down to an Iridium phone on the ground or to a satellite dish, through landlines to the phone of the called person. The big benefit is that the system knows who you are and where you are the moment you turn on your phone ” like a cell phone. This way it can always complete calls from someone calling you who doesn't know ” or does- n't need to know ” where you precisely are. It was called Iridium after the element called iridium, which has 77 electrons, which used to be the number of satellites needed. In 1994, the number got cut to 66. But the name stuck. In November of 1992, Business Week estimated that putting up the full Iridium system would cost $3.4 billion. Iridium started launching satellites in November of 1997 and started service sometime in 1999, after many delays and several launches of new satellites to replace those that had failed. After months and months of trying, I finally got to test an Iridium phone. I was at a trade show in Australia. "Can I test the phone, please ?" I asked the nice man in the Iridium booth . "Sure," he answered, He handed me a brick-sized phone and said step outside. "Why outside?" I asked. "'Cause it doesn't work inside," he answered . I stepped outside with him. It took the phone a couple of minutes to find the satellites it needed, and another minute or so to dial my friend in London. When I finally got through, the quality of the conversation was O.K. But, oh what a cumbersome process to make a phone call! On Friday, August 13, 1999 (note the date), Iridium L.L.C. filed for Chapter 11 bankruptcy protection. The company had been delinquent on a $90 million interest payment and in default on more than $1.5 billion in bank loans. The entire Iridium network was scheduled to be de-commissioned in 2000. The plan was to de- orbit the satellite constellation, and for the satellites to burn up in the Earth's atmosphere. At the last minute, an entrepreneur stepped in and paid a reputed $25 million for the whole Iridium. The entrepreneur then turned around and signed a contract with the US Government to use Iridium for government and military purposes. You can subscribe to Iridium service and use it for data, voice an paging. Iridium owners are selling service to parts of the world with inadequate landline service. According to Iridium, 86% of the earth's landmass and of its oceans (da!) are in areas with inadequate landline service. See also LEO and Teledesic.


See iCalendar.

Irish Corrosion

Nasty English slang for a fiber optic cut.


  1. Inter-Repeater Link. A networking term. A mechanism for connecting two and only two repeater sets.

  2. In Real Life. An Internet term (sort of) ” and (sort of) the opposite of URL (Uniform Resource Locator). People who meet "In Real Life" don't meet in chat rooms over the Internet. Real life is good! The Internet is good, too. It's just not "real life."


InfraRed Link Access Protocol from IRDA, the InfraRed Data Association. IrLAP defines a link protocol for serial infrared links. IrLAP explains how link initialization, device address discovery, connection start-up (including link data rate negotiation), information exchange, disconnection, link shutdown, and device address conflict resolution occur on an IR (Infrared) connection. IRLAP implements the high-level data-link control (HDLC) communications protocol for infrared environments and adds procedures for infrared-based link initialization and shutdown plus connection start-up, disconnection, and information transfer. The rules for discovery and address-conflict resolution are IrLAP's most significant departure from HDLC. Until recently, IRDA's standards characterized infrared ports as serial links operating at speeds up to 115 Kbps. IRDA's latest standards allow transmission rates as high as 4 Mbps and provide for LAN access via a new IRLAN protocol. The 4 Mbps mode uses pulse-position-modulation data encoding with four possible chip or time-slice positions per data symbol. The system can recognize and prevent interference with UART-based systems by including a Serial Infrared physical-layer link Interaction Pulse (SIP) at least every 500 milliseconds . IRDA has developed APIs for accessing the infrared port. The first, IRCOMM, emulates existing communications device drivers to handle legacy serial and parallel-port connectivity. There's also a native API that infrared-aware programs can use to locate and communicate with each other.


InfraRed Link Management Protocol. See IrDA.


In Range of Building. An Underwriters Laboratories term to define where the protection of UL 1459 will apply. See UL 1459.


Hardware, as opposed to firmware and software. See also HEAVY IRON.


I/O Request Packet. Data structures that drivers use to communicate with each other. See Interrupt and IRQs.


Interrupt ReQuests. IRQs are found in PCs. IRQs are also called hardware interrupts. They are the way a device signals the data bus and the CPU that it needs attention. In more technical terms, an IRQ is a signal sent to the central processing unit (CPU) to temporarily suspend normal processing and transfer control to an interrupt handling routine. Interrupts may be generated by conditions such as completion of an I/O process, detection of hardware failure, power failures, etc. Devices that use hardware interrupts include the serial and parallel ports, mouse interface cards, modems, game ports, and even the hard disk on XTs. The original IBM PC and PC-XT had only seven hardware interrupts. The bigger AT bus extended that to 15. Until the advent of the 32-bit PS/2 micro-channel and the 32-bit EISA buses, hardware interrupts could not be shared by two or more devices within the PC. Thus if one device had a specific hardware interrupt, even though you weren't using it that time, nothing else could use it. When you start filling your PC with devices (and remember most PCs still use the old AT bus) ” like serial ports, modems and mice, you may suddenly find your modem no longer works. There are two solutions ” change the interrupts (either in software or using jumpers ), making sure no two devices are trying to share the same interrupt ” or simply remove one of the printed circuit devices you're not using from the bus. (That's typically my solution.) These are the "normal" IRQs used by current hardware devices in PCs. Below is a list of 16-bit IRQs as they have become used.

See also Interrupt and Interrupt Request.


In insulations, the exposure of the material to high energy emissions for the purpose of favorably altering the molecular structure by crosslinking.


Impossible to refute; incontestable; undeniable, as an irrefragable argument; irrefragable evidence.


Annoying entertainment and media spectacles you're unable to stop watching. The O.J. trial is a prime example.


Internet Research Steering Group. See IRTF.


Internet Research Task Force. The IRTF is a community of network researchers, generally with an Internet focus. The work of the IRTF, which is governed by its Internet Research Steering Group (IRSG), focuses on the areas of Internet protocols, applications architecture and technology. The IRSG is supervised by the Internet Architecture Board (IAB). Guidelines and procedures for IRTF Research Groups are described in RFC (Request For Comment) 2014.


Integrated Remote Test Unit.


Indefeasible Right of Use (or User). A term used in the underseas cable and fiber optic carrier business. Someone owning an IRU means he has the right to use the circuit for the time and bandwidth the IRU applies to. An IRU is to a submarine or fiber optic cable what a lease is to a building.


  1. Information Separator. A type of control character used to separate and qualify data logically. Its specific meaning has to be defined for each application.

  2. Interim Standard. EIA/TIA terminology for a "standard" before it becomes a standard. See EIA and TIA.

  3. Intermediate System: OSI terminology for a router, which functionally sits between devices on the originating and terminating ends of a session. Such a system provides forwarding functions or relaying functions or both for a specific service such as Frame Relay or ATM.


The EIA/TIA standard for Data Message Handler (DMH), a method used in the cellular industry for exchanging non-signaling messages between service providers on a near real-time basis. DMH originally was used to facilitate call hand-offs between carriers. It was extended to serve a number of other purposes. The DMH extension for fraud detection and prevention in known as NSDP-F (Non-Signaling Data Protocol for Fraud), and the extension for the transfer of billing and settlement information is known as NSDP-B&S.


Also known as Digital AMPS (D-AMPS). The EIA/TIA Interim Standard which succeeded IS-54, and which addresses digital cellular systems employing TDMA (Time Division Multiple Access). IS-136 also specifies a DCCH (Digital Control CHannel) in support of new features controlled by a signaling and control channel between the cell site and the terminal equipment. IS-136 also allows analog AMPS (Advanced Mobile Phone System) to coexist with North American TDMA on the same cellular network, sharing frequency bands and channels, which supports a smooth transition from analog to digital cellular. IS-136 gave rise to a high-tier standard for PCS (Personal Communications Services), developed by a Joint Technical Committee (JTC) comprising representatives from ATIS and the TIA. High-Tier PCS supports fast-moving vehicular traffic, much like traditional cellular. See also DCCH, PCS and TDMA.


8 Bit XT Bus

16 Bit AT Bus












IRQ3 COM2 & COM4 [a]






IRQ5 LPT2 [a]












IRQ10 Available [a]


IRQ11 Available [a]


IRQ12 Available [a]






IRQ15 Available [a]


[a] Available for assigning to new devices, such as network and video cards.


IRQs in alphabetical order:


ARCnet card


Bus Mouse




CD-ROM drive










Diskette Controller


Ethernet card (old ones)


Ethernet card (new ones)


Floppy Drive


Hard disk drive








Math Coprocessor


PC Timer

Printer 1


Printer 2


PS/2 Mouse


Real time




Sound Card


Tape Backup


This list is not set in concrete. These are suggestions and ideas. Experimentation is the best solution


Interim Standard 2000. The EIA/TIA Interim Standard for cdma2000, the 3G (3rd Generation) wireless mobile standard for cellular networks based on CDMA. See cdma2000 for a full explanation.


Interim Standard 41. A signaling protocol used in the North American standard cellular system. IS-41 defines the processes by which cellular providers accomplish signaling between MSCs (Mobile Switching Centers) and other devices for purposes of intersystem handoff and automatic roaming. IS-41 includes pre-call validation of the ESN/MIN combination in order to ensure the legitimacy of the originating device. The signaling protocol has been effective in countering "Tumbling" fraud. The IS-41 messaging language is supported by ISDN and X.25 networks. IS-41B defines Global Title Translation (GTT) , which translates dialed digits into a point code (network node) address and application address (sub- system number). IS-41C defines the formats and procedures for Short Message Service (SMS). IS-41D includes feature and service support for Calling Number ID (CNID), E911 (Enhanced 911), law enforcement intercept (wire-tapping). See also CNID, ESN, GTT, MIN, MSC, SMS, and Tumbling.


Interim Standard 41 Zero. The initial version of IS-41, which was released in February 1988. IS-410 defined the process for intersystem call hand-off.


Interim Standard 41a. A version of IS-41 which supports automatic roaming.


Interim Standard 41B. A version of IS-41 which defined Global Title Translation (GTT), the process of translating Global Titles (telephone numbers) into Point Codes. Point Codes are unique addresses of SS7 network nodes. See also Global Title, Global Title Translation, Point Code, and SS7.


Interim Standard 41C. A version of IS-41 which supports PCS SMS (Short Messaging Service), defining message formats and authentication standards. See also IS- 41, SMS and Authentication.


Interim Standard 41D. A version of IS-41 which addresses Calling Number ID (also known as Calling Line ID, or CLID), Enhanced 911, and Law Enforcement Intercept. See also IS-41.


Interim Standard 54. It is the dual mode (analog and digital) standard for cellular phone service in North America. In its analog form, it conforms to the AMPS standard. IS-54 is an EIA/TIA, developed with the involvement of the CTIA. Since 1995, IS-54 enhancements fall under IS-136. See IS-54B.


Interim Standard 54B, the second version of IS-54. IS-54B defined TDMA (Time Division Multiple Access), an access technique used in digital cellular networks. See also IS-136 and IS-54.


Interim Standard 55. Standard for TDMA digital cellular service, which is three times the capacity of today's analog cellular service. IS-55 is a fully digital cellular system.


The Interim Standard for the interface between cellular base stations and Mobile Traffic Switching Offices (MTSOs). Issued by the TIA subcommittee TR45.4, IS-634 standardizes the functionality of the A-interface associated with the handling of call processing in order that terminal equipment and MTSOs of disparate origin can interoperate in a predictable fashion. The interim standard is intended to support AMPS, N-AMPS, CDMA and TDMA. The first release of IS-634 employs SS7 and 64-Kbps PCM encoding.


The Interim Standard for a hybrid CDMA/TDMA wireless system.


Interim Standard 95. IS-95 is a TIA standard (1993) for North American cellular systems based on CDMA (Code Division Multiple Access), and is widely deployed in North America and Asia. IS-95a defines what generally is known as cdmaOne, which supports voice and 14.4 Kbps data rates. IS-95b supports data rates up to 115 Kbps. See also cdmaOne and IS-2000.


Intermediate System to Intermediate System. OSI link-state hierarchical routing protocol, based on DECnet Phase V routing, whereby intermediate systems (routers) exchange routing information based on a single metric to determine network topology.


  1. Interactive Services Association.

  2. Industry Standard Architecture. The most common bus architecture on the mother- board of MS-DOS computers. The ISA bus was originally pioneered by IBM on its PC, then its XT and then its AT. ISA is also called classic bus. It comes in an 8-bit and 16-bit version. Most references to ISA mean the 16-bit version (which carries data at up to 5 megabytes per second). Many machines claiming ISA compatibility will have both 8- and 16-bit connectors on the motherboard. In 1987 IBM introduced a 32-bit bus which it called MCA for Micro Channel Architecture, which is the internal bus inside some of IBM's line of PS/2 MCA machines. But MCA isn't popular because it is incompatible with ISA, so the industry (excluding IBM) invented a 32-bit bus called EISA which stands for Extended Industry Standard Architecture, which is compatible with ISA. EISA, however, suffered from some of the same problems as the MCA bus, namely it was complicated to program to get the card's full benefit. As a result, other buses have been invented, including the VL bus from VESA (the Video Electronics Standards Association) and Intel's PCI bus. PCI stands for Peripheral Component Interconnect. Both the VL and PCI buses claim to be more than 20 times faster than the ISA bus. The PCI bus, according to Intel, can transfer data at up to 132 megabytes per second. Until the advent of complex Windows graphics and imaging programs, the speed of the ISA was not a gating factor in a computer. As of writing, a VL bus could only handle three drop-in printed cards, while a PCI bus could handle 10. See also EISA and Microchannel.

ISA Configuration Utility

The Intel Architecture Lab has been co-developing the Plug and Play specifications with industry partners to ensure long-term compatibility across cards, systems and software. IAL has openly licensed the necessary BIOS software to PC manufacturers so they can add Plug and Play capabilities to their systems. Intel Architecture Labs also designed the ISA Configuration Utility for system and add-in card manufacturers to include with their products. This software utility makes it easier for users to install existing ISA cards in their PCs. The software tells the user which resources are available, but configuration is still done manually. The utility also allows the user to optimize the way resources are assigned, which is particularly important for memory addresses.


Internet Security Association and Key Management Protocol. A protocol that provides a method for authentication of communications between peers over the Internet. ISAKMP provides a framework for the management of security keys, and support for the negotiation of security attributes between associated peers. ISAKMP/Oakley is a hybrid protocol that uses the ISAKMP framework to support the Oakley key determination protocol, which defines a method for establishing security keys for use on a session basis by Internet hosts and routers.


Indexed Sequential Access Method. It is a procedure for storing and retrieving data from a disk file. When the programmer designs the format of the file, a set of indexes is created which describes where the records of the file are located on the disk. This provides a quick method of retrieving the data, and eliminates the need to read all the data from the beginning to find the desired information. The indexes can be stored as part of the data file or in a separate index file.


Internet Server Application Program Interface. This API was created by Process Software Corp. and Microsoft and announced by Microsoft at the 1995 Fall Interop show. It is tailored to Internet servers and uses Windows' dynamic link libraries (DLLs) to make processes faster than under other APIs. It allows Internet browsers supporting it to access remote server applications from Microsoft and others. See ISAPI Filter.

ISAPI Filter

A World Wide Web term. An ISAPI Filter A replaceable DLL which the server calls whenever there is an HTTP request. When the filter is first loaded, it communicates to the server what sort of notifications will be accepted. After that, whenever a selected event occurs, the filter is called to process the event. Example applications of ISAPI filters include custom authentication schemes, compression, encryption, logging, traffic analysis or other request analyses.

Isarithmic Flow Control

Approach to flow control in which transmission permits circulate throughout network. Node wishing to transmit must first capture permit and destroy it, then recreate permit after transmission finished.


InterShelf Bus.


International Softswitch Consortium. The ISC describes itself thus: "The International Softswitch Consortium is the premiere public advocate for the worldwide advancement of softswitch network interoperability, promoting the growth of Internet-based multimedia communications and applications. The ISC, which has more than 140 members, was launched in May 1999 to support rapid advancement of application development for the evolving Internet protocol networks. Internet protocol networks are built on distributed servers generally called call agents, media gateway controllers, softswitches, application servers and media gateways. To further the development of open network architectures and standard interfaces, the ISC organizes interoperability test events, holds educational conferences, and establishes work groups to address current and emerging issues vital to the industry." See also Softswitch.


Internet Small Computer Systems Interface. iSCSI is an improved protocol for SANs (Storage Area Networks) or NAS ((Networked Attached Storage) to allow the transfer of large blocks of data between information repositories and hosts (i.e., file servers and clients) using an IP (Internet Protocol) infrastructure. iSCSI essentially is a transport protocol (Layer 4 in terms of the OSI Reference Model) for SCSI, riding on top of TCP/IP. In the past, such storage devices have used proprietary protocols or have appeared on the network as servers. But the devices did not appear as available storage on servers. Furthermore, because they were simply objects on the network, they suffered network traffic congestion along with everything else. iSCSI devices are different in that they are accessed via an iSCSI HBA (host bus adapter). To the computer, the HBA looks just like any other SCSI HBA: It appears to be a storage device that you'd access via the server, just as you would with a directly attached storage device, such as an internal disk or a SAN. To the network, the iSCSI HBA appears to be a NIC. It has an IP address and communicates using standard IP Ethernet network packets. The difference is, when the server needs to move some data to storage, it transfers the data to its HBA, where it becomes standard SCSI-3 data. The data is then enclosed in an IP packet and is sent out via the Ethernet network. Once it gets to the iSCSI storage device, the IP packet information is stripped off, and the data is moved to the device's internal SCSI controller, which in turn transfers it to disk. One advantage of iSCSI is that it's completely transparent. The server software sees only what appears to be a SCSI controller; the network only sees IP traffic. To the IT staff, it means that there's little new to learn. iSCSI uses standard Ethernet infrastructure and standard SCSI provisions in the server software. Because servers are talking to the network through their HBAs, implementing a separate storage network is easy and relatively cheap. Furthermore, because you're talking to your storage through Ethernet rather than Fibre Channel, you gain flexibility. For example, a standard SAN using Fibre Channel is limited to speeds of 2Gbps and fiber lengths of 30 kilometers. The iSCSI is standard TCP/IP ” thus of basically infinite length. Further if you run iSCSI over 10GbE (10 Gigabit Ethernet), you can run at five times as fast as the fastest SAN, and cover more distance. The management of an iSCSI storage network might also be easier than a traditional SAN, which often use proprietary management software. See also Fibre Channel, IP, NIC, SAN, SCSI, and VPN.


Integrated Services Control Point. Bellcore's ISCP software system manages and distributes the information needed to run intelligent networks that provide inexpensive, rapidly deployed customized service, according to Bellcore.


  1. Incremental Service Delivery.

  2. Information Systems Department.


Integrated Services Digital Line. Part of the family of xDSL technologies, ISDL is a means of provisioning ISDN BRI capacity of 128 Kbps to the premise without the need for upgrade of existing cable pairs. Such existing copper pairs are often in such poor condition as to deny the provisioning of conventional ISDN. See ISDN, xDSL, and ADSL.


Integrated Services Digital Network. ISDN is a set of international standards set by the ITU-T (International Telecommunications Union-Telecommunications Services Sector) for a circuit-switched digital network that supports access to any type of service (e.g., voice, data, and video) over a single, integrated local loop from the customer premises to the network edge. ISDN requires that all network elements (e.g., local loops , PBXs, and COs) be ISDN-compatible, and that the SS7 (Signaling System 7) be in place throughout the entire network. ISDN also specifies two standard interfaces ” BRI and PRI.

BRI (Basic Rate Interface) is the North American term for the low speed version known internationally as BRA (Basic Rate Access). It delivers a total of 144,000 bits per second and designed for the desktop. BRI also generically is known as 2B+D. The two B (Bearer) channels are information- bearing ; that is to say that they support end user data (and voice) transfer. The B channels support "clear channel" communications at 64 Kbps each. The D (Data or Delta) channel is intended primarily for signaling and control (e.g., on-hook and off-hook signaling, performance monitoring, synchronization, and error control) at 16 Kbps. The D channel also will support end user packet data transfer at speeds up to 9.6 Kbps, as the signaling and control requirements are not so bandwidth-intensive as to require a full 16 Kbps. BRI is intended primarily for consumer and small business applications. As ISDN- compatible terminal equipment generally is too expensive, most end users opt for an inexpensive Terminal Adapter (TA) that serves as the interface between the ISDN local loop and the non-ISDN terminal equipment.

PRI (Primary Rate Interface) is the North American term for an ISDN T-1 circuit. PRI runs at a total signaling speed of 1.544 Mbps in support of 24 channels. Also known as 23B+D, PRI supports 23 Bearer channels and one D channel. Multiple PRIs can be linked to share a single D channel, as the signaling and control bandwidth requirements are relatively light; however, a backup D channel is recommended in such implementations in order to ensure that the PRI links continue to function should a D channel fail. ITU-T specifications allow as many as five PRIs to be so linked, although some manufacturers support as many as eight. The European/International version is PRA (Primary Rate Access). Also known as 30B+D, PRA supports 30 B channels and one D channel, and is the ISDN equivalent of E-1. PRI and PRA are intended for application in connecting PBXs, ACDs, and data switches, routers and concentrators to the network. All of these various switching and concentrating devices must be ISDN-compatible. A PRI/T-1 is often installed on two unloaded copper pairs, or more commonly, on fiber.

As ISDN essentially is a highly sophisticated enhancement of the traditional circuit- switched PSTN (Public Switched Telephone Network), it offers the advantage of flexibility. As long as IDSN is supported by all network elements at all end user locations and throughout the service provider networks, ISDN capabilities are considerable. First, a single local loop connecting to a single service provider can support any mix of voice, data and video ” channel-by-channel. Second, multiple channels can be linked together in what is known as "bonding" or "rate adaption." For example, rate adaption allows you to link together two 64-Kbps B channels to form a 128 Kbps chunk of bandwidth for a videoconference or, perhaps, a single symmetric (i.e., equal speed in each direction) Internet access experience at 128 Kbps. Third, ISDN is standardized worldwide, so connectivity generally is not an issue. That is not to say that there are not differences from country to country or region to region, but most of those differences are relatively inconsequential at the basic level.

ISDN BRI is useful if you can't get DSL or cable modem service because it can give you videoconferencing, and faster data communications. But it is not an easy service to get up and running. Cost and availability, however, often are issues. The best advice I can give you is:

  1. Figure out what you want to do with your ISDN.

  2. Find which equipment you're going to need that will do the best job for you.

  3. Call the manufacturer of that equipment, tell him where you're located and ask him which ISDN service to order.

  4. After he tells you, order your ISDN service from your local phone company.

  5. Then buy the equipment.

  6. Allow yourself at least two months to get up and running.

  7. Any ISDN equipment you install in a PC will cause major interrupt problems. Make sure you know which "interrupts" your PC is using for what. See also IRQs. ISDN has "enjoyed" many "meanings," including "I Still Don't kNow what it means," referring to the fact that ISDN was not well explained by the service providers; "It Still Does Nothing," referring to the fact that ISDN does relatively little of significance (It took so long for the service provider to make it available that technologies like Frame Relay and DSL made it obsolete, or so some would say.); and "I Smell Dollars Now," referring to the fact that the service providers traditionally charged a lot for ISDN service. ISDN was designed originally to be a totally new concept of what the world's telephone system would eventually become. (Remember this "Vision" came long before the Internet.) According to AT&T, today's public switched phone network has the following limitations:

    1. Each voice line is only 4 KHz, which is very narrow, which limits also the speed you can send data across.

    2. Most signaling is in-band signaling, which is very consuming of bandwidth (i.e. it's expensive and inefficient).

    3. The little out-of-band signaling that exists today runs on lines separate to the network. This includes signaling for PBX attendants, hotel/motel, Centrex and PBX calling information.

    4. Most users have separate voice and data networks, which is inefficient, expensive and limiting.

    5. Premises telephone and data equipment must be separately administered from the network it runs on.

    6. There is a wide and growing variety of voice, data and digital interface standards, many of which are incompatible. ISDN's "vision" was to overcome these deficiencies in four ways:

    7. By providing an internationally accepted standard for voice, data and signaling. That standard has pretty well achieved, though don't try and take North American ISDN equipment to Europe.

    8. By making all transmission circuits end-to-end digital.

    9. By adopting a standard out-of-band signaling system.

    10. By bringing significantly more bandwidth to the desktop. One of the best features of ISDN is the speed of dialing. Instead of 20 seconds for a call to go through on today's still partially analog network, with ISDN it takes less than a second. The speed is truly beautiful. Here are some sample ISDN services (some of which are now available on non-ISDN phone lines): Call waiting: A line is busy. A call comes in. The user knows who is calling. He can then accept, reject, ignore, transfer the call. Citywide Centrex: A myriad of services: Specialized numbering and dialing plans. Central management of all ISDN terminals, including PBXs, key systems, etc. Credit card calling: Automatic billing of certain or all calls into accounts independent of the calling line/s. Calling line identification presentation: Provides the calling party the ISDN "phone" number, possibly with additional address information, of the called party. Such information may flash across the screen of an ISDN phone or be announced by a synthesized voice. The called party can then accept, reject or transfer the call. If the called party is not there, then his/her phone will automatically record the incoming call's phone number and allow automatic callbacks when he/she returns or calls back in from elsewhere. Calling line identification restriction: Restricts presentation of the calling party's ISDN "phone" number, possibly with additional address information, to the called party. Closed user group: Restricts conversations to or among a select group of phone numbers, local, long distance or international. Collaborative Computing. Work on the same document or drawing or design with someone 10,000 miles away. With ISDN, it doesn't really matter where members of the design team live. Desktop videoconferencing. I have an ISDN desktop videoconferencing device on my desk. It's wonderful to see the person at the other end. It makes for a far more meaningful conversation. EMail (a.k.a. Personal mailbox): ISDN can carry information to and from unattended phones as long as they're equipped with proper hardware and software. Internet Access: It's much nicer to browse the Internet at 128 Kbps than at 53.3 Kbps which is the fastest you can get on a dial-up phone line. But it is much nicer to browse even faster ” see Cable Modem and DSL.) Shared Screen ” Switched data services provided via ISDN lets two people in remote locations, both equipped with a computer terminal, view the same information on their screens and discuss its contents while making changes ” all over one telephone line. Simultaneous Data Calls: Two users can talk and exchange information over the D packet and/or the B circuit or packet switched channel. There are two major problems to the widespread acceptance of ISDN: First, the cost of ISDN terminal equipment is too high. Second, the cost of upgrading central office hardware and software to ISDN is too high. Both costs are coming down. Integral to ISDN's ability to produce new customer services is ITU Signaling System 7. This is a ITU-T recommendation which does two basic things: First, it removes all phone signaling from the present network onto a separate packet switched data network, thus providing enormous economies of bandwidth. Second, it broadens the information that is generated by a call, or call attempt. This information ” like the phone number of the person who's calling ” will significantly broaden the number of useful new services the ISDN telephone network of tomorrow will be able to deliver. For more on ISDN, see also AO/DI, Euro-ISDN, Intel Blue, ISDN 2, ISDN 30, ISDN Standards, ISDN Telephone, ISUP, NT1, NT2, Q.931, Robbed Bit Signaling, S Interface, SS7, SPID, T Interface, TCAP, Terminal Adapter, and U Interface.


What the Americans call ISDN BRI, the British call ISDN 2, which is ISDN with two BRI channels and one D channel.


Euro-ISDN BRI. See ISDN 2 and ISDN.


The name of an ISDN service which delivers 30 ISDN BRI lines over a single line. ISDN 30 is a fancy name for ISDN on an E-1 line. You find it in countries outside North America, especially Europe. ISDN 2, in the UK, is their name for what Americans call ISDN BRI. See ISDN.

ISDN Basic Link Facility

The ISDN Basic Link Facility consists of a local transmission facility terminated in the local central office and in a suitable network interface device that is capable of supporting ANSI standard ISDN Basic Rate 2 Binary 1 Quaternary U interface line coding scheme. The standard ISDN Basic Link Facility is 18,000 cable feet or less from the central office termination or served via appropriate electronic equipment, to the Network Termination One device located on the customer's premises.

ISDN BRI Service

2B+D - Two bearer channels and one D channel to your desktop. There are many varieties of ISDN BRI service. The three most common are National ISDN-1 compliant, AT&T 5ESS Custom (an older form of ISDN BRI) and Northern Telecom DMS 100 ISDN. With ISDN BRI, you choose your ISDN equipment first, figure out what it needs, check whether what it needs is available from your local telephone company, then get your line installed, then buy your equipment. Changing your line specs later is expensive and slow. ISDN is still a very first generation product, though when you get it working, it usually works thereafter relatively flawlessly. See ISDN for a much longer explanation.

ISDN Forum

See Vendors ISDN Association.

ISDN Integrated Access Bridge/Router

A remote access device that connects the computer to an ISDN line and which performs bridging and/or routing as well as a supporting analog devices such as phones or faxes.

ISDN Modem

ISDN Modem is just another name for a Terminal Adapter (TA). See Terminal Adapter.

ISDN Multirate

ISDN Multirate is a network-based ISDN service that allows users' network access equipment to add B channels as needed, depending on bandwidth demands, in increments if 64 Kbps, up to 1.536 Mbps. Access to ISDN Multirate service is obtained over ISDN PRI lines.

ISDN Network Termination Device

You can't plug your ISDN phone directly into an ISDN line like you can with today's analog lines. You need a black box, called a Network Termination device, called an NT1, as in Network Termination 1. In North America you can pick one of these devices up for under $250. The NT1 provides an interface between the ISDN loop and an S or T interface terminal, such as an ISDN phone, or the PCTA (Personal Computer Terminal Adapter). The PCTA is the device which turns a PC into an ISDN terminal/phone. The NT1 is the classic ISDN "black box." It sits on the subscriber's premises at the end of the subscriber loop coming in from the phone company. It talks to the ISDN central office. And, in turn, all ISDN terminals, phones and other devices on the subscriber premises are plugged into this black box. The basic NT1 functions are:

  • Line transmission termination.

  • Layer 1 line maintenance functions and performance monitoring.

  • Layer 1 multiplexing, and

  • Interface termination, including multi drop termination employing layer 1 contention resolution.

Some ISDN devices ” such as LAN hubs ” now come with NT1s built in. See ISDN.

ISDN Overflow/Diversion

A feature of Rockwell Galaxy ACDs. ISDN Overflow/Diversion allows Galaxy ACD users to overflow calls between multiple switches using PRI D-channels and B-channels through the public network. This gives the user a virtual private network without the cost of dedicated trunks. By using ISDN messages to overflow a call, specific information associated with the call can be passed to the destination switch, such as ANI, DNIS, and delay time in queue at the originating switch.


PRI stands for Primary Rate Interface. In North America, ISDN PRI can be thought of as "enhanced T-1." And some long distance carriers are only delivering T-1 in this format. In this ISDN-PRI format, it has major benefits ” chiefly the extra bandwidth and benefits derived from the much richer and much faster out-of-band signaling. For example, ANI (Automatic Number Identification, DNIS (Dialed Number Identification Service), etc. are delivered much better this way. ISDN PRI is 24 B (bearer) channels, each of which is a full 64,000 bits per second. One of these channels is typically used to carry signaling information for the 23 other channels. If you're running voice on a single ISDN-PRI, you get 23 voice channels, compared to 24 if you run voice on a T-1 line. However, if you get multiple ISDN-PRI lines, you can often carry the signaling for those voice lines on that one B channel and thus get 24 on each of the others. For example, some voice processing cards will let you support up to eight ISDN PRI channels on one B channel ” i.e. the first PRI gives you 23 voice channels. All seven others will give you 24 channels. In Europe, ISDN PRI is 30 bearer channels of 64 Kbps and two signaling channels, each of 64 KBps.

ISDN Repeaters

ISDN repeaters let telephone companies extend ISDN lines up to 48,000 feet from their central office. This means they can send ISDN to people further away.

ISDN Router

You have a local area network in your office. You want to join that LAN to the Internet and/or your company's private Intranet. You can do the joining with any number of communications lines, from slow dial-up analog lines to high-speed T-3 and everything in between. One of those in-betweens is an ISDN BRI line. An ISDN router is a device which joins a LAN to an ISDN line. It combines the functionality of an ISDN Terminal Adapter (TA) and a TCP/IP router for access to an ISDN network. The TA function accomplishes the interface between the ISDN network and devices which are not ISDN compatible. The router function allows multiple workstations to access the ISDN network, as well each other, through what essentially is a LAN hub with TCP/IP routing capabilities. See also ISDN Terminal Adapter.

ISDN Standards

The path of a call in an ISDN network is based on standards:

  1. ISDN User A signals the public network over a standard interface. The 2B1Q protocol is used by the terminal as well as the line card in the telephone company central office. The 2B1Q arranges the bits of a digital ISDN signal in a standard manner over the twisted pair connecting the user and the central office. Bellcore TR268 establishes protocols for signaling between the caller and the network.

  2. TR444 and TR448 define the standard protocols that allow ISDN services to be carried by the SS7 network.

  3. TR317 defines the protocols for standard SS7 networking between the LEC's intraLATA switches that, when combined with TR444 and TR448, can deliver ISDN services.

  4. TR394 defines the protocols for standard SS7 networking of the interLATA switches that, when combined with TR444 and TR448, provide the interface for ISDN services and the interexchange network.

  5. ISDN UserB, equipped with the standard network interface and using the 2B1Q and TR268 protocols, is prepared to receive the ISDN call from User A. The network delivers the ISDN call information carried over SS7 from User A to User B in the call set-up message.

ISDN Teladapter

A Nortel term for a device which connects a national ISDN 1 telephone and a Macintosh to a Nortel switch via an ISDN line card.

ISDN Telephone

An ISDN phone can attach to an ISDN basic rate interface. It typically has one digital voice (at 64 kbps) channel and two data options ” one for packet switched services (up to 9600 bps) and another for circuit switched data (up to 64 kbps). It will also have an RS-232-C connector on its back and a two line, 48-character LCD adjustable display. It will also have a bunch of dedicated buttons for standard stuff ” last number redial, speed dial, on-hook dialing, listen-on-hold, etc. Some ISDN phones work behind most ISDN central offices ” e.g. the Telrad phones. Most don't. They have to work behind the central office they were designed for. Or did have to. In February, 1991, Bellcore issued a technical specification for a standard ISDN phone line. The idea of National ISDN-1 is that it be a set of standards which every manufacturer can conform to. A consumer can buy an ISDN phone (one conforming to National ISDN-1) at his local Radio Shack (or other store) take it home, plug it in and know it will work, irrespective of whose central office he's connected to. At time of writing most ISDN phones cost over $600. Some cost nearly $1,000. Some cost more than a personal computer. In late fall of 1992 there was increasing talk that PCs will soon come with telecom ports ” able to accept the ISDN signal directly from the central office, without the need for a separate (and expensive ISDN) phone instrument. The PC and the software within it, will then become the phone (presumably with a handset, headset or earset attached to the back of the PC). See ISDN.

ISDN Terminal Adapter

ISDN terminal adapters are devices that typically allow analog devices to speak on digital ISDN lines. Terminal adapters are essentially similar to modems, with the following difference. Modems connect terminals to the traditional analog network, and terminal adapters connect those analog-network (non-ISDN) terminals to the digital ISDN network.


Integrated Switching Element.


Incoming Service Group or Grouping. A fancy name for hunting or rollover. You receive many incoming calls. You don't want to miss a call, so you ask your phone company to set your phone lines up to roll over, also called hunt, also called ISG (Incoming Service Group) in telephonese. You order five lines in hunt. The calls come into the first. If the first one is busy, the second rings. If it's busy, the third rings. If they're all busy, then the caller receives a busy. The commonest types of hunting are sequential and circular hunting. Sequential hunting starts at the number dialed, keeps trying one number after another in number order and ends at the last number in the group. It's typically descending. For example, it starts at 691-8215, goes to 691-8216, then 691-8217, etc. But it can also be ascending ” from 691-8217 up. Circular hunting hunts all the lines in the hunting group, regardless of the starting point. Circular hunting, according to our understanding, circles only once (though your phone company may be able to program it circle a couple of times). The differences between sequential and circular are subtle. Circular seems to work better for large groups of numbers. You don't need consecutive phone numbers to do rollovers. Nowadays you can roll lines forwards, backwards and jump around, for example most idle, least idle. Rollovers are now done in software. This also has its downside, since software fails. For example, theoretically if a rollover strikes a dead trunk, it should bounce to the next live trunk. But sometimes it hangs on the dead trunk and many of your incoming calls never get answered. They might ring and ring. They might hit a busy. My recommendation: Test your rollovers at least twice a day. In particular, test that your callers ultimately get a busy if all your lines are busy. Nothing worse your customer should receive a ring-no-answer or a constant busy when calling your company. See also Terminal Number.


See Intersymbol Interference.


Internal Switch Interface System.


Area that contains the software programs used for each Engine. Because slots are set up as a logical section of the computer's memory, each node may have a combination of program slots.


InterSatellite Link. A relatively new development in satellite technology, ISLs allow LEOs (Low Earth Orbiting satellites) and MEOs (Middle Earth Orbiting satellites) to communicate directly, rather than through earth stations. ISL functions include selection of the shortest circuit path between originating and terminating device, selection of lowest cost terrestrial route, and complete bypass of terrestrial carriers. In the case of this last function, the following scenario best explains: A user of the Iridium LEO system, for instance, places a call from his satellite phone to another user of a satellite phone on the same system. The caller connects directly to a LEO, which finds the other user through querying a GEO (Geosynchronous Earth Orbiting satellite) which then queries the other 65 LEOs in the satellite constellation over ISL signaling links. As the target user answers the call, the connection is established and maintained over another ISL, perhaps established directly between the LEOs in best positions to communicate with the users. The terrestrial networks, both local and long-haul, are bypassed completely, and any charges associated with those terrestrial networks are avoided. As the satellites communicate directly, no earth stations are involved, and precious bandwidth is conserved. Also, issues of propagation delay are minimized, as only one uplink/downlink combination is required, as are the number of systems and processes that must act on the call. This process effectively is the same as in a cellular network, although it is much more complex ” the satellites are whizzing around, the users may be mobile and, therefore, multiple handoffs may be required from satellite to satellite on both ends of the connection. While cellular users also typically are mobile, at least the cell sites are stationary. While at the time of this writing there are no ISL standards, either radio or laser light frequencies are appropriate.

ISM Band

Industrial, Scientific and Medical Band. A term describing several bands in the RF (Radio Frequency) spectrum, also referred to as Part 15.247 of FCC regulations. Specifically, ISM bands include 902-928 MHz, 2.4-2.483 GHz, and 5.725-5.850 GHz. ISM frequencies are unlicensed. In other words, they can be used for any variety of applications without the requirement for FCC permission. Traditionally used for in-building and system applications such as bar code scanners , industrial microwave ovens, and wireless monitoring of patient sensors, ISM also is used in many WLANs (Wireless Local Area Networks), including HomeRF and 802.11b. As there is no licensing requirement, there exists the potential for interference from other applications in close physical proximity. Therefore, spread spectrum technology is often used to protect the data transmission integrity of a Wireless LAN. See also 802.11b, HomeRF, Spread Spectrum, and WLAN.


  1. Intelligent Services Node.

  2. AT&T's Information Systems Network.


Intelligent Services Network Applications Processor.


  1. The Greek prefix which means equal or symmetrical, as in isometric. See also Isochronous.

  2. Most people believe that ISO stands for The International Standards Organization in Paris. Actually the organization is strictly called the International Organization for Standardization (IOS) and is based in Geneva. ISO is a voluntary, non-treaty organization chartered by the United Nations. It began to function officially on February 23, 1947 and in 1951 published its first standard, entitled "Standard reference temperature for industrial length measurement." Its role is to define international standards covering all fields other than electrical and electronic engineering, which is the responsibility of the IEC (International Electrotechnical Commission). In the world of communications, the ISO is best known for the 7-layer OSI (Open Systems Interconnection) Reference Model. The U.S. representative to the ISO is ANSI. If you go to the ISO's home page,, you will find the following explanation: The International Organization for Standardization (ISO) is a worldwide federation of national standards bodies from some 130 countries, one from each country. ISO is a non-governmental organization established in 1947. The mission of ISO is to promote the development of standardization and related activities in the world with a view to facilitating the international exchange of goods and services, and to developing cooperation in the spheres of intellectual, scientific, technological and economic activity. ISO's work results in international agreements which are published as International Standards. Many people will have noticed a seeming lack of correspondence between the official title when used in full, International Organization for Standardization, and the short form, ISO. Shouldn't the acronym be "IOS"? Yes, if it were an acronym - which it is not. In fact, "ISO" is a word, derived from the Greek isos, meaning "equal", which is the root of the prefix "iso-" that occurs in a host of terms, such as "isometric" (of equal measure or dimensions) and "isonomy" (equality of laws, or of people before the law). >From "equal" to "standard", the line of thinking that led to the choice of "ISO" as the name of the organization is easy to follow. In addition, the name ISO is used around the world to denote the organization, thus avoiding the plethora of acronyms resulting from the translation of "International Organization for Standardization" into the different national languages of members, e.g. IOS in English, OIN in French (from Organisation internationale de normalisation). Whatever the country, the short form of the Organization's name is always ISO. See ANSI and IEC.

  3. ISO also stands for Independent Service Organizations or Independent Sales Organizations in the computer sales community.

ISO 8073-DAD2 (TP4)

Layer 4 (transport) Connection-Mode Protocol. TP4 (Transport Protocol Class 4) provides guaranteed delivery and sequencing end-to-end. ISO's version of Transmission Control Protocol (TCP). See ISO.

ISO 8473

Layer 3 (Network) Connectionless Network Protocol (CLNP). "Datagram" routing. No guaranteed delivery nor sequencing. ISO's version of Internet Protocol. See ISO.

ISO 11172

ISO 11172 MPEG-1 and ISO 13818 MPEG-2 Specifications define audio compression algorithms at bit rates from 32 kbps to 384 kbps. The MPEG-1 define three similar compression techniques which are referred to as layer I, II and III. In progressing from layer I to layer III, improvements in compression efficiency are achieved at the expense of additional complexity and algorithmic delay. All layers support two audio channels at sample rates of 32, 44.1 or 48kHz at bit-rats from 16 to 384 kbps. The MPEG-2 standard extends the number of audio channels to five plus a low frequency effects channel. MPEG-2 also provides the additional sample rate options of 16, 22.05 and 24kHz. See ISO and MPEG.

ISO 13818

See ISO and ISO-11172 above.

ISO 8877

Information Processing Systems Q Interface Connector and Contact Assignment for ISDN Basic access interface located at reference points S and T - International Organization for Standardization. Part of this standard describes pin/pair assignments for 8-line modular connectors. The assignments are the same as EIA's T-568A. See ISO.

ISO 9000 Series

The ISO 9000 series, published in 1987, outlines the requirements for the quality system of an organization. It is a set of generic standards that provide quality assurance requirements and quality management guidance. It is now evolving into a mandatory requirement, especially for manufacturers of regulated products such as medical and telecommunications equipment. ISO 9001, the most comprehensive of three compliance standards ” 9001, 9002, 9003 ” is a model for quality assurance for companies involved with designing, testing, manufacturing, delivering and servicing of products. ISO 9002 covers manufacturing and installation only. ISO 9003 covers product testing and final inspection of standards. See ISO and ISO 9001.

ISO 9001

ISO 9001 is a rigorous international quality standard covering a company's research and development, design, production, installation and service procedures. Compliance with the standard is of increasing significance for vendors trading in international markets, in particular in Europe where ISO 9001 registration is widely recognized as an indication of the integrity of a supplier's quality processes. ISO 9001 is the most rigorous of the three standards. See ISO and ISO 9000 Series.

ISO 9002

ISO 9002 covers manufacturing and installation only. See ISO and ISO 9000 Series.

ISO 9003

ISO 9003 covers testing and final inspections of manufactured products. See ISO and ISO 9000 Series.

ISO 9660

The CD-ROM logical file format standard adopted by ISO in 1987. Describes a table of contents but not the format of the actual data. This has led to incompatibilities between different computers. Based on a specification developed by the High Sierra Group (HSG) which included Apple, Microsoft, 3M, Philips, Hitachi, DEC. Also know as Yellow Book and High Sierra. See ISO.


The International Organization for Standardization (IOS) and the International ElectroTechnical Commission.


A non-profit organization that fosters the voluntary interconnection of computer networks into a global communications and information infrastructure. According to ISOC, the society provides leadership in addressing issues that confront the future of the Internet. ISOC is the umbrella organization for the IAB (Internet Architecture Board), IETF (Internet Engineering Task Force) and IRTF (Internet Research Task Force). The ISOC has approximately 150 organizational and 6,000 individual members in more than 100 countries. See also IOPS and NANOG.


Isochronous transmission means "two-way without delay." Normal everyday voice conversations are isochronous. They have always been isochronous. We could not tolerate delays. We just never called them isochronous. The word isochronous appeared when we started digitizing voice, then joining it with data on a single channel. The data guys suddenly woke up to the fact that users would only tolerate joining voice and data ” if the voice went through without delays. So they came up with this fancy new term "isochronous." By accepting this realization, they then could design buses ” e.g. Universal Serial Bus ” where other flows of data (e.g. printing, keyboard entry, data communications from the Internet) could be delayed minute amounts of time, while voice went through without delay.

Isochronous comes from the Greek "iso" (equal) and "chronous" (time). Isochronous transmission is used to move stuff which must get to its destination with absolutely no delays. Voice and video need isochronous transmission. Let me explain. In the beginning, the phone network switched a call from A to B. It kept the circuit open. Whatever you said at one end went to the other end at the speed of electricity or light, effectively instantly. Then they invented other methods of transmission, where the circuit isn't open 100% from end to end during the "conversation." One example is packet switching, used widely for sending data. If you're sending an electronic mail, it clearly doesn't matter if your electronic letter arrives half a second faster or slower. It does matter with voice and video. See Isoethernet and Universal Serial Bus.

Isochronous transmission needs to be defined technically. "Instantaneous" is not a technical description. It must be delivered within certain time constraints. For example, in multimedia transmission you have to make sure that the video arrives at the same time as the audio. Isochronous can be contrasted with asynchronous, which refers to data streams broken by random intervals, and synchronous processes, in which data streams can be delivered only at specific intervals. Isochronous service is not as rigid as synchronous service, but not as lenient as asynchronous service. Certain types of networks, such as ATM, are said to be isochronous because they can guarantee a specified throughput. Likewise, new buses, such as IEEE 1394, support isochronous delivery. See also Asynchronous, Isochronous Ethernet, and Synchronous.

Isochronous Ethernet

A 10 Mbps LAN topology that sets aside 96 ISDN channel to carry voice, data and video. See Isochronous and Isoethernet.


ISO Development Environment. An implementation of OSI's upper layers on a TPC/IP protocol stack. Pronounced "eye-so-dee-eee".

ISODE Consortium

X.500 directories.


Another word for IsoEthernet. See IsoEthernet.


Isochronous Ethernet Integrated Services. An extension to the Ethernet LAN standard proposed by IBM and National Semiconductor and first demonstrated at Fall Comdex 1992, and standardized as IEEE 802.9a. IsoEthernet adds six megabits per second of capacity to regular Ethernet, specifically to carry low delay, constant bit rate (CBR), isochronous data, especially voice and video. This isochronous capacity appears as up to 97 telephony channels of 64 Kbps each ” 96 for transmission of information (voice, video, data, etc.) and one (called the D channel) for signaling. Like FDDI-II, IsoEthernet has the potential to carry both live voice or video calls together with LAN packet data on the same cable. IsoEthernet is limited to a single-workgroup solution in support of collaborative communications as videoconferencing and whiteboarding. It never caught on, and has been rendered obsolete by Switched Ethernet, ATM, and other high-speed LAN technologies. See also Ethernet, Isochronous, FDDI-II.

Isolated Ground

IG. In AC electricity, an isolated ground is a type of outlet characterized by the following features and uses:

  • It may be orange and must have a Greek "delta" on the front of the outlet. (A delta looks like a triangle.)

  • It must be grounded by an insulated green wire.

  • It must have an insulator between the ground terminal and the mounting bracket .

  • It is used primarily to power electronic equipment because it reduces the incidence of electrical "noise" on the ground path.


See Power Conditioning.


A device that permits microwave energy to pass in one direction while providing high isolation to reflected energy in the reverse direction. Used primarily at the input of communications-band microwave amplifiers to provide good reverse isolation and minimize VSWR. Consists of microwave circulator with one port (port 3) terminated in the characteristic impedance. See Optical Isolator.


Exhibiting properties of the same values when measured along axes in all directions.

Isotropic Antenna

A hypothetical omni-directional point-source antenna that serves as an engineering reference for the measurement of antenna gain. See also EIRP and Isotropic Radiator.

Isotropic Radiator

A completely omni-directional antenna, i.e., one which radiates equally well in all directions. This antenna exists only as a mathematical concept and is used as a known reference to measure antenna gain expressed as dBi. See also dBi.


  1. Internet Service Provider. A vendor who provides access for customers (companies and private individuals) to the Internet and the World Wide Web. The ISP also typically provides a core group of internet utilities and services like E-mail, News Group Readers and sometimes weather reports and local restaurant reviews. The user typically reaches his ISP by either dialing-up with their own computer, modem and phone line, or over a dedicated line installed by a the Internet Service Provider, a CLEC, or a local or long distance telephone company. An ISP makes money from as many as four ways ” monthly subscriptions for connecting customers to the Internet and providing them email, extra services (such as additional email addresses), a cut of inbound telephone revenues , advertising and commission fees. An ISP is also known as a Telecommunications Service Provider or an ITSP, for Internet Telephony Service Provider. See also IAP.

  2. Information Service Provider. A company which provides information over the phone in response to touchtones punched in by a subscriber. That information may be weather, stock prices, etc. Often it is provided over 900 number, in which a phone company (local or long distance) bills the end user for calls to the ISP (Information Service Provider), paying part of the revenue collected to the ISP and keeping some of it as its collection billing and network fee. In many states, ISPs also use special local numbers, like those in New York beginning with 970 and 976.

  3. Integrated Service Provider. This is a term for a new (or relatively new) company that delivers all of the different data and voice services including: Voice over IP, dialtone and Internet service.

  4. ISDN Signal Processor.

  5. Information Services Platform.


Integrated Services Private Branch eXchange.


International Signaling Point Code.


Instituto Superiore delle Poste e delle Telcomunicazioni. (Superior Institute for Posts and Telecommunications, Italy).


International Simple Resale. A system which allows international carriers to buy transmission capacity in bulk, to plug it into the public network at each end, and to resell it, one call at a time. This eliminates the need for settlements between international carriers.


Intelligent Services Switch.


InterSwitching Interface. An interface between two SMDS switching systems within a LATA.


Integrated Special Services Network.


A euphemism for "problem." Margaret Horak, wonderful wife Ray Horak, my Contributing Editor, is a top- notch consultant involved in customer service and certain related OSSs (Operations Support Systems). Seems as though her clients lately refer to "problems" as "issues." It's less scary that way.


Initial Service Term.


Integrated Services Test Facility.


Integrated Services Digital Network User Part. The call control part of the SS7 protocol. ISUP determines the procedures for setting up, coordinating, and taking down trunk calls on the SS7 network. ISUP is defined by ITU-T recommendations Q.761 and Q.764. ISUP also provides:

  • Calling party number information (including privacy indicator).

  • Call status checking, to keep trunks in consistent states at both ends.

  • Trunk management, and

  • Relates of trunks and the application of tones and/or announcements in the originating switch upon encountering error, blockage or busy conditions. There are seven ISUP Messages: Initial Address Message (IAM), Continuity Check Message (COT), Address Complete Message (ACM), Answer Message (ANM), Release Message (REL), Release Complete Message (RLC) and Exit Message (EXM). For you to benefit from these capabilities, your phone equipment must first be able to access the CCS7 network. One suggested way (but not the only way) is through the ISDN primary rate access (PRA) standard, which supports Q.931 protocol. See IAM, ISDN and Common Channel Signaling.


Independent Software Vendor. Typically a company which writes and sells software, but not hardware. Manufacturers of hardware and operating systems, i.e. IBM or Northern Telecom, often contract with ISVs to produce specialized software to make their hardware and operating system more attractive.


  1. Information Technology. A fancy name for data processing (DP), which became management information systems (MIS), which became information technology. All mean the same thing ” computers, software and networking. IT (pronounced eye tee) may have come from Europe. I heard it first from Siemens and Nixdorf who merged in 1989. IT means all the equipment, processes, procedures and systems used to provide and support information systems (computerized and manual) within an organization and those reaching out to customers and suppliers. These days virtually all IT is networked, i.e. it travels over phone lines of various sizes and speeds. Thus IT today includes control over data telecom ” but typically not voice telecom. As data and voice merge onto a common transmission and switching path (it's called convergence), then IT will increasingly take over telecom management in the corporation. But right now, they're often separate.

  2. Inter-Toll Trunk.


Information Technology and Telecommunications. Not a common term. IT is more common. See IT.


A shortened form of "It is." Not to be confused with Its, which is the possessive of it. Its house. It's a house.


Integrated Trunk Access.


Information Technology Association of America. ITAA was founded in 1961 as ADAPSO (Automated Data Processing and Services Association). ITAA says its 9,000+ members are IT companies who create and market products and services associated with computers, communications and data. ITAA divisions are Software, IT Services, Information Services and E-Commerce, and Enterprise Solutions.


International Traffic in Arms Regulations. A U.S. government document which established the rules for import and export of goods and services which have significance in terms of national security. Such goods and services are assigned to the U.S. Munitions List, and cannot be exported. The most complex, (read "effective) encryption technologies are included in this list. For example, PGP and DES are on the list. Don't take your laptop out of the country if you have these encryption algorithms loaded on it, unless you want to spend a few years in a federal prison .


Intermediate Block Character. A transmission control character that terminates an intermediate block. A Block Check Character (BCC) usually follows. Using ITBs allows for error checking of smaller blocks in data communications.


  1. Information To Controller.

  2. International Teletraffic Congress.

  3. Japan's Telecommunications Technology Committee.

  4. Independent Telephone Company. Monopoly local service provider in a given area not serviced by an RBOC.


International TeleConferencing Association. A professional association organized to promote the use of teleconferencing, including audio, videographics, video, business TV, and distance education. Membership is open to service and product providers, consultants and users.


An ITCO is an Independent Telephone COmpany. "Independent" as in independent from the original bell system, An ITCO is kind of like a cross between a CLEC and an RBOC, or any other ILEC. Usually they're collections of small mom-and-pop rural local phone companies that have been around for a while. ITCOs are used to being the incumbent telecom provider (thus like an ILEC or RBOC) in some small corner of the country, and they're used to providing basic local voice service. With telecom deregulation of 1996, they can move into other pockets of the country to sell more voice services. Now, however, they see the aggressive big national CLECs popping up in their back yards, advertising single-sourced local voice and data, and they're scared. They only know voice, and they're nowhere near as big powerful or marketing savvy. So they know they have to do something NOW to keep and attract customers... but many don't know what, or how. See Telecommunications Act of 1996, U.S.

Iterative Development

An approach to application development in which prototypes are continually refined into increasingly complete and correct systems. Similar to prototyping.

Iterative Process

The process of repeatedly processing a bunch of instructions. Each repetition, theoretically, comes progressively closer to the desired result, the "correct" answer, etc.


Internet Traffic Engineering Solutions Forum. An initiative of Bellcore formed in 2Q 1997 at the request of several Incumbent LECs (ILECs) to address common issues of Internet congestion of the Public Switched Telephone Network (PSTN). The ITESF seeks to develop generic requirements for products and features designed to off-load Internet traffic from the PSTN-such traffic is characterized by very long holding times during which relatively bursty traffic is supported. In other words, sometimes the circuit-switched network is used to full capacity while, at other times, little or no data is transmitted-regardless, the network is committed to supporting the traffic, whether or not it is present and whether or not the capacity of the network is required. The ITESF's solution, in abbreviated form, is to recognize Internet traffic for what it is by virtue of the dialed number, and to shunt it off to an IP data network. While this seems very obvious and very simple to do, it does require that some entity recognize the issue, take charge, and do something about it (i.e., set standards). Therefore, the ITESF is forming. See also Bellcore.


  1. Instructional Television Fixed Service. A service provided by one or more fixed microwave stations operated by an educational organization and used mainly to transmit instructional, cultural and other educational information to fixed receiving stations.

  2. International Toll Free Service. A service which allows callers to dial a Freephone (i.e., toll-free) number from one country, with the call terminating in another country. The traditional approach to providing IFTS is to use the toll-free dialing pattern of the originating country. For example "1-800-XXX-XXXX" in the U.S., "0044-22-XXXXXX" or 0066- 33-X-XXXXX in Japan, and 989-9-XX-XXXX in Columbia. This approach works, but requires that a multinational company have at least one different Freephone number in each country. A much better approach is UIFN (Universal International Freephone Number), which involves a universal, standardized numbering scheme in the format "+ 800 XXXX XXXX." See also UIFN.


AT&T's Integrated Telemarketing Gateway. This is a set of specs for hooking up an outside computer to an AT&T switch. Under ITG, information travels in both directions ” from the switch to the host computer and from the host computer to the switch. See also IG (one-directional link), ASAI and Open Application Interface.


  1. Idle Trunk Indicator.

  2. Information Technology Industry Council. ITI, according to ITI, represents the leading U.S. providers of information technology products and services. Its members had worldwide revenues of $323 billion in 1994. They employ more than one million people in the United States. 202-626-5725.


Information Technology Industry Council.


iCalendar Transport Independent Interoperability Protocol. See iCalendar.


See Information Technology Management.


IntraLATA Toll Originating Responsibility Plan. Performs a similar function to CMDS, but for IntraLATA toll calls within an RBOC's geographic territory. A settlement plan used between ITCs and the RBOC.


  1. Institute for Telecommunications Sciences. The research and engineering branch of the National Telecommunications and Information Administration (NTIA), which is part of the U.S. Department of Commerce (DoC).

  2. Intelligent Transportation System. A concept for a transportation system using IT (Information Technologies) to reduce highway transit time, provide necessary emergency services and traffic advisories, reduce traffic congestion, and improve travel safety. The concept is being translated into reality through the development of a number of wireless applications. For example, vehicle navigation systems relying on GPS (Global Positioning System) satellites can track your location, with directions to your destination offered through graphic maps displayed on a monitor. The same terminal can be used to display alternate routes as traffic congestion develops. The same terminal also can display emergency messages. Trucks no longer need to stop at weigh-in stations, as the gross weight of the truck can be transmitted on a wireless basis. The Intelligent Transportation Society of America (ITSA) is heavily involved in the promotion of the concept, as well as the underlying technologies and applications.


The European Information Technology Security classification and evaluation initiative.


Internet Telephony Service Provider. See ISP.


International Telephone and Telegraph. A company that once was the largest manufacturer of telecommunications equipment outside the U.S.


The ITU, an organization based in Geneva, Switzerland, is the most important telecom standards-setting body in the world. In actual fact, it has no power to set standards. But if its members agree on a standard, it effectively becomes a world standard. Why fight city hall? "ITU" stands for "International Telecommunication Union," a name that the organization adopted in 1934. The ITU presently consists of three major sectors that were established in 1992: the Radiocommunication Sector (ITU-R), the Telecommunication Development Sector (ITU-D), and the Telecommunication Standardization Sector (ITU-T). When it was created, the ITU-T took over the work formerly done by the CCITT (Comite Consultatif Internationale de Telegraphique et Telephonique or, in English, International Telegraph and Telephone Consultative Committee, which until 1992 had been the most influential telecom standards organization in the world. For some reason, most reference works that mention the ITU and the ITU-T consistently use "Telecommunications" in the full form of the acronyms. Even one of the ITU's own acronyms databases lists "Telecommunications Standardization Sector" as the meaning of the "-T" in "ITU-T." However, the official names of the organizations are "International Telecommunication Union" and "International Telecommunication Union- Telecommunication Standardization Sector."

The scope of the ITU's work is now much broader than just telegraphy and telephony. It now also includes IP voice, telematics , data, new services, systems and networks (like ISDN). The ITU is a United Nations Agency and all UN members may also belong to the ITU, represented by their governments. In most cases, the governments hand their rights on their national telecom standards to their telecommunications administrations (PTTs). But other national bodies (in the US, for example, the State Department) may additionally authorize Recognized Private Operating Agencies (RPOAs) to participate in the work of the ITU. After approval from their relevant national governmental body, manufacturers and scientific organizations may also be admitted, as well as other international organizations. This means, says the ITU, that participants are drawn from the broad arena. The activities of the ITU-T divide into three areas: Study Groups (at present 15) to set up standard ("recommendations") for telecommunications equipment, systems, networks and services. Plan Committees (World Plan Committee and Regional Plan Committee) for developing general plans for a harmonized evolution of networks and services. Specialized Autonomous Groups (GAS, at present three) to produce handbooks, strategies and case studies for support mainly of developing countries. Each of the 15 Study Groups draws up standards for a certain area ” for example, Study Group XVIII specializes in digital networks, including ISDN. Members of Study Groups are experts from administrations , RPOAs, manufacturing companies, scientific or other international organizations - at times there are as many as 500 to 600 delegates per Study Group. They develop standards which have to be agreed upon by consensus. This, says the ITU, can sometimes be rather time-consuming , yet it is a democratic process, permitting active participation from all ITU member organizations. The long-standing term for such standards is "ITU (ITU-T) recommendations." As the name implies, recommendations have a non-binding status and they are not treaty obligations. Therefore, everyone is free to use ITU-T recommendations without being forced to do so. However, there is increasing awareness of the fact that using such recommendations facilitates interconnection and interoperability which is in the interest of network providers, manufacturers and customers. This is the reason why ITU-T recommendations are now being increasingly applied ” not by force, but because the advantages of standardized equipment are obvious. ISDN is a good example of this. ISDN and other standards recommendations include options which allow for multiple "standards," in recognition of differing national and regional legacy "standards;" as a result, international standards recommendations do not necessarily yield evenly applied standards options. The ITU-T has no power of enforcement, except moral persuasion. Sometimes, manufacturers adopt the ITUT specs. Sometimes they don't. Mostly they do, as for example with modem specifications, including V.90, H.XXX standards. The ITU-T standardization process runs in a four-year cycle ending in a Plenary Session. Every four years a series of standards known as Recommendations are published in the form of books. These books are color -coded to represent different four cycles. In 1980 the ITU published the Orange Books, in 1984 the Red Books and, in 1988, the Blue Books. See ITU STUDY GROUPS and ITU V.XX below. The ITU has now been incorporated into its parent organization, the International Telecommunication Union (ITU). Telecommunication standards are now covered under Telecommunications Standards Sector (TSS). ITU-T (ITU-Telecommunications) replaces ITU. For example, the Bell 212A standard for 1200 bps communication in North America was referred to as ITU V.22. It is now referred to as ITU-T V.22.

ITU itself says that it specializes in three main activities ” defining and adopting telecommunications standards, regulating the use of the radio frequency spectrum and furthering telecommunications development around the world, particularly in the developing countries. It also holds a major trade show in Geneva every four years. As satellites have become more important as a method of long distance communications, so the ITU's allocation of scarce satellite frequencies among countries has become a hot bed of controversy. There are many who believe the ITU to be the most important telecommunications organization in the world. The organization owes its origins to Union Telegraphique which was formed in 1865, with the specific aim of developing standards for the telegraph industry. In 1947, under a United Nations charter, it was reformed as the ITU. This body has three main aims:

  1. To maintain and extend, international cooperation for the improvement and interconnectivity of equipment and systems, through the establishment of technical standards.

  2. To promote the development of the technical and natural facilities (the spectrum) for most efficient applications.

  3. To harmonize the actions of national standards bodies to attain these common aims. In particular, to encourage the growth of communications facilities in developing countries.

Due to the rapid growth of the telecommunications industry, it was necessary to set up the International Consultative Committees (ITU, CCIR and IFRB) within the ITU's jurisdiction in order to adequately manage this expansion. The aims are achieved by organizing international conferences and meetings, by sponsoring technical cooperation, and by publishing information and promoting world exhibitions. Currently, the ITU has about 170 member nations. I.T.U., Place des Nations, CH-1211 Geneve 20, Switzerland. Tel +41 22 99 51 11. Fax +41 22 33 72 56. International Telecommunication Union. See the following definitions. ITU can be contacted at, (where CH stands for Switzerland. Do not type com.)

ITU calls its recommendations for standards "pre-published." According to the ITU, this means the text of the recommendation, as approved, is supplied by the responsible "author" (normally the chairman of the Study Group which approved it). It is however not yet edited. Therefore there may be changes (mostly of an editorial nature). Here are the categories of ITU pre-published Recommendations:

Series E. Overall network operation, telephone service, service operation and human factors.

Series F. Non-telephone telecommunication services. Series G. Transmission systems and media, digitals systems and networks. Series H. Audiovisual and multimedia systems. Series I. Integrated services digital network (ISDN). Series J. Transmission of television, sound programme and other multimedia signals. Series M. TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits.

Series O. Specifications of measuring equipment. Series P. Telephone transmission quality telephone installations, local line networks. Series Q. Switching and signaling.

Series T. Terminals for telematic services. Series V. Data communication over the telephone network. Series X. Data networks and open systems communication. Series Y. Global information infrastructure. Series Z. Languages and general software aspects for telecommunication systems.

ITU E.169

An ITU-T Recommendation allowing International Freephone customers to be allocated a unique Universal Freephone Number (UIFN) which will remain the same throughout the world, regardless of country or telecommunications carrier.

ITU H.222

An ITU-T Study Group 15 standard that addresses the multiplexing of multimedia data on an ATM network. See H.222 and other H.XXX entries.


See all the definitions beginning with Q.

ITU Study Groups

The ITU operates as a series of groups considering specialist areas. Key study groups applicable to networking and communications are: Study Group VII responsible for terminal equipment for telematic services, including fax and higher level OSI standards; Study Group X covering Languages and methods for telecommunications applications; Study Group XI covering ISDN, telephone network including V-series Recommendations; Study Group XVIII covering digital networks including ISDN. See ITU above and ITU-T.


A set of evolving telecom standards. For more on those standards, see under the letter "V."


The Telecommunications Standards Section (TSS) is one of four organs of the ITU. Any specification with an ITU-T or ITU-TSS designation refers to the TSS organ.


Information Technology Users' Standards Association.


Interactive TV. Also abbreviated to I-TV.


Interface Unit.


Implementation Under Test: The particular portion of equipment which is to be studied for testing. The implementation may include one or more protocols.


The ISDN Users Workshop.


Installation Verification Certification Program.


Incremental Volume Discount.


Integrated Voice and Data Multiplexer. A device that Northern Telecom uses to provide DIALAN, a central office provided local area network offering completely digital, full duplex data transmission at speeds of 300 bps through 19.2 asynchronous and 1,200 bps through 64 kbps synchronous. DIALAN users use existing telephone sets and an Integrated Voice and Data Multiplexer (IVDM) that plugs into a telephone jack.


Interactive Video and Data Service. See 218-219 MHz.


Integrated Voice/Data Terminal. A device with a terminal keyboard/display and a voice telephone with or without its own processing power. See Integrated Voice/Data Terminal.


Interactive Voice Response. Think of IVR as a voice computer. Where a computer has a keyboard for entering information, an IVR uses remote touchtone telephones. Where a computer has a screen for showing the results, an IVR uses snippets of recordings of human voice or a synthesized voice (computerized voice). Recordings are used for repetitive messages, "Thanks for calling ABC Company. Push one for our sales department. Push two for our service department." Synthesized voice (also called Text-ToSpeech) is used for reading information from files which contain information that can't be put into neat "sound bites," like numbers and dates, e.g. reading my incoming email. Whatever a computer can do, an IVR can too ” from looking up train timetables to moving calls around an automatic call distributor (ACD). The only limitation on an IVR is that you can't present as many alternatives on a phone as you can on a screen. The caller's brain simply won't remember more than a few. With IVR, you have to present the menus in smaller, cascading chunks .

The benefits of Interactive Voice Response are obvious. By automating the retrieval and processing of information by phone, you can "give data a voice" and "add intelligence to the phone call." By doing that, you can:

Put information to work. The classic IVR "killer app" takes an existing database (e.g., a magazine's article archives, a freight company's package-tracking system) and makes it available by phone (or other media, such as fax, e-mail, or DSVD ” Digital Simultaneous Voice and Data). You can automate telephone-based tasks. From "bank by phone" to "find my package" to "sell me an airline ticket," to "validate my new credit card," IVR gives access to and takes in information; performs record-keeping , and makes sales, 24 hours a day ” supplementing or standing in for human personnel. IVR can add value to communications. Any call-handling phone system (e.g. an automatic call distributor used by airlines) can profit from IVR. Used as a front-end for an ACD, an IVR system can ask questions (e.g., "what's your product serial code?") that help routing and enable more intelligent and informed call processing (by people or automatic systems). IVR can add interactive value to what would otherwise be wait-time. The IVR can be used to distribute info, make callers aware of specials ” even provide entertainment. The result: fewer callers drop off queue; you make more sales.

Periphonics, a early and leading IVR company, explains it thus: IVR systems allow individuals to access information in an organization's computer database and to receive that information either verbally, using an ordinary touch-tone phone, or on a PC, via the Internet. In addition, these systems enable customers to execute certain transactions on-line without the intervention of customer service personnel. Typically, 30-60% of the repetitive and/or routine inbound calls are automated, which can maximize the effectiveness of the current customer service staff.

Benefits of IVR:

  1. Reduces costs.

  2. Improves access to information (24 hours a day - 7 days a week).

  3. Enhances customer service.

  4. Improves competitive position with increased customer retention.

  5. Streamlines operations.

  6. Generates new revenues.

  7. Better utilization of telephone and computer systems capabilities.

  8. Improves productivity of customer support staff and reduces the need to increase staff for peak periods.

  9. Provides more services in less time and at lower costs.

  10. Reduces errors in data capture/input, with feedback for valid entries.

  11. Gives a typical ROI of six to nine months.


Interactive Voice Service.


  1. Interworking.

  2. Information Warfare.

  3. Inside Wire.


iWarp is a form of remote direct memory access (RDMA) that will be independent of switch fabrics and applications protocols. The goal of one of the people working on this new standard "is to unify IP and InfiniBand." According to a news magazine report, Cisco Systems hopes to use iWarp to power its efforts at delivering storage network that link servers and large storage arrays over IP instead of the fast but more costly Fibre Channel links often used today."


Intelligent Workstation.


International Wireless Telecommunications Association. An organization created to represent the interests of the worldwide commercial trunked radio industry, which generally is known as SMR (Switched Mobile Radio) in the U.S. IWTA grew out of its sister organization AMTA (American Mobile Telecommunications Association. See also SMR.


German for pulse dialing. The German is ImpulseWahlFerfahren.


  1. IntereXchange carrier, i.e. a long distance phone company. More commonly known as IXC (IntereXchange Carrier) or IEC (InterExchange Carrier). Since the Modified Final Judgement (MFJ) took effect in the U.S. in 1984, the IXs have enjoyed the virtually exclusive right to haul traffic across LATA (Local Access and Transport Area) boundaries. The ILECs (Incumbent Local Exchange Carriers), on the other hand, are limited to providing local service and short-haul long distance within the LATA boundaries. See also IEC, ILEC, IXC, LATA, and MFJ.

  2. Internet eXchange. A commercial peering point at which ISPs (Internet Service Providers) outside the U.S. exchange traffic directly on a regional basis, avoiding the costs of exchanging traffic through the U.S. NAPs (Network Access Points). IXs include the Amsterdam Internet Exchange (AMS-IX), Hong Kong Internet Exchange (HKIX), Japan Internet Exchange (JPIX), London Internet Exchange (LINX), and Service for French Internet Exchange (SFINX). See also MAE, NAP, and Peering Point.


IntereXchange Carrier. Also known as IEC (InterExchange Carrier) and IC. Long-haul long distance carriers, IXCs include all facilities-based inter-LATA carriers. The largest IXCs are AT&T, MCI, Sprint and Worldcom; a huge number of smaller, regional companies also fit this definition. The term generally applies to voice and data carriers, but not to Internet carriers. IXC is in contrast to LEC (Local Exchange Carrier), a term applied to traditional telephone companies which provide local service and intraLATA toll service. IXCs also provide intraLATA toll service and operate as CLECs (Competitive Local Exchange Carriers) in many states. Once upon a time, the non-AT&T IXCs were called OCCs (Other Common Carriers), a status which they resented for understandable reasons.


Inter-Exchange Mileage.


Interconnection revenue. Only issued in reciprocal compensation states and only paid out to wholesale from the ILECs to the CLECs.


A one-way protocol for ASCII-based communications between the Internet and wireless pagers , IXO was named for the company that allegedly invented it. Others suggest that it was invented by Robert Edwards, the paging pioneer who owned Radiofone Corp. In any event, it was renamed APE (Alphanumeric Paging Entry), and then TAP (Telocator Alphanumeric Protocol). Motorola calls it PET (Personal Entry Protocol). It largely has been replaced by SNPP (Simple Network Paging Protocol). See also SNPP and TAP.


The little i stands for Intel and the numbers that follow refer to the particular microprocessor chip. For example, i386 refers to the 80386 chip.

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133 © 2008-2017.
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