Въведение
FrameRelay(framerelay)isanewpublicdatanetworkcommunicationprotocolthatemergedin1992,anditbegantodeveloprapidlyin1994.Framerelayisaneffectivedatatransmissiontechnologythatcantransmitdigitalinformationquicklyandinexpensivelyinone-to-oneorone-to-manyapplications.Itcanbeusedforvoiceanddatacommunication,andcanbeusedforlocalareanetwork(LAN)orwideareanetwork(WAN)communication.Eachframerelayuserwillgetadedicatedlineconnectedtotheframerelaynode.Forendusers,aframerelaynetworkhandlesdatatransmissionwithotherusersthroughachannelthatchangesfrequentlyandisinvisibletousers.
Mainfeatures:Userinformationistransmittedinunitsofframes.Thenetworkcheckstheframestructureandtransmissionerrorsduringthetransmissionprocess,anddirectlydiscardstheerrorframes.Atthesametime,throughtheframeTheidentificationofthemiddleaddresssegmentDLCIrealizesthestatisticalmultiplexingofuserinformation.
Framerelayisadatapacketswitchingcommunicationnetwork,whichisgenerallyusedintheDataLinkLayerintheOpenSystemInterconnectionReferenceModel.PermanentvirtualcircuitPVCisusedonphysicalnetworkswitchedvirtualcircuits(SVCs)toformanend-to-endlogicallink,similartocircuitswitchinginthepublicswitchedtelephonenetwork,andisalsopartofthedescriptionofframerelay,butitisnowveryItisrarelyusedinpractice.Inaddition,framerelaywasoriginallydesignedforthecompactformatversionoftheX.25protocol.
ThedatalinkconnectionidentifierDLCIisanumericalvaluewithlocalmeaningusedtoidentifyeachendpoint.MultiplePVCscanbeconnectedtothesamephysicalterminal.PVCsgenerallyspecifythecommittedinformationrateCIRandtheadditionalinformationrateEIR.
FrameRelayisdesignedtomakemoreeffectiveuseofexistingphysicalresources.Sincemostcustomerscannotusedataservices100%,itallowscustomerstoprovidemorethansupplytotelecomoperators.Dataservices.Itispreciselybecausetelecomoperatorshavebookedtoomuchbandwidth,whichhascausedframerelaytogainabadreputationinsomemarkets.
Telecomcompanieshavebeensellingframerelayservicestocustomerswhoarelookingforcheaperthandedicatedlines.Accordingtothepoliciesofthegovernmentandtelecommunicationscompanies,itisusedinvariousapplicationareas.
FramerelayisgraduallybeingreplacedbyATM,IPandotherprotocols(includingIPvirtualprivatenetwork).
PublicDataNetwork
PublicDataNetworkisacommunicationnetworkestablishedandoperatedbythetelecommunicationsauthorityorawidelyrecognizedprivateorganization.Thecommunicationnetworkprovidesacertainwayofdatatransmissionservicestothepublic.
Например в Китай китайската мрежа на ChinaTelecom е публична мрежа за данни.
Интернет протокол
Интернет протокол(English:Интернет протокол,abbreviatedasIP),alsotranslatedasИнтернет протокол,isapacket-switcheddatanetworkKindofagreement.
IPisthemainprotocolofthenetworklayerintheTCP/IPprotocolsuite.Thetaskisonlytotransmitdatabasedontheaddressesofthesourcehostandthedestinationhost.Forthispurpose,IPdefinesanaddressingmethodanddatagramencapsulationstructure.Themajorversionofthefirstarchitecture,nowcalledIPv4,isstillthemostimportantInternetprotocol,althoughIPv6isbeingactivelydeployedaroundtheworld.
AsynchronousTransferMode
AsynchronousTransferMode(English:AsynchronousTransferMode,ATM),alsocalledcellrelay.ATMusescircuitswitching,whichusescellsasaunit.Eachcellis53byteslong.Theheaderoccupies5bytes.
ATMcanideallyrealizeavarietyofQoS,anditcansupportconnectedservicesaswellasconnectionlessservices.ItisamodelofbroadbandISDN(B-ISDN)technology.ATMisaswitchingtechnology.Whensendingdata,thedigitaldataisfirstcutintomultiplefixed-lengthdatapackets,andthensentusingopticalfiberorDS1/DS3.Afterarrivingatthedestination,regroup.TheATMnetworkcanintegratesound,videoanddataatthesametime.Providethebesttransmissionenvironmentforvariousinformationtypes.