Tanenbaum《计算机网络》原版课件第4章

TheMediumAccessControlSublayerChapter4TheChannelAllocationProblem•StaticChannelAllocationinLANsandMANs•DynamicChannelAllocationinLANsandMANsDynamicChannelAllocationinLANsandMANs1.StationModel.2.SingleChannelAssumption.3.CollisionAssumption.4.(a)ContinuousTime.(b)SlottedTime.5.(a)CarrierSense.(b)NoCarrierSense.MultipleAccessProtocols•ALOHA•CarrierSenseMultipleAccessProtocols•Collision-FreeProtocols•Limited-ContentionProtocols•WavelengthDivisionMultipleAccessProtocols•WirelessLANProtocolsPureALOHAInpureALOHA,framesaretransmittedatcompletelyarbitrarytimes.PureALOHA(2)Vulnerableperiodfortheshadedframe.PureALOHA(3)ThroughputversusofferedtrafficforALOHAsystems.PersistentandNonpersistentCSMAComparisonofthechannelutilizationversusloadforvariousrandomaccessprotocols.CSMAwithCollisionDetectionCSMA/CDcanbeinoneofthreestates:contention,transmission,oridle.Collision-FreeProtocolsThebasicbit-mapprotocol.Collision-FreeProtocols(2)Thebinarycountdownprotocol.Adashindicatessilence.Limited-ContentionProtocolsAcquisitionprobabilityforasymmetriccontentionchannel.AdaptiveTreeWalkProtocolThetreeforeightstations.WavelengthDivisionMultipleAccessProtocolsWavelengthdivisionmultipleaccess.WirelessLANProtocolsAwirelessLAN.(a)Atransmitting.(b)Btransmitting.WirelessLANProtocols(2)TheMACAprotocol.(a)AsendinganRTStoB.(b)BrespondingwithaCTStoA.Ethernet•EthernetCabling•ManchesterEncoding•TheEthernetMACSublayerProtocol•TheBinaryExponentialBackoffAlgorithm•EthernetPerformance•SwitchedEthernet•FastEthernet•GigabitEthernet•IEEE802.2:LogicalLinkControl•RetrospectiveonEthernetEthernetCablingThemostcommonkindsofEthernetcabling.EthernetCabling(2)ThreekindsofEthernetcabling.(a)10Base5,(b)10Base2,(c)10Base-T.EthernetCabling(3)Cabletopologies.(a)Linear,(b)Spine,(c)Tree,(d)Segmented.EthernetCabling(4)(a)Binaryencoding,(b)Manchesterencoding,(c)DifferentialManchesterencoding.EthernetMACSublayerProtocolFrameformats.(a)DIXEthernet,(b)IEEE802.3.EthernetMACSublayerProtocol(2)Collisiondetectioncantakeaslongas2.EthernetPerformanceEfficiencyofEthernetat10Mbpswith512-bitslottimes.SwitchedEthernetAsimpleexampleofswitchedEthernet.FastEthernetTheoriginalfastEthernetcabling.GigabitEthernet(a)Atwo-stationEthernet.(b)AmultistationEthernet.GigabitEthernet(2)GigabitEthernetcabling.IEEE802.2:LogicalLinkControl(a)PositionofLLC.(b)Protocolformats.WirelessLANs•The802.11ProtocolStack•The802.11PhysicalLayer•The802.11MACSublayerProtocol•The802.11FrameStructure•ServicesThe802.11ProtocolStackPartofthe802.11protocolstack.The802.11MACSublayerProtocol(a)Thehiddenstationproblem.(b)Theexposedstationproblem.The802.11MACSublayerProtocol(2)TheuseofvirtualchannelsensingusingCSMA/CA.The802.11MACSublayerProtocol(3)Afragmentburst.The802.11MACSublayerProtocol(4)Interframespacingin802.11.The802.11FrameStructureThe802.11dataframe.802.11Services•Association•Disassociation•Reassociation•Distribution•IntegrationDistributionServices802.11Services•Authentication•Deauthentication•Privacy•DataDeliveryIntracellServicesBroadbandWireless•Comparisonof802.11and802.16•The802.16ProtocolStack•The802.16PhysicalLayer•The802.16MACSublayerProtocol•The802.16FrameStructureThe802.16ProtocolStackThe802.16ProtocolStack.The802.16PhysicalLayerThe802.16transmissionenvironment.The802.16PhysicalLayer(2)Framesandtimeslotsfortimedivisionduplexing.The802.16MACSublayerProtocolServiceClasses•Constantbitrateservice•Real-timevariablebitrateservice•Non-real-timevariablebitrateservice•BesteffortsserviceThe802.16FrameStructure(a)Agenericframe.(b)Abandwidthrequestframe.Bluetooth•BluetoothArchitecture•BluetoothApplications•TheBluetoothProtocolStack•TheBluetoothRadioLayer•TheBluetoothBasebandLayer•TheBluetoothL2CAPLayer•TheBluetoothFrameStructureBluetoothArchitectureTwopiconetscanbeconnectedtoformascatternet.BluetoothApplicationsTheBluetoothprofiles.TheBluetoothProtocolStackThe802.15versionoftheBluetoothprotocolarchitecture.TheBluetoothFrameStructureAtypicalBluetoothdataframe.DataLinkLayerSwitching•Bridgesfrom802.xto802.y•LocalInternetworking•SpanningTreeBridges•RemoteBridges•Repeaters,Hubs,Bridges,Switches,Routers,Gateways•VirtualLANsDataLinkLayerSwitchingMultipleLANsconnectedbyabackbonetohandleatotalloadhigherthanthecapacityofasingleLAN.Bridgesfrom802.xto802.yOperationofaLANbridgefrom802.11to802.3.Bridgesfrom802.xto802.y(2)TheIEEE802frameformats.Thedrawingisnottoscale.LocalInternetworkingAconfigurationwithfourLANsandtwobridges.SpanningTreeBridgesTwoparalleltransparentbridges.SpanningTreeBridges(2)(a)InterconnectedLANs.(b)AspanningtreecoveringtheLANs.Thedottedlinesarenotpartofthespanningtree.RemoteBridgesRemotebridgescanbeusedtointerconnectdistantLANs.Repeaters,Hubs,Bridges,Switches,RoutersandGateways(a)Whichdeviceisinwhichlayer.(b)Frames,packets,andheaders.Repeaters,Hubs,Bridges,Switches,RoutersandGateways(2)(a)Ahub.(b)Abridge.(c)aswitch.VirtualLANsAbuildingwithcentralizedwiringusinghubsandaswitch.VirtualLANs(2)(a)FourphysicalLANsorganizedintotwoVLANs,grayandwhite,bytwobridges.(b)Thesame15machinesorganizedintotwoVLANsbyswitches.TheI