英文原文及翻译.docx

英文原文及翻译.docx

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英文原文及翻译

英文原文：

TITLE:

MAPCon:

ANEXPERTSYSTEMTOCONFIGURE

COMMUNICATIONSNETWORKS

CONTACT:

H.VanDykeParunak,JamesKindrick,andTihamerToth-Fejel

IndustrialTechnologyInstitute

POBox1485

AnnArbor,MI48106

van%iti@umix.cc.umich.edu

（313）769-4049

TOPIC:

CaseStudy:

configuration.

ABSTRACT:

MAPConisanexpertsystemthatperformsoff-lineparameter

configurationforlocalareanetworksthatuseMAP,the

ManufacturingAutomationProtocol.Thispaperdescribesthe

configurationtaskingeneralandMAPConinparticular,and

describesitsperformanceasafunctionofnetworksize.

MAPCon:

ANEXPERTSYSTEMTO

CONFIGURECOMMUNICATIONSNETWORKS

H.VanDykeParunak,JamesKindrick,andTihamerToth-Fejel

IndustrialTechnologyInstitute

1.ProblemDefinition

ThissectionoutlinesthechallengeofnetworkmanagementingeneralandtheMAParchitectureinparticular,anddescribesthespecificfunctionsthatMAPConfulfills.

1.1.TheChallengeofNetworkManagement

Managementofmulti-vendornetworksisdifficult,sincemostnetworkmanagementproductsaredesignedforasingleproductline.NetworkmanagementisespeciallycriticalinmanufacturingLANs,wherereal-timemanufacturingoperationsrelyheavilyonconsistentnetworkoperation.Onewaytoaddressthisproblemistoconformthenetworktoastandard,suchastheManufacturingAutomationProtocol（MAP）.MAPcon11,thesystemdescribedinthiscasestudy,isthesecondgeneration（11ofaknowledgebasedsystemdesignedtoassistinconfiguringMAPnetworks.Thisfunction,thefirstthatmustbeaccomplishedwhendesigninganetwork,requiresthecorrelationofalargenumberofparametersincomplexwaysinorderforthe

networktobehaveproperly.

1.2.MAPArchitectureMAPcomplieswiththearchitectureofasetofinternationalstandardsdefinedbytheInternationalOrganizationforStandardization（ISO）,basedonareferencemodelforOpenSystemsInterconnection（OSI）.OS1decomposestheproblemofcommunicatingreliablybetweenapplicationsintosevenlayers:

physical,data-link,network,transport,session,presentation,andapplication.

Thephysicalanddata-linklayersofMAPusetheIEEE802.4tokenbusspecifications,incontrasttotheCSMA/CDtechnologyfamiliarfromEthernet.Thephysicallayercanbeeitherbroadbandorcarrierband.WCondistinguishesbetweenbroadbandandcarrierband,andcanconfigurebothtypesofnetworks.InMAP,thenetworklayerusestheISOconnection-lessprotocolorthe=calledInternetprotocol.ThetransportlayerusestheIS0class4transportprotocol.1,SessionusesISOsessionversion2,whichisasmall,basicsubsetofISOsessionprotocol.PresentationusestheISOpresentationlayer.

MAPspecifiesseveralapplicationlayerprotocols:

amanufacturingmessagespecificationprotocol;anassociationcontrolserviceelement;afiletransfer,accessandmanagementprotocol;adirectoryservicesprotocol;andanetworkmanagementprotocol.Theprotocolsatlayers1,2,and7ofMAPwerepartiallyorcompletelydesignedwithmanufacturingautomationinmind.

TheentitiesintheMAPnetworkarchitectureincludestationsorendsystems,subnetworksorLAN[LocalAreaNetwork）segments,andinterconnectionsorintermediatesystems.

StationscombinehardwareandsoftwaretoprovidecommunicationsaccordingtotheMAPspecification.TheycanhaveeitherafullMAP,amini-MAP,oraMAPIEPA（EnhancedPerjormanceArchitecture）configuration.ThecurrentversionofMAPConhandlesonlyfullMAPstations.

AsubnetworkorLANsegmentisasectionofalocalareanetworkonwhichallstationssharethesametoken.Allstations.onasegmentcandirectlycornmunitatetoallotherstationsonthesamesegmentwithoutanyintermediatesystems.Subnetworksareoftwotypes:

broadbandandcarrierband.MAPConhandlesbothtypesofsubnetworks.

Interconnectionentities（intermediatesystems）aredevicesthatconnectmultiplesubnetworkstoformtheoverallMAPnetwork.Theyareofthreetypes:

bridges,routers,andgateways.Abridgeinterconnectstwoormoresubnetworkswithsimilarmediaaccesscontrolservices.Arouterinterconnectstwoormoresubnetworksornptworksofdifferenttypes.Agatewayinterconnectstwoormoresubnetworksornetworksofdifferentnetworkarchitecturebyperformingprotocoltranslation.ThecurrentversionofMAPConsupportsbridgesandthe

MAPsideofroutersandgateways.

1.3.ConfigurationManagement

Configurationmanagementisthecollectionofnetworkmanagementactivitiesthatallowtheusertoknowandcontrolthearrangementandstateofanetworkanditsentities.ThepresentversionofMAPConletstheusersetthenetworkconfigurationoff-line,andthusknowitsarrangementandstate.Afutureversionwilllettheusercontrolthenetworkconfigurationasthenetworkoperates.ThefollowingparagraphsdiscussthefunctionscurrentlyprovidedbyMAPCon.

Addingordeletingstationsinthesubnetworkdefinestheactualtopologyofthenetwork.Stationsandinterconnectionsthatareattachedtoasubnetworkarespecifiedinordertoconfigurethenetwork.Thiscapabilitynotonlyallowsforexaminingthecurrentconfigurationofthenetworkbutalsopermitsincrementalchangestotheconfiguration.

Subnetworksareinterconnectedbyattachinginterconnectiondevicessuchasbridges,routers,andgateways.Addingsuchdevicesrequiressettingormodifyingtherelationshipsbetweentwoormoresubnetworks.

Usersneedtosettheinitialcharacteristicsofentitiesandmodifythemiftheoriginalsettingsareinconsistent.Ingeneral,thecharacteristicsthataresetormodifiedcorrespondtooperationalparametersandstatisticalcountersrequiredandmaintainedbytheentities.Eachstationorinterconnectionhasseverallayers.

Dependingontheconfigurationofthestationortheinterconnection,specificlayersmustbepresentaccordingtotheMAP3.0specification.Severalcharacteristicsineachlayermustbesetproperlyacrossthesubnetworkandnetworkinordertoconfigureanoperationalnetwork.Thesecharacteristicsincludeoperationalparameters,timers,andthresholdsonstatisticalcounters.Someofthesecharacteristicsarederivedfromnetwork-wideparameterssuchasthetypeofthetrafficintendedonthenetworkandthenatureoftheenvironmentunderwhichnetworkwilloperate（lownoise,mediumnoise,andhighnoise）.Othercharacteristicsarederivedfromoneanother.Forexample,inactivitytimeattransportisderivedfromretransmissiontimeandnumberofretransmissions.

StationsandinterconnectionswithinasubnetworkmusthaveuniquenamesandMACaddresses.However,therearecertainrestrictionsonnamesandaddressesfromaglobalnetworkpointofview.ItmaybepossibletohaveidenticalMACaddressesinsubnetworksinterconnectedbyarouter.Theconfigurationfunction

mustcheckaddressconsistency.

Similartonamesandaddresses,networkmanagersandloadserversmustbeassignedtostationsandinterconnections.Allstationsandinterconnectionsneedanassociatedmanager.Itispossibletohavemultiplemanagersinanetwork,uptoonepersubnetwork.Aloadserverforthenetworkisneededifthereareany

loadablestationsorinterconnectionsinthenetworkconfiguration.

Configurationalsorequiresconsistencycheckstomakesurethatallentitiesareconfiguredcorrectly.Mechanismsmustbeprovidedtorecognizeandidentifytheinconsistenciesforcorrectiveactions.Consistencyinaddresses,networkmanagers,andloadserversmustbecheckedbeforetheconfigurationobjectiveiscompleted.

2.PreviousApproaches

AIapplicationsinnetworkmanagementhaveconcentratedintheareaofdiagnosisandfaultmanagementratherthanconfiguration.

Expertsystemsfornetworkconfigurationhavebeenintroducedbysomevendors,includingBBNandCASECommunications.Technicalcasestudiesofthesecommercialproductshavenotbeenreleased,sofewdetailsoftheirstructureandfunctionareavailable.AtleastoneusesOPS-83rulesasitsmajorknowledgerepresentationmechanism.WhileMAPCondoesusesomeOPSrules,itreliesheavilyonknowledgerepresentedinframes,tosupportastructuralmodelofthenetwork.ThistypeofstructurehasalsobeenreportedinBBN’sDesignet.

Previoussystemsdealwithwide-areanetworks,andfocusonproblemsofroutingandresourceallocation.Onesuggestedformalizationistoallocatenetworkcapacitybymaximizinganeconomiccriterionrelatedtonetworkrevenues.1151However,thecomplexityoftheproblemprecludesuseofstandardoperationsresearchtechniquestoaddressthisproblem.[I21BBN’sofferingincludesafacilitytoallocateparts,suchascables,boards,andracks,tonodesites,muchalongthelinesofRI.

MAP’Sopenarchitectureandbusstructureremoveproblemsthatothernetworksmustaddress.BecauseMAPnetworksuseabusratherthanapoint-bpointarchitecture,routingislessofaproblem.BecauseMAPisanopenarchitecture,supportingequipmentfromdifferentvendors,problemsofconfiguringtheboardsandcablesinasinglestationarealsooutsideofitsscope.ThemajorproblemaddressedbyWConisconsistencyofparametersettingsacrossdifferentstations.Thisproblemisnotacriticaloneinthenetworksservedbytheotherprogramsnamedabove,becausetheyarepredominantlysingle-vendornetworks,inwhichconsistencyamongoperatingparameterscanbeenforcedatthedesignormanufacturingstageofastation’slife.TheopenarchitecturethatallowsMAF’Contopushthe”boardandcable”problembacktothemanufacturer,alsoforcesthenetworkadministrator（ratherthanthemanufacturer）toworryaboutparameterconsistency.Furthermore,MAPdiffersfromtheseothernetworksinconfor