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Technology Glossary


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Select a letter above to access the technology glossary in alphabetical order.
Select + for miscellaneous.

i960cf - The Intel 960 family is a RISC based processor designed for embedded applications. The "cf" series does not allow for dual SCP operation.

i960ha - The Intel 960 family is a RISC based processor designed for embedded applications. The "ha" series pushes performance to more than 80 MIPS and allows for dual SCP operation.

I/O Input/Output.

I/O Module - Marconi's interface cards for the LAX-20 LAN Access Switch, designed to connect Ethernet, Token Ring, and FDDI LANs to ForeRunner ATM networks.

I&R (Installation And Repair) - The telephone company department responsible for these jobs.

IC (Integrated Circuit) - A single electronic device that contains hundreds of thousands of previously separate (discrete) components. The “computer on a chip” is a special purpose integrated circuit.

ICD (International Code Designator) - One format of ATM Addressing, it is administered by the British Standards Institute. Identifies an international organization responsible for the NSAP structure (in Marconi's case the hex 0005 identifies the US Government). The registration authority under hex 0005 is the National Institute of Standards and Technology (NIST) who has delegated the General Services Administration (GSA) to register AA identifiers. The digits are encoded in BCD syntax. (2 octets)

ICMP (Internet Control Message Protocol) - The protocol that handles errors and control messages at the IP layer. ICMP is actually a part of the IP protocol layer. It can generate error messages, test packets, and informational messages related to IP.

ICR (Initial Cell Rate) - For ABR, the rate at which a source is allowed to start up following an idle period.

IDI (Initial Domain Identifier) - The Initial Domain Identifier can be either a 2-byte data country code (DCC) value as describe in ISO 3166, a 2-byte international code designator (ICD) as maintained in ISO 6523 by the British Standards Institute, or and E.164 number.

IDP (Initial Domain Part) - Specifies the authority allocating the NSAP address.

IDU (Interface Data Unit) - The unit of information transferred to/from the upper layer in a singlesize=+0>interaction across the SAP. Each IDU contains interface control information and may also contain the whole or part of the SDU.

IE (Information Element) - An information bearing entity that is encoded to define specific parameters associated with establishing a contract. UNI signaling messages are comprised of many Information Elements.

IEE (Institution of Electrical Engineers) - The U.K. body for professional electrical engineers.

IEEE (Institute of Electrical and Electronics Engineers) - the world's largest technical professional society. Based in the U.S., the IEEE sponsors technical conferences, symposia & local meetings worldwide, publishes nearly 25% of the world's technical papers in electrical, electronics & computer engineering, provides educational programs for members, and promotes standardization.

IEEE 802 - Standards for the interconnection of LAN computer equipment. Deals with the Data Link Layers of the ISO Reference Model for OSI.

IEEE 802.1 - Defines the high-level network interfaces such as architecture, internetworking and network management.

IEEE 802.1d Spanning Tree Bridging - IEEE standard for bridging; a MAC layer standard for transparently connecting two or more LANs (often called subnetworks) that are running the same protocols and cabling. This arrangement creates an extended network, in which any two workstations on the linked LANs can share data.

IEEE 802.1p - Defines Standard VLANs

IEEE 802.1q - Defines Standard VLANS, a.k.a. VLAN tagging.

IEEE 802.2 - Defines the Logical Link Control interface between the Data Link and Network Layers.

IEEE 802.3 - Defines CSMA/CD (Ethernet).

IEEE 802.3u - Defines 100 BaseT Ethernet.

IEEE 802.3x - Defines full-duplex flow control.

IEEE 802.3y - Defines full-duplex flow control.

IEEE 802.3z - Defines MAC for 1000 Mbps - Gigabit Ethernet.

IEEE 802.3ad - Defines link aggregation and trunking.

IEEE 802.4 - Defines the token-passing bus.

IEEE 802.5 - Defines the Token Ring access methodology. This standard incorporates IBM's Token Ring specifications.

IEEE 802.6 - Defines Metropolitan Area Networks.

IEEE 802.7 - The broadband technical advisory group.

IEEE 802.8 - The fiber optics technical advisory group.

IEEE 802.9- Defines integrated data and voice networks.

IETF (Internet Engineering Task Force) - a large, open, international community of network designers, operators, vendors and researchers whose purpose is to coordinate the operation, management and evolution of the Internet to resolve short- and mid-range protocol and architectural issues.

IG (Information Group) - A collection of parameters used to define a specific PNNI function (i.e., Nodal Hierarchy, List IG).

IISP (Interim-Interswitch Signaling Protocol) - A routing scheme that enables the establishment of PVCs between ATM switches from different vendors. It uses static, hop-by-hop routing tables. (Formerly, P-NNI Phase 0)

ILMI (Interim Local Management Interface) - The standard that specifies the use of the Simple Network Management Protocol (SNMP) and an ATM management information base (MIB) to provide network status and configuration information.

Impedance (Z) - The total opposition by a circuit to the flow of alternating current; a vector sum of all resistance and reactance in a circuit, expressed in ohms.

Indication Of - Lights, bells and buzzers indicating that something has or is about to happen. For example, indication of a camp-on to a station is short bursts of tone transmitted periodically to a busy phone to indicate that another call is camped on and waiting.

Inductance - An electric force field which builds up around a conductor.

Inductor - A coil of wire, usually wound in a special core of high permeability, which provides high inductance without necessarily being of high resistance.

Inelastic - Applications do not adjust their demands based on feedback about available network bandwidth, they run "Open Loop". They are best matched to CBR and VBR service categories.

Ingress - One of two distinctly different roles of the MPC (Multi Protocol Client). As an Ingress MPC, the client detects sustained flows of packets that are currently being sent over the routed path to a router that is enabled as an MPS (Multi Protocol Server).

ingress - When referring to a switch, fabric or port, ingress typically refers to the input, receive or upstream side.

Inhibit - To prevent a device or circuit from operating.

In Phase - Two or more alternating currents and/or voltages (at the same frequency) that have their zero and maximum value occurring simultaneously.

Input - A signal fed into a circuit.

Input-Output Device - Equipment used to put information into or take information out of a computer system.

Input Transformer - Transformer at the input to a device which transforms/matches the impedance of the device to that of the preceding stage.

Inrush Current - The maximum instantaneous value of the input current to a device when it is switched on.

Inside Plant - Everything inside a telephone company central office.

Insulation - A material which will not conduct electricity and is suitable for surrounding conductors to prevent the flow of current.

Insulator - The glass or ceramic cup attached to a crossarm to which a telephone wire is bound

Intelligent Infrastructure - Marconi’s implementation of scalable network technology that allows the network to configure, heal, tune, and protect itself.

Intelligent Multiplexer - A processor-controlled multiplexer that allocates bandwidth utilization.

Intelligent Terminal - A terminal which contains its own computer, as opposed to a dumb terminal, which is only a communication device with another computer.

Interconnect Companies - Companies which sell, install and maintain telephone systems for end users, typically businesses.

Interface - A demarcation between two devices, where the electrical signals, connectors, timing and handshaking meet. Often the procedures, codes and protocols that enable the two devices to interact are included or carried out by the interface.

Interface Data - the unit of information transferred to/from the upper layer in a single interaction across a SAP. Each Interface Data Unit (IDU) controls interface information and may also contain the whole or part of the SDU.

Interface Device - A device which meets a standard electrical interface on one side and meets some other non-standard interface on the other.

Interfacing Relay - A relay used to convert a grounded input alarm to resistance battery, a grounded input alarm to a loop closure, a grounded input from one plant to another ground which is compatible with the termination of the alarm, or a battery input to a grounded output. The relay can also be used to create dry contacts or spare contacts which will allow a given alarm input to be spread to various terminations.

Interior - Denotes that an item (e.g., link, node, or reachable address) is inside of a PNNI routing domain.

Intermittent Fault - A defect in a circuit or medium which is not continually apparent.

Internal Reachable Address - An address of a destination that is directly attached to the logical node advertising the address.

internet - while an internet is a network, the term "internet" is usually used to refer to a collection of networks interconnected with routers.

Internet - (note the capital "I") the largest internet in the world including large national backbone nets and many regional and local networks worldwide. The Internet uses the TCP/IP suite. Networks with only e-mail connectivity are not considered on the Internet.

Internet Addresses - The numbers used to identify hosts on an internet network. Internet host numbers are divided into two parts; the first is the network number and the second, or local, part is a host number on that particular network.

There are also three classes of networks in the Internet, based on the number of hosts on a given network.

Large networks are classified as Class A, having addresses in the range 1-126 and having a maximum of 16,387,064 hosts.

Medium networks are classified as Class B, with addresses in the range 128-191 and with a maximum of 64,516 hosts.

Small networks are classified as Class C, having addresses in the range 192-254 with a maximum of 254 hosts. Addresses are given as dotted decimal numbers in the following format:

In a Class A network, the first of the numbers is the network number, the last three numbers are the local host address.
In a Class B network, the first two numbers are the network, the last two are the local host address.
In a Class C network, the first three numbers are the network address, the last number is the local host address.
The following table summarizes the classes and sizes:

Class First # Max# Hosts
A 1-126 16,387,064
B 129-191 64,516
C 192-223 254

Network mask values are used to identify the network portion and the host portion of the address. For:
Class A - the default mask is
Class B - the default mask is
Class C - the default mask is

Subnet masking is used when a portion of the host ID is used to identify a subnetwork. For example, if a portion of a Class B network address is used for a subnetwork, the mask could be set as This would allow the third byte to be used as a subnetwork address. All hosts on the network would still use the IP address to get on the Internet.

Interoperability - The ability of software and hardware on multiple machines, from multiple vendors, to communicate.

Inverter - Electrical apparatus or equipment that changes DC power to AC power.

Inverter System - A power system that utilizes inverters to change direct current (DC) to alternating current (AC) power for powering AC equipment during a power outage or fluctuation, or where protected AC power is required and commercial power is unacceptable.

Inv. Fail (Inverter Failure) A discrete alarm notation indicative of an inverter failure considered a major alarm.

ION (Internetworking Over NBMA (Non-Broadcast Multi-Access)) - The Internet Engineering Task Force (IETF) formed the group which developed the Next Hop Resolution Protocol (NHRP).

IPD (Intelligent Packet Discard) - A mechanism an ATM switch may use to control data loss in packet traffic. Any method of cell discard would be considered IPD if cells are seen as components of higher-layer packets and discarded on that basis in order to minimize the number of packets affected.

IP (Internet Protocol) - a connectionless, best-effort packet switching protocol that offers a common layer over dissimilar networks.

IP Address - A unique 32-bit integer used to identify a device in an IP network. You will most commonly see IP addresses written in "dot" notation; for instance, (see IP netmask).

IP Netmask - A pattern of 32 bits that is combined with an IP address to determine which bits of an IP address denote the network number and which denote the host number. Netmasks are useful for sub-dividing IP networks. IP netmasks are written in "dot" notation; for instance, (see IP address).

IPX Protocol (Internetwork Packet Exchange) - A NetWare protocol similar to the Xerox Network Systems (XNS) protocol that provides datagram delivery of messages.

IR Drop - Voltage drop across a resistance: I (current in amperes) times R (resistance in ohms).

IS (Intermediate system) - A system that provides forwarding functions or relaying functions or both for a specific ATM connection. OAM cells may be generated and received.

ISA Bus - A bus standard developed by IBM for expansion cards in the first IBM PC. The original bus supported a data path only 8 bits wide. IBM subsequently developed a 16-bit version for its AT class computers. The 16-bit AT ISA bus supports both 8- and 16-bit cards. The 8-bit bus is commonly called the PC/XT bus, and the 16-bit bus is called the AT bus.

ISDN (Integrated Services Digital Network) - A service technology that is offered by many of the telephone carriers of the world. ISDN combines voice and digital network services into a single medium or wire.

ISO (International Standards Organization) - A voluntary, non-treaty organization founded in 1946 that is responsible for creating international standards in many areas, including computers and communications.

Isochronous - Signals carrying embedded timing information or signals that are dependent on uniform timing; usually associated with voice and/or video transmission.

Isolation Condition which prevents interaction between circuits.

ITU-T - International Telecommunications Union Telecommunications: ITU-T is an international body of member countries whose task is to define recommendations and standards relating to the international telecommunications industry. The fundamental standards for ATM have been defined and published by the ITU-T (Previously CCITT).

IWF (Interworking Function) - Provides the means for two different technologies to interoperate.

IXC (Interexchange Carriers) - Long-distance communications companies that provide service between Local Access Transport Areas (LATAs).