Glossary I-P

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• I-Series recommendations ITU-TS (formerly the CCITT) recommendations on B-ISDN, ISDN and aspects of ATM.
• IAB (Internet Activities Board) The technical body that sets policy and standards for TCP/IP and the connected Internet suite of protocols. Its task forces are the IETF and IRTF.
• IBMCS (IBM Cabling System) Cabling system introduced by IBM in 1984 based around Shielded Twisted Pair (STP) cabling.
• ICMP (Internet Control Message Protocol) Protocol allowing status messages to be generated by an internetworking gateway, indicating a variety of error or unusual conditions.
• ICR (Intelligent Character Recognition) Software similar to OCR, but it learns to recognize different fonts and character styles, so is more efficient. Useful to make paper documents accessible via groupware.
• IDA (Integrated Digital Access) The means of providing digital access for subscribers to the BT ISDN service. Two versions: single line IDA and multi-line IDA are available.
• IDAPI (Integrated Database Application Programming Interface) A standard from Borland and others providing a standard interface to a wide range of databases. It is supposed to be a superset of ODBC.
• IEEE Institute of Electrical and Electronic Engineers: a US publishing and standards organization responsible for many LAN standards such as the 802 series.
• IEEE 802.2 The Data Link standard for use with IEEE 802.3, 802.4 and 802.5 standards. It specifies how the basic data connection should be set up over the cable.
• IEEE 802.3 The IEEE standardization of Ethernet. A Physical Layer definition that includes specification for physical cabling plus the method of transmitting data and controlling access to the cable. It uses the CSMA/CD access method on a bus topology LAN.
• IEEE 802.4 The IEEE standardization of Token Bus. A Physical Layer standard that uses the Token Ring passing access method on a bus topology LAN. Used by LANs implementing the Manufacturing Automation Protocol. The older Arcnet operates in a similar way but does not follow 802.4, but Arcnet supporters have been trying to get the technology ratified by IEEE without success.
• IEEE 802.5 The IEEE standardization of IBM Token Ring. A LAN Physical layer standard that uses the Token Ring passing access method on a ring topology LAN.
• IEEE 802.6 The standard that defines Mans, an SMDS-based, short packet ATM transmission.
• IGP (Interior Gateway Protocol) Term applied to any protocol used to propagate network reachability and routing information within an autonomous system. There is no single standard IGP, but RIP is one of the most common.
• IN (Intelligent Network) A sophisticated network capable of recognizing the profile (authorization, chosen services) of its users or subscribers. Carriers offering advanced services will increasingly offer IN services, particularly as the boundary between fixed and mobile networks becomes blurred.
• In-band signaling A communications technique in which the part of asignal bearing the data control information is contained within the bandwidth of the signal it is controlling.
• Installable file system A file system that can be installed in place of the usual file allocation table file system, such as the high-performance file system.
• Intelsat (International Telecommunications Satellite Organization) Founded in 1964 to develop a global satellite communications system, Intelsat has some 120 members, including- BT. The Earlybird (Intelsat 1) satellite was launched in 1965 a s the first in a series. Intelsat VII is planned to replace the dozen aging Intelsat V-types which carry two-thirds of the world's telephone calls.
• Interface The place or piece of equipment where interaction occurs between two regions or systems or processes. A common example is the RS232-C port or the AUI on LANs between the computer and transceiver.
• Internet (1) A group of networks that are interconnected so that they appear to be one continuous network, and can be addressed seamlessly at the Network Layer Three of the OSI model. Typical internets are built using routers, either to form a backbone network comprised of routers, or to link together LANs at the Network Layer.
• Internet (2) A collection of networks and gateways, including the Milnet and NSFNET, all using the TCP/IP protocol suite. It functions as a single, cooperative virtual network. The Internet provides universal connectivity and three levels of network services: connectionless packet delivery; full duplex stream delivery and application level services including electronic mail and EDI.
• Internet address An IP address assigned in blocks of numbers to user organizations accessing the Internet by the US DoD's Network Information Center. Duplicate addresses can cause major headaches on the network, but the NIC trusts organizations to use individual addresses responsibly. Each address is an eight- bit number (0 to 255). There are three classes: A, B and C, depending on how many computers on the site are likely to be connected. The NIC is running out of Class B addresses, so work is in progress to extend the address format to allow expansion into the next century.
• Inter-Process Communications (IPC) Communications between several programs based on one computer or across a number of machines. Alternatively, communication across a network between different processes of the same program between different computers running parts of a single program, or between two programs working together. The most common approaches to IPC in networking circles are probably Application Programming Interfaces such as APPC and NetBios.
• IGP (Interior Gateway Protocol) The term applied to any protocol used to propagate network reachability and routing information within an autonomous system. There is no single standard IGP, but RIP is one of the most common.
• ICMP (Internet Control Message Protocol) An integral part of the Internet Protocol (IP) that handles error and control messages. ICMP also includes an echo request/reply used to test whether a destination is reachable and responding.
• IESG (Internet Engineering Steering Group) A US committee consisting of the IETF chairperson and the six area managers. The IESG coordinates activities among the IETF working groups.
• IETF (Internet Engineering Task Force) A US committee concerned with short-term and medium-term problems with TCP/IP and the connected Internet. The IETF is divided into six areas which are further divided into working groups and its chairpe rson is a member of the TAB.
• Interoperability The ability to exchange information between two systems so that the information can be processed meaningfully.
• IP (Internet Protocol) The TCP/IP standard protocol that defines the IP datagram as the unit of information passed across an Internet and provides the basis for connectionless packet delivery service. IP includes the ICMP control and error m essage protocol as an integral part. It provides the functional equivalent of ISO OSI Network Services.
• IP address The 32-bit address assigned to hosts that want to participate in a TCP/IP Internet. IP datagram - The basic unit of information passed across a TCP/IP Internet.
• IRTF (Internet Research Task Force) A technical group working or problems related to TCP/IP and the connected Internet, The IRTF is divided into a set of research groups. The IRTF chairperson is a member of the IAB.
• ISA (Industry Standard Architecture) The 8/16-bit bus architecture originally developed by IBM and now standard in almost all PCs that use Intel's 8086 and 80X86 chips.
• ISDN (Integrated Services Digital Network) An approach to switched digital networking that can handle a range of digital voice, data and digital image transmission. It is intended to provide end-to-end, simultaneous handling of digitized voice and data traffic on the same digital links via integrated switches. There are different access channels, according to geographic location. These include Basic Rate Access (2 x 64Kbit/s 161 + 16Kbit/s) and Primary Rate Access (1.544 (US) and 2.048 Mbit/ s (Europe). ISDN standards are defined in the ITU-TS's I-Series Recommendations.

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• LAN (Local Area Network) A communications system that links computers into a network, usually via a wiring-based cabling scheme. LANs connect PCs, workstations and servers together to allow users to communicate and share resources like hard disk storage and printers. Devices linked by a LAN may be on the same floor or within a building or campus. It is user-owned and does not run over leased lines, though a LAN may have gateways to the PSTN or other, private, networks.
• LAN Manager for Unix Systems An implementation of LAN Manager for use with Unix. Known colloquially as LM/X.
• LAN Manager LAN Network Operating System developed by Microsoft which runs or top of OS/2 and recently Windows NT.
• LAN Network Manager IBM's network management software for Token Ring networks.
• LAN Segment A part of a LAN that is separated from the rest by one or more bridges.
• LAN Server IBM version of IBM LAN Manager.
• LAP (Link Access Protocol) The Data Link or OSI Layer Two protocol specified by the ITU-TS for the X.25 interface standard.
• LAP-B: A link set-up routine to establish and maintain links between DCE and DTE. Lap-D: The Layer Two protocol for an ISDN D-channel specified in the ITU-TS recommendation Q.921. It is a framed, bit-oriented protocol similar to Lap and Lap- B protocols specified for X.25 circuits. Lap-M: A variation of Lap-B used in the V.42 modem error control standard.
• LAT (Local Area Transport protocol) A DecNet specific protocol for the exchange of small packets of data between typically Dec Vax host computers and terminal servers in a LAN.
• Layer Description of divisions in specifications Such as OSI and SNA communications protocols. Functions are grouped together that comprise one step in the hierarchy necessary for successful data communications.
• Line conditioning A collection of techniques for keeping the quality of transmissions within specified parameters.
• Line driver A signal converter that conditions the digital signal transmitted by an RS232 interface to extend reliable communication beyond the 50ft RS232 limit up to several miles. It is a baseband transmission device.
• Line turnaround The interval on a transmission link between the time one block of data was sent and received and the time the next one can be sent.
• Line signal standards In the US: T1 carries data at 1.544Mbit/s and has 24 voice circuits; T1C 3.152 Mbit/s with 48 voice circuits; T2 6.312Mit/s with 96 voice circuits, and T3, 44.736Mbit/s. In Europe, the standards are of the form En. E1 line speed is 2.048Mbit/s with 3C voice circuits; E2 is 8.448Mit/s with 120 voice channels. E3 is 34.368Mbit/s with 480 voice circuits. In the UK, E1 is often referred to as MegaStream, a BT label for its 2Mbit/s leased circuits.
• Link state algorithm A routing algorithm such as OSPF which takes into account lowest delay when choosing a route: link speed and congestion as well as hop count.
• LLC (Logical Link Control) A data link protocol based or HDLC, developed for LANs by the IEEE 802 Committee and consequently common to all LAN standards for Data Link OSI Layer Two transmission.
• Local bridge Bridge that links two local LANs: in the same building, for example.
• Local security A security method available for 386 and 486 servers running HPFS386. This method extends LAN Manager security measures to protect the files on a server by restricting access of the users working at the server. With local security, a user must be assigned permissions to access any file or directory in an HPFS386 partition, whether or not the resource is shared as part of a LAN Manager resource.
• LocalTalk An Apple cabling scheme underlying its low-cost LANs. A 230Kbit/s baseband network primarily for Mac computers and LaserWriter printers, it uses the CSMA/CA media access method. The current Phase II allows theoretically unlimited networks.
• Lobe The cable between a Token Ring station and the Trunk Coupling Unit to which it is connected. Lobe length comprises a patch cable from the TCU to the main wiring panel, the length of the main wiring to the user station's location, then a patch cable from a floor/desk socket to the station.
• Logon script A batch program containing LAN Manager, NetWare and other operating system commands used to configure workstations. Logon scripts can be written for one or more users.
• Logon server For a domain, a logon server is the primary domain controller and the backup domain controllers. For a user, the server that processes the user's logon request.
• Loopback A diagnostic test that returns the transmitted signal back to the sending device after it has passed through a network or across a particular link. The returned signal can then be compared to the transmitted one. The discrepancy be tween the two help to trace the fault. When trying to locate a faulty piece of equipment, loopbacks will be repeated, eliminating satisfactory machines until the problem is found.
• LU (Logical Unit) An IBM SNA network function defined in layers four, five and six (Transmission Control, Data Flow Control and Presentation Services) of the SNA architecture. In the SNA network, corresponding LUs are able to exchange infor mation. Originally, particular types of LU has specific functions: LU1 for printers, LU2 for displays and so on. As SNA has developed, new types of LU have been introduced that support a broader range of communications facilities. LUs are normally associated with particular Physical Units (PUs), or network devices. LUs provide the services required by Applications (APs) in the IBM SNA environment, sitting between the APs and the PUs. A Dependent LU relies on the host for activation, physically and logically, while an Independent LU can initiate a session without host involvement.
• LU 6.2 An IBM SNA Logical Unit that provides general communications functions, including the communications functions necessary for peer-to-peer networking. Underlying LU 6.2 is a type of node: node type 2.1, which facilitates peer-to-peer networking. Two SNA units which implement rode type 2.1 can set up a full peer-to-peer session without invoking SSCP capabilities in a host processor. This is defined as SNA Low-Entry Networking.

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• MAC (Media Access Control) layer A sub-layer of the Data Link Layer (Level Two) of the ISO OSI Model responsible for media control.
• MAN (Metropolitan Area Network) A high speed network designed to link together sites in a metropolitan or campus area. The IEEE has defined its 802.6 standard for MANs based on the Distributed Queue Dual Bus technology.
• MAP (Manufacturing Automation Protocol) An ISO OSI protocol stack that is defined as a functional profile. Originally developed by General Motors for use in factory floor manufacturing environments it is based around the IEEE 802.4 Token Bu s LAN technology.
• MAPI (Messaging Application Programming Interface) Microsoft's standard for the applications interface to e-mail. See also VIM.
• Master station A device that controls/polls the nodes in multipoint circuits or, in point-to-point circuits, the unit that controls the slave station. In LAN terms, the device on a token passing ring that enables recovery from error conditions, such as lost, busy or duplicate tokens, usually by generating a new token. Servers are sometimes called master stations.
• Matrix switching A form of data switching at the heart of ATM, enabling the appropriate of bandwidth to be available end-to-end for the duration of the session without contention.
• MAU (Medium Attachment Unit) A transceiver (transmitter/receiver) comprising hardware circuitry that provides the correct electrical or optical connection between the computer and IEEE 802.3 LAN media. Since MAUs typically support only one type of network medium, a choice of MAUs is available to support different media. It detects carrier and collision activity, passing the information to the Computer. It can be a standalone unit or incorporated in a circuit board inside the computer,
• Media Access Control driver A LAN device driver that works directly with the network adapter cards, acting as an intermediary between the transport driver and the hardware.
• Medium The physical method or equipment used for transmission, from a tangible fiber optic or copper cable to a satellite link. Alternatively, a little old lady in a shawl used as a last resort to retrieve lost data.
• Medium Interface Controller (MIC) An hermaphrodite connector on IBM patch parels specified in 802.5.
• Member server A server in a domain that keeps and uses a copy of the domain's user accounts database but does rot validate logon requests.
• Monolithic driver A network device driver that acts as network adapter card driver and transport protocol driver combined.
• MMS (Message Handling System) The engine underlying an electronic messaging system. Also a proprietary e-mail integration scheme developed by Action Technologies.
• MIB (Management Information Base) The set of variables or database that a gateway running CMOT, SNMP, or CMIP network management protocols maintains. It defines variables needed by the SNMP protocol to monitor and control components in a ne twork. Managers fetch or store into these variables. MIB-II refers to an extended SNMP management database that contains variables not shared by both CMOT and SNMP. The CMIP and SNMP MIB formats differ in structure and complexity.
• Microchannel A proprietary bus developed by IBM for its PS/2 computer family's internal expansion cards. It offers improved performance over ISA-based machines like the IBM PC/AT.
• Microwave Wireless transmission at very high frequency to deliver telecommunications services, including TV distribution, between two points. It is dependent on line of sight.
• MTBF (Mean Time Between Failures) A term describing the reliability of equipment established by testing kit to its limits and promoting the MTBF as a selling point. As most users know, however, laboratory and operational environments have little in common.
• MNP (Microcom Networking Protocol) A series of protocols designed by Microcom to support error control and data compression for asynchronous modem transmission.
• Milnet (Military Network) Originally part of Arpanet, Milnet was partitioned in 1984 to make it possible for military installations to have a reliable network service while the Arpanet continued to be used for research. Under normal circums tances, Milnet is part of the Internet.
• Modem A device named from an amalgam of the words modulator and demodulator. A modem will modulate an outgoing binary bit stream or to an analog carrier, and demodulate an incoming binary bit stream from an analog carrier.
• Modem Approvals Group Established in January 1993 to raise awareness of the UK law against connecting unapproved devices to the PSTN, this group demands a level playing field in the modem market with better law enforcement or more open standards.
• Modem eliminator A device that can replace a modem in some instances when the distance to be covered is short. It takes the power it needs to operate from the transmission line.
• MSAU (Multi-Station Access Unit) A wiring concentrator on a Token Ring network that allows devices, typically eight to 12 Token Ring stations, to be connected to the ring. Relays in the MAU ensure the integrity of the network when devices a re attached or removed. A Managed Multi-Port/Multi-Station Access Unit has built-in network management support.
• MS-Net Microsoft DOS-based networking system software product (Microsoft Network).
• Multi-drop A transmission circuit with multiple terminals and peripherals. Could also be described as branches off a bus.
• Multi-point A link that connects more than two points. Interchangeable with multi-drop.
• Multi-point connection A single channel or circuit interconnecting devices in different locations. This usually means using polling techniques with each terminal[terminal a unique address. Also know as a multi-drop line.
• Multi-cast bit A bit found in the Ethernet addressing scheme that indicates that the message is to be sent to all stations.
• Multi-cast message A message that is intended for a set of stations on a network.
• Multimedia Generic description of the generation and transfer of voice/data/video traffic between users. Applications to exploit multimedia to the full are emerging in the wake of advanced switching techniques and develop merits in desktop and server processing architectures. It may be essential to a physically separated group that communicates as if it was physically networked.
• Multi-Port Repeater An Ethernet wiring center that allows multiple devices to be attached at one point on an Ethernet. A Managed Multi-Port Repeater has network management capabilities.
• Multiplexer A device that can send several signals over a single line. They are then separated by a similar device at the other end of the link. This can be done in a variety of ways: time division multiplexing, frequency division multiplex ing and statistical multiplexing. Multiplexers are also becoming increasingly efficient in terms of data compression, error correction, transmission speed and multi-drop capabilities.
• Multi-tasking The concurrent execution of two or more tasks or the concurrent use of a single program that can carry out many functions.

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• Named pipe A connection used to transfer data between separate processes, usually on separate computers. Named pipes are the foundation of interprocess communications and underpin Microsoft's LAN Manager Nos.
• Narrowcasting CATV term distinguishing cable from broadcasting, it describes the function of distributing a range of TV channels or programs designed for minority interests rather than mass appeal.
• NCoP (Network Code of Practice) A voluntary code of practice for the design of networks covering transmission quality, safety and technical standards.
• NetBEUI (NetBios Extended User Interface) A network device driver or transport protocol that is the transport driver supplied with LAN Manager, It can bind with as many as eight media access control drivers.
• NetBios (Network Basic Input/Output System) Software developed by IBM that provides the interface between the PC operating system, the i/o bus, and the network. Since its design, NetBIOS has become a de facto standard.
• NETBLT (Network Block Transfer) A Transport Level, flow controlled, bulk data transfer protocol used with TCP/IP internets. NETBLT controls the rate at which data is sent to allow a steady, high speed flow,
• Netlogon service A LAN Manager service that implements logon security. This service verifies the usernarne and password supplied by each user logging on to the local area network. See also LAN Manager.
• NDIS (Network Driver Interface Specification) A de facto standard interface specification developed by Microsoft to separate communications protocols from PC networking hardware. The driver can also run multiple stacks concurrently.
• Network interface card/controller Circuitry connecting a node to a network, usually in the form of a card in a PC expansion slot. In conjunction with the nos and PC operating system it helps transmit and receive messages on the network.
• NetView IBM's network management system. A text message-based system that monitors, manages and controls SNA networks. It is an implementation of IBM's Open Network Management Architecture. The term NetView is normally associated with the focal point of the architecture.
• NetView/PC An implementation of IBM's NetView running on an OS/2 PC-based platform that allows non-IBM networks and equipment to be managed via an SNA network management station. NetView/PC is a service point in IBM's Open Network Management Architecture.
• NetWare LAN Network Operating System and related products developed by Novell. There are three main product lines - NetWare 2.X (latest version 2.2) designed to run on a Intel 80286 platform and above, and NetWare 3.X (latest version NetWare 3.11), designed to run on an Intel 80386 platform and NetWare 4.0. NetWare is currently installed on more than 70 percent of LANs worldwide.
• Network adapter card A printed circuit board, installed in a computer, enabling the computer to join the LAN.
• Network adapter card driver A network device driver that controls the physical function of a network adapter card.
• Network address A group of characters that uniquely identify the location of a node on a network.
• Network architecture The communication equipment, protocols and transmission links that constitute a network, and the methods by which they are arranged.
• Network computing A term analogous to client/server computing.
• Network device A computer, peripheral or other related communications equipment attached to a network.
• Network device driver A program that enables the operating system software to communicate the network adapter cards. Also a software module running on a host or workstation that is responsible for the communications between the computer and the network or a device attached to the network.
• Network topology The different configurations that can be adopted in building networks, such as a ring, bus, star or meshed.
• NETS (Normes Europenne de Telecommunications) The Net program will produce a range of mandatory standards for type approval of telecommunications equipment in all EC states. Once a piece of equipment has passed its Net compliance tests, which could be undertaken in any member state, that piece of equipment can be sold in all EC countries for connection to the public network. Key Nets include: Net 1 - X.21 Access; Net 2 - X.25 Access; Net 3 - ISDN Basic Access; - Net 4 - Public Switched Tele phone Network Access; and Net 5 - Primary Rate ISDN Access. Net 3 can be further subdivided into Net 3 Part 1 which corresponds to the ITU-TS Q.921 standard, and Net 3 Part 2 which is functionally equivalent to ITU-TS Q.931, but Net 3 Part is still incompletely defined.
• Network element A piece of network equipment that can be managed through an element manager as part of a network management system.
• Network interface The point of interconnection between a telephone network operator's communications facilities and terminal equipment, protective apparatus or wiring at a subscriber's premises. This demarcation point is on the subscriber's side of the phone company's protector or its equivalent.
• Network Layer Level Three in the OSI stack responsible for the necessary routing and relaying through one or more networks in multiple link or wide area environments.
• Network management The process and techniques of remotely or locally monitoring and configuring networks. Under the OSI model network management takes account of five key areas: configuration management, fault management, performance management, accounting management, and security management. A major challenge and often a headache to users because there are no complete answers today, only a patchwork of systems covering different parts of the subject. Vendors either concentrate on the physical (hardware) elements or logical (control and management of interprocess communications) sides. The ITU-TS is slowly considering standards for public networks.
• Network management integration The highest level of network management system that brings together information from a number of Element Management Systems.
• Network management protocol The protocol used to transfer network management NetView, and HP OpenView.
• Nodes Devices on a network that demand or supply services or where transmission paths are connected. Node is often used instead of workstation.
• NOS (Network Operating System) The software that connects all the devices on a network so that resources can be shared efficiently and files can be transferred. It handles administration of all network functions, Network operating systems are usually in two parts; server and client/requester. The requester puts the workstation on the server machine and makes disks, software, ports and other facilities available to a node on request. Each device's services requested by a PC are accessed via the requester software.
• NOTA (Novell Open Technology Association) A group of companies that have adopted a suggested software platform suggested by Novell that will lead to the development of a new range of CTI applications.
• NREN (National Education and Research Network) The planned successor in the US to the connected Internet that will provide high speed access to scientific and educational institutions primarily within the US.
• NSF (National Science Foundation) A US government agency that has funded the development of a cross country backbone network as well as regional networks designed to connect scientists to the Internet. It operates a US network, the National Science Foundation Network (NSFNET).
• NSI (NASA Science Internet) A computer networking project started by NASA's Office of Space Science and Applications. It contains two major networks, Span and NSN. Also see NSN, Span
• NSN (NASA Science Network) Using TCP/IP, NSN is part of the connected Internet.
• Null modem cable An RS232 cable that has pins 2 and 3 reversed so that the two connected computers are under the impression they are linked using modems. It is a device that connects two DTE devices directly by emulating the Physical connections of a DCE unit.

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• Object-oriented technology The art and science of manipulating data, like programming, in the form of "objects", streamlining ways of identifying and addressing business problems and creating applications. Its applications are built up from objects containing both information and the intelligence needed to process that data in a single unit; particularly useful in workgroups where it lets a document contain its own security and routing information. Standards are being discussed by several bodies including the Object Management Group with its Object Management Architecture. Dogged by acronyms and competing methodologies, object technology is a growing phenomenon.
• OC-1 Optical Carrier level 1 The lowest optical transmission rate in the incipient Sonet standard at 51.48Mbit/s.
• OC-3 Optical Carrier level 3. The second fastest optical rate in the incipient Sonet standard at 155.52Mbit/s.
• OCR (Optical Character Recognition) Software converting scanned images of documents into text files which can be wordprocessed.
• Octet A grouping of eight bits in packet switched networks similar, but not identical to, a byte.
• ODBC (Open Database Connectivity) Non-proprietary programming SQL interface specified by Microsoft for database connectivity. It offers access to a variety of PC, minicomputer and mainframe systems, plus Apple networks.
• ODLI (Open Data Link Interface) A Novell technique similar in concept to Microsoft's NDIS, it enables PC adapter cards to support ODLI and so run multiple protocols to access various implementations of NetWare.
• ODS Microsoft's Open Data Services: the part of Wosa supporting access from Microsoft's SQL Server to a wide range of data sources and formats, including information from major mainframe databases.
• OEM (Original Equipment Manufacturer) The maker of equipment marketed by another vendor, usually under the name of the reseller. The OEM may make only certain components or complete devices, which can then be configured with software and/or hardware by the reseller.
• OLE, OLE2 (Object Linking and Embedding) A Microsoft specification for implementing object-oriented software developments. An improved form of DDE, it adopts a layered approach and allows a file or program to be embedded as an object in another file. OLE2 (the most recent version) and ODBC drivers altered without affecting core software software applications from different vendors to be accessed seamlessly. More and more organizations are adopting this set-up.
• ONMA (Open Network Management Architecture) IBM's network management architecture comprised of Entry Points, Service Points and Focal Points - implemented as NetView.
• OS/2 An operating system devised by Microsoft and IBM for PCs based on Intel's 80286 and 80386 microprocessors. It supports multi-tasking and programs needing more than 640kbytes of memory, as well as program to program communications. It is a building block on which to base distributed processing. OS/2.2 is the current version. OS/2 EE (Extended Edition) - IBM's extended version of the original OS/2 with enhanced communications facilities.
• OSF (Open Software Foundation) A consortium of hardware manufacturers aimed at setting common standards for open systems, including operating systems and networks. The OSF has defined the Distributed Computing Environment.
• OSI Basic Reference Model (Open Systems Interconnection Reference Model) An architectural model describing how communications can be achieved between different vendors' systems. It is a logical structure for network operations standardized within ISO and containing seven primary layers. It enables any OSI compliant computer or device to communicate with other OS 1-compliant equipment. The seven Layers, starting with the lowest are the Physical, Data Link, Network, Transport, Session, Presen tation and Applications.
• OSN (Office Systems Node) An IBM concept describing a set of functions and services provided to connected nodes in an IBM office system. OSN has a central role in a Document Interchange Architecture-defined office system. Office systems with more limited IBM function sets are termed Source or Recipient Nodes. A typical OSN is a host computer running software as the IBM Distributed Office Support System (Dioss), while an SRN is typically a text-processing PC. A user at a workstation, through the use of commands defined in DIA, can request an OSN to supply document library, document distribution, fiber transfer and applications processing services. DIA enables an SNA network to build an office systems network with multiple remote locations sh aring an OSN.
• OSPF (Open Shortest Path First) A dynamic routing protocol based on a shortest path first algorithm, better suited to larger networks than RIP.
• Out-of-Band signaling An extra signal transmitted alongside the information signal to monitor and control the transmission. It uses a separate channel of the LAN and allows network management devices to access LAN devices even when the LAN itself is not functioning, so providing an additional layer of resilience.

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• PABX (PBX) A Private Automatic Branch eXchange/telephone exchange linked to the PSTN. It handles calls automatically i.e., unattended. Normally a manual, user-owned exchange.
• Packet A collection of bits, including the address, data and control, that are switched and transmitted together. The terms frame and packet are often used synonymously.
• Packet Buffer Memory space reserved for storing a packet awaiting transmission or for storing a received packet.
• Packet Switching A method of switching data in a network. Individual packets of a set size and format are accepted by the network and delivered to their destination. The sequence of packets is maintained, and destination established, by the exchange of control information (also contained in the packets) between the sending terminal and the network before the transmission starts. The network is open to all users, all the time, with packets from the various nodes being interleaved throughout the network. The packets can be sent in any order, as the control information sent at the beginning of the transmission ensures they are interpreted in the correct order at the receiving end. Because each packet carries its own control instructions, it can use any route to reach its destination. The link lasts only as long as the trarsmission. An ITU-TS standard for packet switched networks information.
• Predictive dialing Automated dialing feature in which the systems predicts from pre-set algorithms when an agent/operator will become free and makes the call in advance.
• Preview dialing Automated dialing feature in which the system determines the next call to be made but allows the agent/operator as a supervisor to check and activate the call.
• Presentation Layer The sixth of seven layers in the OSI model. Its job is to ensure that two computers wanting to communicate establish the ground rules for how they can interoperate.
• PRA (Primary Rate Access) An ISDN access method that uses maximum data rates of 2.048 Mbit/s in Europe, or 1.544 Mbit/s in the US and Japan.
• PRI (Primary Rate Interface) ISDN's carrier or large user interface comprising 30BD channels in Europe, supporting around 1,920Mbit/s.
• Primary domain controller The server at which the master copy of a domain's user accounts database is maintained. The primary domain controller also validates logon requests. A LAN Manager term.
• Print Server A computer and/or software to provide users or a network with access to a central printer. The printer server acts as a buffer, holding the information to be printed out in memory until the printer is free. It is possible to program the printer server to print jobs in the order they arrive or to give priority to particular users who, in effect, jump the queue. The advantages of a printer server include maximum exploitation of expensive resources like laser printers and not having to retry if the printer is initially busy.
• Printer driver A program that controls printing and sets options such as print quality and paper size for a particular printer. For example, in LAN Manager, each printer queue has a single printer driver associated with it.
• Private (dedicated) line Term for a dedicated voice or data circuit, usually leased from a Common Carrier.
• Privilege level For user-level security, one of three settings -user, admin or guest is assigned for each user account. The privilege level defines interfaces was drawn up in 1980, known as Recommendation X.25. Hence packet switched networks are often referred to as X.25. In some cases X.25 is being superseded by frame relay and eventually by ATM.
• PAD (Packet Assembler/Disassembler) A device used in a packet switched network to convert data to an appropriate format so that a non X.25 (non-packet switching) device can send information over an X.25 (packet switched) network, The pad is responsible for call set up and addressing routines.
• Paging A one-way alert or alphanumeric message service. Messages are normally left via a bureau with a human or automatic operator.
• Parallel interface An interface that can handle a group of bits transmitted at the same time, by sending each bit over a separate wire. Probably the best known parallel interface of all is the one developed by Centronics, a printer manufacturer, that has 36 pins and can handle a byte of data at a time. The transmission of the data is controlled by a computer generated strobe pulse.
• Parity Bit An extra bit added to a group of bits, usually to a seven-bit byte. The parity bit can be of 0 or 1 value so that every byte will then add up to an odd or even number, depending on whether odd or even parity is chosen. When the transmitting device frames a character, it counts the numbers of 0s and 1s in the frame and attaches the appropriate parity bit. The recipient counts all the 0s and 1s and compares the total to the odd or even message contained in the parity bit. If there' s a discrepancy the recipient asks for the data to be resent.
• PCM (Pulse Code Modulation) One of the most common ways of converting an analog signal to a digital signal. This is done by sampling the signal and coding the sample. It usually samples at 8,000 times per second; each sampling representing 8bits. This produces a transmission rate of 641Kbit/s, with the traffic on the line in interleaved data format. At the receiving end, the interleaved signals are separated and converted back to analog.
• Phase Modulation One of the three ways of modulating or altering a signal so that it is able to carry information. The other two are amplitude and frequency modulation. Phase modulation is used in high speed modems.
• Polling Method of controlling terminals on a multi-point line by which a computer acting as master calls or polls each of the terminals in turn to find out if they have any data to send. This access method is used in star topology networks but is generally being superseded by the preferred interrupt method.
• Port A computer interface capable of attachment to another device, such as a modem for communicating with a remote terminal, or, if the port is within a hub, to a workstation.
• PPP (Point to Point Protocol) An addition to the Internet protocol suite to help connect devices where dissimilar transport protocols exist, for example for the transfer of routing the range of actions a user can perform on the network.
• Profile A set of parameters defining the way in which a device acts. In the LAN world, a profile is often used by one or more workstations to determine the connection they will have with other devices. Profiles work like batch files, executing a number of commands to save a user time and effort.
• Protocol A set of rules governing the information flow within a communications infrastructure, often known as "data link control". Protocols control format, timing, error essential correction and running order. They are essential for a device to be able to interpret incoming information. Suites of protocols are often used in networks, with each protocol responsible for one part of a communications function.
• Protocol converter A device that translates between two protocols to facilitate communications between different computers or different systems.
• Protocol Independent Routing A proprietary routing method designed for IBM networks developed by General DataComm, improving on Source Routing. The router checks all LAN packets for their source address contained in each frame. Adopting the proprietary DSPF (Discover Shortest Path First) router-to-router protocol, a PIR router finds the best path between pairs of LANs, rather than simply between pairs of routers as OSPF (Open Shortest Path First). Because a router can have several LANs connected to it, OSPF does not necessarily produce the best result, whereas PIR load-balances across each available LAN link for improved throughput and performance. From a Token Ring LAN, PIR looks like a Source Routing bridge; in an Ethernet environment, PIR appears as a Transparent bridge.
• Proxy agent A network management agent that sits in front of a device attached to a network that needs to be managed, but has no intrinsic network management capabilities. The proxy agent provides network management "by proxy" for that device.
• PSN (Packet Switching Node) The name of an Arpanet packet switch; PSNs were formerly called IMPS.
• PDN (Public Data Network) A network established by a PTT, PTO or TA to provide data transmission services for public use.
• PUP (Parc Universal Packet) In the internet system developed by Xerox Corporation, a PUP is the fundamental unit of transfer, just as the IP datagram in a TCP/IP internet. The name was derived from the name of the laboratory at which the Xerox internet was developed, the Palo Alto Research Center (PARC).
• Punch-down block Telephony term describing the connector arrangements for distributing and connecting UTP/STP wiring inside a building. Typically found in phone wiring closets.
• PVC (Permanent Virtual Circuit) A fixed virtual circuit between two users: the public data network equivalent of a leased line. No call setup or clearing procedures are needed.