单项选择题
A. Layer 2
B. Layer 3
C. Layer 4
D. out-of-band
单项选择题 ToensurevoicepacketsarekeptwithintheCommittedInformationRate（CIR）ofaFrameRelaylink，whatshouldbeusedintheCPE？（）
单项选择题 WhichQoSrequirementappliestostreamingvideotraffic？（）
单项选择题 TheCiscoMDS9000SeriesMultilayerSANSwitchescanhelplowerthetotalcostofownershipofthemostdemandingstorageenvironments.Bycombiningarobustandflexiblehardwarearchitecturewithmultiplelayersofnetworkandstorage-managementintelligence，theCiscoMDS 9000Serieshelpsyoubuildhighlyavailable，scalablestoragenetworkswithadvancedsecurityandunifiedmanagement.WhatmethoddoestheCiscoMDS9000Seriesusetosupporttrunking？（）