IBM Transmission Control Protocol/ Internet Protocol for VM

IBM Transmission Control Protocol/ Internet Protocol for VM:

Glossary

IBM IBM Transmission Control Protocol/ Internet Protocol for VM:

Glossary

ii VM TCP/IP Glossary

About This Glossary

This glossary contains technical terms that are used in the current TCP/IP for VM publications. It includes IBM product terminology as well as other company and product terms. Select terms have also been included from: The IBM Dictionary of Computing, New York:McGraw-Hill, 1994. The Internet Request for Comments: 1208, Glossary of Networking Terms.

Notices IBM may have patents or pending patent applications covering subject matter in this document. The furnishing of this document does not give you any license to these patents. You can send license inquiries, in writing, to the IBM Director of Licensing, IBM Corporation, 500 Columbus Avenue, Thornwood, NY 10594, USA.

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ACF/VTAM AIX BookManager Common User Access CUA ES/9000 GDDM IBM Library Reader NetView Officevision OS/2 PC Network PROFS PS/2 RISC System/6000 SQL/DS System Application Architecture SAA System/370 VTAM Virtual Machine/Enterprise Systems Architecture VM/ESA

Other company, product, and service names, which may be denoted by a double asterisk (**), may be trademarks or service marks of others.

iv VM TCP/IP Glossary Glossary

Glossary

This glossary describes the most common terms associated with TCP/IP communication in an A internet environment, as used in this book. abend. The abnormal termination of a program or task. If you do not find the term you are looking for, see the IBM Dictionary of Computing, New York: abstract syntax. A description of a data McGraw-Hill, 1994. structure that is independent of machine-oriented structures and encodings. For abbreviations, the definition usually consists only of the words represented by the letters; for Abstract Syntax Notation One (ASN.1). The complete definitions, see the entries for the words. OSI language for describing abstract syntax.

Numerics active gateway. A gateway that is treated like a network interface in that it is expected to 3172. IBM Interconnect Controller. exchange routing information, and if it does not do so for a period of time, the route associated with 3174. IBM Establishment Controller. the gateway is deleted.

3270. Refers to a series of IBM display devices; active open. The state of a connection that is for example, the IBM 3275, 3276 Controller actively seeking a service. Contrast with passive Display Station, 3277, 3278, and 3279 Display open. Stations, the 3290 Information Panel, and the 3287 and 3286 printers. A specific device type is adapter. (1) A piece of hardware that connects a used only when a distinction is required between computer and an external device. (2) An auxiliary device types. Information about display terminal device or unit used to extend the operation of usage also refers to the IBM 3138, 3148, and another system. 3158 Display Consoles when used in display mode, unless otherwise noted. address. The unique code assigned to each device or workstation connected to a network. A 37xx Communication Controller. A network standard internet address uses a two-part, 32-bit interface used to connect a TCP/IP for VM or address field. The first part of the address field MVS network that supports X.25 connections. contains the network address; the second part NCP with X.25 NPSI must be running in the contains the local address. controller, and VTAM must be running on the host. address mask. A bit mask used to select bits 6611. IBM Network Processor. from an Internet address for subnet addressing. The mask is 32 bits long and selects the network 8232. IBM LAN Station. portion of the Internet address and one or more bits of the local portion. It is sometimes called a 9370. Refers to a series of processors, namely subnet mask. the IBM 9373 Model 20, the IBM 9375 Models 40 and 60, and the IBM 9377 Model 90 and other address resolution. A means for mapping models. network layer addresses onto media-specific addresses. See ARP.

Address Resolution Protocol (ARP). A protocol used to dynamically bind an internet address to a hardware address. ARP is implemented on a single physical network and is limited to networks that support broadcast addressing.

address space. A collection of bytes that are responsible for establishing voluntary industry allocated, and in many ways managed, as a single standards. entity by CP. Each byte within an address space is identified by a unique address. An address ANSI. American National Standards Institute. space represents an extent of storage available to a program. Address spaces allocated by VM API. Application Program Interface. range in size from 64KB to 2GB. APPC. Advanced Program-to-Program Advanced Interactive Executive (AIX). IBM’s Communications. licensed version of the UNIX operating system. application. The use to which an information Advanced Program-to-Program processing system is put, for example, a payroll Communications (APPC). The interprogram application, an airline reservation application, a communication service within SNA LU 6.2 on network application. which the APPC/VM interface is based. application layer. The seventh layer of the OSI Advanced Research Projects Agency (ARPA). (Open Systems Interconnection) model for data Now called DARPA, its the U.S. Government communication. It defines protocols for user or agency that funded the ARPANET. application programs.

Advanced Research Projects Agency Network Application Program Interface (API). The (ARPANET). A packet switched network formally defined programming-language interface developed in the early 1970’s that is the between an IBM system control program or forerunner of today’s Internet. It was licensed program and its user. APIs allow decommissioned in June 1990. programmers to write application programs that use the TCP, UDP, and IP layers of the TCP/IP agent. As defined in the SNMP architecture, an protocol suite. agent, or an SNMP server is responsible for performing the network management functions argument. A parameter passed between a requested by the network management stations. calling program and a called program.

AIX. Advanced Interactive Executive. ARP. Address Resolution Protocol.

American National Standard Code for ARPA. Advanced Research Projects Agency. Information Interchange (ASCII). (1) The standard code, using a coded character set ARPANET. Advanced Research Projects Agency consisting of 7-bit coded characters (8 bits Network. including parity check), used for information interchange among data processing systems, data ASCII. (1) American National Standard Code for communication systems, and associated Information Interchange. (2) The default file equipment. The ASCII set consists of control transfer type for FTP, used to transfer files that characters and graphic characters. (2) The contain ASCII text characters. default file transfer type for FTP, used to transfer ASN.1. Abstract Syntax Notation One. files that contain ASCII text characters. ASYNC. Asynchronous. American National Standards Institute (ANSI). An organization consisting of producers, asynchronous (ASYNC). Without regular time consumers, and general interest groups that relationship; unexpected or unpredictable with establishes the procedures by which accredited respect to the execution of program instruction. organizations create and maintain voluntary See synchronous. industry standards in the United States. ANSI is sponsored by the Computer and Business asynchronous communication. A method of Equipment Manufacturer Association and is communication supported by the operating system that allows an exchange of data with remote vi VM TCP/IP Glossary Glossary

device, using either a start-stop line or an X.25 Sometimes incorrectly grouped under the term line. Asynchronous communications include the ASN.1, which correctly refers only to the abstract file transfer and the interactive terminal facility description language, not the encoding technique. support. Basic Input/Output System (BIOS). A set of Athena Widgets. The X Window widget set routines that permanently resides in read-only developed by MIT for Project Athena. memory (ROM) in a PC. The BIOS performs the most basic tasks, such as sending a character to Attachment Unit Interface (AUI). Connector the printer, booting the computer, and reading the used with thick Ethernet that often includes a drop keyboard. cable. batch. (1) An accumulation of data to be AUI. Attachment Unit Interface. processed. (2) A group of records or data processing jobs brought together for processing or attention key. A function key on terminals that, transmission. (3) Pertaining to activity involving when pressed, causes an I/O interruption in the little or no user action. See interactive processing unit. Bayonet Neill-Concelman (BNC). A authentication server. The service that reads a standardized connector used with Thinnet and Kerberos database to verify that a client making a coaxial cable. request for access to an end-service is the client named in the request. The authentication server Because It’s Time NETwork (BITNET). A provides an authenticated client ticket as network of hosts that use the Network Job Entry permission to access the ticket-granting server. (NJE) protocol to communicate. The network is primarily composed of universities, nonprofit authenticator. Information encrypted by a organizations, and research centers. BITNET has Kerberos authentication server that a client recently merged with the Computer and Science presents along with a ticket to an end-server as Network (CSNET) to form the Corporation for permission to access the service. Research and Educational Networking (CSNET). See CSNET. authorization. The right granted to a user to communicate with, or to make use of, a computer BER. Basic Encoding Rules. system or service. Berkeley Software Distribution (BSD). Term B used when describing different versions of the Berkeley UNIX software, as in “4.3BSD UNIX”. backbone. (1) In a local area network BFS. Byte File System. multiple-bridge ring configuration, a high-speed link to which rings are connected by means of big-endian. A format for storage or transmission bridges. A backbone can be configured as a bus of binary data in which the most significant bit (or or as a ring. (2) In a wide area network, a byte) comes first. The reverse convention is high-speed link to which nodes or data switching little-endian. exchanges (DSES) are connected. BIOS. Basic Input/Output System. background task. A task with which the user is not currently interacting, but continues to run. BITNET. Because It’s Time NETwork.

baseband. Characteristic of any network block. A string of data elements recorded, technology that uses a single carrier frequency processed, or transmitted as a unit. The elements and requires all stations attached to the network to can be characters, words, or physical records. participate in every transmission. See broadband. blocking mode. If the execution of the program Basic Encoding Rules (BER). Standard rules cannot continue until some event occurs, the for encoding data units described in ASN.1.

Glossary vii Glossary

operating system suspends the program until that Byte File System (BFS). A file system in which event occurs. a file consists of an ordered sequence of bytes rather than records. BFS files can be organized BNC. Bayonet Neill-Concelman. into hierarchical directories. Byte file systems are enrolled as file spaces in CMS file pools. BOOTP. Bootstrap Protocol.

Bootstrap Protocol (BOOTP). The Bootstrap C Protocol allows a diskless client machine to discover its own IP address, the address of a Carrier Sense Multiple Access with Collision server host, and the name of a file to be loaded Detection (CSMA/CD). The access method used into memory and executed. by local area networking technologies such as Ethernet. bridge. (1) A router that connects two or more networks and forwards packets among them. The case-sensitive. A condition in which entries for operations carried out by a bridge are done at the an entry field must conform to a specific physical layer and are transparent to TCP/IP and lowercase, uppercase, or mixed-case format to be TCP/IP routing. (2) A functional unit that valid. connects two local area networks (LANs) that use the same logical link control (LLC) procedures but CCITT. Comite Consultatif International may use different medium access control (MAC) Telegraphique et Telephonique. procedures. channel. A path in a system that connects a broadband. Characteristic of any network that processor and main storage with an I/O device. multiplexes multiple, independent network carriers channel-attached. (1) pertaining to attachment onto a single cable. This is usually done using of devices directly by data channels (I/O frequency division multiplexing. Broadband channels)to a computer. (2) Pertaining to devices technology allows several networks to coexist on attached to a controlling unit by cables, rather one single cable; traffic from one network does not than by telecommunication lines. interfere with traffic from another, because the (3) Synonymous with local, locally attached. “conversations” happen on different frequencies in the ether, similar to a commercial radio system. checksum. The sum of a group of data associated with the group and used for checking broadcast. The simultaneous transmission of purposes. data packets to all nodes on a network or subnetwork. CICS. Customer Information Control System. broadcast address. An address that is common Class A network. An internet network in which to all nodes on a network. the high-order bit of the address is 0. The host number occupies the three, low-order octets. BSD. Berkeley Software Distribution. Class B network. An internet network in which bus topology. A network configuration in which the high-order bit of the address is 1, and the next only one path is maintained between stations. high-order bit is 0. The host number occupies the Any data transmitted by a station is concurrently two low-order octets. available to all other stations on the link. Class C network. An internet network in which byte-ordering. The method of sorting bytes the two high-order bits of the address are 1 and under specific machine architectures. Of the two the next high-order bit is 0. The host number common methods, little endian byte ordering occupies the low-order octet. places the least significant byte first. This method is used in Intel** microprocessors. In the second CLAW. Common Link Access to Workstation. method, big endian byte ordering, the most significant byte is placed first. This method is used in Motorola** microprocessors. viii VM TCP/IP Glossary Glossary

client. (1) A function that requests services from communications adapter. A hardware feature a server, and makes them available to the user. that enables a computer or device to become a (2) In MVS, an address space that is using part of a data network. TCP/IP services. community name. A password used by hosts client-server model. A common way to describe running Simple Network Management Protocol network services and the model user processes (SNMP) agents to access remote network (programs) of those services. Examples include management stations. the name server and resolver paradigm of the DNS and file server/file client relationships such compile. (1) To translate a program written in a as NFS and diskless hosts. high-level language into a machine language program. (2) The computer actions required to client-server relationship. Any device that transform a source file into an executable object provides resources or services to other devices on file. a network is a server. Any device that employs the resources provided by a server is a client.A compiler. A program that translates a source machine can run client and server processes at program into an executable program (an object the same time. program).

CLIST. Command List. Computer and Science Network (CSNET). A large computer network, mostly in the U.S. but CLPA. Create Link Pack Area. with international connections. CSNET sites include universities, research labs, and some CMS. Conversational Monitor System. commercial companies. It is now merged with BITNET to form CREN. See BITNET. Comite Consultatif International Telegraphicque et Telephonique (CCITT). The connection. (1) An association established International Telegraph and Telephone between functional units for conveying information. Consultative Committee. A unit of the (2) The path between two protocol modules that International Telecommunications Union (ITU) of provides reliable stream delivery service. In an the United Nations. CCITT produces technical internet, a connection extends from a TCP module standards, known as “recommendations,” for all on one machine to a TCP module on the other. internationally controlled aspects of analog and digital communication. Control Program (CP). The VM operating system that manages the real processor’s command. The name and any parameters resources and is responsible for simulating associated with an action that can be performed System/370s or 390s for individual users. by a program. The command is entered by the user; the computer performs the action requested conversational monitor system (CMS). A by the command name. virtual machine operating system that provides general interactive time sharing, problem solving, Command List (CLIST). A list of commands and and program development capabilities, and statements designed to perform a specific function operates only under control of the VM//ESA for the user. control program.

command prompt. A displayed symbol, such as Corporation for Research and Educational [C:\] that requests input from a user. Networking (CREN). A large computer network formed from the merging of BITNET and CSNET. Common Link Access to Workstation (CLAW). See BITNET and CSNET. A continuously executing duplex channel program designed to minimize host interrupts while CP. Control Program. maximizing channel utilization. Create Link Pack Area (CLPA). A parameter specified at startup, which says to create the link pack area.

Glossary ix Glossary

CREN. Corporation for Research and DB2. DATABASE 2. Educational Networking. DBA. Database administrator. CSMA/CD. Carrier Sense Multiple Access with Collision Detection. DBCS. Double Byte Character Set.

CSNET. Computer and Science Network. DDN. Defense Data Network.

Customer Information Control System (CICS). decryption. The unscrambling of data using an An IBM-licensed program that enables algorithm that works under the control of a key. transactions entered at remote terminals to be The key allows data to be protected even when processed concurrently by user written application the algorithm is unknown. Data is unscrambled programs. It includes facilities for building, using, after transmission. and maintaining databases. default. A value, attribute, or option that is assumed when none is explicitly specified. D Defense Advanced Research Projects Agency daemon. A background process usually started (DARPA). The U.S. government agency that at system initialization that runs continuously and funded the ARPANET. performs a function required by other processes. Some daemons are triggered automatically to Defense Data Network (DDN). Comprises the perform their task; others operate periodically. MILNET and several other Department of Defense networks. DASD. Direct Access Storage Device. destination node. The node to which a request DARPA. Defense Advanced Research Projects or data is sent. Agency. DHCP. Dynamic Host Configuration Protocol DATABASE 2 (DB2). An IBM relational database management system for the MVS operating Direct Access Storage Device (DASD). A system. device in which access to data is independent of where data resides on the device. database administrator (DBA). An individual or group responsible for the rules by which data is directory. A named grouping of files in a file accessed and stored. The DBA is usually system. responsible for database integrity, security, performance and recovery. Disk Operating System (DOS). An operating system for computer systems that use disks and datagram. A basic unit of information that is diskettes for auxiliary storage of programs and passed across the internet, it consists of one or data. more data packets. display terminal. An input/output unit by which a data link layer. Layer 2 of the OSI (Open user communicates with a data-processing system Systems Interconnection) model; it defines or sub-system. Usually includes a keyboard and protocols governing data packetizing and always provides a visual presentation of data; for transmission into and out of each node. example, an IBM 3179 display. data set. The major unit of data storage and Distributed Program Interface (DPI). A retrieval in MVS, consisting of a collection of data programming interface that provides an extension in one of several prescribed arrangements and to the function provided by the SNMP agents. described by control information to which the system has access. Synonymous with file in VM DLL. Dynamic Link Library. and OS/2. DNS. Domain Name System.

x VM TCP/IP Glossary Glossary

domain. In an internet, a part of the naming dynamic link library (DLL). A module containing hierarchy. Syntactically, a domain name consists dynamic link routines that is linked at load or run of a sequence of names (labels) separated by time. periods (dots).

Domain Name System (DNS). A system in E which a resolver queries name servers for EBCDIC. Extended binary-coded decimal resource records about a host. interchange code. domain naming. A hierarchical system for EGP. Exterior Gateway Protocol. naming network resources. encapsulation. A process used by layered DOS. Disk Operating System. protocols in which a lower-level protocol accepts a dotted-decimal notation. The syntactic message from a higher-level protocol and places it representation for a 32-bit integer that consists of in the data portion of the low-level frame. As an four 8-bit numbers, written in base 10 and example, in Internet terminology, a packet would separated by periods (dots). Many internet contain a header from the physical layer, followed application programs accept dotted decimal by a header from the network layer (IP), followed notations in place of destination machine names. by a header from the transport layer (TCP), followed by the application protocol data. double-byte character set (DBCS). A set of characters in which each character is represented encryption. The scrambling or encoding of data by two bytes. Languages such as Japanese, using an algorithm that works under the control of Chinese, Korean, which contain more symbols a key. The key allows data to be protected even than can be represented by 256 code points, when the algorithm is unknown. Data is require double-byte character sets. Because each scrambled prior to transmission. character requires 2 bytes, the typing, display, and ES/9370 Integrated Adapters. An adapter you printing of DBCS characters requires hardware can use in TCP/IP for VM to connect into and programs that support DBCS. Token-Ring networks and Ethernet networks, as doubleword. A contiguous sequence of bits or well as TCP/IP networks that support X.25 characters that comprises two computer words connections. and is capable of being addressed as a unit. Ethernet. The name given to a local area DPI. Distributed Program Interface. packet-switched network technology invented in the early 1970s by Xerox**, Incorporated. Dynamic Host Configuration Protocol (DHCP). Ethernet uses a Carrier Sense Multiple The Dynamic Host Configuration Protocol provides Access/Collision Detection (CSMA/CD) a framework for passing configuration information mechanism to send packets. to hosts on a TCPIP network. DHCP is based on the Bootstrap Protocol (BOOTP), adding the EXEC. In a VM operating system, a user-written capability of automatic allocation of reusable command file that contains CMS commands, other network addressed and additional configuration user-written commands, and execution control options. DHCP captures the behavior of BOOT statements, such as branches. relay agents; DHCP participants can interoperate extended binary-coded decimal interchange with BOOTP participants. code (EBCDIC). A coded character set dynamic resource allocation. An allocation consisting of 8-bit coded characters. technique in which the resources assigned for extended character. A character other than a execution of computer programs are determined 7-bit ASCII character. An extended character can by criteria applied at the moment of need. be a 1-bit code point with the 8th bit set (ordinal 128-255) or a 2-bit code point (ordinal 256 and greater).

Glossary xi Glossary

Exterior Gateway Protocol (EGP). A foreign node. See foreign host. reachability routing protocol used by gateways in a two-level internet. frame. The portion of a tape on a line perpendicular to the reference edge, on which eXternal Data Representation (XDR). A binary characters can be written or read standard developed by Sun Microsystems, simultaneously. Incorporated for representing data in machine-independent format. FTAM. File Transfer Access and Management.

FTP. File Transfer Protocol. F fullword. A computer word. In System/370, 32 FAT. File Allocation Table. bits or 4 bytes.

FDDI. Fiber Distributed Data Interface. Also used to abbreviate Fiber Optic Distributed Data G Interface. gadget. A windowless graphical object that looks Fiber Distributed Data Interface (FDDI). The like its equivalent like-named widget but does not ANSI standard for high-speed transmission over support the translations, actions, or pop-up widget fiber optic cable. children supplied by that widget.

Fiber Optic Network. A network based on the gateway. (1) A functional unit that interconnects technology and standards that define data a local data network with another network having transmission using cables of glass or plastic fibers different protocols. (2) A host that connects a carrying visible light. Fiber optic network TCP/IP network to a non-TCP/IP network at the advantages are: higher transmission speeds, application layer. See also router. greater carrying capacity, and lighter, more compact cable. gather and scatter data. Two related operations. During the gather operation, data is file. In VM and OS/2, a named set of records taken from multiple buffers and transmitted. In the stored or processed as a unit. Synonymous with scatter operation, data is received and stored in data set in MVS. multiple buffers.

File Allocation Table (FAT). A table used to GC. Graphics Context. allocate space on a disk for a file. GContext. See Graphics Context. File Transfer Access and Management (FTAM). An application service element that GCS. Group Control System. enables user application processes to manage and access a file system, which may be GDDM. Graphical Data Display Manager. distributed. GDDMXD. Graphical Data Display Manager File Transfer Protocol (FTP). A TCP/IP protocol interface for X Window System. A graphical used for transferring files to and from foreign interface that formats and displays alphanumeric, hosts. FTP also provides the capability to access data, graphics, and images on workstation display directories. Password protection is provided as devices that support the X Window System. part of the protocol. GDF. Graphics data file. foreign host. Any machine on a network that Graphical Display Data Manager (GDDM). A can be interconnected. group of routines that allows pictures to be defined foreign network. In an internet, any other and displayed procedurally through function network interconnected to the local network by routines that correspond to graphic primitives. one or more intermediate gateways or routers. xii VM TCP/IP Glossary Glossary

Graphics Context (GC). The storage area for management, and task management functions graphics output. Also known as GC and such as control of job flow, ordering of tasks, and GContext. Used only with graphics that have the spooling. same root and depth as the graphics content. HPFS. High Performance File System.

Group Control System (GCS). A component of HYPERchannel Adapter. A network interface VM/ESA, consisting of a shared segment that you used to connect a TCP/IP for VM or MVS host can Initial Program Load (IPL) and run in a virtual into an existing TCP/IP HYPERchannel network, machine. It provides simulated MVS services and or to connect TCP/IP hosts together to create a unique supervisor services to help support a TCP/IP HYPERchannel network. native SNA network. I H IAB. Internet Activities Board. handle. A temporary data representation that identifies a file. ICMP. Internet Control Message Protocol.

halfword. A contiguous sequence of bits or IEEE. Institute of Electrical and Electronic characters that constitutes half a fullword and can Engineers. be addressed as a unit. IETF. Internet Engineering Task Force. HASP. Houston automatic spooling priority system. IGP. Interior Gateway Protocol.

HDLC. High-level Data Link Control. include file. A file that contains preprocessor text, which is called by a program, using a header file. A file that contains constant standard programming call. Synonymous with declarations, type declarations, and variable header file. declarations and assignments. Header files are supplied with all programming interfaces. IMS. Information Management System.

High-level Data Link Control (HDLC). An ISO Information Management System (IMS). A protocol for X.25 international communication. database/data communication (DB/DC) system that can manage complex databases and High Performance File System (HPFS). An networks. OS/2 file management system that supports high-speed buffer storage, long file names, and initial program load (IPL). The initialization extended attributes. procedure that causes an operating system to commence operation. hop count. The number of gateways or routers through which a packet passes on its way to its instance. Indicates a label that is used to destination. distinguish among the variations of the principal name. An instance allows for the possibility that host. A computer connected to a network, which the same client or service can exist in several provides an access method to that network. A forms that require distinct authentication. host provides end-user services and can be a client, a server, or a client and server Institute of Electrical and Electronic Engineers simultaneously. (IEEE). An electronics industry organization.

Houston automatic spooling priority system Integrated Services Digital Network (ISDN). A (HASP). A computer program that provides digital, end-to-end telecommunication network that supplementary job management, data supports multiple services including, but not limited to, voice and data.

Glossary xiii Glossary

interactive. Pertaining to a program or a system routers, bridges, and hosts to function as a single, that alternately accepts input and then responds. coordinated, virtual network. An interactive system is conversational; that is, a continuous dialog exists between user and internet address. The unique 32-bit address system. See batch. identifying each node in an internet. See also address. Interior Gateway Protocol (IGP). The protocol used to exchange routing information between Internet Control Message Protocol (ICMP). collaborating routers in the Internet. RIP is an The part of the Internet Protocol layer that handles example of an IGP. error messages and control messages.

Internet. The largest internet in the world Internet Protocol (IP). The TCP/IP layer consisting of large national backbone nets (such between the higher level host-to-host protocol and as MILNET, NSFNET, and CREN) and a myriad the local network protocols. IP uses local area of regional and local campus networks all over the network protocols to carry packets, in the form of world. The Internet uses the Internet protocol datagrams, to the next gateway, router, or suite. To be on the Internet, you must have IP destination host. connectivity (be able to TELNET to, or PING, other systems). Networks with only electronic mail interoperability. The capability of different connectivity are not actually classified as being on hardware and software by different vendors to the Internet. effectively communicate together.

Internet Activities Board (IAB). The technical Inter-user communication vehicle (IUCV). A body that oversees the development of the VM facility for passing data between virtual Internet suite of protocols (commonly referred to machines and VM components. as TCP/IP). It has two task forces (the IRTF and the IETF) each charged with investigating a intrinsics X-Toolkit. A set management particular area. mechanism that provides for constructing and interfacing between composite X Window widgets, Internet address. A 32-bit address assigned to their children, and other clients. Also, intrinsics hosts using TCP/IP. An internet address consists provide the ability to organize a collection of of a network number and a local address. Internet widgets into an application. addresses are represented in a dotted-decimal notation and are used to route packets through IP. Internet Protocol. the network. IP datagram. The fundamental unit of Internet Engineering Task Force (IETF). One of information passed across the Internet. An IP the task forces of the IAB. The IETF is datagram contains source and destination responsible for solving short-term engineering addresses along with data and a number of fields needs of the Internet. that define such things as the length of the datagram, the header checksum, and flags to say International Organization for Standardization whether the datagram can be (or has been) (ISO). An organization of national standards fragmented. bodies from various countries established to promote development of standards to facilitate IPL. Initial Program Load. international exchange of goods and services, and ISDN. Integrated Services Digital Network. develop cooperation in intellectual, scientific, technological, and economic activity. ISO. International Organization for Standardization. internet or internetwork. A collection of packet switching networks interconnected by gateways, IUCV. Inter-User Communication Vehicle.

xiv VM TCP/IP Glossary Glossary

Line Printer Daemon (LPD). The remote printer J server that allows other hosts to print on a printer local to your host. JCL. Job Control Language. little-endian. A format for storage or JES. Job Entry Subsystem. transmission of binary data in which the least JIS. Japanese Institute of Standards. significant bit (or byte) comes first. The reverse convention is big-endian. Job Control Language (JCL). A problem-oriented language designed to express LLB. Local Location Broker. statements in a job that are used to identify the local area network (LAN). A data network job or describe its requirements to an operating located on the user’s premises in which serial system. transmission is used for direct data communication Job Entry Subsystem (JES). An IBM among data stations. System/370 licensed program that receives jobs local host. In an internet, the computer to which into the system and processes all output data a user’s terminal is directly connected without produced by the jobs. using the internet. JUNET. The Japanese Academic and Research Local Location Broker (LLB). In Network Network that connects various UNIX operating Computing System (NCS) Location Broker, a systems. server that maintains information about objects on the local host and provides the Location Broker K forwarding facility.

Kanji. A graphic character set consisting of local network. The portion of a network that is symbols used in Japanese ideographic alphabets. physically connected to the host without Each character is represented by 2 bytes. intermediate gateways or routers.

katakana. A character set of symbols used on logical character delete symbol. A special one of the two common Japanese phonetic editing symbol, usually the at (@) sign, which alphabets, which is used primarily to write foreign causes CP to delete it and the immediately words phonetically. See also kanji. preceding character from the input line. If many delete symbols are consecutively entered, the Kerberos. A system that provides authentication same number of preceding characters are deleted service to users in a network environment. from the input line.

Kerberos Authentication System. An Logical Unit (LU). An entity addressable within authentication mechanism used to check an SNA-defined network. LUs are categorized by authorization at the user level. the types of communication they support.

L LPD. Line Printer Daemon. LPR. Line Printer Client. LaMail. The client that communicates with the OS/2 Presentation Manager to manage mail on LU. Logical Unit. the network. LU-LU session. In SNA, a session between two LAN. Local area network. logical units (LUs). It provides communication between two end users, or between an end user Line Printer Client (LPR). A client command and an LU services component. that allows the local host to submit a file to be printed on a remote print server. LU type. In SNA, the classification of an LU-LU session in terms of the specific subset of SNA

Glossary xv Glossary

protocols and options supported by the logical make it possible for military installations to have units (LUs) for that session. reliable network service, while the ARPANET continued to be used for research. See DDN.

M minidisk. Logical divisions of a physical direct access storage device. MAC. Media Access Control. modem (modulator/demodulator). A device that mail gateway. A machine that connects two or converts digital data from a computer to an analog more electronic mail systems (often different mail signal that can be transmitted on a systems on different networks) and transfers telecommunication line, and converts the analog messages between them. signal received to data for the computer. Management Information Base (MIB). A Motif. see OSF/Motif**. standard used to define SNMP objects, such as packet counts and routing tables, that are in a mouse. An input device that is used to move a TCP/IP environment. pointer on the screen and select items. mapping. The process of relating internet MTU. Maximum Transmission Unit. addresses to physical addresses in the network. multicast. The simultaneous transmission of mask. (1) A pattern of characters used to control data packets to a group of selected nodes on a retention or elimination of portions of another network or subnetwork. pattern of characters. (2) To use a pattern of characters to control retention or elimination of multiconnection server. A server that is another pattern of characters. (3) A pattern of capable of accepting simultaneous, multiple characters that controls the keeping, deleting, or connections. testing of portions of another pattern of characters. Multiple Virtual Storage (MVS). Implies Maximum Transmission Unit (MTU). The MVS/370, the MVS/XA product, and the MVS/ESA largest possible unit of data that can be sent on a product. given physical medium. multitasking. A mode of operation that provides media access control (MAC). The method used for the concurrent performance execution of two or by network adapters to determine which adapter more tasks. has access to the physical network at a given time. MVS. Multiple Virtual Storage.

Message Handling System (MHS). The system of message user agents, message transfer N agents, message stores, and access units that together provide OSI electronic mail. name server. The server that stores resource records about hosts. MHS. Message Handling System. National Science Foundation (NSF). Sponsor MIB. Management Information Base. of the NSFNET. microcode. A code, representing the instructions National Science Foundation Network of an instruction set, which is implemented in a (NSFNET). A collection of local, regional, and part of storage that is not program-addressable. mid-level networks in the U.S. tied together by a high-speed backbone. NSFNET provides MILNET. Military Network. scientists access to a number of supercomputers across the country. Military Network (MILNET). Originally part of the ARPANET, MILNET was partitioned in 1984 to NCK**. Network Computing Kernel.

xvi VM TCP/IP Glossary Glossary

NCP. Network Control Program. Network Control Program (NCP). An IBM-licensed program that provides NCS. Network Computing System. communication controller support for single-domain, multiple-domain, and NDB. Network Database. interconnected network capability.

NDIS. Network Driver Interface Specification. network database (NDB). An IBM-licensed program that provides communication controller Netman. This device keyword specifies that this support for single-domain, multiple-domain, and device is a 3172 LAN Channel Station that interconnected network capability. NDB allows supports IBM Enterprise-Specific SNMP interoperability among different database systems, Management Information Base (MIB) variables for and uses RPC protocol with a client/server type of 3172. TCP/IP for VM supports SNMP GET and relationship. NDB is used for data conversion, SNMP GETNEXT operations to request and security, I/O buffer management, and transaction retrieve 3172 Enterprise-Specific MIB variables. management. These requests are answered only by those 3172 devices with the NETMAN option in the PROFILE Network Driver Interface Specification (NDIS). TCPIP file. An industry-standard specification used by applications as an interface with network adapter NetView. A system 390-based, IBM-licensed device drivers. program used to monitor, manage, and diagnose the problems of a network. network elements. As defined in the SNMP architecture, network elements are gateways, network. An arrangement of nodes and routers, and hosts that contain management connecting branches. Connections are made agents responsible for performing the network between data stations. Physical network refers to management functions requested by the network the hardware that makes up a network. Logical management stations. network refers to the abstract organization overlaid on one or more physical networks. An internet is network file system (NFS). The NFS protocol, an example of a logical network. which was developed by Sun Microsystems, Incorporated, allows computers in a network to network adapter. A physical device, and its access each other’s file systems. Once accessed, associated software, that enables a processor or the file system appears to reside on the local host. controller to be connected to a network. Network Information Center (NIC). Originally network administrator. The person responsible there was only one, located at SRI International for the installation, management, control, and and tasked to serve the ARPANET (and later configuration of a network. DDN) community. Today, there are many NICs operated by local, regional, and national networks Network Computing Kernel (NCK). In the all over the world. Such centers provide user Network Computing System (NCS), the assistance, document service, training, and more. combination of the remote procedure call runtime library and the Location Broker. Network Interface Definition Language (NIDL). A declarative language for the definition of Network Computing System (NCS). A set of interfaces that has two forms, a Pascal-like syntax software components developed by Apollo, and a C-like syntax. NIDL is a component of the Incorporated, that conform to the Network Network Computing Architecture. Computing Architecture (NCA). NCS is made up of two parts: the nidl compiler and Network Network Job Entry (NJE). In object distribution, Computing Kernel (NCK). NCS is a programming an entry in the network job table that specifies the tool kit that allows programmers to distribute system action required for incoming network jobs processing power to other hosts. sent by a particular user or group of users. Each entry is identified by the user ID of the originating user or group.

Glossary xvii Glossary

network layer. Layer 3 of the Open Systems host that is handling the TCP/IP Offload Interconnection (OSI) model; it defines protocols processing. governing data routing. open system. A system with specified standards network management stations. As defined in and that therefore can be readily connected to the SNMP architecture, network management other systems that comply with the same stations, or SNMP clients, execute management standards. applications that monitor and control network elements. Open Systems Interconnection (OSI). (1) The interconnection of open systems in accordance NFS. Network file system. with specific ISO standards. (2) The use of standardized procedures to enable the NIC. Network Information Center. interconnection of data processing systems.

NIDL. Network Interface Definition Language. Operating System/2 (OS/2). Pertaining to the IBM licensed program that can be used as the NJE. Network Job Entry. operating system for personal computers. The OS/2 licensed program can perform multiple tasks node. (1) In a network, a point at which one or at the same time. more functional units connect channels or data circuits. (2) In a network topology, the point at an OS/2. Operating System/2. end of a branch. OSF/Motif. OSF/Motif is an X Window System nonblocking mode. If the execution of the toolkit defined by Open Software Foundation, Inc. program cannot continue until some event occurs, (OSF), which enables the application programmer the operating system does not suspend the to include standard graphic elements that have a program until that event occurs. Instead, the 3-D appearance. Performance of the graphic operating system returns an error message to the elements is increased with gadgets and program. windowless widgets.

NPSI. X.25 NCP Packet Switching Interface. OSI. Open Systems Interconnection.

NSF. National Science Foundation. out-of-band data. Data that is placed in a secondary channel for transmission. Primary and NSFNET. National Science Foundation Network. secondary communication channels are created physically by modulation on a different frequency, O or logically by specifying a different logical channel. A primary channel can have a greater octet. A byte composed of eight binary elements. capacity than a secondary one.

OfficeVision (OV). IBM’s new proprietary, OV. OfficeVision. integrated office management system used for sending, receiving, and filing electronic mail, and a P variety of other office tasks. OfficeVision replaces PROFS. packet. A sequence of binary digits, including data and control signals, that is transmitted and Offload host. Any device that is handling the switched as a composite whole. TCP/IP processing for the MVS host where TCP/IP for MVS is installed. Currently, the only Packet Switching Data Network (PSDN). A supported Offload host is the 3172-3. network that uses packet switching as a means of transmitting data. Offload system. Represents both the MVS host where TCP/IP for MVS is installed and the Offload parameter. A variable that is given a constant value for a specified application. xviii VM TCP/IP Glossary Glossary

parse. To analyze the operands entered with a manage, through the PU, resources of the node command. such as attached links. passive open. The state of a connection that is PING. The command that sends an ICMP Echo prepared to provide a service on demand. Request packet to a host, gateway, or router with Contrast with active open. the expectation of receiving a reply.

Partitioned data set (PDS). A data set in direct PM. Presentation Manager. access storage that is divided into partitions, called members, each of which can contain a PMANT. In OS/2, the 3270 client terminal program, part of a program, or data. emulation program that is invoked by the PMANT command. PC. Personal computer. polling. (1) On a multipoint connection or a PCA. Personal Channel Attach. point-to-point connection, the process whereby data stations are invited one at a time to transmit. PC Network. A low-cost, broadband network that (2) Interrogation of devices for such purposes as allows attached IBM personal computers, such as to avoid contention, to determine operational IBM 5150 Personal Computers, IBM Computer status, or to determine readiness to send or ATs, IBM PC/XTs, and IBM Portable Personal receive data. Computers to communicate and to share resources. POP. Post Office Protocol.

PDS. Partitioned data set. port. (1) An endpoint for communication between devices, generally referring to a logical PDN. Public Data Network. connection. (2) A 16-bit number identifying a particular Transmission Control Protocol or User PDU. Protocol data unit. Datagram Protocol resource within a given TCP/IP node. peer-to-peer. In network architecture, any functional unit that resides in the same layer as PORTMAP. Synonymous with Portmapper. another entity. Portmapper. A program that maps client Personal Channel Attach (PCA). see Personal programs to the port numbers of server programs. System Channel Attach. Portmapper is used with Remote Procedure Call (RPC) programs. Personal Computer (PC). A microcomputer primarily intended for stand-alone use by an Post Office Protocol (POP). A protocol used for individual. exchanging network mail.

Personal System Channel Attach (PSCA). An presentation layer. Layer 6 of the Open adapter card to connect a micro-channel based Systems Interconnections (OSI) model; it defines personal computer (or processor) to a System/370 protocols governing data formats and conversions. parallel channel. Presentation Manager (PM). A component of physical layer. Layer 1 of the Open Systems OS/2 that provides a complete graphics-based Interconnection (OSI) model; it details protocols user interface, with pull-down windows, action governing transmission media and signals. bars, and layered menus. physical unit (PU). In SNA, the component that principal name. Specifies the unique name of a manages and monitors the resources, such as user (client) or service. attached links and adjacent link stations, associated with a node, as requested by an SSPC PostScript. A standard that defines how text and via an SSPC-PU session. An SSPC activates a graphics are presented on printers and display session with the physical unit in order to indirectly devices.

Glossary xix Glossary

process. (1) A unique, finite course of events defined by its purpose or by its effect, achieved R under defined conditions. (2) Any operation or RACF. Resource access control facility. combination of operations on data. (3) A function being performed or waiting to be performed. RARP. Reverse Address Resolution Protocol. (4) A program in operation; for example, a daemon is a system process that is always read-only access. An access mode associated running on the system. with a virtual disk directory that lets a user read, but not write or update, any file on the disk Professional Office Systems (PROFS). IBM’s directory. proprietary, integrated office management system used for sending, receiving, and filing electronic read/write access. An access mode associated mail, and a variety of other office tasks. PROFS with a virtual disk directory that lets a user read has been replaced by OfficeVision. See and write any file on the disk directory (if write OfficeVision. authorized).

PROFS. Professional Office Systems. realm. One of the three parts of a Kerberos name. The realm specifies the network address protocol. A set of semantic and syntactic rules of the principal name or instance. This address that determines the behavior of functional units in must be expressed as a fully qualified domain achieving communication. Protocols can name, not as a “dot numeric” internet address. determine low-level details of machine-to-machine interfaces, such as the order in which bits from a recursion. A process involving numerous steps, byte are sent; they can also determine high-level in which the output of each step is used for the exchanges between application programs, such as successive step. file transfer. reduced instruction-set computer (RISC). A Protocol data unit (PDU). A set of commands computer that uses a small, simplified set of used by the SNMP agent to request management frequently used instructions for rapid execution. station data. reentrant. The attribute of a program or routine protocol suite. A set of protocols that cooperate that allows the same copy of a program or routine to handle the transmission tasks for a data to be used concurrently by two or more tasks. communication system. Remote Execution Protocol (REXEC). A PSCA. Personal System Channel Attach. protocol that allows the execution of a command or program on a foreign host. The local host PSDN. Packet Switching Data Network. receives the results of the command execution. This protocol uses the REXEC command. PU. Physical unit. remote host. A machine on a network that Public Data Network (PDN). A network requires a physical link to interconnect with the established and operated by a telecommunication network. administration or by a Recognized Private Operating Agency (RPOA) for the specific purpose remote logon. The process by which a terminal of providing circuit-switched, packet-switched, and user establishes a terminal session with a remote leased-circuit services to the public. host. Q queue. A line or list formed by items in a system waiting for service; for example, tasks to be performed or messages to be transmitted. To arrange in, or form, a queue. xx VM TCP/IP Glossary Glossary

Remote Procedure Call (RPC). A facility that a return code. (1) A code used to influence the client uses to request the execution of a execution of succeeding instructions. (2) A value procedure call from a server. This facility includes returned to a program to indicate the results of an a library of procedures and an eXternal data operation requested by that program. representation. Reverse Address Resolution Protocol (RARP). Remote Spooling Communications Subsystem A protocol that maintains a database of mappings (RSCS). An IBM-licensed program that transfers between physical hardware addresses and IP spool files, commands, and messages between addresses. VM users, remote stations, and remote and local batch systems, through HASP-compatible REXEC. Remote Execution Protocol. telecommunication facilities. REXX. Restructured Extended Executor Request For Comments (RFC). A series of language. documents that covers a broad range of topics affecting internetwork communication. Some RFC. Request For Comments. RFCs are established as internet standards. RIP. Routing Information Protocol. resolver. A program or subroutine that obtains information from a name server or local table for RISC. Reduced instruction-set computer. use by the calling program. router. A device that connects networks at the resource access control facility (RACF). An ISO Network Layer. A router is IBM-licensed program that provides for access protocol-dependent and connects only networks control by identifying and by verifying the users to operating the same protocol. Routers do more the system, authorizing access to protected than transmit data; they also select the best resources, logging the detected unauthorized transmission paths and optimum sizes for packets. attempts to enter the system, and logging the In TCP/IP, routers operate at the Internetwork detected accesses to protected resources. layer. See also gateway. resource records. Individual records of data Routing Information Protocol (RIP). The used by the Domain Name System. Examples of protocol that maintains routing table entries for resource records include the following: a host’s gateways, routers, and hosts. Internet Protocol addresses, preferred mail routing table. A list of network numbers and the addresses, and aliases. information needed to route packets to each. response unit (RU). In SNA, a message unit RPC. Remote Procedure Call. that acknowledges a request unit. It may contain prefix information received in a request unit. If RSCS. Remote Spooling Communications positive, the response unit may contain additional Subsystem. information such as session parameters in response to BIND SESSION. If negative, it RU. Response unit. contains sense data defining the exception condition. S Restructured Extended Executor (REXX) language. A general purpose programming SAA. Systems Application Architecture. language, particularly suitable for EXEC procedures, XEDIT macros, or programs for SBCS. Single Byte Character Set. personal computing. Procedures, XEDIT macros, and programs written in this language can be SDLC. Synchronous data link control. interpreted by the Procedures Language VM/REXX interpreter. Sendmail. The OS/2 mail server that uses Simple Mail Transfer Protocol to route mail from one host to another host on the network.

Glossary xxi Glossary

serial line. A network media that is a de facto SNA. Systems Network Architecture. standard, not an international standard, commonly used for point-to-point TCP/IP connections. SNALINK. SNA Network Link. Generally, a serial line consists of an RS-232 connection into a modem and over a telephone SNA Network Link. An SNA network link line. function of TCP/IP for VM and MVS hosts running TCP/IP to communicate through an existing SNA semantics. (1) The relationships of characters or backbone. groups of characters to their meanings, independent of the manner of their interpretation SNMP. Simple Network Management Protocol. and use. (2) The relationships between symbols and their meanings. SOA. Start of authority record. server. A function that provides services for socket. (1) An endpoint for communication users. A machine can run client and server between processes or applications. (2) A pair processes at the same time. consisting of TCP port and IP address, or UDP port and IP address. SFS. Shared File System. socket address. An address that results when Shared File System (SFS). A part of CMS that the port identification number is combined with an lets users organize their files into groups known internet address. as directoires and selectively share those files and directories with other users. socket interface. An application interface that allows users to write their own applications to Simple Mail Transfer Protocol (SMTP). A supplement those supplied by TCP/IP. TCP/IP application protocol used to transfer mail between users on different systems. SMTP SPOOL. Simultaneous peripheral operations specifies how mail systems interact and the format online. of control messages they use to transfer mail. spooling. The processing of files created by or Simple Network Management Protocol intended for virtual readers, punches, and printers. (SNMP). A protocol that allows network The spool files can be sent from one virtual device management by elements, such as gateways, to another, from one virtual machine to another, routers, and hosts. This protocol provides a and to read devices. means of communication between network elements regarding network resources. SQL. Structured Query Language. simultaneous peripheral operations online SQL/DS. Structured Query Language/Data (SPOOL). (1) (Noun) An area of auxiliary storage System. defined to temporarily hold data during its transfer start of authority record (SOA). In the Domain between peripheral equipment and the processor. Name System, the resource record that defines a (2) (Verb) To use auxiliary storage as a buffer zone. storage to reduce processing delays when transferring data between peripheral equipment stream. A continuous sequence of data elements and the processing storage of a computer. being transmitted, or intended for transmission, in character or binary-digit form, using a defined single-byte character set (SBCS). A character format. set in which each character is represented by a one-byte code. Contrast with double-byte Structured Query Language (SQL). Fourth character set. generation English-like programming language used to perform queries on relational databases. SMI. Structure for Management Information. Structured Query Language/Data System SMTP. Simple Mail Transfer Protocol. (SQL/DS). An IBM relational database xxii VM TCP/IP Glossary Glossary

management system for the VM and VSE operating systems. T TALK. An interactive messaging system that Structure for Management Information (SMI). sends messages between the local host and a The rules used to define the objects that can be foreign host. accessed through a network management protocol. See also MIB. TCP. Transmission Control Protocol. subagent. In the SNMP architecture, a subagent TCP/IP. Transmission Control Protocol/Internet provides an extension to the utility provided by the Protocol. SNMP agent. Telnet. The Terminal Emulation Protocol, a subdirectory. A directory contained within TCP/IP application protocol for remote connection another directory in a file system hierarchy. service. Telnet allows a user at one site to gain access to a foreign host as if the user's terminal subnet. A networking scheme that divides a were connected directly to that foreign host. single logical network into smaller physical networks to simplify routing. terminal emulator. A program that imitates the function of a particular kind of terminal. subnet address. The portion of the host address that identifies a subnetwork. Terminate and Stay Resident (TSR) program. A TSR is a program that installs part of itself as subnet mask. A mask used in the IP protocol an extension of DOS when it is executed. layer to separate the subnet address from the host portion of the address. TFTP. Trivial File Transfer Protocol. subnetwork. Synonymous with subnet. ticket. Encrypted information obtained from a Kerberos authentication server or a ticket-granting subsystem. A secondary or subordinate system, server. A ticket authenticates a user and, in usually capable of operating independent of, or conjunction with an authenticator, serves as asynchronously with, a controlling system. permission to access a service when presented by SYNC. Synchronous. the authenticated user. synchronous (SYNC). (1) Pertaining to two or ticket-granting server. Grants Kerberos tickets more processes that depend on the occurrences to authenticated users as permission to access an of a specific event such as common timing signal. end-service. (2) Occurring with a regular or predictable time Time Sharing Option (TSO). An operating relationship. See asynchronous. system option; for System/370 system, the option synchronous data link control (SDLC). A data provides interactive time sharing from remote link over which communication is conducted using terminals the synchronous data protocol. time stamp. (1) To apply the current system Systems Application Architecture (SAA). A time. (2) The value on an object that is an formal set of rules that enables applications to be indication of the system time at some critical point run without modification in different computer in the history of the object. (3) In query, the environments. identification of the day and time when a query report was created that query automatically Systems Network Architecture (SNA). The provides on each report. description of the logical structure, formats, protocols, and operational sequences for TN3270. An informally defined protocol for transmitting information units through, and transmitting 3270 data streams over Telnet. controlling the configuration and operation of, networks.

Glossary xxiii Glossary

token. In a local network, the symbol of authority passed among data stations to indicate the station U temporarily in control of the transmission medium. UDP. User Datagram Protocol. token-bus. See bus topology. user. A function that uses the services provided by a server. A host can be a user and a server at token ring. As defined in IEEE 802.5, a the same time. See client. communication method that uses a token to control access to the LAN. The difference User Datagram Protocol (UDP). A datagram between a token bus and a token ring is that a level protocol built directly on the IP layer. UDP is token-ring LAN does not use a master controller to used for application-to-application programs control the token. Instead, each computer knows between TCP/IP hosts. the address of the computer that should receive the token next. When a computer with the token user exit. A point in an IBM-supplied program at has nothing to transmit, it passes the token to the which a user routine may be given control. next computer in line. user profile. A description of a user, including token-ring network. A ring network that allows user ID, user name, defaults, password, access unidirectional data transmission between data authorization, and attributes. stations by a token-passing procedure over one transmission medium, so that the transmitted data returns to the transmitting station. V

Transmission Control Protocol (TCP). The virtual address. The address of a location in TCP/IP layer that provides reliable, virtual storage. A virtual address must be process-to-process data stream delivery between translated into a real address to process the data nodes in interconnected computer networks. TCP in processor storage. assumes that IP (Internet Protocol) is the underlying protocol. Virtual Machine (VM). A licensed machine whose full name is Virtual Machine/Enterprise Transmission Control Protocol/Internet Systems Architecture (VM/ESA) It is a software Protocol (TCP/IP). A suite of protocols designed operating system that manages the resources of a to allow communication between networks real processor to provide virtual machines to end regardless of the technologies implemented in users. As a time-sharing system control program each network. (CP), the conversational monitor system (CMS), the group control system (GCS), and the dump transport layer. Layer 4 of the Open Systems viewing facility (DVF). Interconnection (OSI) model; it defines protocols governing message structure and some error Virtual Machine Communication Facility checking. (VMCF). A connectionless mechanism for communication between address spaces. TRAP. An unsolicited message that is sent by an SNMP agent to an SNMP network management Virtual Machine/System Product (VM/SP). An station. IBM-licensed program that manages the resources of a single computer so that multiple computing Trivial File Transfer Protocol (TFTP). The systems appear to exist. Each virtual machine is TFTP daemon (TFTPD servser) transfers files the functional equivalent of a real machine. between the Byte File System (BFS) and TFTP clients. TFTPD supports access to files virtual storage. Storage space that can be maintained in a BFS directory that is mounted. regarded as addressable main storage by the user of a computer system in which virtual addresses TSO. Time Sharing Option. are mapped into real addresses. The size of virtual storage is limited by the addressing scheme TSR. Terminate and stay resident. TSR usually refers to a terminate-and-stay-resident program. xxiv VM TCP/IP Glossary Glossary

of the computing system and by the amount of directory becomes the current directory when the auxiliary storage available, not by the actual application is started. number of main storage locations.

Virtual Telecommunications Access Method X (VTAM). An IBM-licensed program that controls X Client. An application program which uses the communication and the flow of data in an SNA X protocol to communicate windowing and network. It provides single-domain, graphics requests to an X Server. multiple-domain, and interconnected network capability. XDR. eXternal Data Representation. VM. Virtual Machine. XEDIT. The CMS facility, containing the XEDIT command and XEDIT subcommands and macros, VMCF. Virtual Machine Communication Facility. that lets a user create, change, and manipulate VM/ESA. Virtual Machine/Enterprise System CMS files. Architecture X Server. A program which interprets the X VMSES/E. Virtual Machine Serviceability protocol and controls one or more screens, a Enhancements Staged/Extended. pointing device, a keyboard, and various resources associated with the X Window System, VTAM. Virtual Telecommunications Access such as Graphics Contexts, Pixmaps, and color Method. tables.

X Window System. The X Window System is a W protocol designed to support network transparent windowing and graphics. TCP/IP for VM and MVS WAN. Wide area network. provides client support for the X Window System application program interface. well-known port. A port number that has been preassigned for specific use by a specific protocol X Window System API. An application program or application. Clients and servers using the interface designed as a distributed, same protocol communicate over the same network-transparent, device-independent, well-known port. windowing and graphics system. wide area network (WAN). A network that X Window System Toolkit. Functions for provides communication services to a geographic developing application environments. area larger than that served by a local area network. X.25. A CCITT communication protocol that defines the interface between data terminal widget. The basic data type of the X Window equipment and packet switching networks. System Toolkit. Every widget belongs to a widget class that contains the allowed operations for that X.25 NCP Packet Switching Interface (X.25 corresponding class. NPSI). An IBM-licensed program that allows users to communicate over packet switched data window. An area of the screen with visible networks that have interfaces complying with boundaries through which a panel or portion of a Recommendation X.25 (Geneva** 1980) of the panel is displayed. CCITT. It allows SNA programs to communicate with SNA equipment or with non-SNA equipment working directory. The directory in which an over such networks. application program is found. The working

Glossary xxv Glossary

zone. In the Domain Name System, a zone is a Z logical grouping of domain names that is assigned to a particular organization. Once an organization ZAP. To modify or dump an individual text controls its own zone, it can change the data in file/data set using the ZAP command or the the zone, add new tree sections connected to the ZAPTEXT EXEC. zone, delete existing nodes, or delegate new ZAP disk. The virtual disk in the VM operating subzones under its zone. system that contains the user-written modifications to VTAM code.

xxvi VM TCP/IP Glossary

IBM

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