计算机网络双语论文1Word格式.docx

计算机网络双语论文1Word格式.docx

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专业：

自动化

题目：

WANanditsapplicationinintelligentbuildings

指导者：

陈东淼

评阅者：

2011-12吉林

TitleWANanditsapplicationinintelligentbuildings

Abstract

ipsecVPNandsslVPNaretwodifferenttechniques,canachievelargeamountsofdataremoteaccess,providingpeoplewithalowoperatingcost,highproductionefficiencyofremoteaccessmethods,accordingtothedifferentcharacteristicsofbusiness,chooseadifferentVPNtechnologies,makegooduseVPN,thecommunicationefficiencyforbusinesses,businessrunninggreatupgrade.

Intelligentbuildingsrequireintegrationofavarietyofcomputer-basedbuildingautomationandcontrolsystemproductsthatareusuallymadebydifferentmanufacturers.BACnetTMisastandardcommunicationprotocolforBuildingAutomationandControlNetworksdevelopedbytheAmericanSocietyofHeating,RefrigeratingandAir-ConditioningEngineers（ASHRAE）[1].BACnetprovidesthecommunicationinfrastructureneededtointegrateproductsmadebydifferentvendorsandtointegratebuildingservicesthatarenowindependent.ThispaperdescribesthemainfeaturesoftheBACnetprotocolandearlyexperienceimplementingit.

ThispaperdescribesthetechnicalsummaryofWAN,anditsapplicationBACnet.

Keywords:

WAN,buildingautomationandcontrolnetwork,intelligentbuildings,directdigitalcontrol,BACnet.

Comments

1.1ThetechnologyofWAN

1.2ThecompositionandcharacteristicsofWAN

1.3WAN-relatedtechnicalissues

1.4PointtoPointConnection

1.5Circuit-switched

1.6WANPort

1.7Firewall

2.1Routerandroutings

2.2Theroleofrouter

2.3Theshortestpath

2.4RoutingAlgorithm——Dijkstraalgorithm

3.1TheHistoryofBACnetTMDevelopment

3.2ATechnicalOverviewofBACnet

3.3BACnetApplicationLayer

3.4ApplicationServices

ChapterOneSummaryofWAN

1.1ThetechnologyofWAN

WAN（WideAreaNetwork）-WideAreaNetwork,iscurrentlyadivisionofthenetwork,thenetworkdivisionofthemostcommonisbasedonthescopeandroleofthenetworkinterconnectionbetweencomputersintothedistance,thereareWAN,LANandMANthreetypes.

Suchanetwork,thelargestofitsscope,coveringawiderscopethanmetro（MAN）wider,whichisusuallyindifferentcitiesoftheLANorMANnetworkbetweentheInternet,canbetensofkilometerstotensofthousandsofkilometers.Theestablishmentofnationalorinternationalnetworksarewideareanetworks.Withinthewideareanetworkforcommunicationstransmissiondevicesandtransmissionmediacanbethetelecommunicationssector.Atpresent,theworld'

slargestinformationnetworkInternethasbeencovered,includingmyownmorethan180countriesandregions,connectingtensofthousandsofnetworks,end-userhasreachedthenumberofstemmillion.Andthemonthlygrowthrateof15%.Becauseofdistance,informationdecaymoreserious,sothisisgenerallytobeleased-linenetwork,throughtheIMP（InterfaceInformationProcessing）protocolandlinelinkuptoformnetworkstructuretosolvetheproblemthroughthepath.Fromthecomputernetworktermsofthefunctionsofitscomponentparts,thepartstocompletetwokindsofmajorfunctions,namely,networkcommunicationsandresourcesharing.Thecomputernetworktoachievenetworkcommunicationdeviceanditssoftware,acollectionknownasthenetworkcommunicationsub-net,thenetworktoachieveresourcesharingofequipmentandsoftwareresourcesofacollectionknownasthesubnet.Inthewideareanetwork,thecommunicationnetworkbyanumberofdedicatedcommunicationprocessor（Internetexplore,thenodeswitches）andrunthesoftware,concentratorsandotherequipmentandconnectthesenodesformthecommunicationlink.Resourcesubnetsfromaccessingallofthecompositionsofthehostanditsexternaldevices.

1.2ThecompositionandcharacteristicsofWAN

Wideareanetworkisgeographicallyfarapartmultiplecomputersystems,throughthecommunicationlinesinaccordancewithnetworkprotocolstoconnecttoachievebetweencomputerscommunicatewitheachotheracollectionofcomputersystems.WANfromtheswitches,routers,gateways,modemsandotherdataexchangeequipment,dataconnectivitydevicespose.Ithasastrongtechnicalcomplexity,managementcomplexity,type,variety,connectiondiversity,structuraldiversification,diversificationoftheagreement,applicationcharacteristicsofdiverse.Wideareanetworkisgenerallydividedintothreetypes:

circuit-switchednetworks,packetswitchingnetworkandprivatelinenetworks.

Agroupofswitchesconnectedtoeachotherconstituteawideareanetwork.Aswitchtypicallyhasmultipleinput/outputinterface,makingittheformationofmanydifferenttopologiestoconnectmultiplecomputers.

1.3WAN-relatedtechnicalissues

WiththeWANintroducesthetechnicalissuesrelatedtothefollowingthree.

（1）Routing:

Sincethesourceanddestinationstationsarenotdirectlyconnected,sothenetworkmustberoutedpacketstransmittedfromonenodetoanothernode,thefinaladoptionoftheentirenetwork.

（2）packetswitching:

ThebasiccomponentofaWANisapacketswitchbecauseitmovespacketsfromoneconnectiontoanother;

itconsistsofspecial-purposehardwarewithaprocessor,memory,andI/Oconnectors.ApacketswitchisillustratedinFigure1.

Figure1Packetswitch

Routingtodeterminetheoutputportandthenextonenode,youmustusepacketswitchingtechnologytotransmitfromtheinputporttotheoutputporttoachievetransferbitsthroughthenetworknodes.WANpacketswitchingtechnologyusesasharedcarrierinfrastructure,itisnottheexchangeofprivatelinenetworkconfiguration,andoneononecommunicationpairs.Thiswillenablecarrierstomoreeffectivelyuseofitsinfrastructure,whichusuallyallowsuserstoobtainthesameservicewhilereducingcosts.Inthepacketswitchingenvironment,asharedWANmediaaredistributedandusedinawiderangeofuserbase,sothatthedeliveryofsitesinagroupcreatedforthepackettransmissionbetweenthevirtualconnection.

Thistopologyisthecloudstructure,italsoincludesanumberofagreements,suchasasynchronoustransfermode（AsynchronousTransferMode,ATM）,FrameRelay（FrameRelay）,SwitchedMulti-megabitDataService（SwitchedMultimegabitDataService,SMDS）---andrelativelyrareintheUnitedStates-X.25.Iftheorganization'

sWANitselfa"

suddenincrease"

orvolatility,anddoesnotrequirestrictdedicatedbandwidthoralways-onWANlinks,packet-switchedconnectionisthebestway.

AninterconnectedsetofpacketswitchesformstheWAN.AsmallWANisillustratedinFigure2.

Figure2SmallWAN

Asshown,theWANdonotsymmetrical-theinterconnectionbetweentheswitchandthecapacityofeachconnectionaredeterminedbasedonanticipatedtraffic,andtoprovideredundancytopreventfailure.Intheexampleabove,thesiteofaswitchtoconnecttwocomputersandhaveanexternalconnection（Forexample,aT1line）connectedwithanotherswitch.Inthesite,onlytwoswitchestoconnectacomputer,andtherearetwoexternallinkstoothersitesconnectedtotheswitch.Summarizedasfollows:

Packetswitchisthebasicbuildingblocksofwide-areanetwork.Wideareanetworkbyanumberofinterconnectedpacketswitches,andthusconstitutesaconnectedcomputer.Otherswitchorconnectionmaybenecessarytoexpandthewideareanetworktojoin.

（3）Congestioncontrol:

theamountoftrafficenteringthenetworkandnetworktransmissioncapacitymustbecoordinatedinordertoobtainefficient,stable,goodperformance.

1.4PointtoPointConnection

Suppliersfromtheusertosetupacommunicationpathisknownaspointtopointconnection.Inthisstructure,theoperator'

snetwork（suchaslocaltelephonecompanies）throughleasedlines（whichmayincludecopperandothernecessaryhardware,suchasCSU/DSUunit）toprovideadirectconnectiontotheuser'

slocation.Soitisusuallyusedtoconnectthetwosetsarethesameasaserviceprovider'

snetworklayout.

Linesusuallyarebasedonbandwidthrequirementsandthedistancebetweenthetwoconnectionpointsandpricing.Pointtopointconnectivitypricesaregenerallyhigherthanframerelayconnectionsatthesametimeitisneededregardlessofthesizeoftheallocationofbandwidth,willbeamongthesuppliersanduserstoprovidepermanentestablishmentofadedicatedconnection.Thisconnectionisanothercommontermisadedicatedleasedline（referringtothecontinuedretentionbetweenthetwoterminalconnection）.

1.5Circuit-switched

Theuseofcircuit-switchedcommunications,thedatapathwillneedtocreate,andendedwiththecessationofuse.Thissetupsimilartothetypicaloperationofspecialtelephonenetwork,where"

conversations"

isanarbitrarycreationandtermination,andonlyinthe"

call"

duringtheexistence（infactthereareatleasttwopartsofthisperiodthereisanactivedataconnection）.

ISDNisthistechnologyaprimeexample:

Whendealingwitharouterwhentheremotesitedatatoinitializeaswitchingcircuit,which,inessence,istotheremotesitetomakeadirectdial-upline.Oncethepartieshavebeencertifiedandsuccessfullyconnected,theybegantotransferdatafromsourcetodestination.Whenthetransferiscompleted,theconnectionwasterminated.

1.6WANPort

WANisarelativelybroadergeographiccoverage,datacommunicationnetworks,whichoftenprovidetheconditionsforuseofpubliccarrierfortransmission.Internetisahugewideareanetwork.UsuallytherouterwillhaveaWANport,alsoreferstotherelativelywideraccesstoInternetandotherdatacommunicationnetworkport.