了解流量监管整形

TrafficPolicingandShapingUnderstandingTrafficPolicingandShapingTrafficPolicingandShapingOverviewThesemechanismsmustclassifypacketsbeforepolicingorshapingthetrafficrate.Trafficshapingqueuesexcesspacketstostaywithinthedesiredtrafficrate.Trafficpolicingtypicallydropsormarksexcesstraffictostaywithinatrafficratelimit.TrafficPolicingExampleRate-limitfile-sharingapplicationtrafficto56kbps.Donotrate-limittrafficfrommission-criticalserver.TrafficShapingExampleBothsituationsresultinbufferingandindelayedordroppedpacketsCentraltoremotesitespeedmismatchRemotetocentralsiteoversubscriptionPolicingvs.ShapingingandoutgoingdirectionsOut-of-profilepacketsaredroppedDroppingcausesTCPretransmitsSupportspacketmarkingor

re-markingLessbufferusage(shapingrequiresanadditionalshapingqueuingsystem)OutgoingdirectiononlyOut-of-profilepacketsarequeueduntilabuffergetsfullBufferingminimizesTCPretransmitsMarkingorre-markingnotsupportedShapingsupportsinteractionwithFrameRelaycongestionindicationSingleTokenBucketIfsufficienttokensareavailable(conformaction):Tokensequivalenttothepacketsizeareremovedfromthebucket.Thepacketistransmitted.SingleTokenBucket(Cont.)IfsufficienttokensareNOTavailable(exceedaction):Drop(ormark)thepacketSingleTokenBucketClass-BasedPolicingBcisnormalburstsizeTcisthetimeintervalCIRisthecommittedinformationrateCIR=Bc/Tc

police的token注入方法是：每当police一个数据包，就注入tokenEverytimeapacketispoliced,CBpolicingputs

sometokensbackintotheBucket.Thenumberoftokensplacedinto

注入数量如下：(Current_packet_arrival_time–Previous_packet_arrival_time)*Police_rate/8DualTokenBucket(SingleRate)

Class-BasedPolicingBe:ExcessburstsizeTc:TokensinBcbucketTe:TokensinBebucketThereturnvalueisconformorexceedorviolateDual-RateClass-BasedPolicingTc:TokensinCIRbucketTp:TokensinPIRbucketEnforcetrafficpolicingaccordingtotwoseparaterates:CommittedInformationRatePeakInformationRateDual-RateClass-Based

Policing(Cont.)Two-ratepolicermarkspacketsaseitherconforming,exceeding,orviolatingaspecifiedrate.If(B>Tp),thepacketismarkedasviolatingthespecifiedrate都不减少token数量If(Tp>B>Tc),thepacketismarkedasexceedingthespecifiedrate,andtheTptokenbucketisupdatedas

Tp=Tp–B此时有个问题，下次再来一个数据包，可能Tp<Tc；Ifthepacketismarkedasconformingtothespecifiedrate,andbothtokenbuckets(TcandTp)areupdatedasTp=Tp–BandTc=Tc–B.同时减少token的数量单速率配置方法：以下4个配置命令含义一样police8000010001000policecir8000010001000policecir80000bc1000be1000policerate80000bpsburst1000bytespeak-burst1000bytes双速率配置方法：policy-mapyeslab7classp1policecir8000bc1500pir10000be5000conform-actiontransmitexceed-actionset-prec-transmit1violate-actionset-prec-transmit1

r2#showpolicy-mapinterfaces2/0Serial2/0Service-policyoutput:yeslab7Class-map:p1(match-all)15packets,1052bytes5minuteofferedrate0bps,droprate0bpsMatch:anypolice:

cir8000bps,bc1500bytespir10000bps,be5000bytesconformed1packets,48bytes;actions:transmitexceeded0packets,0bytes;actions:set-prec-transmit1violated0packets,0bytes;actions:set-prec-transmit1conformed0bps,exceed0bps,violate0bpsClass-BasedTrafficShaping每隔Tc，往桶里注入Bc个token，是一次性注入，不是匀速注入。然后shapergateopen，什么时候关闭呢？在桶里没有token的时候就关闭了，然后在下一个Tc开始的时候在打开并一次性注入Bc个token1.发送单个数据包的速率等于link的物理层速率2.通过减少发送时间来降低速率如上图：link速率128K，限制到64k，就只能用一半的时间用来发送数据流，设置TC的值为125ms，因此每次发送数据包的时间就为62.5ms，Bc＝62.5ms*128Kbps＝8000bit填充token的方法：每125ms的开始就填充Bc个tokenWhenconfiguringshaping,youtypicallyconfiguretheshapingrateandoptionallytheBc（典型假设TC为4ms）.Ifyouconfigurebothvalues,IOSchangestheTcsothattheformulaismet配置举例：shapeaveragepercent10

125ms红色为CIR的值，用带宽比例表示紫色为TC的值，单位为ms自动计算出的BC值为：19300Service-policyoutput:yeslabClass-map:p1(match-all)138packets,37338bytes5minuteofferedrate0bps,droprate0bpsMatch:anyQueueingqueuelimit64packets(queuedepth/totaldrops/no-bufferdrops)0/0/0(pktsoutput/bytesoutput)0/0shape(average)cir154400,bc19300,be19300targetshaperate154400无Beshaping配置——1配置举例：shapeaverage1000000

12000红色表示CIR紫色表示BCTC值将会自动计算：12000/1000000＝120msService-policyoutput:yeslabClass-map:p1(match-all)298packets,113530bytes5minuteofferedrate0bps,droprate0bpsMatch:anyQueueingqueuelimit64packets(queuedepth/totaldrops/no-bufferdrops)0/0/0(pktsoutput/bytesoutput)160/76614shape(average)cir1000000,bc12000,be12000targetshaperate1000000无Beshaping配置——2对shaping的单桶单速率无BE，桶的大小为BC，如果一个数据包来，token够用，转发，同时减少token相应的数量；如果一个数据包来，token不够，等下一个tc的注入的token。从宏观效果来看，总体速率保持为CIR对shaping的单桶单速率有BE，桶的大小为BE+BC。该类型的shaping增加了对bursty流量的容忍能力，但是从宏观效果来看，总体速率还是保持为CIR有Beshaping配置policy-mapyeslab8classp1shapeaverage1000000120006000r2#showpolicy-mapinters2/0Serial2/0Service-policyoutput:yeslab8Class-map:p1(match-all)38packets,2527bytes5minuteofferedrate0bps,droprate0bpsMatch:anyQueueingqueuelimit64packets(queuedepth/totaldrops/no-bufferdrops)0/0/0(pktsoutput/bytesoutput)38/2588shape(average)cir1000000,bc12000,be6000targetshaperate1000000用peak配置速率policy-mapyeslab8classp1shapepeak1000000120006000However,usingpeakrateshaping,thetrafficsentabovetheCIR(thedelta)couldbedroppedifthenetworkescongested.Ifyournetworkhasadditionalbandwidthavailable(overtheprovisionedCIR)andtheapplicationorclasscantolerateoccasionalpacketloss,thatextrabandwidthcanbeexploitedthroughtheuseofpeakrateshaping.However,theremaybeoccasionalpacketdropswhennetworkcongestionoccurs.IfthetrafficbeingsenttothenetworkmuststrictlyconformtotheconfigurednetworkprovisionedCIR,thenyoushoulduseaveragetrafficshaping.对peakrate的说明CiscoIOSTraffic-PolicingMechanismsCiscoIOSTraffic-ShapingMechanismsApplyingRateLimitingSummaryTrafficshapingandpolicingaremechanismsthatuseclassificationtolimittrafficrate.Trafficshapingqueuesexcesspacketstostaywithinthecontractualrate.Trafficpolicingtypicallydropsexcesstraffictostaywithinthelimit;alternatively,itcanre-mark,thensendexcesstraffic.Bothtrafficpolicingandshapingensurethattrafficdoesnotexceedabandwidthlimit,buttheyhavedifferentimpactsonthetraffic.Trafficrateismeteredusingatokenbucketmathematicalmodel.Withtrafficpolici