DeployingHighPerformanceWi-FiandOptimizingYourEntireNetwork

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ExecutiveSummaryWi-Finetworksarethemostvolatilebecausethey’resubjecttoexternalfactorsthatarethemostdifficulttocontrol.RFinterference,fading,orchannelaccessconflictdrivenbyasuddenincreaseinuserscaninducejitterthatcausesthroughputandperformancetocollapse.This“last-mile”Wi-Finetworkjitteriscompoundedbytoday’sstreamingfastdata,voice,videoandIoTapplicationsthattransmithugevolumesofdatainunpredictablebursts,aswellasvirtualizationjitterfromthecloudenvironmentsthatoftenhostthem.Asaresult,jitterhasnowbecometheleadingcauseofnetworkthroughputcollapse.JitteronanysegmentofthepathfromtheapplicationservertotheWi-FiAP(accesspoint/router),andfinallytotheuser’sWi-Ficonnecteddevice,cantriggerathroughputreductionacrosstheentirepath.Therefore,it’samistaketothinkofthewiredandwirelesssegmentsasseparate.Theyareultimatelypartofthesamenetwork,andadjustmentstobothareoftenrequired.OnthewiredsegmentofthepathfromtheapplicationservertotheAP,mostnetworkadministratorstrytoaddresspoorthroughputbyupgradingbandwidthand/orimplementingoptimizationsolutionsthatrelyoncompression,cachinganddeduplicationdesignedtoacceleratetrafficbyreducingitsvolume.Theycombinethiswithfaster,highercapacityAPsinWi-Finetworkstoprovidebetterperformanceformoremobiledevicesinthesameservicearea.However,theseapproachesdon’tworkwellfordatathat’sencryptedoralreadycompressed,andtheycan’teffectivelyaddressjitter.Infact,theyoftenintroduceadditionalperformanceoverheadandcausetheincidenceofjitter-inducedthroughputcollapsetoincrease,eveninthemostwellarchitectednetworks.Tounderstandthereasonsforthisandhowtoaddressit,it’simportanttofirstunderstandthebasicsofTCPdatatransfer.

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TCPOverviewWhenTCPacceptsastreamofdatafromaserver,itbreaksitintoaseriesofsequencedpacketsthatarereassembledinthesameorderbythereceivingclientapplication.WhenTCPwasdesignedover40yearsago,thefocuswasonguaranteeingorderlypacketdeliverybetweenendpoints.Basedonthenatureofapplicationsdeployedatthetime,theunderlyingassumptionwasthatnetworkpacketswouldarriveinrelativelyconsistenttimeintervalsunlessthenetworkbecamecongestedduetotoomuchtraffic,orsomehardwarefailureinthepath.Toguaranteepacketdeliveryandguardagainstdataloss,TCPreliesontwovariablestomeasurecongestionandcontrolthroughput:aRetransmissionTimeout(RTO)valuebasedonamovingaveragecalculationoftheRound-TripTime(RTT)foreachpackettobesentandanacknowledgement(ACK)tobereceived,andaCongestionWindow(CWND)thatdefinesthemaximumamountofdatathatcanbesentthroughaconnection.TCPsetsitsretransmissiontimertotheRTOvalueasit’ssendingeachpacket.IfanACKisn’treceivedbeforetheretransmissiontimerexpires,theunacknowledgedpacketisretransmitted,asTCPflagsthepacketasdropped.WitheachretransmissionattempttheRTOvalueisincreased,andCWNDisreducedontheassumptionthenetworkhasbecomecongested,leadingtoadecreaseinthroughputtoavoiddataloss.AfterthreeRTOsthroughputishalved.AftersevenRTOsthroughputcollapsesbecauseTCPtreatsthepacketsaslostratherthanmerelydelayed,andpreventstrafficfrombeingsent.Afterasub-secondwaitingperiod,TCPbeginsitsrecoveryprocessbyincrementallyincreasingCWNDwitheachsuccessfulpackettransmissionbacktoitspre-RTO,orpre-collapselevel.ThismeansTCP’srecoveryprocesseffectivelydoublestheimpactofRTOs,bydoublingtheamountoftimeavailablebandwidthisunderutilized,andthroughputandperformancearesuboptimal.

ContrarytoTCP’soriginaldesignassumptionsoforderlypacketdeliveryinrelativelyconsistenttimeintervals,today’sstreamingapplicationsgeneratenetworktrafficcharacterizedbyperiodicburstsofdatathatcausesignificantvariationinRTT.ThisRTTvariance,orjitterfrequentlytriggersspuriousRTOs,causingTCPtoreactasifthenetworkiscongested,reducingthroughputbyreducingCWNDtopreventdatalosseventhoughplentyofbandwidthisavailable.Therapidadoptionofcloudservicesand“last-mile”mobileandWi-Finetworksaddjitteroftheirowntotoday’snetworkenvironments.

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Wi-FiJitterTriggersThroughputCollapseOvertheEntireNetworkPathAllWirelessnetworksoperateatthePhysicalandDataLinklayers-layersoneandtwooftheOpenSystemsIntercommunication(OSI)seven-layermodelthatdefinesfunctionalityfornetworkcommunications.Wi-Fisystemsusetheselayerstoformatandcontrolthedatatoconformwith802.11wirelessnetworkcommunicationstandards.Wi-FilayeronephysicalbandwidthissetbytheDynamicRateSwitching(DRS)algorithmrunningontheuser’slaptop,tablet,ormobilephonebasedontheradiofrequency(RF)signaltonoiseratiosdetectedbytheuser’smobiledevice.DRSadjuststhemobiledevice’sdatatransferratetoreduceretransmissionsinresponsetoRFinterference,whichtypicallyincreaseswithdistancefromanAP.IfthedatatransferrateremainshighwhenthereissignificantRFinterference,itwillresultinsomanyretransmissionsandcorrespondingRTOsthatthroughputandperformancedeclinedramatically.Wi-FilayertwochannelaccesstimevariesdependingonthenumberofmobiledeviceWi-FitransmittersaccessinganAP,andthetrafficpatternsgeneratedbyapplicationsrunningonthosedevices.ThemoreWi-Fitransmitterslocatedneareachother,thegreaterthelikelihoodofchannelaccessconflict,asnumerousdevicestrytoaccessthesamechannelsimultaneouslyforuploadsordownloads.That’swhyit’snotuncommonforthroughputtosuddenlycollapseatsportsarenas,conferencecentersandotherpublicvenueswhenthenumberofusersgoesfromzerotothousandsinamatterofminutes,overwhelmingtheavailableWi-Fiinfrastructure.TheserverconnectedtothewiredsegmentofthepathwillalsodropitstransmissionrateinreactiontoRTOstriggeredbyRFinterferenceand/orchannelaccessconflictontheWi-Filasthoptoavoidpacketloss,eventhoughplentyofbandwidthisavailableacrossallsegmentsoftheend-to-endpath.CompoundingtheseissuesisthefactthatmaximumRTOimpactoccursonshortdistancenetworks.Inbusyhigh-speedmobileandWi-FinetworkswithshortRTTsandhighjitter,theimpactofRTOsmisinterpretedascongestioncanbedevastating,causinguptoaten-foldreductioninthroughputovertheentirenetworkpathbacktotheserver.TCP’sresponsetojitterbecomesthebottleneckovertheentirenetworkpathfromthesendingservertransmittingdataoverthewiredsegmenttothewirelesslastmile,preventingfulluseofavailablebandwidthanddeliveringapooruserexperience.

StandardApproachesFallShortMostnetworkadministratorstrytoaddresspoorthroughputbyupgradingbandwidthandimplementingoptimizationsolutionsonthewiredportionofthepathleadingtotheAP,combinedwithincreasingWi-Finetworkbandwidthbyintroducingadditionalhighcapacity,highspeedAPstoprovidebetterperformanceformoremobiledevicesinthesameservicearea.

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Overthewiredportion,networkoptimizationsolutionsincludededuplication,compression,andlocalcachingtoreducebandwidthusage,withtrafficshapingtoprioritizeselectedapplications.Whilethesetechniquescanyieldsomebenefits,noneofthemtacklejitter-inducedthroughputcollapse.Inaddition,techniquessuchasdeduplicationandcompressioncan’tacceleratetrafficthat’salreadycompressed,andtheyrequireaccesstothepayload.Withthemassrolloutofend-to-endencryption,thisneedforpayloadaccessintroducestheaddedperformanceoverheadofencryption/decryptionateachendpoint,aswellastheriskofexposingsensitivesecuritykeystothird-partyvendorsolutions.Wi-FinetworkbandwidthcanbeupgradedbydeployingfasterAPsthatsupport5Ghzsignals,offeringupto8xmorechannelsthanpreviousgeneration2.4GhzAPs.However,it’susuallynotpossibletotakeadvantageofallthisaddedbandwidth.Ifchannelsaren’tappropriatelyspaced,deploying5Ghzwillleadtoadjacentchannelinterference(ACI),anothersourceofWi-Fijitterthatleadstopoorthroughput.Inaddition,5GhzWi-Fisignalsaremuchshorterrange,resultinginmorefading,andhaveahardertimepenetratingwallsandotherobstacles.Finally,notalldevicessupport5Ghz.MoreAPscanbeaddedtoaWi-FinetworktoreduceRFinterference,whichalongwithfadingtendstoincreasewithdistancefromanAP,causingpacketlossandretransmissions.However,sinceAPs,liketheend-userdevicesthatconnecttothemarealsoWi-Fitransmitters,addingmoreAPsoftenleadstogreaterRFinterferenceintheformofco-channelinterference(CCI)orcrosstalkthatbecomesanothersourceofjitter.CCIoccurswhenAPsinterferewitheachotherbyusingthesamechannelorradiofrequencytotransmitandreceiveWi-Fisignals.It’svirtuallyunavoidabledespitethebesteffortsofnetworkarchitectstospaceAPsappropriatelyapart,eveninlargepublicWi-Finetworks.

TacklingJitterHead-onToproperlyaddressjitter,thefirststepmustbetodeterminewhethercongestionisreal,orTCPisreducingthroughputinreactiontojittermisinterpretedascongestionfromapplicationsthatgeneratetrafficininconsistentbursts,and/orjitterfromcommonWi-FinetworkissuessuchasRFinterference,fadingandchannelaccessconflict.Ineffect,TCPisoftenthebottleneck. BaduNetworks’patentedWarpTCP™technologyofferstheonlysolutionfocusedsquarelyonthisTCPbottleneckissueforbothwiredandwirelessnetworks.WarpTCPanalyzestrafficinreal-timetodetermineifcongestionexists,andpreventsTCPfromunnecessarilyreducingthroughputinresponsetospuriousRTOsduetojitter.WarpTCP‘sproprietaryalgorithmsdetermineactualbandwidthavailabletoaTCPsessioninreal-time,sotheimpactoftransientfluctuationsinRTTandpacketlossarefilteredout.WarpTCPwasspecificallydesignedtodealwithrapidlychangingbandwidth,losspatterns,serverloads,andRTTvariance,enablingittodowellinvolatileenvironmentslikemobileandWi-Finetworks.WarpTCPimprovesboth

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downloadanduploadthroughputbyasmuchas10xinwirelessenvironments,evenwhentheclientisfarfromtheAP,andtheWi-FiconnectionissubjecttogreaterRFinterferenceandchannelaccessconflict.

WarpTCP’salgorithmicapproachtooptimizationoffersanotherkeyadvantagenowthatover80%ofinternettrafficisencryptedorcompressed:sinceWarpTCPdoesn’trelyoncompressionanddeduplicationthatrequireaccesstothepayload,iteliminatestheperformanceoverheadofencryption/decryptionateachendpoint,aswellastheadditionalsecurityriskofexposingencryptionkeys.Thismeansperformancestaysatconsistentlyhighlevelsforalltypesoftraffic:unencrypted,encrypted,orcompressed,eveninthefaceofextremefluctuations.

WarpTCP™ArchitectureWarpTCPconsistsoftwocomponentsthatworkhandinhandtopreventTCPthroughputcollapseandoptimizetheuseofallavailablebandwidthformaximumperformance:

• ATCPde-bottleneckmodulethatimplementsWarpTCP’sproprietaryalgorithmsthatdetermineifjitterisduetocongestionbasedonactualbandwidthavailabletoeachTCPsessioninrealtime,andpreventTCPfromreducingthesizeofthecongestionwindow(CWND)andhencethroughputifit’snot

• ATransparentTCPProxythatimplementsTCPsessionsplicingbysplittingtheconnectionbetweentheserverandtheclientintotwoindependentsessions.Eachsplicedserver-to-clientTCPsessionisreplacedbyaserver-to-proxysub-sessionandaproxy-to-clientsub-session.Thetwosub-sessionshaveindependentsequencenumbers,aswellasindependentACKflows.WarpTCPretainstheIPaddressesandportnumbersassociatedwiththeoriginalTCPsourceanddestinationtomapthemtothenewsub-sessions.

ThissessionindependenceenablesWarpTCPtoimplementitsownflowcontrolalgorithmsbasedonspeedmatchingthatarefarsuperiortoTCP’s.Withspeedmatching,theproxyreceivesasmanypacketsaspossible,asfastaspossible,buffersthemwithoutmodification,

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andthenforwardsthemtotheclientatdifferentspeedsandtimes.Speed-matchingenablesanotherperformanceenhancingfeature-opportunisticbursting.OpportunisticburstingallowsWarpTCPtofill-inunusedgapsinbandwidthwithpacketsthatwouldotherwisebestalled.Thesecapabilitiesareimplementedinamulti-core,multi-threadedarchitecturethatsupportsover5millionparallelTCPsessions,enablingusecasesthatarewellbeyondthereachofanythingelseonthemarket.

Finally,althoughWarpTCPistransparenttousers,itsarchitectureenablesdramaticimprovementinoneofthemostvisibleaspectsofuserexperience-pageloadtimes.BrowsersonlysupportestablishmentoftwotofourTCPsessionssimultaneously,whereasawebpagecaneasilyhaveover100objects,eachrequiringitsownTCPsessiontosendandreceivedata.SinceWarpTCPconnectionswiththebrowserareindependentoftheserverandcanbeestablishedinparallel,pagestypicallyload2-3xfaster.

DeploymentOptions

WarpTCPrequiresnochangestoclientsorservers,andcanbeinstalledatanysinglepointonthenetworkclosesttothesourceofjitter,unlikecompetingdual-endedoptimizationofferings.However,jitteronanysegmentofthenetworkpathfromanapplicationrunninginanon-premisesdatacenteroracloudenvironment,totheuser’sWi-Ficonnecteddevicecantriggerathroughputcollapse.Forthisreason,BaduofferssolutionsforbothwiredandwirelessnetworksthatleverageWarpTCP.Whendeployedincombination,theycomplementeachothertofilterouttheimpactofjitterovertheentirepathbetweentheoriginserverandtheend-user.Examplesoftypicaldeploymentscenariosarediscussedbelow.

Wi-FiDeploymentInWi-Finetworks,Badu’sWarpGateway™isinstalledbetweentheWANgatewaymodemconnectingthehomeorbusinesstotheinternetandtheWi-FIAP/Router.Onceinstalled,WarpGatewayfiltersouttheimpactofjittercausedbyfading,aswellasRF,crosschannelandadjacentchannelinterferencethatcanleadtothroughputcollapseovertheentirepath.

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5GFWADeploymentWhen5GFWA(FixedWirelessAccess)isimplemented,thedeploymentarchitectureisessentiallythesame,withthemobilenetworkoperator’sCPE(CustomerPremisesEquipment)whichconvertsthe5GsignalintoWi-Fitakingtheplaceofthegatewayasshownbelow.Ina5GFWAenvironment,WarpGatewaywillcontinuetofilterouttheimpactofjitteronWi-Fiperformanceandthroughput.

In-HouseDataCentertoRemoteBranchOfficeToaddressjittercausedbyapplicationshostedatin-housedatacenters,WarpEngine™canbeinstalledonthenetworkclosetotheserverstofilterouttheimpactofapplicationjittertopreventitfromtriggeringthroughputcollapse.WarpEngineinstalledatthedatacentercomplementsWarpGatewayinstalledatbranchofficelocationstoeliminateWi-Fijitter.WarpEnginecanworkinconjunctionwithexistingWANoptimizationsolutionsandADCsusedtobalanceworkloadacrossserversatthedatacenter.

CloudArchitecture

Toeliminatepoorperformancecausedbycloud-hostedapplicationjitter,aswellasvirtualizationjitterduetoVMcrosstalkandhypervisorpackettransferdelays,aWarpVM™instancecanbeinstalledinanypublicorprivatecloudenvironment,workingincombinationwithWarpGatewaybehindthefirewalltopreventWi-Fijitter,asshowninthediagrambelow.

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ConclusionActualuserexperienceinaWi-Finetworkisalmostalwaysimpactedbythe“lastmile”betweentheWi-Firouter(AP)andthemobiledevice.ThisWi-Fi“lastmile”isthemostvolatilebecauseit’ssubjecttoexternalfactorsthataremoredifficulttocontrol.JitterfromRFinterferenceandchannelaccessconflictscaninstantlyarisewithanysuddenanddramaticincreaseinusers–acommonscenarioinWi-Finetworksatsportsstadiums,touristdestinationsandotherpublicvenues.JitteroriginatingontheWi-FinetworkalsocausesTCPonthewiredportionbetweentheserverandtheAPtotreatanyRTTvarianceascongestion,slowingthetransmissionrate.WhenWi-Fijitteriscombinedwithjitteronthewiredportionofthepathdrivenbythenatureoftoday’sstreamingfastdata,voice,videoandwebapplicationtraffic,throughputcollapsesandapplicationsstall.Thisoccurseventhoughplentyofbandwidthisavailable.OnlyBaduNetworks’patentedWarpTCPtechnologydealsdirectlywiththeproblemofjitter-inducedthroughputcollapseonbothwiredandwirelessnetworksandoffersasolutionthatfuture-proofsyournetworkfor5G.WarpTCP’suniquepatentedabilitytoalgorithmicallydetermineinreal-timewhethercongestionexists,andpreventTCPfromreducingthroughputwhenplentyofbandwidthisavailable,addressesTCP’sreactiontojitterhead-on.Asaresult,onlyWarpTCPeliminatestoday’smostcommoncauseofnetworkthroughputcollapseandpooruserexperience,aswellastheunnecessaryrisk,disruptionandexpenseofnetworkinfrastructureupgrades.

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