Table of Contents




Internet Architecture Board. Board of internetwork researchers who discuss issues pertinent to Internet architecture. Responsible for appointing a variety of Internet-related groups such as the IANA, IESG, and IRSG. The IAB is appointed by the trustees of the ISOC. See also IANA, IESG, IRSG, and ISOC.


Internet International Ad Hoc Committee. Coalition of participants from the broad Internet community, working to satisfy the requirement for enhancements to the Internet's global DNS. Organizations naming members to the committee include Internet Society (ISOC), Internet Assigned Numbers Authority (IANA), Internet Architecture Board (IAB), Federal Networking Council (FNC), International Telecommunication Union (ITU), International Trademark Association (INTA), and World Intellectual Property Organization (WIPO).


Internet Assigned Numbers Authority. Organization operated under the auspices of the ISOC as a part of the IAB. IANA delegates authority for IP address-space allocation and domain-name assignment to the InterNIC and other organizations. IANA also maintains a database of assigned protocol identifiers used in the TCP/IP stack, including autonomous system numbers. See also ICP cell, ISOC, and InterNIC.


International Code Designator. One of two ATM address formats developed by the ATM Forum for use by private networks. Adapted from the subnetwork model of addressing in which the ATM layer is responsible for mapping network layer addresses to ATM addresses. Compare with DCC.


Internet Control Message Protocol. Network layer Internet protocol that reports errors and provides other information relevant to IP packet processing. Documented in RFC 792.

ICMP Router Discovery Protocol


ICP cell

IMA control protocol cell used for aligning the cells in multiple links.


initial cell rate.


Internet-Draft. Working documents of the IETF, from its Areas and Working Groups. They are valid for a maximum of 6 months and might be updated, replaced, or obsoleted by other documents at any time. Very often, I-Ds are precursors to RFCs.


initial domain identifier. Portion of an NSAP or NSAP-format ATM address that specifies the address allocation and administration authority. See also NSAP.


International Data Number. See X.121.


initial domain part. Part of a CLNS address that contains an authority and format identifier, and a domain identifier.


Interdomain Policy Routing. Interdomain routing protocol that dynamically exchanges policies between autonomous systems. IDPR encapsulates interautonomous system traffic and routes it according to the policies of each autonomous system along the path. IDPR is currently an IETF proposal. See also policy-based routing.


IS-IS Interdomain Routing Protocol. OSI protocol that specifies how routers communicate with routers in different domains.


information element.


International Electrotechnical Commission. Industry group that writes and distributes standards for electrical products and components.


Institute of Electrical and Electronics Engineers. Professional organization whose activities include the development of communications and network standards. IEEE LAN standards are the predominant LAN standards today.

IEEE 802.1

IEEE specification that describes an algorithm that prevents bridging loops by creating a spanning tree. The algorithm was invented by Digital Equipment Corporation. The Digital algorithm and the IEEE 802.1 algorithm are not exactly the same, nor are they compatible. See also spanning tree, spanning-tree algorithm, and Spanning-Tree Protocol.

IEEE 802.12

IEEE LAN standard that specifies the physical layer and the MAC sublayer of the data link layer. IEEE 802.12 uses the demand priority media-access scheme at 100 Mbps over a variety of physical media. See also 100VG-AnyLAN.

IEEE 802.2

IEEE LAN protocol that specifies an implementation of the LLC sublayer of the data link layer. IEEE 802.2 handles errors, framing, flow control, and the network layer (Layer 3) service interface. Used in IEEE 802.3 and IEEE 802.5 LANs. See also IEEE 802.3 and IEEE 802.5.

IEEE 802.3

IEEE LAN protocol that specifies an implementation of the physical layer and the MAC sublayer of the data link layer. IEEE 802.3 uses CSMA/CD access at a variety of speeds over a variety of physical media. Extensions to the IEEE 802.3 standard specify implementations for Fast Ethernet. Physical variations of the original IEEE 802.3 specification include 10Base2, 10Base5, 10BaseF, 10BaseT, and 10Broad36. Physical variations for Fast Ethernet include 100BaseT, 100BaseT4, and 100BaseX.

IEEE 802.4

IEEE LAN protocol that specifies an implementation of the physical layer and the MAC sublayer of the data link layer. IEEE 802.4 uses token-passing access over a bus topology and is based on the token bus LAN architecture. See also token bus.

IEEE 802.5

IEEE LAN protocol that specifies an implementation of the physical layer and MAC sublayer of the data link layer. IEEE 802.5 uses token passing access at 4 or 16 Mbps over STP cabling and is similar to IBM Token Ring. See also Token Ring.

IEEE 802.6

IEEE MAN specification based on DQDB technology. IEEE 802.6 supports data rates of 1.5 to 155 Mbps. See also DQDB.


Internet Engineering Planning Group. Group, primarily composed of Internet service operators, whose goal is to promote a globally coordinated Internet operating environment. Membership is open to all.


Internet Engineering Steering Group. Organization, appointed by the IAB, that manages the operation of the IETF. See also ICP cell and IETF.


Internet Engineering Task Force. Task force consisting of over 80 working groups responsible for developing Internet standards. The IETF operates under the auspices of ISOC. See also ISOC.


International Federation for Information Processing. Research organization that performs OSI prestandardization work. Among other accomplishments, IFIP formalized the original MHS model. See also MHS.


Information frame. One of three SDLC frame formats. See also S-frame and U-frame.


Internet Group Management Protocol. Used by IP hosts to report their multicast group memberships to an adjacent multicast router. See also multicast router.


Interior Gateway Protocol. Internet protocol used to exchange routing information within an autonomous system. Examples of common Internet IGPs include IGRP, OSPF, and RIP. See also OSPF and RIP. See also IGRP (Interior Gateway Routing Protocol) in the "Cisco Systems Terms and Acronyms" section.


See IGRP (Interior Gateway Routing Protocol) in the "Cisco Systems Terms and Acronyms" section.


IS-IS Hello. Message sent by all IS-IS systems to maintain adjacencies. See also IS-IS.


Interagency Interim National Research and Education Network. Evolving operating network system. Near term research and development activities will provide for the smooth evolution of this networking infrastructure into the future gigabit NREN.


Internet Inter-ORB Protocol. Protocol used in the CORBA framework for accessing objects across the Internet. See also CORBA.


Interim-Interswitch Signaling Protocol. ATM signaling protocol for inter-switch communication using manually configured prefix tables. When a signaling request is received by a switch, the switch checks the destination ATM address against the prefix table and notes the port with the longest prefix match. It then forwards the signaling request across that port using UNI procedures. IISP is an interim solution until PNNI Phase 1 is completed. Formerly known as PNNI Phase 0. Contrast with Dynamic IISP.


Information Infrastructure Technology and Applications. Component of the HPCC program intended to ensure U.S. leadership in the development of advanced information technologies. See also HPCC.


Internet Key Exchange


Interim Local Management Interface. Specification developed by the ATM Forum for incorporating network-management capabilities into the ATM UNI.


inverse multiplexing over ATM. Standard protocol defined by the ATM Forum in 1997.

IMA group

Physical links grouped to form a higher-bandwidth logical link whose rate is approximately the sum of the individual link rates.


Internet Message Access Protocol. Method of accessing e-mail or bulletin board messages kept on a mail server that can be shared. IMAP permits client electronic mail applications to access remote message stores as if they were local without actually transferring the message.


"In My Humble Opinion." One of many short-form phrases seen in e-mail messages, newsgroups, and so on.


interface message processor. Old name for ARPANET packet switches. See also ARPANET and packet switch.


Inter-Machine Trunk.


Intelligent Network/Advanced Intelligent Network


Information Networking Architecture. Bellcore object-oriented architecture for the management of ATM and SONET equipment and services in an operating company environment.


Bellcore implementation of INA. See also INA.


Install Busy. Entity has just been created but has not been commanded In-Service or Out-of-Service yet.

in-band signaling

Transmission within a frequency range normally used for information transmission. Compare with out-of-band signaling.

Industry-Standard Architecture

See ISA.

information element

In ATM, the portion of a signaling packet that carries information, such as addresses, used in the UNI specification. See also UNI.

Information Infrastructure Technology and Applications



Electromagnetic waves whose frequency range is above that of microwaves, but below that of the visible spectrum. LAN systems based on this technology represent an emerging technology.


Intelligent Network Element. Network element that can be provisioned from a remote OSS.

initial domain identifier

See IDI.

initial domain part

See IDP.


Internet Network Operations Center. BBN group that in the early days of the Internet monitored and controlled the Internet core gateways (routers). INOC no longer exists in this form.



Institute of Electrical and Electronics Engineers


insured burst

In an ATM network, the largest burst of data above the insured rate that will be temporarily allowed on a PVC and not tagged by the traffic policing function for dropping in the case of network congestion. The insured burst is specified in bytes or cells. Compare with maximum burst. See also insured rate.

insured rate

Long-term data throughput, in bits or cells per second, that an ATM network commits to support under normal network conditions. The insured rate is 100 percent allocated; the entire amount is deducted from the total trunk bandwidth along the path of the circuit. Compare with excess rate and maximum rate. See also insured burst.

insured traffic

Traffic within the insured rate specified for an ATM PVC. This traffic should not be dropped by the network under normal network conditions. See also CLP and insured rate.


Interoperability Technology Association for Information Processing. Technical organization that has the official charter to develop Japanese OSI profiles and conformance tests.

Integrated IS-IS

Routing protocol based on the OSI routing protocol IS-IS, but with support for IP and other protocols. Integrated IS-IS implementations send only one set of routing updates, making it more efficient than two separate implementations. Formerly called Dual IS-IS. Compare with IS-IS.

Integrated Services Digital Network


Integrated Services Internet

IETF proposal for enhancing IP to allow it to support integrated or multimedia services, including traffic management mechanisms that closely match the traffic management mechanisms of ATM. An example is RSVP.

Intelligent QoS Management Suite

Composed of Automatic Routing Management, Advanced CoS Management, Optimized Bandwidth Management, and Dynamic Buffer Management. Formerly called Advanced Networking Features.

interarea routing

Term used to describe routing between two or more logical areas. Compare with intra-area routing.

Interdomain Policy Routing



1. Connection between two systems or devices.

2. In routing terminology, a network connection.

3. In telephony, a shared boundary defined by common physical interconnection characteristics, signal characteristics, and meanings of interchanged signals.

4. Boundary between adjacent layers of the OSI model.

interface message processor

See IMP.

interface processor

See interface processor in the "Cisco Systems Terms and Acronyms" section.


Unwanted communication channel noise.

Interim Local Management Interface


Interior Gateway Protocol

See IGP.

Interior Gateway Routing Protocol

See IGRP in the "Cisco Systems Terms and Acronyms" section.

intermediate routing node

See IRN.

Intermediate Session Routing

See ISR.

intermediate system

See IS.

Intermediate System-to-Intermediate System

See IS-IS.

International Code Designator

See ICD.

International Data Number

See X.121.

International Electrotechnical Commission

See IEC.

International Federation for Information Processing


International Organization for Standardization

See ISO.

International Standards Organization

Erroneous expansion of the acronym ISO. See ISO.

International Telecommunication Union Telecommunication Standardization Sector

See ITU-T.


Largest global internetwork, connecting tens of thousands of networks worldwide and having a "culture" that focuses on research and standardization based on real-life use. Many leading-edge network technologies come from the Internet community. The Internet evolved in part from ARPANET. At one time, called the DARPA Internet. Not to be confused with the general term internet. See also ARPANET.


Short for internetwork. Not to be confused with the Internet. See internetwork.

Internet Architecture Board

See ICP cell.

Internet address

See IP address.

Internet Assigned Numbers Authority


Internet Control Message Protocol



See I-D.

Internet Engineering Planning Group


Internet Engineering Steering Group


Internet Engineering Task Force


Internet Group Management Protocol


Internet Message Access Protocol


Internet Network Operations Center


Internet protocol

Any protocol that is part of the TCP/IP protocol stack. See IP. See also TCP/IP.

Internet Protocol (IP, IPv4)

Network layer for the TCP/IP protocol suite. Internet Protocol (version 4) is a connectionless, best-effort packet switching protocol. Defined in RFC 791.

Internet Protocol (IPng, IPv6)

See IPv6.

Internet Registry

See IR.

Internet Relay Chat

See IRC.

Internet Research Steering Group


Internet Research Task Force


Internet service provider

See ISP.

Internet Society


Internet telephony

Generic term used to describe various approaches to running voice telephony over IP.


Collection of networks interconnected by routers and other devices that functions (generally) as a single network. Sometimes called an internet, which is not to be confused with the Internet.


General term used to refer to the industry devoted to connecting networks together. The term can refer to products, procedures, and technologies.

Internetwork Packet Exchange

See IPX.


Organization that serves the Internet community by supplying user assistance, documentation, training, registration service for Internet domain names, and other services. Formerly called NIC.


Ability of computing equipment manufactured by different vendors to communicate with one another successfully over a network.

Inter-Switching System Interface


Inter-Switch Link

See ISL in the "Cisco Systems Terms and Acronyms" section.

intra-area routing

Term used to describe routing within a logical area. Compare with interarea routing.

Inverse Address Resolution Protocol

See Inverse ARP.

Inverse ARP

Inverse Address Resolution Protocol. Method of building dynamic routes in a network. Allows an access server to discover the network address of a device associated with a virtual circuit.

inverse multiplexing

Process whereby physical links are grouped to form a higher-bandwidth logical link whose rate is approximately the sum of the individual link rates.




independent operating company. Independently owned company providing local telephone services to residential and business customers in a geographic area not served by an RBOC.


I/O channel controller.


Internal Organization of the Network Layer. 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.


See Cisco IOS in the "Cisco Systems Terms and Acronyms" section.


Internet Protocol. Network layer protocol in the TCP/IP stack offering a connectionless internetwork service. IP provides features for addressing, type-of-service specification, fragmentation and reassembly, and security. Defined in RFC 791.

IP address

32-bit address assigned to hosts using TCP/IP. An IP address belongs to one of five classes (A, B, C, D, or E) and is written as 4 octets separated by periods (dotted decimal format). Each address consists of a network number, an optional subnetwork number, and a host number. The network and subnetwork numbers together are used for routing, while the host number is used to address an individual host within the network or subnetwork. A subnet mask is used to extract network and subnetwork information from the IP address. CIDR provides a new way of representing IP addresses and subnet masks. Also called an Internet address. See also CIDR, IP, and subnet mask.

IP datagram

Fundamental unit of information passed across the Internet. Contains source and destination addresses along with data and a number of fields that define such things as the length of the datagram, the header checksum, and flags to indicate whether the datagram can be (or was) fragmented.


interprocess communication.


IP Control Protocol. Protocol that establishes and configures IP over PPP. See also IP and PPP.

IP multicast

Routing technique that allows IP traffic to be propagated from one source to a number of destinations or from many sources to many destinations. Rather than sending one packet to each destination, one packet is sent to a multicast group identified by a single IP destination group address.


See IPv6.


IP version 6. Replacement for the current version of IP (version 4). IPv6 includes support for flow ID in the packet header, which can be used to identify flows. Formerly called IPng (next generation).

IP Security Option



IP Security Option. U.S. government specification that defines an optional field in the IP packet header that defines hierarchical packet security levels on a per interface basis.


Internetwork Packet Exchange. NetWare network layer (Layer 3) protocol used for transferring data from servers to workstations. IPX is similar to IP and XNS.


IPX Control Protocol. Protocol that establishes and configures IPX over PPP. See also IPX and PPP.


IPX wide-area network. Protocol that negotiates end-to-end options for new links. When a link comes up, the first IPX packets sent across are IPXWAN packets negotiating the options for the link. When the IPXWAN options are successfully determined, normal IPX transmission begins. Defined by RFC 1362.


Internet Registry. IR was delegated the responsibility of network address and autonomuous system identifiers from the IANA, which has the discretionary authority to delegate portions of its responsibility.


integrated routing and bridging

Integrated Services Digital Network (ISDN) User Part. An upper-layer application supported by SS7 for connection set up and tear down.


Internet Relay Chat. World-wide "party line" protocol that allows one to converse with others in real time. IRC is structured as a network of servers, each of which accepts connections from client programs, one per user.


ICMP Router Discovery Protocol. Protocol that enables a host to determine the address of a router that it can use as a default gateway. Similar to ES-IS, but used with IP. See also ES-IS.


intermediate routing node. In SNA, a subarea node with intermediate routing capability.


Internet Research Steering Group. Group that is part of the IAB and oversees the activities of the IRTF. See also ICP cell and IRTF.


Internet Research Task Force. Community of network experts that considers Internet-related research topics. The IRTF is governed by the IRSG and is considered a subsidiary of the IAB. See also ICP cell and IRSG.


1. intermediate system. Routing node in an OSI network.

2. Telecommunications: In-Service. Entity is fully operational and capable of providing service to a requesting entity.


Industry-Standard Architecture. 16-bit bus used for Intel-based personal computers. See also EISA.

isarithmic flow control

Flow control technique that permits travel through the network. Isarithmic flow control is not commonly implemented.


Integrated Services Digital Network. Communication protocol, offered by telephone companies, that permits telephone networks to carry data, voice, and other source traffic. See also BISDN, BRI, N-ISDN, and PRI.


Intermediate System-to-Intermediate System. OSI link-state hierarchical routing protocol based on DECnet Phase V routing, whereby ISs (routers) exchange routing information based on a single metric, to determine network topology. Compare with Integrated IS-IS. See also ES-IS and OSPF.

IS-IS Hello

See IIH.

IS-IS Interdomain Routing Protocol



See ISL (Inter-Switch Link) in the "Cisco Systems Terms and Acronyms" section.


internetwork status monitor .


International Organization for Standardization. International organization that is responsible for a wide range of standards, including those relevant to networking. ISO developed the OSI reference model, a popular networking reference model.

ISO 3309

HDLC procedures developed by ISO. ISO 3309:1979 specifies the HDLC frame structure for use in synchronous environments. ISO 3309:1984 specifies proposed modifications to allow the use of HDLC in asynchronous environments as well.

ISO 9000

Set of international quality-management standards defined by ISO. The standards, which are not specific to any country, industry, or product, allow companies to demonstrate that they have specific processes in place to maintain an efficient quality system.


Internet Society. International nonprofit organization, founded in 1992, that coordinates the evolution and use of the Internet. In addition, ISOC delegates authority to other groups related to the Internet, such as the IAB. ISOC is headquartered in Reston, Virginia, (United States). See also ICP cell.

isochronous transmission

Asynchronous transmission over a synchronous data link. Isochronous signals require a constant bit rate for reliable transport. Compare with asynchronous transmission, plesiochronous transmission, and synchronous transmission.


ISO development environment. Large set of libraries and utilities used to develop upper-layer OSI protocols and applications.

ISO development environment



Internet service provider. Company that provides Internet access to other companies and individuals.


Intermediate Session Routing. Initial routing algorithm used in APPN. ISR provides node-to-node connection-oriented routing. Network outages cause sessions to fail because ISR cannot provide nondisruptive rerouting around a failure. ISR was replaced by HPR. Compare with HPR. See also APPN.


Inter-Switching System Interface. Standard interface between SMDS switches.


ISDN User Part.


International Telecommunication Union Telecommunication Standardization Sector. International body that develops worldwide standards for telecommunications technologies. The ITU-T carries out the functions of the former CCITT. See also CCITT.


interactive voice response. Term used to describe systems that provide information in the form of recorded messages over telephone lines in response to user input in the form of spoken words or more commonly DTMF signaling. Examples include banks that allow you to check your balance from any telephone and automated stock quote systems.


inter-exchange carrier. Common carrier providing long distance connectivity between LATAs. The three major IXCs are AT&T, MCI, and Sprint, but several hundred IXCs offer long distance service in the United States.

Posted: Tue Sep 21 15:34:45 PDT 1999
Copyright 1989-1999©Cisco Systems Inc.