~~~~ethernet 基础

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1、BobMetcalfe‘s“Ethernet“Fig.1AdrawingofthefirstEthernetsystem-fromBobMetcalfe(,3)Ethernet-FramestructurePreamble前导码SFD帧起始定界符Destination目的地址Source源地址Typefield类型DataField数据FCS帧校验序列7Byte1Byte6Byte6Byte2ByteVariableLength64ByteFrameSize<1518Byte1519ByteJumboFrame<9018Byte4ByteFig.2EthernetFrameStru

2、cture(,7)Ethernet-MAC-Address6Octets12hex.digits48bits123456ManufacturerEquipment123456789101112Fig.3EthernetMACAddress(,7)TrafficControl(Policing&Shaping)EthernetPriorization(IEEE802.1p,etc.)VirtualLAN(IEEE802.1Q)SpanningTreeProtocol(IEEE802.1D)EthernetRingProtection(ERP)LinkAggregationGroup(IE

3、EE802.3ad)EthernetFirstMile(IEEE802.3ah)Multicast(IGMP)RoutingProtocolsAdditionalFeatures(JumboFrameSupport,MAC-AddressTranslation,DHCPRelayAgent,…)MultiProtocolLabelSwitching-MPLSTechnologiesusedinCarrierEthernetFig.4ProtocolsandTechnologies(,9)IPMultiserviceNetworkE-mailServersMainframePCPCTe

4、lephonePBXCoSisdescribingasetoffeaturesandothercharacteristicsavailablewithaspecificserviceorservicepackageBestEffortStandardPremiumClassofServiceWhatisClassofService(CoS)?Fig.5WhatisCOS-ClassofService?(,11)Real-TimeFlowRouterRouterWorkgroupSwitchRemoteSwitchDataServerVoIPServerVoIPServerDataSer

5、verIPMultiserviceNetworkQoSisamorepreciseterm,usedtomeasureaspecifiedsetofperformanceattributestypicallyassociatedwithaservice.IPQoSreferstotheperformanceofIPpacketsflowingthroughoneormorenetworks.Non-Real-TimeFlowNon-real-timeserviceflowsmaynotrequirespecifiedthroughput,delay,delayvariation,pac

6、ketlossandavailabilityparametersReal-timeserviceflowsrequirespecifiedthroughput,delay,delayvariation,packetlossandavailabilityparametersWhatisQualityofService(QoS)?Fig.6:WhatisQoS-QualityofService?(,11)BasicConceptstohandleUserTrafficPacketIncomingTrafficPacketPacketForwardedTrafficPacketFilte

7、ringPacketQueuingPacketFragmentingPacketForwardingPacketDroppingFig.7:BasicConceptstohandleUserTraffic(,13)PrecedencePriorityQueuePriorityPacketDroppingIncomingTrafficForwardedTrafficPacketPacketPackethighlowmiddlePacketPa