软考网络工程师资料OSI体系模型

国家软件资格水平考试

－－网络工程师

ObjectivesOnpletionofthischapter,youwillbeabletoperformthefollowingtasks:DescribehowdatatrafficisexchangedbetweensourceanddestinationdevicesIdentifytherolesandfunctionsofahub,switch,androuter,andwheretheybestfitinthenetworkIdentifytheIPprotocolstack,itsprotocollayerfunctions,andmonlyusedIPprotocolsIdentifyIPaddressclasses,IPaddresses,IPsubnetmasks,IPnetworknumbers,subnetnumbers,andpossiblehostnumbers.网络体系结构网络体系结构网络计算模型网络分类按拓扑分类按地理范围分类体系结构协议分层服务类型服务原语参考类型OSI参考模型TCP/IP参考模型两种模型比较DefiningponentsoftheNetworkMainOfficeBranchOffice

Home

Office

MobileUsersInternetFloor2Floor1ServerFarmDefiningtheponentsofaNetworkBranchOfficeTelmuterISDNRemoteCampusNetworkStructureDefinedbyHierarchyDistributionLayerCoreLayerAccessLayerAccessLayerCharacteristicsEndstationentrypointtothenetworkAccessLayerDistributionLayercharacteristicsAccessLayer

AggregationPointRoutestrafficBroadcast/Multicast

DomainsMediaTranslationSecurityPossiblepointforremoteaccessDistributionLayerCoreLayerCharacteristicsFasttransporttoenterpriseservicesNopacketmanipulationCoreLayerOSIModelOverviewApplication(Upper)LayersSessionPresentationApplicationOSIModelOverviewDataFlowLayersTransportLayerDataLinkNetworkLayerPhysicalApplication(Upper)LayersSessionPresentationApplicationRoleofApplicationLayersTelnetFTPUserInterfaceEXAMPLESApplicationTelnetFTPASCIIEBCDICJPEGUserInterfaceHowdataispresentedSpecialprocessingsuchasencryptionEXAMPLESPresentationApplicationRoleofApplicationLayersTelnetFTPASCIIEBCDICJPEGKeepingdifferentapplications’dataseparateUserInterfaceHowdataispresentedSpecialprocessingsuchasencryptionOperatingSystem/ApplicationAccessSchedulingEXAMPLESSessionPresentationApplicationRoleofApplicationLayersKeepingdifferentapplications’dataseparateUserInterfaceHowdataispresentedSpecialprocessingsuchasencryptionTelnetFTPASCIIEBCDICJPEGOperatingSystem/ApplicationAccessSchedulingTransportLayerDataLinkNetworkLayerPhysicalEXAMPLESSessionPresentationApplicationRoleofApplicationLayersRoleofDataFlowLayersEIA/TIA-232

V.35EXAMPLESPhysicalMovebitsbetweendevicesSpecifiesvoltage,wirespeedand

pin-outcables802.3/802.2HDLCEIA/TIA-232

V.35EXAMPLESRoleofDataFlowLayersDataLinkPhysicalbinesbitsintobytesand

bytesintoframesAccesstomediausingMACaddressErrordetectionnotcorrectionMovebitsbetweendevicesSpecifiesvoltage,wirespeedand

pin-outcables802.3/802.2HDLCEIA/TIA-232

V.35IPIPXEXAMPLESRoleofDataFlowLayersNetworkDataLinkPhysicalbinesbitsintobytesand

bytesintoframesAccesstomediausingMACaddressErrordetectionnotcorrectionMovebitsbetweendevicesSpecifiesvoltage,wirespeedand

pin-outcablesProvidelogicaladdressingwhichroutersuseforpathdeterminationTCPUDPSPX802.3/802.2HDLCEIA/TIA-232

V.35IPIPXEXAMPLESRoleofDataFlowLayersTransportDataLinkPhysicalReliableorunreliabledeliveryErrorcorrectionbeforeretransmitbinesbitsintobytesand

bytesintoframesAccesstomediausingMACaddressErrordetectionnotcorrectionMovebitsbetweendevicesSpecifiesvoltage,wirespeedand

pin-outcablesNetworkProvidelogicaladdressingwhichroutersuseforpathdeterminationTCPUDPSPX802.3/802.2HDLCEIA/TIA-232

V.35IPIPXPresentationApplicationSessionEXAMPLESRoleofDataFlowLayersReliableorunreliabledeliveryErrorcorrectionbeforeretransmitbinesbitsintobytesand

bytesintoframesAccesstomediausingMACaddressErrordetectionnotcorrectionMovebitsbetweendevicesSpecifiesvoltage,wirespeedand

pin-outcablesTransportDataLinkPhysicalNetworkProvidelogicaladdressingwhichroutersuseforpathdeterminationEncapsulatingDataTransportDataLinkPhysicalNetworkUpperLayerDataUpperLayerDataTCPHeaderDataIPHeaderDataLLCHeader0101110101001000010DataMACHeaderPresentationApplicationSessionSegmentPacketBitsFramePDUFCSFCSUpperLayerDataDe-encapsulatingDataLLCHdr+IP+TCP+UpperLayerDataMACHeaderIP+TCP+UpperLayerDataLLCHeaderTCP+UpperLayerDataIPHeaderUpperLayerDataTCPHeader0101110101001000010TransportDataLinkPhysicalNetworkPresentationApplicationSessionApplicationPresentationSessionTransportNetworkDataLinkPhysicalOSIModelPDUFunctionalResponsibilitiesExamplesWrittenExercise:OSIModel

PhysicalLayerFunctionsDefinesMediatypeConnectortypeSignalingtypeEthernet802.3V.35PhysicalEIA/TIA-232PhysicalLayer:Ethernet/802.3HubHostsHost10Base2—ThinEthernet

10Base5—ThickEthernet10BaseT—TwistedPairHubsOperateatPhysicallayerABCDPhysicalAlldevicesinthesamecollisiondomainAlldevicesinthesamebroadcastdomainDevicessharethesamebandwidthHubs:OneCollisionDomainMoreendstationsmeansmorecollisionsCSMA/CDisusedDataLinklayerFunctionsDefinesPhysicalsourceand

destinationaddressesHigherlayerprotocol

(ServiceAccessPoint)

associatedwithframeNetworktopologyFramesequencingFlowcontrolConnection-oriented

orconnectionlessDataLinkPhysicalEIA/TIA-232v.35EthernetFrameRelayHDLC802.2802.3DataSourceaddFCSLengthDestaddVariable26640000.0Cxx.xxxxVendorassignedIEEEassignedMACLayer-802.3DataLinkLayerFunctions(cont.)PreambleEthernetIIuses“Type”hereanddoesnotuse802.2.MACAddress8#BytesEachsegmenthasitsowncollisiondomainAllsegmentsareinthesamebroadcastdomainDataLinkSwitchesandBridgesOperateatDataLinkLayerOR123124SwitchesEachsegmenthasitsowncollisiondomainBroadcastsareforwardedtoallsegmentsMemorySwitchNetworkLayerFunctionsDefineslogicalsourceanddestinationaddressesassociatedwithaspecificprotocolDefinespathsthroughnetworkInterconnectsmultipledatalinksNetworkIP,IPXDataLinkPhysicalEIA/TIA-232v.35EthernetFrameRelayHDLC802.2802.3DataSource

addressDestination

addressIPNetworkLayerFunctions(cont.)HeaderNodeNetworkLogicalAddressNetworkLayerEndStationPacketNetworkLayerFunctions(cont.)

11111111

11111111

00000000

00000000

10101100

00010000

01111010

11001100Binary

MaskBinary

Address0417216122204255AddressMask25500NetworkHostRoutingTableNETINTMetric124S0S0E01001.04.01.3E04.3S02.2E02.1S04.14.21.11.2RoutingTableNETINTMetric124E0S0S0001LogicaladdressingallowsforhierarchicalnetworkConfigurationrequiredUsesconfiguredinformationtoidentifypathstonetworksNetworkLayerFunctions(cont.)Routers:OperateattheNetworkLayerBroadcastcontrolMulticastcontrolOptimalpathdeterminationTrafficmanagementLogicaladdressing