了解流量監(jiān)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：每當(dāng)police一個(gè)數(shù)據(jù)包，就注入tokenEverytimeapacketispoliced,CBpolicingputs

sometokensbackintotheBucket.Thenumberoftokensplacedinto

注入數(shù)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都不減少token數(shù)量If(Tp>B>Tc),thepacketismarkedasexceedingthespecifiedrate,andtheTptokenbucketisupdatedas

Tp=Tp–B此時(shí)有個(gè)問(wèn)題，下次再來(lái)一個(gè)數(shù)據(jù)包，可能Tp<Tc；Ifthepacketismarkedasconformingtothespecifiedrate,andbothtokenbuckets(TcandTp)areupdatedasTp=Tp–BandTc=Tc–B.同時(shí)減少token的數(shù)量單速率配置方法：以下4個(gè)配置命令含義一樣police8000010001000policecir8000010001000policecir80000bc1000be1000policerate80000bpsburst1000bytespeak-burst1000bytes雙速率配置方法：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個(gè)token，是一次性注入，不是勻速注入。然后shapergateopen，什么時(shí)候關(guān)閉呢？在桶里沒(méi)有token的時(shí)候就關(guān)閉了，然后在下一個(gè)Tc開(kāi)始的時(shí)候在打開(kāi)并一次性注入Bc個(gè)token1.發(fā)送單個(gè)數(shù)據(jù)包的速率等于link的物理層速率2.通過(guò)減少發(fā)送時(shí)間來(lái)降低速率如上圖：link速率128K，限制到64k，就只能用一半的時(shí)間用來(lái)發(fā)送數(shù)據(jù)流，設(shè)置TC的值為125ms，因此每次發(fā)送數(shù)據(jù)包的時(shí)間就為62.5ms，Bc＝62.5ms*128Kbps＝8000bit填充token的方法：每125ms的開(kāi)始就填充Bc個(gè)tokenWhenconfiguringshaping,youtypicallyconfiguretheshapingrateandoptionallytheBc（典型假設(shè)TC為4ms）.Ifyouconfigurebothvalues,IOSchangestheTcsothattheformulaismet配置舉例：shapeaveragepercent10

125ms紅色為CIR的值，用帶寬比例表示紫色為TC的值，單位為ms自動(dòng)計(jì)算出的BC值為：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無(wú)Beshaping配置——1配置舉例：shapeaverage1000000

12000紅色表示CIR紫色表示BCTC值將會(huì)自動(dòng)計(jì)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無(wú)Beshaping配置——2對(duì)shaping的單桶單速率無(wú)BE，桶的大小為BC，如果一個(gè)數(shù)據(jù)包來(lái)，token夠用，轉(zhuǎn)發(fā)，同時(shí)減少token相應(yīng)的數(shù)量；如果一個(gè)數(shù)據(jù)包來(lái)，token不夠，等下一個(gè)tc的注入的token。從宏觀效果來(lái)看，總體速率保持為CIR對(duì)shaping的單桶單速率有BE，桶的大小為BE+BC。該類型的shaping增加了對(duì)bursty流量的容忍能力，但是從宏觀效果來(lái)看，總體速率還是保持為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.對(duì)peakrate的說(shuō)明CiscoIOSTraffic-PolicingMechanismsCiscoIOSTraffic-ShapingMechanismsApplyingRateLimitingSummaryTrafficshapingandpolicingaremechanismsthatuseclassificationtolimittrafficrate.Trafficshapingqueuesexcesspacketstostaywithinthecontractualrate.Trafficpolicingtypicallydropsexcesstraffictostaywithinthelimit;alternatively,itcanre-mark,thensendexcesstraffic.Bothtrafficpolicingandshapingensurethattrafficdoesnotexceedabandwidthlimit,buttheyhavedifferentimpactsonthetraffic.Trafficrateismeteredusingatokenbucketmathematicalmodel.Withtrafficpolici