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ID:48732639
大小:196.00 KB
页数:28页
时间:2020-01-20
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1、RivierCollegeCS575:AdvancedLANsATMAdaptationLayerCS5751ATMAdaptationLayerATMAdaptationLayerFunctionsTheATMAdaptationLayer(AAL)isdesignedtosupportdifferenttypesofapplicationsanddifferenttypesoftraffic,suchasvoice,video,imagery,anddataItsbasicfunctionistheenhancedadapta
2、tionofservicesprovidedbytheATMlayertotherequirementsofthehigherlayerItmapshigherlayerPDUsintotheinformationfieldoftheATMcellAALisdividedintotheConvergenceSublayer(CS)andtheSegmentationandReassembly(SAR)SublayerTheConvergenceSublayerisservicedependentandprovidestheAALse
3、rvicesattheAAL-SAPThefunctionsoftheSARsublayeraresegmentationofhigherlayerPDUsintoasuitablesizefortheinformationfieldoftheATMcell(48octets)atthetransmittingendandreassemblyoftheinformationfieldsintohigherlayerPDUsatthereceivingendCS5752ATMAdaptationLayerATMAdaptationSu
4、blayersConvergenceSublayer(CS):Handlinglost/misdeliveredcellsTimingrecoveryInterleavingSegmentationandReassemblySublayer(SAR):Splitframes/bitstreamintocellsfortransmissionReassembleframes/bitstreamforreceivingSupportmultipleprotocolsHigherLayersATMAdaptationLayer(AAL)C
5、onvergenceSublayer(CS)SegmentationandReassemblySublayer(SAR)ATMLayer(ATM)VirtualChannel(VC)VirtualPath(VP)PhysicalLayer(PL)TransmissionConvergenceSublayer(TC)PhysicalMediumSublayer(PM)CS5753ATMAdaptationLayerAALProtocolsandServiceClassesTominimizethenumberofAALprotocol
6、s,ITU-TproposedaserviceclassificationspecifictotheAALTheclassificationwasmadewithrespecttothefollowingparameters:TimingrelationshipbetweensenderandreceiverRelatedNotrelatedBitrateConstantbitrateVariablebitrateConnectionmodeConnection-orientedConnectionlessCS5754ATMAdap
7、tationLayerAALProtocolsandServiceClasses(Concluded)FourAALprotocolshavebeendefinedtosupportfourAALserviceclassesAALserviceclassesClassAClassBClassCClassDAALprotocolsAAL1AAL2AAL3/4AAL5CS5755ATMAdaptationLayerAALServicesConnectionlessDateTransferBitRateConnectionModeExam
8、plesofServicesCircuitEmulationConstantBitRateVideoandAudioConstantVariableConnectionOrientedConnectionlessVariableBit
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