Packet switching network

Overview

PacketSwitchingNetwork

Thepacketswitchingnetworkisthebasicnetworkofdatacommunication,andvariousvalue-addedservicescanbedevelopedusingitsnetworkplatform,suchas:e-mail,Electronicdataexchange,visualtext,faxstorageandforwarding,databaseretrieval.

Theoutstandingadvantageofpacketswitchingnetworkisthatmultiplevirtualcircuitscanbeopenedononecircuitatthesametime,whichcanbeusedbymultipleusersatthesametime.Thenetworkhasdynamicroutingfunctionandadvancederrorcorrectionfunction,andthenetworkperformanceisthebest.good.ChinaPublicPacketSwitchedDataNetworkisanationwidepacketswitcheddatanetworkoperatedbyChinaTelecom.Thenetworkhasdirectlycoveredallprefecturesandcitiesandmostcounties.Thetelephonenetworkcancoverallcitiesaccessibletothetelephonenetwork.Userscanusededicatedlinesnearby.Ordialintothenetworkbytelephoneandusepacketswitchingservices.

Packetswitching

Packetswitchingisastore-and-forwardswitchingmethod.Itdividestheuser’smessageintopacketsofacertainlengthandusesthepacketasstore-and-forward.Therefore,itismoreCircuitswitchinghasahighutilizationrate,whichissmallerthanthetimedelayofmessageswitching,andhasthecapabilityofreal-timecommunication.Packetswitchingusestheprincipleofstatisticaltimedivisionmultiplexingtomultiplexadatalinkintomultiplelogicalchannels,andfinallyconstituteaninformationtransmissionpathbetweenthecallingandcalledusers,whichiscalledavirtualcircuit(VC)torealizedatagroupingTransmit.

Packetswitchingisanadvancedcommunicationmethoddevelopedtoadapttocomputercommunication.ItisbasedontheCCITTX.25recommendationandcanmeettherequirementsofdifferentspeeds,differenttypesofterminalsandterminals,terminalsandcomputers,andcomputers.Thecommunicationbetweencomputersandlocalareanetworksrealizesthesharingofdatabaseresources.

PacketswitchingisthefoundationoftheInternet.Itisaformofstatisticaltimedivisionmultiplexing,allowingmany-to-manycommunication.Thesendermustdividethemessageintoaseriesofpackets.Aftersendingapacket,thesenderallowsothersenderstosendthepacketbeforesendingsubsequentpackets.

Features

Thepacketswitchingnetworkhasthefollowingcharacteristics:

(1)Packetswitchinghasthecapabilityofmultiplelogicalchannels,sothecircuitutilizationrateofthetrunklineishigh;

(2)Itcanrealizetheterminalintercommunicationbetweendifferentcodetypes,ratesandproceduresonthepacketswitchingnetwork;

(3)Sincethepacketswitchinghastheabilityoferrordetectionandcorrection,soThebiterrorrateofcircuittransmissionisextremelysmall;

(4)Thenetworkmanagementfunctionofpacketswitchingisstrong.

(5)Hightransmissionquality.

(6)Highreliabilityanddynamicroutingfunction.Whenanetworkfails,aslongasthereisacommunicationroute,theswitchcanchooseatrouble-freeroutetotransmitpackets.

(7)HighlineutilizationThecommunicationnetworkresourcesadoptstatisticaltimedivisionmultiplexing.

(8)Therate,codetype,andprocedurescanbeconverted,allowingterminalsofdifferenttypes,rates,encodingformats,andcommunicationprocedurestocommunicatewitheachother,andflowcontrolmeasurescanbeadopted.

Basicbusiness

Thebasicbusinessofpacketswitchingincludesswitchedvirtualcircuit(SVC)andpermanentvirtualcircuit(PVC).Switchingvirtualcircuitsisthesameasatelephonecircuit,thatis,whentwodataterminalswanttocommunicate,theyfirstestablishacircuit(ievirtualcircuit)withacallprogram,thensenddata,anduseadisconnectprogramtoremovethevirtualcircuitafterthecommunicationisover.Thepermanentvirtualcircuitislikeadedicatedline.Apermanentlogicalconnectionisprovidedbetweentwoterminalsinthepacketnetworkduringthecontractapplicationperiod,withouttheneedforcallestablishmentanddisconnectionprocedures.Inthedatatransmissionstage,itisthesameastheswitchedvirtualcircuit.

Thepacketswitcheddatanetworkiscomposedofpacketswitches,networkmanagementcenters,remoteconcentrators,subassemblyanddisassemblyequipment,andtransmissionequipment.

(1)Thepacketswitchimplementstheinterfaceprotocol(X·25)betweenthedataterminalandtheswitch,thesignalingprotocolbetweentheswitches(suchasX·75orinternalprotocol),andthepacketStoreandforward,providepacketnetworkservicesupport,andcoordinatewiththenetworkmanagementcentertocompleterouting,monitoring,billing,control,etc.Accordingtothestatusofthepacketswitchinthenetwork,itcanbedividedintotwotypes:transitswitchandlocalswitch;

(2)Thenetworkmanagementcenter(NMC)andthepacketswitchworktogethertoensurethenormaloperationofthenetwork.Itsmainfunctionsincludenetworkmanagement,usermanagement,measurementmanagement,billingmanagement,operationandmaintenancemanagement,routingmanagement,networkstatisticscollection,andnecessarycontrolfunctions,etc.,whicharethecoreoftheentirenetworkmanagement;

(3)Themainfunctionofthesubassemblyanddisassemblyequipment(PAD)istoconvertthenon-packetformatoftheordinarycharacterterminalintoagroupformat,andgroupthedatastreamsofeachterminalintogroups,whichareinterleavedandmultiplexedontheaggregatechannel.Theotherpartythenconvertsthereceivedpacketformatintheoppositedirection.

(4)Thefunctionoftheremoteconcentratorissimilartothepacketswitch,andusuallycontainsthefunctionofPAD.Itisonlyconnectedtoapacketswitchwithoutroutingfunction.Itisusedinareaswhereusersarerelativelyconcentrated,andisgenerallyinstalledintelecommunications.Department.