CCIP-v2 2 pptQOS22S06L03

CongestionAvoidance,ConfiguringClass-BasedWeightedRED,WREDcanusemultipledifferentREDprofiles.Eachprofileisidentifiedby:MinimumthresholdMaximumthresholdMaximumdropprobabilityWREDprofileselectionisbasedon:IPprecedence(8profiles)DSCP(64profiles)WREDdropslessimportantpacketsmoreaggressivelythanmoreimportantpackets.WREDcanbeappliedattheinterface,VC,orclasslevel.,WeightedRandomEarlyDetection,Class-BasedWRED,Class-basedWREDisavailablewhenconfiguredincombinationwithCBWFQonly.Class-basedconfigurationofWREDisidenticaltostandaloneWRED.,WREDBuildingBlocks,WREDProfiles,WREDprofilescanbemanuallyset.WREDhas8defaultvaluesetsforprecedence-basedWRED.WREDhas64defaultvaluesetsforDSCP-basedWRED.,IPPrecedenceandClassSelectorProfiles,DSCP-BasedWRED(ExpeditedForwarding),DSCP-BasedWRED(AssuredForwarding),ConfiguringCB-WRED,class-mapmatch-any|match-allclass-name,router(config)#,policy-mappolicy-name,router(config)#,service-policyinput|outputpolicy-map-name,router(config-if)#,Createclassmap:Usedformatchingpacketstoaspecifiedclass,Createpolicymap(servicepolicy):Specifiesatrafficpolicythatcanbeattachedtooneormoreinterfaces,Attachservicepolicy:AssociatesthepolicymaptoanoutputinterfaceorVC,ConfiguringCB-WRED(Cont.),random-detect,router(config-pmap-c)#,EnablesIPprecedence-basedWREDintheselectedclasswithintheservicepolicyconfigurationmode.Defaultserviceprofileisused.Commandcanbeusedattheinterface,per-VC(withrandom-detect-group),ortheclasslevel(service-policy).Precedence-basedWREDisthedefaultmode.WREDtreatsnon-IPtrafficasprecedence0.,ChangingtheWREDTrafficProfile,random-detectprecedenceprecedencemin-thresholdmax-thresholdmark-prob-denominator,ChangesWREDprofileforspecifiedIPprecedencevalue.Packetdropprobabilityatmaximumthresholdis:1/mark-prob-denominatorNon-weightedREDisachievedbyusingthesameWREDprofileforallprecedencevalues.,router(config-pmap-c)#,WREDtakestheaveragequeuesizetodeterminethecurrentWREDmode(nodrop,randomdrop,fulldrop).HighvaluesofNallowshortbursts.LowvaluesofNmakeWREDmoreburst-sensitive.Defaultvalue(9)shouldbeusedinmostscenarios.AverageoutputqueuesizewithN=9isQave(t+1)=Qave(t)*0.998+Qt*0.002,ChangingWREDSensitivitytoBursts,random-detectexponential-weighting-constantn,router(config-pmap-c)#,Example:CBWFQUsingIPPrecedencewithCB-WRED,EnableCBWFQtoprioritizetrafficaccordingtotheserequirements:Classmission-criticalismarkedwithIPprecedencevalues3and4(3ishigh-drop,4islow-drop)andshouldget30%ofinterfacebandwidth.ClassbulkismarkedwithIPprecedencevalues1and2(1ishigh-drop,2islow-drop)andshouldget20%ofinterfacebandwidth.Allothertrafficshouldbeper-flowfair-queued.UsedifferentiatedWREDtopreventcongestioninallthreeclasses.,Example:CBWFQUsingIPPrecedencewithCB-WRED,ConfiguringDSCP-BasedCB-WRED,random-detectdscp-based,EnablesDSCP-basedWRED.Commandcanbeusedattheinterface,per-VC(withrandom-detect-group),ortheclasslevel(service-policy).Defaultserviceprofileisused.TheWREDrandom-detectcommandandtheWFQqueue-limitcommandaremutuallyexclusiveforclasspolicy.,router(config-pmap-c)#,ChangingtheWREDTrafficProfile,random-detectdscpdscpvaluemin-thresholdmax-thresholdmark-prob-denominator,router(config-pmap-c)#,ChangesWREDprofileforspecifiedDSCPvaluePacketdropprobabilityatmaximumthresholdis:1/mark-prob-denominator,Example:CB-WREDUsingDSCPwithCBWFQ,EnableCBWFQtoprioritizetrafficaccordingtotheserequirements:Classmission-criticalismarkedusingDSCPAF2andshouldget30%ofinterfacebandwidth.ClassbulkismarkedusingDSCPAF1andshouldget20%ofinterfacebandwidth.Allothertrafficshouldbeper-flowfair-queued.UsedifferentiatedWREDtopreventcongestioninallthreeclasses.Makesurethenewconfigurationsstillconformtothedesignandimplementationfromthepreviousexample.,Example:CB-WREDUsingDSCPwithCBWFQ(Cont.),MonitoringCB-WRED,showpolicy-mapinterfaceinterface-name,router#,Displaystheconfigurationofallclassesconfiguredforallservicepoliciesonthespecifiedinterface,router#showpolicy-mapinterfaceEthernet0/0Ethernet0/0Service-policyoutput:Policy1Class-map:Mission-critical(match-all)0packets,0bytes5minuteofferedrate0bps,droprate0bpsMatch:ipprecedence2Match:ipdscp182022WeightedFairQueueingOutputQueue:Conversation265Bandwidth30(%)Bandwidth3000(kbps)(pktsmatched/bytesmatched)0/0(depth/totaldrops/no-bufferdrops)0/0/0exponentialweight:9meanqueuedepth:0DscpTransmittedRandomdropTaildropMinimumMaximumMark(Prec)pkts/bytespkts/bytespkts/bytesthresholdthresholdprobability0(0)0/00/00/020401/1010/00/00/022401/1020/00/00/024401/10.,Summary,WREDcombinesREDwithIPprecedenceorDSCPandperformspacketdroppingbasedonIPprecedenceorDSCPmarkings.EachWREDprofiledefinestheminimumandmaximumthresholdandthemaximumdropprobability.ProfilesarealreadydefinedbydefaultforIPprecedenceandDSCP.Therandom-detectcommandisusedtoenableWREDonaninterface.Therandom-detectdscp-basedcom