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 VMpublications. It includes IBM product terminology as well as other company andproduct 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.

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

Licensees of this program who wish to have information about it for the purpose ofenabling: (i) the exchange of information between independently created programsand other programs (including this one) and (ii) the mutual use of the informationwhich has been exchanged, should contact theIBM Corporation, Mail Station P300,522 South Road, Poughkeepsie, NY 12601-5400, USA, Attention: InformationRequest. Such information may be available, subject to appropriate terms andconditions, including in some cases, payment of a fee.

The licensed programs described in this document and all licensed materialavailable for them are provided by IBM under terms of the IBM CustomerAgreement.

TrademarksThe following terms are trademarks of IBM Corporation in the United States orother countries or both:

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

ACF/VTAM AIXBookManager Common User AccessCUA ES/9000GDDM IBMLibrary Reader NetView OfficevisionOS/2 PC NetworkPROFS PS/2RISC System/6000 SQL/DSSystem Application Architecture SAASystem/370 VTAMVirtual Machine/Enterprise Systems Architecture VM/ESA

Copyright IBM Corp. 1987, 1997 iii

iv VM TCP/IP Glossary

Glossary

Glossary

This glossary describes the most common termsassociated with TCP/IP communication in aninternet environment, as used in this book.

If you do not find the term you are looking for, seethe IBM Dictionary of Computing, New York:McGraw-Hill, 1994.

For abbreviations, the definition usually consistsonly of the words represented by the letters; forcomplete definitions, see the entries for the words.

Numerics

3172. IBM Interconnect Controller.

3174. IBM Establishment Controller.

3270. Refers to a series of IBM display devices;for example, the IBM 3275, 3276 ControllerDisplay Station, 3277, 3278, and 3279 DisplayStations, the 3290 Information Panel, and the3287 and 3286 printers. A specific device type isused only when a distinction is required betweendevice types. Information about display terminalusage also refers to the IBM 3138, 3148, and3158 Display Consoles when used in displaymode, unless otherwise noted.

37xx Communication Controller . A networkinterface used to connect a TCP/IP for VM orMVS network that supports X.25 connections.NCP with X.25 NPSI must be running in thecontroller, and VTAM must be running on the host.

6611. IBM Network Processor.

8232. IBM LAN Station.

9370. Refers to a series of processors, namelythe IBM 9373 Model 20, the IBM 9375 Models 40and 60, and the IBM 9377 Model 90 and othermodels.

A

abend . The abnormal termination of a programor task.

abstract syntax . A description of a datastructure that is independent of machine-orientedstructures and encodings.

Abstract Syntax Notation One (ASN.1) . TheOSI language for describing abstract syntax.

active gateway . A gateway that is treated like anetwork interface in that it is expected toexchange routing information, and if it does not doso for a period of time, the route associated withthe gateway is deleted.

active open . The state of a connection that isactively seeking a service. Contrast with passiveopen.

adapter . (1) A piece of hardware that connects acomputer and an external device. (2) An auxiliarydevice or unit used to extend the operation ofanother system.

address . The unique code assigned to eachdevice or workstation connected to a network. Astandard internet address uses a two-part, 32-bitaddress field. The first part of the address fieldcontains the network address; the second partcontains the local address.

address mask . A bit mask used to select bitsfrom an Internet address for subnet addressing.The mask is 32 bits long and selects the networkportion of the Internet address and one or morebits of the local portion. It is sometimes called asubnet mask.

address resolution . A means for mappingnetwork layer addresses onto media-specificaddresses. See ARP.

Address Resolution Protocol (ARP) . A protocolused to dynamically bind an internet address to ahardware address. ARP is implemented on asingle physical network and is limited to networksthat support broadcast addressing.

Copyright IBM Corp. 1987, 1997 v

Glossary

address space . A collection of bytes that areallocated, and in many ways managed, as a singleentity by CP. Each byte within an address spaceis identified by a unique address. An addressspace represents an extent of storage available toa program. Address spaces allocated by VMrange in size from 64KB to 2GB.

Advanced Interactive Executive (AIX) . IBM’slicensed version of the UNIX operating system.

Advanced Program-to-ProgramCommunications (APPC) . The interprogramcommunication service within SNA LU 6.2 onwhich the APPC/VM interface is based.

Advanced Research Projects Agency (ARPA) .Now called DARPA, its the U.S. Governmentagency that funded the ARPANET.

Advanced Research Projects Agency Network(ARPANET) . A packet switched networkdeveloped in the early 1970’s that is theforerunner of today’s Internet. It wasdecommissioned in June 1990.

agent . As defined in the SNMP architecture, anagent, or an SNMP server is responsible forperforming the network management functionsrequested by the network management stations.

AIX. Advanced Interactive Executive.

American National Standard Code forInformation Interchange (ASCII) . (1) Thestandard code, using a coded character setconsisting of 7-bit coded characters (8 bitsincluding parity check), used for informationinterchange among data processing systems, datacommunication systems, and associatedequipment. The ASCII set consists of controlcharacters and graphic characters. (2) Thedefault file transfer type for FTP, used to transferfiles that contain ASCII text characters.

American National Standards Institute (ANSI) .An organization consisting of producers,consumers, and general interest groups thatestablishes the procedures by which accreditedorganizations create and maintain voluntaryindustry standards in the United States. ANSI issponsored by the Computer and BusinessEquipment Manufacturer Association and is

responsible for establishing voluntary industrystandards.

ANSI. American National Standards Institute.

API. Application Program Interface.

APPC. Advanced Program-to-ProgramCommunications.

application . The use to which an informationprocessing system is put, for example, a payrollapplication, an airline reservation application, anetwork application.

application layer . The seventh layer of the OSI(Open Systems Interconnection) model for datacommunication. It defines protocols for user orapplication programs.

Application Program Interface (API) . Theformally defined programming-language interfacebetween an IBM system control program orlicensed program and its user. APIs allowprogrammers to write application programs thatuse the TCP, UDP, and IP layers of the TCP/IPprotocol suite.

argument . A parameter passed between acalling program and a called program.

ARP. Address Resolution Protocol.

ARPA . Advanced Research Projects Agency.

ARPANET . Advanced Research Projects AgencyNetwork.

ASCII. (1) American National Standard Code forInformation Interchange. (2) The default filetransfer type for FTP, used to transfer files thatcontain ASCII text characters.

ASN.1. Abstract Syntax Notation One.

ASYNC. Asynchronous.

asynchronous (ASYNC) . Without regular timerelationship; unexpected or unpredictable withrespect to the execution of program instruction.See synchronous.

asynchronous communication . A method ofcommunication supported by the operating systemthat allows an exchange of data with remote

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device, using either a start-stop line or an X.25line. Asynchronous communications include thefile transfer and the interactive terminal facilitysupport.

Athena Widgets . The X Window widget setdeveloped by MIT for Project Athena.

Attachment Unit Interface (AUI) . Connectorused with thick Ethernet that often includes a dropcable.

AUI. Attachment Unit Interface.

attention key . A function key on terminals that,when pressed, causes an I/O interruption in theprocessing unit.

authentication server . The service that reads aKerberos database to verify that a client making arequest for access to an end-service is the clientnamed in the request. The authentication serverprovides an authenticated client ticket aspermission to access the ticket-granting server.

authenticator . Information encrypted by aKerberos authentication server that a clientpresents along with a ticket to an end-server aspermission to access the service.

authorization . The right granted to a user tocommunicate with, or to make use of, a computersystem or service.

B

backbone . (1) In a local area networkmultiple-bridge ring configuration, a high-speedlink to which rings are connected by means ofbridges. A backbone can be configured as a busor as a ring. (2) In a wide area network, ahigh-speed link to which nodes or data switchingexchanges (DSES) are connected.

background task . A task with which the user isnot currently interacting, but continues to run.

baseband . Characteristic of any networktechnology that uses a single carrier frequencyand requires all stations attached to the network toparticipate in every transmission. See broadband.

Basic Encoding Rules (BER) . Standard rulesfor encoding data units described in ASN.1.

Sometimes incorrectly grouped under the termASN.1, which correctly refers only to the abstractdescription language, not the encoding technique.

Basic Input/Output System (BIOS) . A set ofroutines that permanently resides in read-onlymemory (ROM) in a PC. The BIOS performs themost basic tasks, such as sending a character tothe printer, booting the computer, and reading thekeyboard.

batch . (1) An accumulation of data to beprocessed. (2) A group of records or dataprocessing jobs brought together for processing ortransmission. (3) Pertaining to activity involvinglittle or no user action. See interactive

Bayonet Neill-Concelman (BNC) . Astandardized connector used with Thinnet andcoaxial cable.

Because It’s Time NETwork (BITNET) . Anetwork of hosts that use the Network Job Entry(NJE) protocol to communicate. The network isprimarily composed of universities, nonprofitorganizations, and research centers. BITNET hasrecently merged with the Computer and ScienceNetwork (CSNET) to form the Corporation forResearch and Educational Networking (CSNET).See CSNET.

BER. Basic Encoding Rules.

Berkeley Software Distribution (BSD) . Termused when describing different versions of theBerkeley UNIX software, as in “4.3BSD UNIX”.

BFS. Byte File System.

big-endian . A format for storage or transmissionof binary data in which the most significant bit (orbyte) comes first. The reverse convention islittle-endian.

BIOS. Basic Input/Output System.

BITNET. Because It’s Time NETwork.

block . A string of data elements recorded,processed, or transmitted as a unit. The elementscan be characters, words, or physical records.

blocking mode . If the execution of the programcannot continue until some event occurs, the

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Glossary

operating system suspends the program until thatevent occurs.

BNC. Bayonet Neill-Concelman.

BOOTP. Bootstrap Protocol.

Bootstrap Protocol (BOOTP) . The BootstrapProtocol allows a diskless client machine todiscover its own IP address, the address of aserver host, and the name of a file to be loadedinto memory and executed.

bridge . (1) A router that connects two or morenetworks and forwards packets among them. Theoperations carried out by a bridge are done at thephysical layer and are transparent to TCP/IP andTCP/IP routing. (2) A functional unit thatconnects two local area networks (LANs) that usethe same logical link control (LLC) procedures butmay use different medium access control (MAC)procedures.

broadband . Characteristic of any network thatmultiplexes multiple, independent network carriersonto a single cable. This is usually done usingfrequency division multiplexing. Broadbandtechnology allows several networks to coexist onone single cable; traffic from one network does notinterfere with traffic from another, because the“conversations” happen on different frequencies inthe ether, similar to a commercial radio system.

broadcast . The simultaneous transmission ofdata packets to all nodes on a network orsubnetwork.

broadcast address . An address that is commonto all nodes on a network.

BSD. Berkeley Software Distribution.

bus topology . A network configuration in whichonly one path is maintained between stations.Any data transmitted by a station is concurrentlyavailable to all other stations on the link.

byte-ordering . The method of sorting bytesunder specific machine architectures. Of the twocommon methods, little endian byte orderingplaces the least significant byte first. This methodis used in Intel** microprocessors. In the secondmethod, big endian byte ordering, the mostsignificant byte is placed first. This method isused in Motorola** microprocessors.

Byte File System (BFS) . A file system in whicha file consists of an ordered sequence of bytesrather than records. BFS files can be organizedinto hierarchical directories. Byte file systems areenrolled as file spaces in CMS file pools.

C

Carrier Sense Multiple Access with CollisionDetection (CSMA/CD) . The access method usedby local area networking technologies such asEthernet.

case-sensitive . A condition in which entries foran entry field must conform to a specificlowercase, uppercase, or mixed-case format to bevalid.

CCITT. Comite Consultatif InternationalTelegraphique et Telephonique.

channel . A path in a system that connects aprocessor and main storage with an I/O device.

channel-attached . (1) pertaining to attachmentof devices directly by data channels (I/Ochannels)to a computer. (2) Pertaining to devicesattached to a controlling unit by cables, ratherthan by telecommunication lines.(3) Synonymous with local, locally attached.

checksum . The sum of a group of dataassociated with the group and used for checkingpurposes.

CICS. Customer Information Control System.

Class A network . An internet network in whichthe high-order bit of the address is 0. The hostnumber occupies the three, low-order octets.

Class B network . An internet network in whichthe high-order bit of the address is 1, and the nexthigh-order bit is 0. The host number occupies thetwo low-order octets.

Class C network . An internet network in whichthe two high-order bits of the address are 1 andthe next high-order bit is 0. The host numberoccupies the low-order octet.

CLAW . Common Link Access to Workstation.

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client . (1) A function that requests services froma server, and makes them available to the user.(2) In MVS, an address space that is usingTCP/IP services.

client-server model . A common way to describenetwork services and the model user processes(programs) of those services. Examples includethe name server and resolver paradigm of theDNS and file server/file client relationships suchas NFS and diskless hosts.

client-server relationship . Any device thatprovides resources or services to other devices ona network is a server. Any device that employsthe resources provided by a server is a client. Amachine can run client and server processes atthe same time.

CLIST. Command List.

CLPA . Create Link Pack Area.

CMS. Conversational Monitor System.

Comite Consultatif InternationalTelegraphicque et Telephonique (CCITT) . TheInternational Telegraph and TelephoneConsultative Committee. A unit of theInternational Telecommunications Union (ITU) ofthe United Nations. CCITT produces technicalstandards, known as “recommendations,” for allinternationally controlled aspects of analog anddigital communication.

command . The name and any parametersassociated with an action that can be performedby a program. The command is entered by theuser; the computer performs the action requestedby the command name.

Command List (CLIST) . A list of commands andstatements designed to perform a specific functionfor the user.

command prompt . A displayed symbol, such as[C:\] that requests input from a user.

Common Link Access to Workstation (CLAW) .A continuously executing duplex channel programdesigned to minimize host interrupts whilemaximizing channel utilization.

communications adapter . A hardware featurethat enables a computer or device to become apart of a data network.

community name . A password used by hostsrunning Simple Network Management Protocol(SNMP) agents to access remote networkmanagement stations.

compile . (1) To translate a program written in ahigh-level language into a machine languageprogram. (2) The computer actions required totransform a source file into an executable objectfile.

compiler . A program that translates a sourceprogram into an executable program (an objectprogram).

Computer and Science Network (CSNET) . Alarge computer network, mostly in the U.S. butwith international connections. CSNET sitesinclude universities, research labs, and somecommercial companies. It is now merged withBITNET to form CREN. See BITNET.

connection . (1) An association establishedbetween functional units for conveying information.(2) The path between two protocol modules thatprovides reliable stream delivery service. In aninternet, a connection extends from a TCP moduleon one machine to a TCP module on the other.

Control Program (CP) . The VM operatingsystem that manages the real processor’sresources and is responsible for simulatingSystem/370s or 390s for individual users.

conversational monitor system (CMS) . Avirtual machine operating system that providesgeneral interactive time sharing, problem solving,and program development capabilities, andoperates only under control of the VM//ESAcontrol program.

Corporation for Research and EducationalNetworking (CREN) . A large computer networkformed from the merging of BITNET and CSNET.See BITNET and CSNET.

CP. Control Program.

Create Link Pack Area (CLPA) . A parameterspecified at startup, which says to create the linkpack area.

Glossary ix

Glossary

CREN. Corporation for Research andEducational Networking.

CSMA/CD. Carrier Sense Multiple Access withCollision Detection.

CSNET. Computer and Science Network.

Customer Information Control System (CICS) .An IBM-licensed program that enablestransactions entered at remote terminals to beprocessed concurrently by user written applicationprograms. It includes facilities for building, using,and maintaining databases.

D

daemon . A background process usually startedat system initialization that runs continuously andperforms a function required by other processes.Some daemons are triggered automatically toperform their task; others operate periodically.

DASD. Direct Access Storage Device.

DARPA . Defense Advanced Research ProjectsAgency.

DATABASE 2 (DB2) . An IBM relational databasemanagement system for the MVS operatingsystem.

database administrator (DBA) . An individual orgroup responsible for the rules by which data isaccessed and stored. The DBA is usuallyresponsible for database integrity, security,performance and recovery.

datagram . A basic unit of information that ispassed across the internet, it consists of one ormore data packets.

data link layer . Layer 2 of the OSI (OpenSystems Interconnection) model; it definesprotocols governing data packetizing andtransmission into and out of each node.

data set . The major unit of data storage andretrieval in MVS, consisting of a collection of datain one of several prescribed arrangements anddescribed by control information to which thesystem has access. Synonymous with file in VMand OS/2.

DB2. DATABASE 2.

DBA . Database administrator.

DBCS. Double Byte Character Set.

DDN. Defense Data Network.

decryption . The unscrambling of data using analgorithm that works under the control of a key.The key allows data to be protected even whenthe algorithm is unknown. Data is unscrambledafter transmission.

default . A value, attribute, or option that isassumed when none is explicitly specified.

Defense Advanced Research Projects Agency(DARPA) . The U.S. government agency thatfunded the ARPANET.

Defense Data Network (DDN) . Comprises theMILNET and several other Department of Defensenetworks.

destination node . The node to which a requestor data is sent.

DHCP. Dynamic Host Configuration Protocol

Direct Access Storage Device (DASD) . Adevice in which access to data is independent ofwhere data resides on the device.

directory . A named grouping of files in a filesystem.

Disk Operating System (DOS) . An operatingsystem for computer systems that use disks anddiskettes for auxiliary storage of programs anddata.

display terminal . An input/output unit by which auser communicates with a data-processing systemor sub-system. Usually includes a keyboard andalways provides a visual presentation of data; forexample, an IBM 3179 display.

Distributed Program Interface (DPI) . Aprogramming interface that provides an extensionto the function provided by the SNMP agents.

DLL . Dynamic Link Library.

DNS. Domain Name System.

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domain . In an internet, a part of the naminghierarchy. Syntactically, a domain name consistsof a sequence of names (labels) separated byperiods (dots).

Domain Name System (DNS) . A system inwhich a resolver queries name servers forresource records about a host.

domain naming . A hierarchical system fornaming network resources.

DOS. Disk Operating System.

dotted-decimal notation . The syntacticrepresentation for a 32-bit integer that consists offour 8-bit numbers, written in base 10 andseparated by periods (dots). Many internetapplication programs accept dotted decimalnotations in place of destination machine names.

double-byte character set (DBCS) . A set ofcharacters in which each character is representedby two bytes. Languages such as Japanese,Chinese, Korean, which contain more symbolsthan can be represented by 256 code points,require double-byte character sets. Because eachcharacter requires 2 bytes, the typing, display, andprinting of DBCS characters requires hardwareand programs that support DBCS.

doubleword . A contiguous sequence of bits orcharacters that comprises two computer wordsand is capable of being addressed as a unit.

DPI. Distributed Program Interface.

Dynamic Host Configuration Protocol (DHCP) .The Dynamic Host Configuration Protocol providesa framework for passing configuration informationto hosts on a TCPIP network. DHCP is based onthe Bootstrap Protocol (BOOTP), adding thecapability of automatic allocation of reusablenetwork addressed and additional configurationoptions. DHCP captures the behavior of BOOTrelay agents; DHCP participants can interoperatewith BOOTP participants.

dynamic resource allocation . An allocationtechnique in which the resources assigned forexecution of computer programs are determinedby criteria applied at the moment of need.

dynamic link library (DLL) . A module containingdynamic link routines that is linked at load or runtime.

E

EBCDIC. Extended binary-coded decimalinterchange code.

EGP. Exterior Gateway Protocol.

encapsulation . A process used by layeredprotocols in which a lower-level protocol accepts amessage from a higher-level protocol and places itin the data portion of the low-level frame. As anexample, in Internet terminology, a packet wouldcontain a header from the physical layer, followedby a header from the network layer (IP), followedby a header from the transport layer (TCP),followed by the application protocol data.

encryption . The scrambling or encoding of datausing an algorithm that works under the control ofa key. The key allows data to be protected evenwhen the algorithm is unknown. Data isscrambled prior to transmission.

ES/9370 Integrated Adapters . An adapter youcan use in TCP/IP for VM to connect intoToken-Ring networks and Ethernet networks, aswell as TCP/IP networks that support X.25connections.

Ethernet . The name given to a local areapacket-switched network technology invented inthe early 1970s by Xerox**, Incorporated.Ethernet uses a Carrier Sense MultipleAccess/Collision Detection (CSMA/CD)mechanism to send packets.

EXEC. In a VM operating system, a user-writtencommand file that contains CMS commands, otheruser-written commands, and execution controlstatements, such as branches.

extended binary-coded decimal interchangecode (EBCDIC) . A coded character setconsisting of 8-bit coded characters.

extended character . A character other than a7-bit ASCII character. An extended character canbe a 1-bit code point with the 8th bit set (ordinal128-255) or a 2-bit code point (ordinal 256 andgreater).

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Glossary

Exterior Gateway Protocol (EGP) . Areachability routing protocol used by gateways in atwo-level internet.

eXternal Data Representation (XDR) . Astandard developed by Sun Microsystems,Incorporated for representing data inmachine-independent format.

F

FAT. File Allocation Table.

FDDI. Fiber Distributed Data Interface. Alsoused to abbreviate Fiber Optic Distributed DataInterface.

Fiber Distributed Data Interface (FDDI) . TheANSI standard for high-speed transmission overfiber optic cable.

Fiber Optic Network . A network based on thetechnology and standards that define datatransmission using cables of glass or plastic fiberscarrying visible light. Fiber optic networkadvantages are: higher transmission speeds,greater carrying capacity, and lighter, morecompact cable.

file . In VM and OS/2, a named set of recordsstored or processed as a unit. Synonymous withdata set in MVS.

File Allocation Table (FAT) . A table used toallocate space on a disk for a file.

File Transfer Access and Management(FTAM). An application service element thatenables user application processes to manageand access a file system, which may bedistributed.

File Transfer Protocol (FTP) . A TCP/IP protocolused for transferring files to and from foreignhosts. FTP also provides the capability to accessdirectories. Password protection is provided aspart of the protocol.

foreign host . Any machine on a network thatcan be interconnected.

foreign network . In an internet, any othernetwork interconnected to the local network byone or more intermediate gateways or routers.

foreign node . See foreign host.

frame . The portion of a tape on a lineperpendicular to the reference edge, on whichbinary characters can be written or readsimultaneously.

FTAM. File Transfer Access and Management.

FTP. File Transfer Protocol.

fullword . A computer word. In System/370, 32bits or 4 bytes.

G

gadget . A windowless graphical object that lookslike its equivalent like-named widget but does notsupport the translations, actions, or pop-up widgetchildren supplied by that widget.

gateway . (1) A functional unit that interconnectsa local data network with another network havingdifferent protocols. (2) A host that connects aTCP/IP network to a non-TCP/IP network at theapplication layer. See also router.

gather and scatter data . Two relatedoperations. During the gather operation, data istaken from multiple buffers and transmitted. In thescatter operation, data is received and stored inmultiple buffers.

GC. Graphics Context.

GContext . See Graphics Context.

GCS. Group Control System.

GDDM. Graphical Data Display Manager.

GDDMXD. Graphical Data Display Managerinterface for X Window System. A graphicalinterface that formats and displays alphanumeric,data, graphics, and images on workstation displaydevices that support the X Window System.

GDF. Graphics data file.

Graphical Display Data Manager (GDDM) . Agroup of routines that allows pictures to be definedand displayed procedurally through functionroutines that correspond to graphic primitives.

xii VM TCP/IP Glossary

Glossary

Graphics Context (GC) . The storage area forgraphics output. Also known as GC andGContext. Used only with graphics that have thesame root and depth as the graphics content.

Group Control System (GCS) . A component ofVM/ESA, consisting of a shared segment that youcan Initial Program Load (IPL) and run in a virtualmachine. It provides simulated MVS services andunique supervisor services to help support anative SNA network.

H

handle . A temporary data representation thatidentifies a file.

halfword . A contiguous sequence of bits orcharacters that constitutes half a fullword and canbe addressed as a unit.

HASP. Houston automatic spooling prioritysystem.

HDLC. High-level Data Link Control.

header file . A file that contains constantdeclarations, type declarations, and variabledeclarations and assignments. Header files aresupplied with all programming interfaces.

High-level Data Link Control (HDLC) . An ISOprotocol for X.25 international communication.

High Performance File System (HPFS) . AnOS/2 file management system that supportshigh-speed buffer storage, long file names, andextended attributes.

hop count . The number of gateways or routersthrough which a packet passes on its way to itsdestination.

host . A computer connected to a network, whichprovides an access method to that network. Ahost provides end-user services and can be aclient, a server, or a client and serversimultaneously.

Houston automatic spooling priority system(HASP). A computer program that providessupplementary job management, data

management, and task management functionssuch as control of job flow, ordering of tasks, andspooling.

HPFS. High Performance File System.

HYPERchannel Adapter . A network interfaceused to connect a TCP/IP for VM or MVS hostinto an existing TCP/IP HYPERchannel network,or to connect TCP/IP hosts together to create aTCP/IP HYPERchannel network.

I

IAB . Internet Activities Board.

ICMP. Internet Control Message Protocol.

IEEE. Institute of Electrical and ElectronicEngineers.

IETF. Internet Engineering Task Force.

IGP. Interior Gateway Protocol.

include file . A file that contains preprocessortext, which is called by a program, using astandard programming call. Synonymous withheader file.

IMS. Information Management System.

Information Management System (IMS) . Adatabase/data communication (DB/DC) systemthat can manage complex databases andnetworks.

initial program load (IPL) . The initializationprocedure that causes an operating system tocommence operation.

instance . Indicates a label that is used todistinguish among the variations of the principalname. An instance allows for the possibility thatthe same client or service can exist in severalforms that require distinct authentication.

Institute of Electrical and Electronic Engineers(IEEE). An electronics industry organization.

Integrated Services Digital Network (ISDN) . Adigital, end-to-end telecommunication network thatsupports multiple services including, but notlimited to, voice and data.

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Glossary

interactive . Pertaining to a program or a systemthat alternately accepts input and then responds.An interactive system is conversational; that is, acontinuous dialog exists between user andsystem. See batch.

Interior Gateway Protocol (IGP) . The protocolused to exchange routing information betweencollaborating routers in the Internet. RIP is anexample of an IGP.

Internet . The largest internet in the worldconsisting of large national backbone nets (suchas MILNET, NSFNET, and CREN) and a myriadof regional and local campus networks all over theworld. The Internet uses the Internet protocolsuite. To be on the Internet, you must have IPconnectivity (be able to TELNET to, or PING,other systems). Networks with only electronic mailconnectivity are not actually classified as being onthe Internet.

Internet Activities Board (IAB) . The technicalbody that oversees the development of theInternet suite of protocols (commonly referred toas TCP/IP). It has two task forces (the IRTF andthe IETF) each charged with investigating aparticular area.

Internet address . A 32-bit address assigned tohosts using TCP/IP. An internet address consistsof a network number and a local address. Internetaddresses are represented in a dotted-decimalnotation and are used to route packets throughthe network.

Internet Engineering Task Force (IETF) . One ofthe task forces of the IAB. The IETF isresponsible for solving short-term engineeringneeds of the Internet.

International Organization for Standardization(ISO). An organization of national standardsbodies from various countries established topromote development of standards to facilitateinternational exchange of goods and services, anddevelop cooperation in intellectual, scientific,technological, and economic activity.

internet or internetwork . A collection of packetswitching networks interconnected by gateways,

routers, bridges, and hosts to function as a single,coordinated, virtual network.

internet address . The unique 32-bit addressidentifying each node in an internet. See alsoaddress.

Internet Control Message Protocol (ICMP) .The part of the Internet Protocol layer that handleserror messages and control messages.

Internet Protocol (IP) . The TCP/IP layerbetween the higher level host-to-host protocol andthe local network protocols. IP uses local areanetwork protocols to carry packets, in the form ofdatagrams, to the next gateway, router, ordestination host.

interoperability . The capability of differenthardware and software by different vendors toeffectively communicate together.

Inter-user communication vehicle (IUCV) . AVM facility for passing data between virtualmachines and VM components.

intrinsics X-Toolkit . A set managementmechanism that provides for constructing andinterfacing between composite X Window widgets,their children, and other clients. Also, intrinsicsprovide the ability to organize a collection ofwidgets into an application.

IP. Internet Protocol.

IP datagram . The fundamental unit ofinformation passed across the Internet. An IPdatagram contains source and destinationaddresses along with data and a number of fieldsthat define such things as the length of thedatagram, the header checksum, and flags to saywhether the datagram can be (or has been)fragmented.

IPL. Initial Program Load.

ISDN. Integrated Services Digital Network.

ISO. International Organization forStandardization.

IUCV. Inter-User Communication Vehicle.

xiv VM TCP/IP Glossary

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J

JCL . Job Control Language.

JES. Job Entry Subsystem.

JIS. Japanese Institute of Standards.

Job Control Language (JCL) . Aproblem-oriented language designed to expressstatements in a job that are used to identify thejob or describe its requirements to an operatingsystem.

Job Entry Subsystem (JES) . An IBMSystem/370 licensed program that receives jobsinto the system and processes all output dataproduced by the jobs.

JUNET. The Japanese Academic and ResearchNetwork that connects various UNIX operatingsystems.

K

Kanji . A graphic character set consisting ofsymbols used in Japanese ideographic alphabets.Each character is represented by 2 bytes.

katakana . A character set of symbols used onone of the two common Japanese phoneticalphabets, which is used primarily to write foreignwords phonetically. See also kanji.

Kerberos . A system that provides authenticationservice to users in a network environment.

Kerberos Authentication System . Anauthentication mechanism used to checkauthorization at the user level.

L

LaMail . The client that communicates with theOS/2 Presentation Manager to manage mail onthe network.

LAN . Local area network.

Line Printer Client (LPR) . A client commandthat allows the local host to submit a file to beprinted on a remote print server.

Line Printer Daemon (LPD) . The remote printerserver that allows other hosts to print on a printerlocal to your host.

little-endian . A format for storage ortransmission of binary data in which the leastsignificant bit (or byte) comes first. The reverseconvention is big-endian.

LLB . Local Location Broker.

local area network (LAN) . A data networklocated on the user’s premises in which serialtransmission is used for direct data communicationamong data stations.

local host . In an internet, the computer to whicha user’s terminal is directly connected withoutusing the internet.

Local Location Broker (LLB) . In NetworkComputing System (NCS) Location Broker, aserver that maintains information about objects onthe local host and provides the Location Brokerforwarding facility.

local network . The portion of a network that isphysically connected to the host withoutintermediate gateways or routers.

logical character delete symbol . A specialediting symbol, usually the at (@) sign, whichcauses CP to delete it and the immediatelypreceding character from the input line. If manydelete symbols are consecutively entered, thesame number of preceding characters are deletedfrom the input line.

Logical Unit (LU) . An entity addressable withinan SNA-defined network. LUs are categorized bythe types of communication they support.

LPD. Line Printer Daemon.

LPR. Line Printer Client.

LU. Logical Unit.

LU-LU session . In SNA, a session between twological units (LUs). It provides communicationbetween two end users, or between an end userand an LU services component.

LU type . In SNA, the classification of an LU-LUsession in terms of the specific subset of SNA

Glossary xv

Glossary

protocols and options supported by the logicalunits (LUs) for that session.

M

MAC. Media Access Control.

mail gateway . A machine that connects two ormore electronic mail systems (often different mailsystems on different networks) and transfersmessages between them.

Management Information Base (MIB) . Astandard used to define SNMP objects, such aspacket counts and routing tables, that are in aTCP/IP environment.

mapping . The process of relating internetaddresses to physical addresses in the network.

mask . (1) A pattern of characters used to controlretention or elimination of portions of anotherpattern of characters. (2) To use a pattern ofcharacters to control retention or elimination ofanother pattern of characters. (3) A pattern ofcharacters that controls the keeping, deleting, ortesting of portions of another pattern of characters.

Maximum Transmission Unit (MTU) . Thelargest possible unit of data that can be sent on agiven physical medium.

media access control (MAC) . The method usedby network adapters to determine which adapterhas access to the physical network at a giventime.

Message Handling System (MHS) . The systemof message user agents, message transferagents, message stores, and access units thattogether provide OSI electronic mail.

MHS. Message Handling System.

MIB. Management Information Base.

microcode . A code, representing the instructionsof an instruction set, which is implemented in apart of storage that is not program-addressable.

MILNET. Military Network.

Military Network (MILNET) . Originally part of theARPANET, MILNET was partitioned in 1984 to

make it possible for military installations to havereliable network service, while the ARPANETcontinued to be used for research. See DDN.

minidisk . Logical divisions of a physical directaccess storage device.

modem (modulator/demodulator) . A device thatconverts digital data from a computer to an analogsignal that can be transmitted on atelecommunication line, and converts the analogsignal received to data for the computer.

Motif . see OSF/Motif**.

mouse . An input device that is used to move apointer on the screen and select items.

MTU. Maximum Transmission Unit.

multicast . The simultaneous transmission ofdata packets to a group of selected nodes on anetwork or subnetwork.

multiconnection server . A server that iscapable of accepting simultaneous, multipleconnections.

Multiple Virtual Storage (MVS) . ImpliesMVS/370, the MVS/XA product, and the MVS/ESAproduct.

multitasking . A mode of operation that providesfor the concurrent performance execution of two ormore tasks.

MVS. Multiple Virtual Storage.

N

name server . The server that stores resourcerecords about hosts.

National Science Foundation (NSF) . Sponsorof the NSFNET.

National Science Foundation Network(NSFNET). A collection of local, regional, andmid-level networks in the U.S. tied together by ahigh-speed backbone. NSFNET providesscientists access to a number of supercomputersacross the country.

NCK**. Network Computing Kernel.

xvi VM TCP/IP Glossary

Glossary

NCP. Network Control Program.

NCS. Network Computing System.

NDB. Network Database.

NDIS. Network Driver Interface Specification.

Netman . This device keyword specifies that thisdevice is a 3172 LAN Channel Station thatsupports IBM Enterprise-Specific SNMPManagement Information Base (MIB) variables for3172. TCP/IP for VM supports SNMP GET andSNMP GETNEXT operations to request andretrieve 3172 Enterprise-Specific MIB variables.These requests are answered only by those 3172devices with the NETMAN option in the PROFILETCPIP file.

NetView . A system 390-based, IBM-licensedprogram used to monitor, manage, and diagnosethe problems of a network.

network . An arrangement of nodes andconnecting branches. Connections are madebetween data stations. Physical network refers tothe hardware that makes up a network. Logicalnetwork refers to the abstract organization overlaidon one or more physical networks. An internet isan example of a logical network.

network adapter . A physical device, and itsassociated software, that enables a processor orcontroller to be connected to a network.

network administrator . The person responsiblefor the installation, management, control, andconfiguration of a network.

Network Computing Kernel (NCK) . In theNetwork Computing System (NCS), thecombination of the remote procedure call runtimelibrary and the Location Broker.

Network Computing System (NCS) . A set ofsoftware components developed by Apollo,Incorporated, that conform to the NetworkComputing Architecture (NCA). NCS is made upof two parts: the nidl compiler and NetworkComputing Kernel (NCK). NCS is a programmingtool kit that allows programmers to distributeprocessing power to other hosts.

Network Control Program (NCP) . AnIBM-licensed program that providescommunication controller support forsingle-domain, multiple-domain, andinterconnected network capability.

network database (NDB) . An IBM-licensedprogram that provides communication controllersupport for single-domain, multiple-domain, andinterconnected network capability. NDB allowsinteroperability among different database systems,and uses RPC protocol with a client/server type ofrelationship. NDB is used for data conversion,security, I/O buffer management, and transactionmanagement.

Network Driver Interface Specification (NDIS) .An industry-standard specification used byapplications as an interface with network adapterdevice drivers.

network elements . As defined in the SNMParchitecture, network elements are gateways,routers, and hosts that contain managementagents responsible for performing the networkmanagement functions requested by the networkmanagement stations.

network file system (NFS) . The NFS protocol,which was developed by Sun Microsystems,Incorporated, allows computers in a network toaccess each other’s file systems. Once accessed,the file system appears to reside on the local host.

Network Information Center (NIC) . Originallythere was only one, located at SRI Internationaland tasked to serve the ARPANET (and laterDDN) community. Today, there are many NICsoperated by local, regional, and national networksall over the world. Such centers provide userassistance, document service, training, and more.

Network Interface Definition Language (NIDL) .A declarative language for the definition ofinterfaces that has two forms, a Pascal-like syntaxand a C-like syntax. NIDL is a component of theNetwork Computing Architecture.

Network Job Entry (NJE) . In object distribution,an entry in the network job table that specifies thesystem action required for incoming network jobssent by a particular user or group of users. Eachentry is identified by the user ID of the originatinguser or group.

Glossary xvii

Glossary

network layer . Layer 3 of the Open SystemsInterconnection (OSI) model; it defines protocolsgoverning data routing.

network management stations . As defined inthe SNMP architecture, network managementstations, or SNMP clients, execute managementapplications that monitor and control networkelements.

NFS. Network file system.

NIC. Network Information Center.

NIDL. Network Interface Definition Language.

NJE. Network Job Entry.

node . (1) In a network, a point at which one ormore functional units connect channels or datacircuits. (2) In a network topology, the point at anend of a branch.

nonblocking mode . If the execution of theprogram cannot continue until some event occurs,the operating system does not suspend theprogram until that event occurs. Instead, theoperating system returns an error message to theprogram.

NPSI. X.25 NCP Packet Switching Interface.

NSF. National Science Foundation.

NSFNET. National Science Foundation Network.

O

octet . A byte composed of eight binary elements.

OfficeVision (OV) . IBM’s new proprietary,integrated office management system used forsending, receiving, and filing electronic mail, and avariety of other office tasks. OfficeVision replacesPROFS.

Offload host . Any device that is handling theTCP/IP processing for the MVS host whereTCP/IP for MVS is installed. Currently, the onlysupported Offload host is the 3172-3.

Offload system . Represents both the MVS hostwhere TCP/IP for MVS is installed and the Offload

host that is handling the TCP/IP Offloadprocessing.

open system . A system with specified standardsand that therefore can be readily connected toother systems that comply with the samestandards.

Open Systems Interconnection (OSI) . (1) Theinterconnection of open systems in accordancewith specific ISO standards. (2) The use ofstandardized procedures to enable theinterconnection of data processing systems.

Operating System/2 (OS/2) . Pertaining to theIBM licensed program that can be used as theoperating system for personal computers. TheOS/2 licensed program can perform multiple tasksat the same time.

OS/2. Operating System/2.

OSF/Motif . OSF/Motif is an X Window Systemtoolkit defined by Open Software Foundation, Inc.(OSF), which enables the application programmerto include standard graphic elements that have a3-D appearance. Performance of the graphicelements is increased with gadgets andwindowless widgets.

OSI. Open Systems Interconnection.

out-of-band data . Data that is placed in asecondary channel for transmission. Primary andsecondary communication channels are createdphysically by modulation on a different frequency,or logically by specifying a different logicalchannel. A primary channel can have a greatercapacity than a secondary one.

OV. OfficeVision.

P

packet . A sequence of binary digits, includingdata and control signals, that is transmitted andswitched as a composite whole.

Packet Switching Data Network (PSDN) . Anetwork that uses packet switching as a means oftransmitting data.

parameter . A variable that is given a constantvalue for a specified application.

xviii VM TCP/IP Glossary

Glossary

parse . To analyze the operands entered with acommand.

passive open . The state of a connection that isprepared to provide a service on demand.Contrast with active open.

Partitioned data set (PDS) . A data set in directaccess storage that is divided into partitions,called members, each of which can contain aprogram, part of a program, or data.

PC. Personal computer.

PCA. Personal Channel Attach.

PC Network . A low-cost, broadband network thatallows attached IBM personal computers, such asIBM 5150 Personal Computers, IBM ComputerATs, IBM PC/XTs, and IBM Portable PersonalComputers to communicate and to shareresources.

PDS. Partitioned data set.

PDN. Public Data Network.

PDU. Protocol data unit.

peer-to-peer . In network architecture, anyfunctional unit that resides in the same layer asanother entity.

Personal Channel Attach (PCA) . see PersonalSystem Channel Attach.

Personal Computer (PC) . A microcomputerprimarily intended for stand-alone use by anindividual.

Personal System Channel Attach (PSCA) . Anadapter card to connect a micro-channel basedpersonal computer (or processor) to a System/370parallel channel.

physical layer . Layer 1 of the Open SystemsInterconnection (OSI) model; it details protocolsgoverning transmission media and signals.

physical unit (PU) . In SNA, the component thatmanages and monitors the resources, such asattached links and adjacent link stations,associated with a node, as requested by an SSPCvia an SSPC-PU session. An SSPC activates asession with the physical unit in order to indirectly

manage, through the PU, resources of the nodesuch as attached links.

PING. The command that sends an ICMP EchoRequest packet to a host, gateway, or router withthe expectation of receiving a reply.

PM. Presentation Manager.

PMANT. In OS/2, the 3270 client terminalemulation program that is invoked by the PMANTcommand.

polling . (1) On a multipoint connection or apoint-to-point connection, the process wherebydata stations are invited one at a time to transmit.(2) Interrogation of devices for such purposes asto avoid contention, to determine operationalstatus, or to determine readiness to send orreceive data.

POP. Post Office Protocol.

port . (1) An endpoint for communicationbetween devices, generally referring to a logicalconnection. (2) A 16-bit number identifying aparticular Transmission Control Protocol or UserDatagram Protocol resource within a given TCP/IPnode.

PORTMAP. Synonymous with Portmapper.

Portmapper . A program that maps clientprograms to the port numbers of server programs.Portmapper is used with Remote Procedure Call(RPC) programs.

Post Office Protocol (POP) . A protocol used forexchanging network mail.

presentation layer . Layer 6 of the OpenSystems Interconnections (OSI) model; it definesprotocols governing data formats and conversions.

Presentation Manager (PM) . A component ofOS/2 that provides a complete graphics-baseduser interface, with pull-down windows, actionbars, and layered menus.

principal name . Specifies the unique name of auser (client) or service.

PostScript . A standard that defines how text andgraphics are presented on printers and displaydevices.

Glossary xix

Glossary

process . (1) A unique, finite course of eventsdefined by its purpose or by its effect, achievedunder defined conditions. (2) Any operation orcombination of operations on data. (3) A functionbeing performed or waiting to be performed.(4) A program in operation; for example, adaemon is a system process that is alwaysrunning on the system.

Professional Office Systems (PROFS) . IBM’sproprietary, integrated office management systemused for sending, receiving, and filing electronicmail, and a variety of other office tasks. PROFShas been replaced by OfficeVision. SeeOfficeVision.

PROFS. Professional Office Systems.

protocol . A set of semantic and syntactic rulesthat determines the behavior of functional units inachieving communication. Protocols candetermine low-level details of machine-to-machineinterfaces, such as the order in which bits from abyte are sent; they can also determine high-levelexchanges between application programs, such asfile transfer.

Protocol data unit (PDU) . A set of commandsused by the SNMP agent to request managementstation data.

protocol suite . A set of protocols that cooperateto handle the transmission tasks for a datacommunication system.

PSCA. Personal System Channel Attach.

PSDN. Packet Switching Data Network.

PU. Physical unit.

Public Data Network (PDN) . A networkestablished and operated by a telecommunicationadministration or by a Recognized PrivateOperating Agency (RPOA) for the specific purposeof providing circuit-switched, packet-switched, andleased-circuit services to the public.

Q

queue . A line or list formed by items in a systemwaiting for service; for example, tasks to beperformed or messages to be transmitted. Toarrange in, or form, a queue.

R

RACF. Resource access control facility.

RARP. Reverse Address Resolution Protocol.

read-only access . An access mode associatedwith a virtual disk directory that lets a user read,but not write or update, any file on the diskdirectory.

read/write access . An access mode associatedwith a virtual disk directory that lets a user readand write any file on the disk directory (if writeauthorized).

realm . One of the three parts of a Kerberosname. The realm specifies the network addressof the principal name or instance. This addressmust be expressed as a fully qualified domainname, not as a “dot numeric” internet address.

recursion . A process involving numerous steps,in which the output of each step is used for thesuccessive step.

reduced instruction-set computer (RISC) . Acomputer that uses a small, simplified set offrequently used instructions for rapid execution.

reentrant . The attribute of a program or routinethat allows the same copy of a program or routineto be used concurrently by two or more tasks.

Remote Execution Protocol (REXEC) . Aprotocol that allows the execution of a commandor program on a foreign host. The local hostreceives the results of the command execution.This protocol uses the REXEC command.

remote host . A machine on a network thatrequires a physical link to interconnect with thenetwork.

remote logon . The process by which a terminaluser establishes a terminal session with a remotehost.

xx VM TCP/IP Glossary

Glossary

Remote Procedure Call (RPC) . A facility that aclient uses to request the execution of aprocedure call from a server. This facility includesa library of procedures and an eXternal datarepresentation.

Remote Spooling Communications Subsystem(RSCS). An IBM-licensed program that transfersspool files, commands, and messages betweenVM users, remote stations, and remote and localbatch systems, through HASP-compatibletelecommunication facilities.

Request For Comments (RFC) . A series ofdocuments that covers a broad range of topicsaffecting internetwork communication. SomeRFCs are established as internet standards.

resolver . A program or subroutine that obtainsinformation from a name server or local table foruse by the calling program.

resource access control facility (RACF) . AnIBM-licensed program that provides for accesscontrol by identifying and by verifying the users tothe system, authorizing access to protectedresources, logging the detected unauthorizedattempts to enter the system, and logging thedetected accesses to protected resources.

resource records . Individual records of dataused by the Domain Name System. Examples ofresource records include the following: a host’sInternet Protocol addresses, preferred mailaddresses, and aliases.

response unit (RU) . In SNA, a message unitthat acknowledges a request unit. It may containprefix information received in a request unit. Ifpositive, the response unit may contain additionalinformation such as session parameters inresponse to BIND SESSION. If negative, itcontains sense data defining the exceptioncondition.

Restructured Extended Executor (REXX)language . A general purpose programminglanguage, particularly suitable for EXECprocedures, XEDIT macros, or programs forpersonal computing. Procedures, XEDIT macros,and programs written in this language can beinterpreted by the Procedures LanguageVM/REXX interpreter.

return code . (1) A code used to influence theexecution of succeeding instructions. (2) A valuereturned to a program to indicate the results of anoperation requested by that program.

Reverse Address Resolution Protocol (RARP) .A protocol that maintains a database of mappingsbetween physical hardware addresses and IPaddresses.

REXEC. Remote Execution Protocol.

REXX. Restructured Extended Executorlanguage.

RFC. Request For Comments.

RIP. Routing Information Protocol.

RISC. Reduced instruction-set computer.

router . A device that connects networks at theISO Network Layer. A router isprotocol-dependent and connects only networksoperating the same protocol. Routers do morethan transmit data; they also select the besttransmission paths and optimum sizes for packets.In TCP/IP, routers operate at the Internetworklayer. See also gateway.

Routing Information Protocol (RIP) . Theprotocol that maintains routing table entries forgateways, routers, and hosts.

routing table . A list of network numbers and theinformation needed to route packets to each.

RPC. Remote Procedure Call.

RSCS. Remote Spooling CommunicationsSubsystem.

RU. Response unit.

S

SAA . Systems Application Architecture.

SBCS. Single Byte Character Set.

SDLC. Synchronous data link control.

Sendmail . The OS/2 mail server that usesSimple Mail Transfer Protocol to route mail fromone host to another host on the network.

Glossary xxi

Glossary

serial line . A network media that is a de factostandard, not an international standard, commonlyused for point-to-point TCP/IP connections.Generally, a serial line consists of an RS-232connection into a modem and over a telephoneline.

semantics . (1) The relationships of characters orgroups of characters to their meanings,independent of the manner of their interpretationand use. (2) The relationships between symbolsand their meanings.

server . A function that provides services forusers. A machine can run client and serverprocesses at the same time.

SFS. Shared File System.

Shared File System (SFS) . A part of CMS thatlets users organize their files into groups knownas directoires and selectively share those files anddirectories with other users.

Simple Mail Transfer Protocol (SMTP) . ATCP/IP application protocol used to transfer mailbetween users on different systems. SMTPspecifies how mail systems interact and the formatof control messages they use to transfer mail.

Simple Network Management Protocol(SNMP). A protocol that allows networkmanagement by elements, such as gateways,routers, and hosts. This protocol provides ameans of communication between networkelements regarding network resources.

simultaneous peripheral operations online(SPOOL). (1) (Noun) An area of auxiliary storagedefined to temporarily hold data during its transferbetween peripheral equipment and the processor.(2) (Verb) To use auxiliary storage as a bufferstorage to reduce processing delays whentransferring data between peripheral equipmentand the processing storage of a computer.

single-byte character set (SBCS) . A characterset in which each character is represented by aone-byte code. Contrast with double-bytecharacter set.

SMI. Structure for Management Information.

SMTP. Simple Mail Transfer Protocol.

SNA. Systems Network Architecture.

SNALINK . SNA Network Link.

SNA Network Link . An SNA network linkfunction of TCP/IP for VM and MVS hosts runningTCP/IP to communicate through an existing SNAbackbone.

SNMP. Simple Network Management Protocol.

SOA. Start of authority record.

socket . (1) An endpoint for communicationbetween processes or applications. (2) A pairconsisting of TCP port and IP address, or UDPport and IP address.

socket address . An address that results whenthe port identification number is combined with aninternet address.

socket interface . An application interface thatallows users to write their own applications tosupplement those supplied by TCP/IP.

SPOOL. Simultaneous peripheral operationsonline.

spooling . The processing of files created by orintended for virtual readers, punches, and printers.The spool files can be sent from one virtual deviceto another, from one virtual machine to another,and to read devices.

SQL. Structured Query Language.

SQL/DS. Structured Query Language/DataSystem.

start of authority record (SOA) . In the DomainName System, the resource record that defines azone.

stream . A continuous sequence of data elementsbeing transmitted, or intended for transmission, incharacter or binary-digit form, using a definedformat.

Structured Query Language (SQL) . Fourthgeneration English-like programming languageused to perform queries on relational databases.

Structured Query Language/Data System(SQL/DS). An IBM relational database

xxii VM TCP/IP Glossary

Glossary

management system for the VM and VSEoperating systems.

Structure for Management Information (SMI) .The rules used to define the objects that can beaccessed through a network managementprotocol. See also MIB.

subagent . In the SNMP architecture, a subagentprovides an extension to the utility provided by theSNMP agent.

subdirectory . A directory contained withinanother directory in a file system hierarchy.

subnet . A networking scheme that divides asingle logical network into smaller physicalnetworks to simplify routing.

subnet address . The portion of the host addressthat identifies a subnetwork.

subnet mask . A mask used in the IP protocollayer to separate the subnet address from the hostportion of the address.

subnetwork . Synonymous with subnet.

subsystem . A secondary or subordinate system,usually capable of operating independent of, orasynchronously with, a controlling system.

SYNC. Synchronous.

synchronous (SYNC) . (1) Pertaining to two ormore processes that depend on the occurrencesof a specific event such as common timing signal.(2) Occurring with a regular or predictable timerelationship. See asynchronous.

synchronous data link control (SDLC) . A datalink over which communication is conducted usingthe synchronous data protocol.

Systems Application Architecture (SAA) . Aformal set of rules that enables applications to berun without modification in different computerenvironments.

Systems Network Architecture (SNA) . Thedescription of the logical structure, formats,protocols, and operational sequences fortransmitting information units through, andcontrolling the configuration and operation of,networks.

T

TALK . An interactive messaging system thatsends messages between the local host and aforeign host.

TCP. Transmission Control Protocol.

TCP/IP. Transmission Control Protocol/InternetProtocol.

Telnet . The Terminal Emulation Protocol, aTCP/IP application protocol for remote connectionservice. Telnet allows a user at one site to gainaccess to a foreign host as if the user's terminalwere connected directly to that foreign host.

terminal emulator . A program that imitates thefunction of a particular kind of terminal.

Terminate and Stay Resident (TSR) program .A TSR is a program that installs part of itself asan extension of DOS when it is executed.

TFTP. Trivial File Transfer Protocol.

ticket . Encrypted information obtained from aKerberos authentication server or a ticket-grantingserver. A ticket authenticates a user and, inconjunction with an authenticator, serves aspermission to access a service when presented bythe authenticated user.

ticket-granting server . Grants Kerberos ticketsto authenticated users as permission to access anend-service.

Time Sharing Option (TSO) . An operatingsystem option; for System/370 system, the optionprovides interactive time sharing from remoteterminals

time stamp . (1) To apply the current systemtime. (2) The value on an object that is anindication of the system time at some critical pointin the history of the object. (3) In query, theidentification of the day and time when a queryreport was created that query automaticallyprovides on each report.

TN3270. An informally defined protocol fortransmitting 3270 data streams over Telnet.

Glossary xxiii

Glossary

token . In a local network, the symbol of authoritypassed among data stations to indicate the stationtemporarily in control of the transmission medium.

token-bus . See bus topology.

token ring . As defined in IEEE 802.5, acommunication method that uses a token tocontrol access to the LAN. The differencebetween a token bus and a token ring is that atoken-ring LAN does not use a master controller tocontrol the token. Instead, each computer knowsthe address of the computer that should receivethe token next. When a computer with the tokenhas nothing to transmit, it passes the token to thenext computer in line.

token-ring network . A ring network that allowsunidirectional data transmission between datastations by a token-passing procedure over onetransmission medium, so that the transmitted datareturns to the transmitting station.

Transmission Control Protocol (TCP) . TheTCP/IP layer that provides reliable,process-to-process data stream delivery betweennodes in interconnected computer networks. TCPassumes that IP (Internet Protocol) is theunderlying protocol.

Transmission Control Protocol/InternetProtocol (TCP/IP) . A suite of protocols designedto allow communication between networksregardless of the technologies implemented ineach network.

transport layer . Layer 4 of the Open SystemsInterconnection (OSI) model; it defines protocolsgoverning message structure and some errorchecking.

TRAP. An unsolicited message that is sent by anSNMP agent to an SNMP network managementstation.

Trivial File Transfer Protocol (TFTP) . TheTFTP daemon (TFTPD servser) transfers filesbetween the Byte File System (BFS) and TFTPclients. TFTPD supports access to filesmaintained in a BFS directory that is mounted.

TSO. Time Sharing Option.

TSR. Terminate and stay resident. TSR usuallyrefers to a terminate-and-stay-resident program.

U

UDP. User Datagram Protocol.

user . A function that uses the services providedby a server. A host can be a user and a server atthe same time. See client.

User Datagram Protocol (UDP) . A datagramlevel protocol built directly on the IP layer. UDP isused for application-to-application programsbetween TCP/IP hosts.

user exit . A point in an IBM-supplied program atwhich a user routine may be given control.

user profile . A description of a user, includinguser ID, user name, defaults, password, accessauthorization, and attributes.

V

virtual address . The address of a location invirtual storage. A virtual address must betranslated into a real address to process the datain processor storage.

Virtual Machine (VM) . A licensed machinewhose full name is Virtual Machine/EnterpriseSystems Architecture (VM/ESA) It is a softwareoperating system that manages the resources of areal processor to provide virtual machines to endusers. As a time-sharing system control program(CP), the conversational monitor system (CMS),the group control system (GCS), and the dumpviewing facility (DVF).

Virtual Machine Communication Facility(VMCF). A connectionless mechanism forcommunication between address spaces.

Virtual Machine/System Product (VM/SP) . AnIBM-licensed program that manages the resourcesof a single computer so that multiple computingsystems appear to exist. Each virtual machine isthe functional equivalent of a real machine.

virtual storage . Storage space that can beregarded as addressable main storage by the userof a computer system in which virtual addressesare mapped into real addresses. The size ofvirtual storage is limited by the addressing scheme

xxiv VM TCP/IP Glossary

Glossary

of the computing system and by the amount ofauxiliary storage available, not by the actualnumber of main storage locations.

Virtual Telecommunications Access Method(VTAM). An IBM-licensed program that controlscommunication and the flow of data in an SNAnetwork. It provides single-domain,multiple-domain, and interconnected networkcapability.

VM. Virtual Machine.

VMCF. Virtual Machine Communication Facility.

VM/ESA. Virtual Machine/Enterprise SystemArchitecture

VMSES/E. Virtual Machine ServiceabilityEnhancements Staged/Extended.

VTAM. Virtual Telecommunications AccessMethod.

W

WAN. Wide area network.

well-known port . A port number that has beenpreassigned for specific use by a specific protocolor application. Clients and servers using thesame protocol communicate over the samewell-known port.

wide area network (WAN) . A network thatprovides communication services to a geographicarea larger than that served by a local areanetwork.

widget . The basic data type of the X WindowSystem Toolkit. Every widget belongs to a widgetclass that contains the allowed operations for thatcorresponding class.

window . An area of the screen with visibleboundaries through which a panel or portion of apanel is displayed.

working directory . The directory in which anapplication program is found. The working

directory becomes the current directory when theapplication is started.

X

X Client . An application program which uses theX protocol to communicate windowing andgraphics requests to an X Server.

XDR. eXternal Data Representation.

XEDIT. The CMS facility, containing the XEDITcommand and XEDIT subcommands and macros,that lets a user create, change, and manipulateCMS files.

X Server . A program which interprets the Xprotocol and controls one or more screens, apointing device, a keyboard, and variousresources associated with the X Window System,such as Graphics Contexts, Pixmaps, and colortables.

X Window System . The X Window System is aprotocol designed to support network transparentwindowing and graphics. TCP/IP for VM and MVSprovides client support for the X Window Systemapplication program interface.

X Window System API . An application programinterface designed as a distributed,network-transparent, device-independent,windowing and graphics system.

X Window System Toolkit . Functions fordeveloping application environments.

X.25. A CCITT communication protocol thatdefines the interface between data terminalequipment and packet switching networks.

X.25 NCP Packet Switching Interface (X.25NPSI). An IBM-licensed program that allowsusers to communicate over packet switched datanetworks that have interfaces complying withRecommendation X.25 (Geneva** 1980) of theCCITT. It allows SNA programs to communicatewith SNA equipment or with non-SNA equipmentover such networks.

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Glossary

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ZAP. To modify or dump an individual textfile/data set using the ZAP command or theZAPTEXT EXEC.

ZAP disk . The virtual disk in the VM operatingsystem that contains the user-written modificationsto VTAM code.

zone . In the Domain Name System, a zone is alogical grouping of domain names that is assignedto a particular organization. Once an organizationcontrols its own zone, it can change the data inthe zone, add new tree sections connected to thezone, delete existing nodes, or delegate newsubzones under its zone.

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