资源描述：
《e-计算机网络基础1-L2+MAC课件.ppt》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。
1、OSILayeredProtocolStackApplicationSocketAPI,RPC/XDR,client/servermodelTransportLayer：End2Endreliablestreamcomm.TCP、UDPDataLink：interface2interfaceoverthesamelinkErrorCorrection、MACprot.stackNetworkLayer：unreliablehost2hostpacketswitchIP、ICMP、ARP、routediscovery(RIP，OSPF、BGP）tcp_out
2、puttcp_inputip_outputip_inputnic_intputnic_outputWhatdoesData-linkdo?Bitstransmissionbetweeninterfacesoverasinglelink.Todothis,wehavetodealwith:Addressing:MACAddressInformationFormatting:FrameErrorcorrecting/detectingFlowAdjustingMediaAccessControlE.g.,CSMA/CD、FDDI、802.11and802.15
3、Pre-notice:What’sthedifferencebetweenIPaddress?MACAddress:Uniqueglobally,identifyingNICL2.InformationUnit(FrameFormat)Example:EithernetframeSync.Dest.MACSrc.MACTypePayloadCRC(8B)(6B)(6B)(2B)(46-1500B)(4B)IPHeaderIPPayload(i.e.,data)ContentsCarriedbyframe,e.g.,IPpacketTCPheaderTCPp
4、ayload(e.g.,HTTP/HTMLstream)ContentscarriedbyanIPpacket,e.g.,TCPsegmentDataTransmissionMechanisminL2Datacoding:(1)datacompression(sourcecoding)notions:lossless、lossy、compressionratio(2)errorcorrection(channelencoding/decoding)blockcoding、convolutioncoding、redundanvyMeasurementfort
5、ransmissionspeed(传输速度的度量):(带宽/位速率)bit-per-secondModulation/Demodulation(调制/解调)：Mappingdigitalsignalsto(optimal)waveforms(将数字信号映射为特定的物理波形)ModemSpeed：Howmanybitscanbecarriedbyeachwave/pulse?（bits-per-second)LogicStructureforDigitalComm.Sys.Src.Encod.Chan.Encod.Mod.MediaSrc.Dec.Chan.
6、Dec.Dem.NoiseSignalTransmitterReceiverReal-worldexamples：wiredcomm.、wirelesscomm.、magneticstoragesys.MeadiaAccessControl(1)MACNotion：Howtocoordinate(time,bandwidth)resourceconflictsonthe(physically)sharedmedia?KeyPoint:Howtoresolveorevencompletelyavoidconflicts?A.ResourcePre-alloc
7、ationApproach:FDMA，TDMA，CDMA,noconflicts!Suitableforstableandcontiguouslyhighvolumetraffic,e.g.,Voice.B.RandomAccessApproach:ALOHA/slotted-ALOHA，CSMA/CD，CSMA/CA及RTS/CTS协议Suitableforstochasticandbursttraffic，e.g.,datacomm.MACMechanism(2)MACMechanism(3)MACMechanism(4)MACMechanism(5：
8、CSMA/CD)Foreveryinterface：1）Liste
