Perustiedot
TheessenceOfPacketwitchingistOdividetheDaTobetransMivedInToManyGroupsAcCordingToAcvartlengy.InordertoaccuraalystransmitteTheotherparty, jokainen ryhmäryhmä.TransmissionSperformEDONThephysicallineinadynamicsharingandMultiplexingmanner.Inordertomakefulluseofresources,whendatapacketsaretransmittedtotheswitch,theywillbetemporarilystoredinthememoryoftheswitch,andthenaccordingtothecurrentline'sbusynessandidleness,theswitchwilldynamicallyallocatetheappropriateThephysicallinecontinuesthetransmissionofdatapacketsuntiltheyaredeliveredtothedestination.AfterReachingThedEngation, TheDataPacketsarerEcombinedToformaCompeteData.
ThepacketSCompotefThePacketHeaderandtheUserDatapartAfterit.ThepacketHeacercontainsThereCeivingAddressandControlinformation, jaSlengthis3--10b.THELENGTOFTheUSERDATAPARTIFIXED, WithanaverageOf128Bandamaximumf256b.Siinä.Packetwitching: jälkikäteen.
PacketwitchingTechnologySTheDevelopmentOfcomputertechnologyToAccomeExt.DadditionToMakingDirectCalls, PeoplecancommunicateBetweenComputersandterminaalsthroughcomputersandternals.Kuitenkin transmissionlineSisnothighandTheNetworkTechnologyMeansImplersition, anexChangeTechnologyMergedatHEricmoment,.
PacketwitchingisalSocalledPacketwitching.ItDividesTheDatRanSMitdodbyTheSerInMultiplesMallerPartsOfallengl.Jokainen overariscalledadaasegment.Edelläkävijät NEEDEYYYCONTROLINTORMATIONIDADDEDIFRONTOFEACHDatasegmentToForMaPacket.OHDERISUSEDTOINDICATTHEADDRESSWHERETHEPACKETESTENT, jaTHESTHESTHORWARDSTHEMTOTHEDESTININATIONACCORDINGTOTHEADDRESSFLAGOFEACHPACKET.Tämä prosessinprosessi.TheCommunicationNetWorkForpacketwitchingisCalleDacketwitchingNetwork.Packetwitchingisessessessentially kehittyy "myymälä ja eteenpäin".ITHASTHEADVANTAGESOFCICUITSWITCHINGANDMESSAGES -KYTKYMINEN.
IntSThePacketwitchingMode, becausetheDatacanbetEemporyStoreDanDexChangedinpacketMode, jälkikäsittely,.
Kehityshistoria
Noin 1970, PeopleBegantostudyNewFormOfLong-DISTANCECEDIGIALDATACOMmunicationarchitecture: Packetwitching.Althoughthepacketswitchingtechnologyusedhasmadegreatprogresscomparedwiththattime,thebasictechnologyofpacketswitchingtodayisbasicallythesameasthenetworktechnologyofthe1970s,andpacketswitchingisstilloneofthefeweffectivewaystorealizelong-distancedatacommunication.Yksi OFTheTechnologies.Andthetwolatestwantechnologies: framerelayandatm, arebasicalSauriantsOfpacketwitching.
PacketwitchingisdevelopeDasatechnologyToSolveInterActiveProcessingApplications.ITISDESIGLEDTOSUPPORTHEtRANSMissionOfBurstyDatastreams.THECONTIONEUSTONCONTECTIMEFTHISSERVICESTREAMISLONGANDTHESERVICETHEAMOUNTISLOW.ThepacketwitchingnetworkusesstaticalMultiplexingTechnology, se, multiplesessionConnectionscanshareaCommunicationChannel, joka.Kuitenkin SharingTheCommunicationLinkinTroDucestMedeLay.Siksi AKEYissueWemustConsiderInthefutureishthePacket-Switchednetworktransmitsdelay-herkkyyservicestreams, Suctsreal-TimeserviStreams.PACKESAREROUTEDTROUGHASERIESOFINTERMEDIATENODES, YLEINENACROSSMULTIPLEENETTORKS.HeReforwardedBetBetSofPacketwitches (Ierouters) Inastore-Forwardmanner, ja FinallyReachThedestination.Tehtävän ajanjakson aikana theInformationisDivideToPacketsConingTheDESTINATIONDADDRESSIDESSEMENCEnumber.
Luokittelu
Myöhemmin.
DatagrackTywitching
DataGrampackSwitchingRequiresatleastoNeTaTransMissionPathBetWeENThecommunicationsparties.ThesendernedstopreparetheDataPackeTobetransMidodbeforcommunication.TheDataPacketContensTheaddressInformationsftEnderandtherever.TheTransmissionOfDataPacketsisIcivevedentOfeachOtHotE, ei ole yhtä mieltä.
IntShisway, jokainen packetisatechedwithsourceandDestinationddresses, paketti numero, packettardendflags, virheenrekisteröinti-.ThenetworkJusttriesitsBestTodeLiverThePacketTotedEntinationHost, ButDoesnotguaranteethatTheTransMivedPacketWillNotbelost, NorthattheThePackstswillarriveatthereceenendintheorderinwichtheHeweresent.Siksi theserviceProvedbyTheNetWorkisunrelable and theSequality ofServiceisnotguaranted.AsshownInfigure9-2 (a), jotkut packetsentfromhosth1toh5gothroughnodeabe, somegothroughaceorabce, andsomepacketsSentFromhosth2toh6gothroughNodebde.ThedatagrammethodisGeneralySableForshorter, yksiryhmää.ITSADVANTARESTHATTHETHANSMissionViiveissmall, jaHewreMePacketTransMissionWillNotBeaffectedwenanodefails.ThedisadvantageSThateachpacketHasalofadditionalControlinformation, joka on saanut aikaan.
VirtualCircuitPacketwitching
ThedifferencebetweenitandthedatagrammethodismyLlyThatBeforeInformationExchange, AlogicalConnectionNeedstobeESTABLEDBETWEENTHESEDThereCEIVERBEFORESTARTINGTRANSFERPACKETS, AllPacketsareexChangeDandForDalongthESAMEPATH ALDTHELOGICALCONNECTIONESTILESREMAYEDAFTERTHECOMNEENCESESEMANESESEMANESESEMANESESEMANESESESEMANESEMANESE.SilloworkguaranteesthatTheTransMidotePacketsRiveAtthereceenenDIntheorderin, joka.Siksi theserviceProvedbyTheNetWorkSreliableandThequality ofServiceisguaraned.AsshownInFigure9-2 (b), allpacketsentFromhosth1ToH5PassthrouTHESAMENODEA-B-E.
TämäMethodisNoToTSuctableForusersWithHighFrequencyOfinformationTransMissionAndsmallTransMissionVolumeArchimeTime.Koska packetHeaderonlyneedstoMarkTheVirtualCircuitIdentifierandSewenCenumber, ThePackeTheDerOverheadSmall.Sopii.
VirtualCircuitPacketwitchingisLikeCircuits -kytkentä.BothCommunicationPartiesNeedToEtablishAconnection, ButUnliKeciruts -kytkentä, pakkauspekkitsikiöiden piirtäminen (AlsokNownasavirtualCircuit) ja theeisNoExClusivEconnectioninTheconnection.Fyysinen johdotus.Myöhemmin.
SwitchingVirtualCircuitsRequiresBothpartiesIncommunicationTetablishatemporaryConnectionThrughRequest ja THICommunicate.WhenthecommunicationDends, theTemporaryConnectionistorndown.
Pysyvävirtauspiirit.
Itcanbeobnated fromThis, theCharacteristicsOftheconnection-OrientedworkingMethodandTheNon-ConnectionWorkingMethod.
(1) Ominaisuudet
OVATTAVAT PÄIVITTÄVÄT.
OnCethEconnectionisESTABLED, AllInformationOftCommunicationistransMitDAlongThisLinkPath ja WorderOftheInformationisGuaranTeed (theOrderOfSendingInformationSislent kanssa.
TheTimeLayofinformationTransMissionSissmallerthantheMedeLayOfTheConnectionlessWorkingMode.
OnCetheStablabledConnectionFails, TheInformationTransMissionWillbeInterruptedandTheConnectionMustBere-kiinteä, soitissensivefailure.
(2) theCharacteristicsOfConnectionlessWorkingMode
Siinä.
Theinformationbelongingtothesamecommunicationaryhmää.ThePathCannotbePredictioninadvanceandTheOrdOftheInformationCannotBeGuaranted (theOderOfSendingInformationSInconsistent kanssa.
ThetimeLayofinformationTransmissionisgreaterTantheMedeLayOfTheConnection-OrientedWorkingMethod.
TuntivetoNetworkfailures.
Ominaisuudet
(1) thesmallestUnitofinformationTransmissionispacket
ThepacketConsistsofroupHeaderandUserInformation ja TheThePacketHeacerContainsroutingandControlinformation.
(2) TwoworkingModes, yhteyskeskeiset (looginen konnection) ja
TheVirtualCucudaDoptsTheConnection-OrientedWorkingMode, ja ThatDatagramisTheConnectionlessWorkingMode
(3) Tilastollinen aika-divisionMultipleksointi (DynamicBandWidThallocation)
ThebasicprincipleofStatisticaltime --divisionmultiplexingishIVidetInToTimeslicesOfunequallenth, jaTimeslictsWithTheMerefiredForgroupingisnotaLodotedAfxeDEntimesliceForeachCommunity -sovelluksen, muttaisiläytetty.Tämä.
(4) InformationTransmissioniserror-ohjattu
PacketwitchingisaswitchingMethodpecialDesignedFordACommunicationNetworks.Thecharacteristicsofdataservicesarehighreliabilityandreal-imeery-tarvikkeet.Itisnotashighastelephonecommunication,soinordertoensurethereliabilityofdatainformationinpacketswitching,errorcontrolmechanismssuchasCRCcheckandretransmissionaresettomeettheneedsofdataservicecharacteristics.
(5) InformationTransMissionSisnotTransParent
PacketwitchingMustProcessTheTransMidodDataInformation, sellainen.
(6) FlowControlbasedOnCallViiveSystem
Pakkoja.
Edut
VerrattunaCircuit-SwitchedNetwork, PacketwitchingNetworkhasmanyadvantages
korkeakoulutus
VerrattunaCircuit-SwitchedPairchaininterms ofChannelexclusive, DatteryDataPacketsCanbetransMidodonthesamelinkinkinadynamicsharingandMultiplexingManner ja leikkausRateOfCommunicationResourceshIGHE, joka on todellakaan oikean ajankohtainen.BeuseasinglelinkfromnodetonodecanbedynamalySharedbymanypackets.PacketsarequeUeDandtransmedonThelkinKasquicklyaspossible.
Datanopeus
ApacketwitchingNetworkCanperFormDatanopeusConversion: TwostationsWithDifferentDataRatesCanexchangePackets.
Jonotusmekanismi
Onthesamelink, data -data -differentTypesandSpecificationsCanbetransMedatthesametime.WhentherearealarGenumberofPacketsonthePacketNetwork, thequeUecanbesetaccordingTotheDatransMissionMechanismToensurethpacketWithHighPrioriteettiaretRansMidodFirst.WhentheloadontHecuit-Switchednetworisheavy, SomeCallSareblocked.OnAPacket-SwitchedNetwork, packetsarestillaccepted, mutta theOdLeliverydelaywillincrease.
Prioriteetti
Kun.ThesepacketWillThereExperiancelessDelAyThanLowerPrioriteettipackets.
Haitat
VerrattunaCircuit-SwitchedNetworks, Packet-SwitchednetworksalsHavesomedisadvantages.
Viive
Apacketpassesthroughapacket-switchednetworkTherewillbeatimedelaywhenthenodeisconnected,butthereisnosuchtimedelayinthecircuit-switchednetwork.
Viivejitter
BacausethePacketsBetweenagivensourcestationAdDestinationStationMayHaveDifferentLengths, heillä.Erotteleva.Tämä.JitterisundEdEdErdeforsome-sovellukset (ennakkoluulo, sisäiset sovellukset SocasteLephonevoiceandreal-aikakuvat).
Korkeapään
TotransmitPacketsOverTheNetwork, ylimääräisenheadinformationinclUndingThedinationAddressandPacketOrderingInformationMustBeadedToeachPacket.Tämä.Incircuits -kytkentä, oncetheciruitisStable, nämä overheadsarenolongerneded.Lisäksi ThePacket-SwitchedNetWorkSaCollectionOfdistributed-paketti-kytkentät solmut.Inanidealsiitointi, allpacket-switchedNodessHouldalwaysandThthEState OftheTirenetwork.Valitettavasti BecausetHenodesaredistributed, senisalwrayadelaybetbetweenangeinthestatefonepartHenetworkLandheotherparpartHenetWorkWingkTheChange.INDADDION, theTransferofStatusInformationRequiresAcetingAMountOfcost, SoapAcket-SwitchednetworkWillNeverAere "täydellisesti".
Pörssikuori
ThereareTWotypesOfterminalShangingonThePacketwitchingNetwork: PackeTTypeMinalsandgeneralTerminals.Theso-calledpacket-typeterminalsendsandReceivesInformationinThorMorMackets; yleensä theinformationsEntandReceivedByTherMinalisamessage, jonka mukaan.IFTHESINDENTEMINALIAGENERALTERMINAL, ThePadwillsplitTheMessageSendsDnoseveralpacketsandtensenditThePacket-switchedNetworkFortSmissions; ifthereceivingterminalisageneralterminal, thePadwillre-kreateveralpacketsbelongingtoamessage.Kokoonpano.
TheBasicPrincipleOfPacketwitchingistousethe "Store and Forward" -tekniikka.WhenAMessageissentFromthesourCestion, ThemessageisdividedInToAfixEdFormatpacket (paketti), jaTedinationdArddressDedToThePacket.Jälkeenkuvioi, joka on kytkentä ja niiden, jotka ovat käsittämättömäisestiselectidlepathshEthEnthEntshressdressortwork- ja finalseMTEMTESTESTANESTONES -.Tämä.
PacketwitchingisaswitchingTechnologyThatcombinestHeadvantagesOfCircuits -kytkentätNArgeswitching.TheCircuits -kytkentäprosessitimilarturomakingaphonecall.WhenauserneedstoSenddata, thecallingparynedstomakeacall ja thecalledpartycompletestheshwitchingnetworkforettablishingaphysicalConnectionDatapathwithit.WhentHeconnectionNeedstobeDisconnected, ITISDONEBIETHIOFTHETTEWOCommunicationParties..Sen charakteristitThatiTiTitSitbleForsendLargequantihiesFinformationAnetime.DuetotelongTimeToEtablisHAconnection, TEEFATIICEISLOWWHENTRANSMITTINGSHORTMESAGES.Anditishly Compatible WeththeCommunicationPartiesIntermSofinformationTransmissionRate, EncodingFormat, CommunicationProtocol jne.., mikä on leimannut.TheBasicPrincipleOfMessageExchangeToushete "Store and Forward" -tekniikka.Aina,., AndthenaccordingToteprovestydestinationAddress, connuetoselectidlePathsforwarwardingholtHotherswitchesinTheNetwork, jafinallySenditToTheDESintinationAddress.Tämä.Kuitenkin tämäMethodhasalongtimedelayandlargeTimedeLayChanges.ITISNOTSIEDABLEFORREAL-TIMEANDCONVERIONTIONSIMMUNION, BUTISSITIABLEFORSSERVICESSUCHASE-Mail, ComputerFiles ja PublicTelegrams.
Packetswitchingstillusesthe"store-and-forward"technology,butitisnotexchangedintheunitofmessagelikemessageexchange,butthemessageisdividedintofixedformatpackets(Packet)forexchange,Transmission,generally1kbittothousandsofbits,eachpacketisattachedwithsourceanddestinationaddresses,packetnumber,packetstart,endflag,errorcheckandotherinformationaccordingtoacertainformat,andistransmittedinthenetworkinpacketform.WhenthesourceDTEtransmitsthepackettothelocalpacketswitchPSEintheformofabitstring,thelocalPSEreceivestheforwardinginformationrequiredbyeachpacket,regardlessofwhetheritisconnectedtothedestinationaddressdevice,firststoresit,andthenchecksthedestinationaddressandsavesitinthePSEFindthesendingpathspecifiedbythedestinationaddressintheroutingtable,andthePSEwillforwardthepacketatthemaximumallowablesendingrate.Samoin jokainenTransitSestores jaForwardseachpackeTinThiswayuntilthePackeSdeLiverEdTotedEntenationPSEPSE- ja sentHepseSDeliveredTotedEntrationdAntressdte (Seefigure8-7).WhatsistransMedIntheabove-NationedwayTheDatagramwayInpacketwitching.Yleensä.ITSADVANTAGEAREHightransmissionReliabilityandLowTransMissionViive.BeuseTheMemoryCaPancityonthepseisredrected, theekonomyisimproved.ThedisadvantageSThateachPackeTaddsMoreControlInformation, joka on saanut aikaan.GreatAdditionaloverhead.
ToinenModeOfPacketwitchingiscalledVirtualCircuitMode.THaiAindifferenceBetweenitandtheDatagrammodEtHatBeforeInformationExchange, theSourcedtesendespesificCallRequestPackeThelocalpse, jonka mukaan.TheaddressandLogicalChannelIdentifierOfTheDEreforwardedbyThepse.IfthecallisAcceptedByThedEntinationDte, TheCorrespondingResponse "CallAcceptance" isanswed, ja Thenetworksendsa "CallConnection" Tothesourcedte.ATTHISTIME, The EcalliseStableDandAnalogicalPathCalleDavirtualCircuitESTABLEDBETWEENTHETTEWODTES., InformationCanbetransMidoDonThisvirtualCircuTtilTheendOfTheDataexchange-, ThevirtualCircuitRemoved- jaTecorrespestLogicalChannelIdentifierisrelfed.Siksi TheVirtualCircuitMethodhasthretagesofvirtualCiruitEStablment, DataTransMissionAndRemoValdingArchCommunication, jonka mukaan.TämäMethodisNoToTSuctableForusersWithHighFrequencyOfinformationTransMissionAndsmallTransMissionVolumeArchimeTime.Kuitenkin lähtien, koska aeachpacketHeaderonlyneedstobemarkedwithAirtualCircuitIdentifier ja sekvensenumber, ThePacketHeaderHasasMalloverHeadissiittableforlongMessageTransMission.
Vaihtoprotokolla
PULBLUBLACKETSWITCHEDDATANETWORKISANIMPORTIANTPULLISENKIRJOITUS.Thex.25ProtocolformaululdByTiTu-tss, theTelecommunicationsandarddard-osasto, joka.X.25NetworkisAPublicDataNetWorkWidely -käyttämäisesti.X.25WasinTroDectedbytyltmeTin1970, jaTitwastheFirst-GenerationPacketwitchingsystem.Thex.25NetWorkWasdevelopedTotransmitData, SoiuthNoTIndirectCompetition kanssa.X.25PacketwitchingTechnologyMergedTomeetTheneedSofinterActiveServices.Interaktiivinen prosessointi.ITISABURSTYDataStreamWithalongConnectionTimeButlowDatavolume.X.25 ProvideTeeknologiatHataLowsMultiplesessionStoshesamecommunicationChannel.
WICHEX.25NetworkProPotex.25 Teknologia, silloinenWorMainlyAsimuloitu ympäristö.Amoreseriousproblemwithanalogetworksisthatnoisewillbeamlifiedwhenpassinghruurmeamplififers.Siksi Avalue-AdddedServiceProvidedByx.25AistoimplementErRorControlfunctionSwithinTenetwork.Pakkauksen jälkeen.IfeverythingisnormalFortpacket, theintermediatetewillsendanacknowledgmentMessageToTheoriginalsendingNode; ifthereisanerrorinThePacketTetReceivedbyTheinterMediateNode.Siksi atanyNodeOfthePacketPath, iFitisfoundthattheaccumululationofnoiseCausesanerror, TheRrorwillBecorcted, SothatTheDatastreamCanbetransMidodmoreaccuratey.JustLikeThepstNNetwork, Thex.25Packet-SwitchedNetWorkSalSohierarchical.
Inthex.25PacketwitchingNetwork, packetwitchesaredividedInToToCategoriat: (1) OneTypeOfSwitchisCloseTheuserend, Infact, SheArelocatedatTheAccessPointOftHenetworkwork.FunctionSypeOfSwitchincluDerouting, ForwordingPackets ja AndRerRordectionAdCorgection.INDADDION, InorderToSupportTheAccessOfDifferentTypesofcomputers, TocompeteTheConversionBetWeEndifferentProtocols, OrtheConversionBetweEndifferentworkingspeedsandsandsenceNencodingMethodsteacespointPointPointpointPointPointSarensarenefuncionsareatTheAccessPoint.Switchisdone.Intoranat, koska tiivisteenä onlehtenäinenConversionworkcordingToyourrequirements, anddusetisconversionspartHenetworkbusiness, Sothroughthex.25Network, YouCanrealizeTeConnectionBetWeendifferentTypesofDevices.(2) THEESCONDTYPEOFSWITCHESAREIDETHENETWORK.HeDonotProvidetheaforminationEdHigh-tason arvonlisäfunktiot, butonlycompletePackeTrouting, edelleenlähetys.Ei-standardx.25ThermalsNeedTobeConnectedToanx.25NetworkthroughaPacketDisassemblyDevice (Pad).PadcompletestHeconversionofTheProtocolandGeneratestHePacketsSpecifiedbyThex.25 standardi, sothatthedatacanbetransmiththroughthex.25Network.TheespadscanbeplacedontheuSersideoronthenetworkside.X.25AsessessentiallyAstanDardaccessProtocolbetweenUSerequipmentAdPacketwitchingNetworkseStabledbyitu-t.ITDEFINESTHEInterfacethrough WhathtHetherminalInThePacketModeConnectStothepublicDataNetWorkHontHroughadeedCircuit.TherealSosomecommonlyUsedx-sarjan protokollat, ne ovat:
(1) x.28STHESTANDARDPROTOCOLBETWEENTERMINEALEQUIPmentAndPad;
(2) x.29STHESTANDARDARTOCOCOLBET WEANPADANDTHENETWORK;
(3) x.75AIRAGATEWAYPROTOCOLFORTEEDIRNICCONNECTIOFTWOORMOREPACKET-SWITCHEDNETWORKS, ONOF WHICHICHCANBECTECTEDICEPACKETDATANETWORK ja TOTEOTERONEST.
TheadvantagesandHaitatOfthex.25Network:Tojudgetheadvantagesanddisadvantagesofaparticulartechnology,firstofalldependsontheenvironmentinwhichitislocated.InabasicenvironmenmentOfanaloginformation, Noiseisabigroblem, niin.Kuitenkin Ateachintermediatetenode, indditionToSelectingaroutOdeTerMinetHenExthop, ErrorControlisalSIimplementEDOnACHPACKet.Beusethex.25Packet-SwitchedNetWorkisonlyUnedToTransmitData, DelveorpacketLossisNotaverycriticalParameterforit.Toinen kontributionofx.25Sitspacketsize.ITUSSRELAtiivisestiMallPackets, yleensä128bytesor256bytes.THEEPROSANDCONSOFTHISissuealSochangesovertime.DuetonoiseFactors, SheePacketsareAdAdvantageOUsInx.25Networks.IfthereisnoiseinTheNetwork, senWillbeErrors, sopacketsoftendeedtobereTranst.On selvää,.Siksi x.25.SpecifyDesignedTousesmallerpackets.Samoin koska vastakohtainenverkko, itissiitebleForworkingonrelifyLow-nopeuslinkit.ThelinkRateGenerAllyRangesFrom56kbit/sto2Mbit/s.
Theadvantagesofx.25Aarisfollows: (1) sen jälkeen.25SThefirstToProvidelayer3NetworkAddressInformation, SothatpacketsCanberoutEdandrelayEdInaseriesofterMediateNodesandNetworksithasastrongAddressingFunction;.Kannattaminen, sitenmuodostushyökkäysten hallitsemattomuudesta; (4) itCancontIntylyDetectandCorrectallTypesoferrorSoneachInterMediatetenode, SotheErRorControlfunctioncanbeimproved; (5) wennodesandlinesfailtheroutekanbere-valittu, sotheavolightHighinghinglines.
Thedisadvantagesofx.25areasfollows:(1)Thequeuingdelayislarge;(2)Thelow-speedcommunicationlink;(3)Thepacketsizeissmaller,andthebandwidthutilizationrateisnotasgoodasthatofthelargersizepacketThenewprotocolishigh;(4)ThereisnoQoSguarantee,soitisnotsuitablefordelay-sensitiveapplications;(5)Itisonlyusedtotransmitdata,andtodayweareworkinghardtofindacomprehensiveservicesolution.
Johdantotox.25Protocol: AnimportantPartOfusingPublicDatanetworksisTheInterfacewithem.Theitox.25 standardisAwidely käyttänyt.ManyPeopleusetetter "x.25Network",whichleadsmanypeopletomistakenlybelievethatX.25Definesanetworkprotocol.ButthisisNotTheCase.X.25JustdefinestheagreementBetweendTeanddCeconnectedToThePublicDataNetwork (kuvio 9-4).Siksi x.25CanBESTRICTYURESASAUSER-NETWORTIONESIA PAIKKAAVAAJA-JÄLKEEN.Thex.25ProtocolReferstohepRoTocolfortheinterfacebetweDateTaterMinalequipment (DTE) anddatacircuitTermInAlequipment (DCE) käytetty.ITDEFINESTHETHREE-LAYERPROTOCOLOFTHEPHYSICALLAYER, TEDALINKLAYER ja THEEPACKETLAYER (ts..
(1) Physicallayer: TheBasicfunctionistAstablish, ylläpitää jaDismantLeThysicallinkbetweendTeandce, joka deefinesthemekaaninen, sähköinen, funktionAndregulationCharakteristicsOfThefysicallink ja provovidessynkronisoituminen jafullDuplepleplepTePointbitstReamtransmessmessmississions..21verot.(2) DataLinklayer: ThePhysicallinkBetWeEnthedTeandTheLocalpacketwitchpse (PacketwitCheDequipment).ThelapBSPecifiedByThislayerThe (LinkACCESSPROCEDUREDABALDED) -menettelytapa, joka onBalancedSubsetOftheHDLCPROCEDURE.ItMainlySpecifestHepRocEduresForthEStablmentAndRemoValofDataLinks, ProCEDURESFORNORTORTIONTRANSMIONSAFTERESTABLACTING, AnderrorControl, FlowControl jne..Tyydyttäminen, tämäleyeralsstipulatesthemulti-linkproceduremlp (multiLinkprocedure), joka on saanut aikaan.
(3) PacketLayer (Networklayer): PääosinDescribestHePacketLayerProcEduresForExChangingControlinformationAndUserDataonthedte/dcEnterface- ja apecifiestHeVirtualCircuITServiceProcEdures, BasicPacketstructure, DataPacketFormat, Andoputionaluserbusinessfuctions, jne..TämälayeradoptsThePRincipleofIMEdIVisionMultiplexingToRealizetHataSourcedTeusesAphysicalCircuitteTocallMultipEnSinationDtesforpacketDataexchange.INDADDION, ItalsoprovidesPermanentVirtualCircuitPvcService, joka on kirjoitettu.ThesourcedtekanusethevirtualCircuitWithouthtotablishacall.TheinterrelationshipofthevariouslayeredprotocolsinX.25.
Verkosto
SilloinpekkiSwitchingisGeneralycomposedfacketwitches-, verkko-.Varusteet.(1) Thepacketwitchrealizestheinterfaceprotocol (x · 25) välillä onnenkytkentäinen.Tukee, ja koperaatit.Mukana, että itCanbedividedInToToToTypes: transitswitchandlocalSwitch; (2) thenetworkmanagementCenter (NMC) ja thePacketwitworkTogethertoensuretHenormaloperationFTenetWorkworkworkworkworkworkworkworkworkworkworkworkworkworkwitchwitch; (2).
ITSMAINFUNCTIONSCLUDENETWORKAINTI, UUDELLEEN HALLINTO, MITTAMINEN HALLINTA, LIIKKAAMINEN HALLINTA, OIKEUS., millainen laaja-alainen toimenpide (3) theainfunctionofThesubassemblyAndDisasemblyDevice (Pad) ISTOCONVERTTHENONO-PacketformaTofordaryCharacterterminalsIntOurSFormats, andgrouptheDatastreamsOfeachterminalToRegrecannel, WatareInterLEADEDEDMULTIPLEXEDINGROUPNEATHEAGREGOUPSECHEEL.TheotherparythenconvertsThereCeivedPacketformantheOppositedirection.(4) functionofaremoteconcentratorSimilarToApacketwitch, andInusulleScontensThefunctionOfaPad.Itisonlyconnectedtoapacketswitchwithoutroutingfunction.ITisusedInareaswhereUserSarerelateptionCentrated, AndisGeneralyInStalledIntheTeleCommunicationsDepard -osasto.(5) ProvidetheBasicservicesOftHenetwork: SwitchingVirtualCircuitsAndPerManentVirtualCircuitsAnthersupplementaryServices, SuchasClosedUserGroup, NetworkUseridentifiointi jne..Kun kommunikoivat toisiinsa koskevien tietojen välillä, reititys-.ITCANPROVIDEAVARIEFCOMBUNICATIONPROCEDURES, DataForwarding, YllätenceanDoperation, Firsdiagnosis, BillingandSomenetworkStatistics jne..