IBM Token-Ring Adapter

Appendix A. Glossary

This glossary includes terms and definitions from the IBM Dictionary of Computing (New York; McGraw-Hill, Inc., 1994).

The following cross-references are used in this glossary:

Contrast with:
This refers to a term that has an opposed or substantively different meaning.

Synonym for:
This indicates that the term has the same meaning as a preferred term, which was defined in its correct place in the glossary.

Synonymous with:
This is a backward reference from a defined term to all other terms that have the same meaning.

See:
This refers the reader to multiple-word terms that have the same last word.

See also:
This refers the reader to related terms that have a related, but not synonymous, meaning.

Deprecated term for:
This indicates that the term should not be used. It refers to a preferred term, which is defined in its proper place in the glossary.


A

active
Able to communicate on the network.
Operational.
Pertaining to a node or device that is connected or is available for connection to another node or device.
Currently transmitting or receiving.

actual data transfer rate
The average number of bits, characters, or blocks per unit of time transferred from a data source and received by a data sink.

adapter
In a communicating device, a circuit card that, with its associated software and/or microcode, enables the device to communicate over the network.

adapter address
The hexadecimal digits that identify an adapter.

address
A character or group of characters that identifies a register, a particular part of storage, or some other data source or destination. (A)  
To refer to a device or an item of data by its address. (I)  (A)  
In word processing, the location, identified by an address code, of a specific section of the recording medium or storage.  (T)  
A name, label, or number identifying a location in storage, a device in a system or network, or any other data source.
In data communication, the unique code assigned to each device or workstation connected to a network.

Address Resolution Protocol (ARP)
A protocol that dynamically maps between Internet addresses, baseband adapter addresses, X.25 addresses, and token-ring adapter addresses on a local area network.

Advanced Program-to-Program Communication (APPC)
The general facility characterizing the LU 6.2 architecture and its various implementations in products.
Sometimes used to refer to the LU 6.2 architecture and its product implementations as a whole, or to an LU 6.2 product feature in particular, such as an APPC application program interface.

agent
In the client-server model, the part of the system that performs information preparation and exchange on behalf of a client or server application. See also client-server model and network management station (NMS).
A customer-service person whose job is to handle outgoing or incoming telephone calls (for example, an agent in an ACD group).

AIX
Advanced Interactive Executive. See AIX operating system.

AIX operating system
IBM's implementation of the UNIX operating system. The RISC System/6000 system, among others, runs the AIX operating system. See UNIX operating system.

alert
A message sent to a management services focal point in a network to identify a problem or an impending problem.
In the NetView and NETCENTER programs, a high priority event that warrants immediate attention.

API
Application program interface.

APPC
Advanced Program-to-Program Communication.

application
The use to which an information processing system is put; for example, a payroll application, an airline reservation application, a network application.
A collection of software components used to perform specific types of user-oriented work on a computer.
In the AS/400 system, the collection of CSP/AE objects that together can be run on the system. An application consists of a program object, up to five map group objects (depending on how many different devices are supported), and any number of table objects.

application program
A program that is specific to the solution of an application problem. Synonymous with application software. (T)  
A program written for or by a user that applies to the user's work, such as a program that does inventory control or payroll.
A program used to connect and communicate with stations in a network, enabling users to perform application-oriented activities.
In SDF/CICS, the program using the physical maps and symbolic description maps generated from a source map set.
Note:
Do not use the term application in place of application program.

application program interface (API)
A functional interface supplied by the operating system or by a separately orderable licensed program that allows an application program written in a high-level language to use specific data or functions of the operating system or the licensed program.
The interface through which an application program interacts with an access method. In VTAM programs, it is the language structure used in control blocks so that application programs can reference them and be identified to VTAM.

architecture
A logical structure that encompasses operating principles including services, functions, and protocols. See computer architecture, network architecture, Systems Application Architecture (SAA), Systems Network Architecture (SNA).

ARP
Address Resolution Protocol.

attach
To make a device a part of a network logically.
Note:
Not to be confused with connect, which implies physically connecting a device to a network.

attaching device
Any device that is physically connected to a network and can communicate over the network. See ring attaching device.

attachment
A port or a pair of ports, optionally including an associated optical bypass, that are managed as a functional unit. A dual attachment includes two ports: a port A, and a port B. A single attachment includes a Port S.

B

backbone
In a local area network multiple-bridge ring configuration, a high-speed link to which the rings are connected by means of bridges or routers. A backbone can be configured as a bus or as a ring.
In a wide area network, a high-speed link to which nodes or data switching exchanges (DSEs) are connected.

bandwidth
The difference, expressed in hertz, between the highest and the lowest frequencies of a range of frequencies. For example, analog transmission by recognizable voice telephone requires a bandwidth of about 3000 hertz (3 kHz).
The bandwidth of an optical link designates the information-carrying capacity of the link and is related to the maximum bit rate that a fiber link can support.

Basic Input/Output System (BIOS)
Code that controls basic hardware operations, such as interactions with diskette drives, hard disk drives, and the keyboard.

binary digit
Synonym for bit.

BIOS
Basic Input/Output System.

bit
Either of the digits 0 or 1 when used in the binary numeration system. Synonymous with binary digit. (T)   See also byte.

block
A string of data elements recorded or transmitted as a unit. The element may be characters, words, or physical records. (T)

bridge
An attaching device that connects two LAN segments to allow the transfer of information from one LAN segment to the other. A bridge can connect the LAN segments directly by network adapters and software in a single device, or it can connect network adapters in two separate devices through software and use of a telecommunications link between the two adapters.
A functional unit that connects two LANs that use the same logical link control (LLC) procedures but may use the same or different medium access control (MAC) procedures. (T) Contrast with gateway and router.

Note:

A bridge connects networks or systems of the same or similar architectures, whereas a gateway connects networks or systems of different architectures.

bridging
The forwarding of a frame from one local area network segment to another. The destination is based upon the medium access control (MAC) sublayer address encoded in the destination address field of the frame header.

broadband local area network (LAN)
A local area network (LAN) in which information is encoded, multiplexed, and transmitted through modulation of carriers. (T)

broadcast
Transmission of the same data to all destinations. (T)  
Simultaneous transmission of the same data to more than one destination.
A packet delivery system where a copy of a given packet is given to all hosts attached to the network. Broadcast can be implemented in hardware (Ethernet, for example) or software. Contrast with multicast.

bus
A facility for transferring data between several devices located between two end points, only one device being able to transmit at a given moment. (T)  
A computer configuration in which processors are interconnected in series. See also hypercube.
A network configuration in which nodes are interconnected through a bidirectional transmission medium.
One or more conductors used for transmitting signals or power. (A)

bypass
To eliminate a station or an access unit from a ring network by allowing the data to flow in a path around it.
The ability of a station to be optically isolated from the network while maintaining the integrity of the ring.
The ability of a node to optically isolate itself from the FDDI network while maintaining the continuity of the cable plant.

byte
A string that consists of a number of bits, treated as a unit, and representing a character. (T)  
A binary character operated upon as a unit and usually shorter than a computer word. (A)  
A group of 8 adjacent binary digits that represent one EBCDIC character.
See n-bit byte. See also bit.

C

cable segment
A section of cable between components or devices on a network. A segment can consist of a single patch cable, multiple patch cables connected together, or a combination of building cable and patch cables connected together. See LAN segment, ring segment.

cache
A special-purpose buffer storage, smaller and faster than main storage, used to hold a copy of instructions and data obtained from main storage and likely to be needed next by the processor. (T)
To place, hide, or store in a cache.
An optional part of the directory database in network nodes where frequently used directory information can be stored to speed directory searches.

carrier
On broadband networks, a continuous frequency signal that can be modulated with an information-carrying signal.
An electric or electromagnetic wave or pulse train that may be varied by a signal bearing information to be transmitted over a communication system. (T)

channel
A path along which signals can be sent, for example, data channel, output channel. (A)  
The portion of a storage medium that is accessible to a given reading or writing station; for example, track, band. (A)  
The portion of a storage medium that is accessible to a given reading or writing station.
In broadband transmission, a designation of a frequency band 6 MH wide.

channel-attached
Pertaining to the connection of devices directly by data channels (I/O channels) to a computer.
Pertaining to devices connected to a controlling unit by cables rather than by telecommunication lines. See also local. Contrast with telecommunication-attached.

claim token
A process whereby one or more stations bid for the right to initialize the ring.

class of service (COS)
A designation of the transport network characteristics, such as route security, transmission priority, and bandwidth, needed for a particular session. The class of service is derived from a mode name specified in the Bind by the initiator of a session.

client
A user.
A functional unit that receives shared services from a server. (T)

client-server
In TCP/IP, the model of interaction in distributed data processing in which a program at one site sends a request to a program at another site and awaits a response. The requesting program is called a client; the answering program is called a server.

client-server model
A common way to describe network services and the model user processes (programs) of those services.

configuration
The manner in which the hardware and software of an information processing system are organized and interconnected. (T)  
The devices and programs that make up a system, subsystem, or network.
The task of defining the hardware and software characteristics of a system or subsystem.
See also system configuration.

configuration parameters
Variables in a configuration definition, the values of which characterize the relationship of a product, such as a bridge, to other products in the same network.

connect
In a LAN, to physically join a cable from a station to an access unit or network connection point. Contrast with attach.

connection
In data communication, an association established between functional units for conveying information. (I) (A)
In Open Systems Interconnection architecture, an association established by a given layer between two or more entities of the next higher layer for the purpose of data transfer. (T)
In SNA, the network path that links two logical units (LUs) in different nodes to enable them to establish communications.
In X.25 communication, a virtual circuit between two data terminal equipments (DTEs). A switched virtual circuit (SVC) connection lasts for the duration of a call; a permanent virtual circuit (PVC) is a permanent connection between the DTEs.
In TCP/IP, the path between two protocol applications that provides reliable data stream delivery service. In Internet, a connection extends from a TCP application on one system to a TCP application on another system.
The path between two protocol functions, usually located in different machines, that provides reliable data delivery service.
A logical association between a call participant (party) and a switch. A party's connection represents that party's participation in a telephone call.

connectivity
The capability of a system or device to be attached to other systems or devices without modification. (T)
The capability to attach a variety of functional units without modifying them.

D

data circuit-terminating equipment (DCE)
In a data station, the equipment that provides the signal conversion and coding between the data terminal equipment (DTE) and the line. (I)

Notes:

  1. The DCE can be separate equipment or an integral part of the DTE or of the intermediate equipment.

  2. A DCE can perform other functions that are usually performed at the network end of the line.

data link control (DLC)
A set of rules used by nodes on a data link (such as an SDLC link or a Token Ring) to accomplish an orderly exchange of information.

data link control (DLC) layer
In SNA or Open Systems Interconnection (OSI), the layer that schedules data transfer over a link between two nodes and performs error control for the link. Examples of DLC are synchronous data link control (SDLC) for serial-by-bit connection and DLC for the System/370 channel.
See Systems Network Architecture (SNA).
See also logical link control (LLC) sublayer, medium access control (MAC) sublayer.

Note:

The DLC layer is usually independent of the physical transport mechanism and ensures the integrity of data that reach the higher layers.

data link control (DLC) protocol
The LAN protocol used to attach a device to and remove a device from the network. The DLC protocol is also used to send information onto and receive information from the network, exchange data, and control information with network higher level protocols and interfaces.

data rate
See data transfer rate, line data rate.

data segment
A control section of a program which contains only data. It is usually addressed with its own hardware segment and offset.

data transfer rate
The average number of bits, characters, or blocks, per unit time passing between corresponding equipment in a data transmission system. (I)  See actual data transfer rate, effective transfer rate. The rate is expressed in bits, characters, or blocks per second, minute, or hour.

DCE
Data circuit-terminating equipment.

device driver
The code needed to attach and use a device on a computer or a network.

device identifier (ID)
An 8-bit identifier that uniquely identifies a physical I/O device.

diagnostics
The process of investigating the cause or the nature of a condition or problem in a product or system.

disable
To make nonfunctional.

disabled
Pertaining to a state of a processing unit that prevents the occurrence of certain types of interruptions.
Pertaining to the state in which a transmission control unit or audio response unit cannot accept incoming calls on a line.
Nonoperational or nonfunctional.

disk
A round, flat, data medium that is rotated in order to read or write data. (T)   See also diskette.

diskette
A small magnetic disk enclosed in a jacket. (T)  
A thin, flexible magnetic disk and a semi-rigid protective jacket, in which the disk is permanently enclosed.

diskette drive
The mechanism used to seek, read, and write data on a diskette.

DLC
Data link control.

dotted decimal notation
The syntactical representation for a 32-bit integer that consists of four 8-bit numbers written in base 10 with periods (dots) separating them. It represents IP addresses in the Internet.

duplex
Pertaining to communication in which data can be sent and received at the same time. Synonymous with full-duplex. Contrast with half-duplex.

E

enable
To make functional.

enabled
On a LAN, pertaining to an adapter or device that is active, operational, and able to receive frames from the network.
to the state in which a transmission control unit or an audio response unit can accept incoming calls on a line.

execute
To perform the actions specified by a program or a portion of a program. (T)

F

feature
A part of an IBM product that can be ordered separately by the customer.
See switch feature.

field
On a data medium or a storage, a specified area used for a particular class of data; for example, a group of character positions used to enter or display wage rates on a screen. (T)

file
A named set of records stored or processed as a unit. (T)

frame
In Open Systems Interconnection architecture, a data structure pertaining to a particular area of knowledge and consisting of slots that can accept the values of specific attributes and from which inferences can be drawn by appropriate procedural attachments. Synonymous with schema. (T)  
A data structure that consists of fields, predetermined by a protocol, for the transmission of user data and control data. The composition of a frame, especially the number and types of fields, may vary according to the type of protocol. Synonymous with transmission frame. (T)  
The unit of transmission in some local area networks, including the IBM Token-Ring Network; it includes delimiters, control characters, information, and checking characters.
In SDLC, the vehicle for every command, every response, and all information that is transmitted using SDLC procedures.
A packet that is transmitted over a serial line or LANs. See also packet.
In FDDI, a PDU transmitted between co-operating MAC entities on a ring, and consisting of a variable number of octets and control symbols.

full-duplex
Synonym for duplex.

function
A specific purpose of an entity, or its characteristic action. (A)
In data communications, a machine action such as carriage return or line feed. (A)
In NetView DM, a function is the specification of a transmission activity on a resource or group of resources. Functions are grouped into phases. In CSCM, resources are known as data objects.

H

half-duplex (HDX)
In data communication, pertaining to transmission in only one direction at a time. Contrast with duplex.

hard disk
A rigid magnetic disk such as the internal disks used in the system units of personal computers and in external hard disk drives. Synonymous with fixed disk.
A rigid disk used in a hard disk drive.

Note:

The term hard disk is also used loosely in the industry for boards and cartridges containing microchips or bubble memory that simulate the operations of a hard disk drive.

hard error
An error condition on a network that requires that the network be reconfigured or that the source of the error be removed before the network can resume reliable operation. Contrast with soft error.
Synonym for hard failure. (T)  

hard failure
An error condition on a network that requires that the network be reconfigured or that the source of the error be removed before the network can resume reliable operation. Synonymous with hard error. (T)  

hardware
All or part of the physical components of an information processing system, such as computers or peripheral devices. (T)   (A)  

hexadecimal
Pertaining to a selection, choice, or condition that has 16 possible different values or states. (I)  
Pertaining to a fixed-radix numeration system, with radix of 16. (I)  
Pertaining to a system of numbers to the base 16; hexadecimal digits range from 0 through 9 and A through F, where A represents 10 and F represents 15.

host
In Internet terminology, an end system.
In interpretive execution mode, the real machine as opposed to the virtual or interpreted machine (the guest).

I

I/O
Input/output.

IBM Token-Ring Network
A baseband local area network with a ring topology that passes tokens from Token-Ring adapter to Token-Ring adapter.

IEEE
Institute of Electrical and Electronics Engineers.

initialize
In a LAN, to prepare the adapter (and adapter support code, if used) for use by an application program.

input/output (I/O)
Pertaining to a device whose parts can perform an input process and an output process at the same time. (I)  
Pertaining to a functional unit or channel involved in an input process, output process, or both, concurrently or not, and to the data involved in such a process.

Note:

The phrase input/output may be used in place of input/output data, input/output signals, and input/output process when such a usage is clear in context.
Pertaining to input, output, or both. (A)  
Pertaining to a device, process, or channel involved in data input, data output, or both.

interface
A shared boundary between two functional units, defined by functional characteristics, signal characteristics, or other characteristics, as appropriate. The concept includes the specification of the connection of two devices having different functions. (T)  
Hardware, software, or both, that links systems, programs, or devices.

International Organization for Standardization (ISO)
An organization of national standards bodies from various countries established to promote development of standards to facilitate international exchange of goods and services, and develop cooperation in intellectual, scientific, technological, and economic activity.

Internet
A worldwide network connecting users through autonomous networks in industry, education, government, and research. The Internet network uses Internet Protocol (IP). The major Internet services include electronic mail, FTP, telnet, World Wide Web, and electronic bulletin boards (Usenet). For network interconnection and routing, and Transmission Control Protocol (TCP) for end-to-end control. (A)

Internet address
A 32-bit address assigned to hosts using TCP/IP. See also TCP/IP.

Internet Engineering Task Force (IETF)
One of the task forces of the Internet Architecture Board (IAB) responsible for solving short-term engineering needs of the Internet.

Internet Packet Exchange (IPX)
The routing protocol used to connect Novell's servers or any workstation or router that implements IPX with other workstations. Although similar to TCP/IP, it uses different packet formats and terminology. See also TCP/IP and Xerox Network Services (XNS).

Internet Protocol (IP)
A protocol that routes data through a network or interconnected networks. IP acts as an interface between the higher logical layers and the physical network. However, this protocol does not provide error recovery, flow control, or guarantee the reliability of the physical network. IP is a connectionless protocol.
A protocol used to route data from its source to its destination in an Internet environment.

interrupt
A suspension of a process, such as execution of a computer program caused by an external event, and performed in such a way that the process can be resumed. (A)
To stop a process in such a way that it can be resumed.
In data communication, to take an action at a receiving station that causes the sending station to end a transmission.
A means of passing processing control from one software or microcode module or routine to another, or of requesting a particular software, microcode, or hardware function.

IP
Internet Protocol.

IP address
A 32-bit address assigned to devices or hosts in an IP internet that maps to a physical address. The IP address is composed of a network and host portion.

IPX
Internet Packet Exchange.

ISO
International Organization for Standardization.

K

KB
For processor storage and real and virtual memory, 1024 bytes.
For disk storage capacity and transmission rates, 1000 bytes.

Kb
Kilobit.

kilobit (Kb)
1000 binary digits.

L

LAN
Local area network.

LAN adapter
The circuit card within a communicating device (such as a personal computer) that, together with its associated software, enables the device to be attached to a LAN.

LAN segment
Any portion of a LAN (for example, a single bus or ring) that can operate independently but is connected to other parts of the establishment network via bridges.
An entire ring or bus network without bridges. See cable segment, ring segment.

line data rate
The rate of data transmission over a telecommunications link.

local area network (LAN)
Physical network technology that transfers data at high speed over short distances.
A network in which a set of devices are connected to one another for communication and that can be connected to a larger network. See also Token Ring and Ethernet.
A computer network located on a user's premises within a limited geographical area. Communication within a local area network is not subject to external regulations; however, communication across the LAN boundary may be subject to some form of regulation. (T) Contrast with wide area network (WAN) and metropolitan area network (MAN).

logical link control (LLC)
The data link control (DLC) LAN sublayer that provides two types of (DLC) operation. The first type is connectionless service, which allows information to be sent and received without establishing a link. The LLC sublayer does not perform error recovery or flow control for connectionless service. The second type is connection-oriented service, which requires the establishment of a link prior to the exchange of information. Connection-oriented service provides sequenced information transfer, flow control, and error recovery.
A sublayer of the OSI link layer that defines formats and protocols for exchanging frames between LLC sublayers attached to a local area network. It has provisions that ensure that error-free, nonduplicated, properly ordered frames are delivered to the appropriate data-link user. See also bridge and medium access control (MAC).

logical link control (LLC) protocol
In a local area network, the protocol that governs the exchange of transmission frames between data stations independently of how the transmission medium is shared. (T) The LLC protocol was developed by the IEEE 802 committee and is common to all LAN standards.

logical link control (LLC) protocol data unit
A unit of information exchanged between link stations in different nodes. The LLC protocol data unit contains a destination service access point (DSAP) address, a source service access point (SSAP), a control field, and user data. See logical link control (LLC).

logical link control (LLC) sublayer
One of two sublayers of the ISO Open Systems Interconnection data link layer (which corresponds to the SNA data link control layer), proposed for LANs by the IEEE Project 802 Committee on Local Area Networks and the European Computer Manufacturers Association (ECMA). It includes those functions unique to the particular link control procedures that are associated with the attached node and are independent of the medium; this allows different logical link protocols to coexist on the same network without interfering with each other. The LLC sublayer uses services provided by the medium access control (MAC) sublayer and provides services to the network layer.

M

MAC
Medium access control.

management information base (MIB)
A collection of objects that can be accessed by means of a network management protocol.

MB
For processor storage and real and virtual memory, 1048 576 bytes.
For disk storage capacity and transmission rates, 1 000 000 bytes.

Mb
Megabit.

media access control (MAC)
In FDDI, the portion of the data link layer responsible for scheduling and routing data transmissions on a shared medium local area network, for example, an FDDI ring.

medium access control (MAC)
The sublayer of the data link control layer that supports media-dependent functions and uses the services of the physical layer to provide services to the logical link control sublayer. The MAC sublayer includes the medium-access port. See logical link control (LLC).
For local area networks, the method of determining which device has access to the transmission medium at any time.

medium access control (MAC) frame
In the IBM Token-Ring Network: (1) An address resolution request frame that has the unique part of a destination address and an "all rings" address. A sender issues this request to determine the ring where the destination station is located and whether the node is active. (2) Response from an active destination node to the requesting source node, providing the source node with the complete address and ring number of the destination node.

medium access control (MAC) procedure
In a local area network, the part of the protocol that governs access to the transmission medium independently of the physical characteristics of the medium, but takes into account the topological aspects of the network, in order to enable the exchange of data between data stations.

medium access control (MAC) protocol
In a local area network, the protocol that governs access to the transmission medium, taking into account the topological aspects of the network, in order to enable the exchange of data between data stations. (T)   See also logical link control protocol.
The LAN protocol sublayer of data link control (DLC) protocol that includes functions for adapter address recognition, copying of message units from the physical network, and message unit format recognition, error detection, and routing within the processor.

medium access control (MAC) segment
An individual LAN communicating through the medium access control (MAC) layer within this network.

medium access control (MAC) service data unit (MSDU)
In a medium access control (MAC) frame, the logical link control protocol data unit (LPDU) and the routing information field (if the destination station is located on a different ring).

medium access control (MAC) sublayer
In a local area network, the part of the data link layer that applies a medium access method. The MAC sublayer supports topology-dependent functions and uses the services of the physical layer to provide services to the logical link control sublayer. (T)

medium access control (MAC) subvector
A group of related fields within a medium access control (MAC) major vector.

medium access control (MAC) vector
The medium access control (MAC) frame information field.

memory
All of the addressable storage space in a processing unit and other internal storages that is used to execute instructions. (T)  

MIB
Management information base.
MIB module.

N

NetBIOS
Network Basic Input/Output System. An operating system interface for application programs used on IBM personal computers that are attached to the IBM Token-Ring Network. See also BIOS.

network
An arrangement of nodes and connecting branches. (T)
A configuration of data processing devices and software connected for information interchange.
A signal path connecting input/output devices to a system. A network can consist of multiple LAN segments connected together with bridging products. See ring (network).
The interconnection of two or more subnets. See also Fiber Distributed Data Interface (FDDI) LAN.

network address
See Internet address.

network administrator
A person who manages the use and maintenance of a network.

network architecture
The logical structure and operating principles of a computer network. (T) See also systems network architecture (SNA) and Open Systems Interconnection (OSI) architecture.

Note:

The operating principles of a network include those of services, functions, and protocols.

network identifier (ID)
A 1- to 8-byte customer-selected name or an 8-byte IBM-registered name that uniquely identifies a specific subnetwork.

network management
The process of planning, organizing, and controlling a communications-oriented system.

network management station (NMS)
The system responsible for managing a network or a portion of a network. The NMS talks to network management agents, that reside in the managed nodes, by means of a network management protocol. See also agent.

network manager
A program or group of programs that is used to monitor, manage, and diagnose the problems of a network.

network operator
A person or program responsible for controlling the operation of all or part of a network.
In a multiple-domain network, a person or program responsible for controlling all domains.

O

operating system (OS)
Software that controls the execution of programs and that may provide services such as resource allocation, scheduling, input/output control, and data management. Although operating systems are predominantly software, partial hardware implementations are possible. (T)

Operating System/2 (OS/2)
A set of programs that control the operation of high-speed large-memory IBM personal computers (such as the IBM Personal System/2 computer, Models 50 and above), providing multitasking and the ability to address up to 16 MB of memory. Contrast with IBM Disk Operating System (DOS).

option
A specification in a statement that can be used to influence the execution of the statement.
A hardware or software function that can be selected or enabled as part of a configuration process.
A piece of hardware (such as a network adapter) that can be installed in a device to modify or enhance device function.

OS
Operating system.

P

packet
In data communication, a sequence of binary digits, including data and control signals, that is transmitted and switched as a composite whole. (I)
Synonymous with data frame. Contrast with frame.

panel
A formatted display of information that appears on a display screen.

parameter
A variable that is given a constant value for a specified application and that may denote the application. (I) (A)
An item in a menu or for which the user specifies a value or for which the system provides a value when the menu is interpreted.
Data passed between programs or procedures.

path
In a network, any route between any two nodes. A path may include more than one branch. (T)  
The route traversed by the information exchanged between two attaching devices in a network.
The series of transport network components (path control and data link control) that are traversed by the information exchanged between two network accessible units (NAUs). A path consists of a virtual route and its route extension, if any. See also explicit route (ER), route extension (REX) and virtual route (VR).

personal computer (PC)
A microcomputer primarily intended for stand-alone use by an individual. (T)  
A desk-top, floor-standing, or portable microcomputer that usually consists of a system unit, a display monitor, a keyboard, one or more diskette drives, internal fixed-disk storage, and an optional printer. PCs are designed primarily to give independent computing power to a single user and are inexpensively priced for purchase by individuals or small businesses.

pointer
An identifier that indicates the location of an item of data. (A)
A data element that indicates the location of another data element. (T)
A physical or symbolic identifier of a unique target.

port
An access point for data entry or exit.
A connector on a device to which cables for other devices such as display stations and printers are attached. Synonymous with socket.
The representation of a physical connection to the link hardware. A port is sometimes referred to as an adapter, however, there can be more than one port on an adapter. A single DLC process can control one or more ports.
An abstraction used by transport protocols to distinguish among multiple destinations within a host machine.
In FDDI, a PHY entity and a PMD entity in a node, together creating a PHY/PMD pair, that can connect to the fiber media and provide one end of a physical connection with another node.

port number
The identification of an application entity to the transport service in IP.

POST
Power-on self-test.

power-on self-test (POST)
A series of diagnostic tests that are run automatically by a device when the power is switched on.

problem determination
The process of determining the source of a problem; for example, a program component, a machine failure, telecommunication facilities, user or contractor-installed programs or equipment, an environment failure such as a power loss, or user error.

procedure
A set of instructions that gives a service representative a step-by-step procedure for tracing a symptom to the cause of failure.

protocol
A set of semantic and syntactic rules that determines the behavior of functional units in achieving communication. (I)  
In Open Systems Interconnection architecture, a set of semantic and syntactic rules that determine the behavior of entities in the same layer in performing communication functions. (T)
In SNA, the meanings of, and the sequencing rules for, requests and responses used for managing the network, transferring data, and synchronizing the states of network components.

R

read-only memory (ROM)
A storage device in which data, under normal conditions, can only be read. (T)  
Memory in which stored data cannot be modified by the user except under special conditions.

remote
Pertaining to a system, program, or device that is accessed through a telecommunication line. Contrast with local. Synonym for link-attached.

remote program load
A function provided by adapter hardware components and software that enables one computer to load programs and operating systems into the memory of another computer, without requiring the use of a diskette or fixed disk at the receiving computer.

return code
A value (usually hexadecimal) provided by an adapter or a program to indicate the result of an action, command, or operation.
A code used to influence the execution of succeeding instructions. (A)

ring attaching device
In a ring network, any device equipped with an adapter that is physically attached to the ring.

ring network
A network configuration in which devices are connected by unidirectional transmission links to form a closed path.
A network in which every node has exactly two branches connected to it and in which there are exactly two paths between any two nodes. (T) See also star/ring network, Token-Ring network.

ring segment
A ring segment is any section of a ring that can be isolated (by unplugging connectors) from the rest of the ring. A segment can consist of a single lobe, the cable between access units, or a combination of cables, lobes, and/or access units. See cable segment, LAN segment.

ring status
The condition of the ring.

ROM
Read-only memory. (A)

router
A computer that determines that path of network traffic flow. The path selection is made from several paths based on information obtained from specific protocols, algorithms that attempt to identify the shortest or best path, and other criteria such as metrics or protocol-specific destination addresses.
An attaching device that connects two LAN segments, which use similar or different architectures, at the reference model network layer. Contrast with bridge and gateway.
In OSI terminology, a router is a network layer intermediate system.

routing
The assignment of the path by which a message is to reach its destination.
In SNA, the forwarding of a message unit along a particular path through a network, as determined by parameters carried in the message unit, such as the destination network address in a transmission header.

routing protocol
A technique for each router to find another router and to keep up to date about the best way to get to every network. Examples of routing protocols are: Routing Information Protocol (RIP), Hello, and Open Shortest Path First (OSPF).

S

segment
In the IBM Token-Ring Network, a section of cable between components or devices. A segment can consist of a single patch cable, several patch cables that are connected, or a combination of building cable and patch cables that are connected.
The unit of transfer between TCP functions in different machines. Each segment contains control and data fields whereby the current byte stream position and actual data bytes are identified along with a checksum to validate received data.
In an OS/2 program, a variable-length area of contiguous storage addresses not exceeding 64 KB. See also data segment, cable segment, LAN segment, ring segment.

select
The process of choosing a single symbol or menu item by placing the cursor on it and clicking the mouse button. To select multiple symbols simultaneously, press and hold the Shift key down while clicking on the symbols you want to select.

server
A functional unit that provides shared services to workstations over a network; for example, a file server, a print server, a mail server. (T)  
In a network, a data station that provides facilities to other stations; for example, a file server, a print server, a mail server. (A)  
A class of adapter in a network node that performs local processing and does not have any physical connections to other devices (as do port adapters and trunk adapters).
A device, program, or code module on a network dedicated to providing a specific service to a network.

session
In network architecture, for the purpose of data communication between functional units, all the activities which take place during the establishment, maintenance, and release of the connection. (T)  
A logical connection between two network accessible units (NAUs) that can be activated, tailored to provide various protocols, and deactivated, as requested. Each session is uniquely identified in a transmission header (TH) accompanying any transmissions exchanged during the session.
The period of time during which a user of a terminal can communicate with an interactive system, usually, elapsed time between logon and logoff.

Simple Network Management Protocol (SNMP)
An IP network management protocol that is used to monitor routers and attached networks.
A TCP/IP-based protocol for exchanging network management information and outlining the structure for communications among network devices. SNMP is an application layer protocol. Information on devices managed is defined and stored in the application's Management Information Base (MIB).

socket
In the AIX operating system: (a) A unique host identifier created by the concatenation of a port identifier with a transmission control protocol/Internet protocol (TCP/IP) address. (b) A port identifier. (c) A 16-bit port number. (d) A port on a specific host; a communications end point that is accessible through a protocol family's addressing mechanism. A socket is identified by a socket address. See also socket address.
An IP address and port number pairing.
In TCP/IP, the Internet address of the host computer on which the application runs, and the port number it uses. A TCP/IP application is identified by its socket.
Synonym for port (2).

switch
On an adapter, a mechanism used to select a value for, enable, or disable a configurable option or feature.
In CallPath, equipment that makes, breaks, or changes the connections between telephone lines to establish, terminate, or change a telephone call. Private branch exchange switches reside on a customer's premises, while central office switches reside within the telephone service provider's network.

switch feature
A service provided by the switch that can be invoked by a program or by manual phoneset activity. "Do not disturb" is an example of a switch feature.

system
In data processing, a collection of people, machines, and methods organized to accomplish a set of specific functions. (I) (A)

system configuration
A process that specifies the devices and programs that form a particular data processing system.

T

TCP
Transmission Control Protocol.

TCP/IP
Transmission Control Protocol/Internet Protocol.

telecommunication-attached
Pertaining to the attachment of devices by teleprocessing lines to a host processor. Synonym for remote. Contrast with channel-attached.

token
In a local area network, the symbol of authority passed successively from one data station to another to indicate the station temporarily in control of the transmission medium. Each data station has an opportunity to acquire and use the token to control the medium. A token is a particular message or bit pattern that signifies permission to transmit. (T)  
A sequence of bits passed from one device to another along the token ring. When the token has data appended to it, it becomes a frame.

Token Ring
A network with a ring topology that passes tokens from one attaching device to another; for example, the IBM Token-Ring Network. See also local area network (LAN).
A group of interconnected Token Rings.

Token-Ring network
A ring network that allows unidirectional data transmission between data stations, by a token passing procedure, such that the transmitted data return to the transmitting station. (T)  
A network that uses a ring topology, in which tokens are passed in a sequence from node to node. A node that is ready to send can capture the token and insert data for transmission.
A group of interconnected Token Rings.

Transmission Control Protocol (TCP)
A communications protocol used in Internet and in any network that follows the U.S. Department of Defense standards for inter-network protocol. TCP provides a reliable host-to-host protocol between hosts in packet-switched communications networks and in interconnected systems of such networks. It assumes that the Internet protocol is the underlying protocol.
A transport protocol in the Internet suite of protocols that provides reliable, connection-oriented, full-duplex data stream service.

Transmission Control Protocol/Internet Protocol (TCP/IP)
A set of protocols that allow cooperating computers to share resources across a heterogeneous network.
A set of communication protocols that support peer-to-peer connectivity functions for both local and wide area networks.

transmission frame
In data transmission, data transported from one node to another in a particular format that can be recognized by the receiving node. In addition to a data or information field, a frame has some kind of delimiter that marks its beginning and end and usually control fields, address information that identifies the source and destination, and one or more check bits that allow the receiver to detect any errors that occur after the sender has transmitted the frame.
In synchronous data link control (SDLC), the vehicle for every command, every response, and all information that is transmitted using SDLC procedures. Each frame begins and ends with a flag.
In high level data link control (HDLC), the sequence of contiguous bits bracketed by and including opening and closing flag (01111110) sequences.
In a Token-Ring network, a bit pattern containing data that a station has inserted for transmission after capturing a token.

transmit
To send information from one place for reception elsewhere. (A)

U

UDP
User Datagram Protocol.

UNIX operating system
An operating system developed by Bell Laboratories that features multiprogramming in a multiuser environment. The UNIX operating system was originally developed for use on minicomputers, but has been adapted for mainframes and microcomputers.

Note:

The AIX operating system is IBM's implementation of the UNIX operating system.

User Datagram Protocol (UDP)
In TCP/IP, a packet-level protocol built directly on the Internet Protocol layer. UDP is used for application-to-application programs between TCP/IP host systems.
A transport protocol in the Internet suite of protocols that provides unreliable, connectionless datagram service.
The Internet Protocol that enables an application programmer on one machine or process to send a datagram to an application program on another machine or process. UDP uses the internet protocol (IP) to deliver datagrams.

V

version
A separately licensed program, based on an existing licensed program, that usually has significant new code or new function.

W

WAN
Wide area network.

wide area network (WAN)
A network that provides communication services to a geographic area larger than that served by a local area network or a metropolitan area network, and that may use or provide public communication facilities. (T)
A data communications network designed to serve an area of hundreds or thousands of miles; for example, public and private packet-switching networks and national telephone networks. Contrast with local area network (LAN) and metropolitan area network (MAN).

window
In computer graphics, a predetermined part of a virtual space.
A division of a screen in which one of several programs being executed concurrently can display information.
One or more parts of a display screen with visible boundaries in which information is displayed.
See also help window.

wrap test
A test that checks attachment or control unit circuitry without checking the mechanism itself by returning the output of the mechanism as input; for example, when unrecoverable communication adapter or machine errors occur, a wrap test can transmit a specific character pattern to or through the modem in a loop and then compare the character pattern received with the pattern transmitted. See also optical wrap.

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