FIA-Serval原版完整課件

Serval:AnEnd-HostStackforService-CentricNetworkingErikNordstrom,DavidShue,PremGopalan,RobertKieferMatveyArye,StevenY.Ko,JenniferRexford,MichaelJ.FreedmanNSDI2012PresentedbyYeTianforCourseCS05112OverviewRethinktheNetworkStackServalAbstractionTheServalNetworkStackExperimentsReviewModernInternetServiceMultiplicity(多重性)MultiplereplicasMultipleinterfacesMultiplepathsDynamism(動(dòng)態(tài)性)ReplicafailureandrecoveryServicemigrationClientmobilityMatchespoorlywithtoday’sTCP/IPstackServiceAccessTodayDNSbindsservicetolocationatclient(earlybinding)DatacenterLBmapssingleIPtomultipleserversLBisapplication-specificMigrateVMstobalanceloadinthecloudFlowsbreakwhenswitchingnetworksorinterfacesRethinktheNetworkStackRethinktheNetworkStackApplication-layerToday’sapplicationsoperateontwolow-levelidentifiers(IPaddressandTCP/UDPport)Clientsmust“earlybind”totheseidentifiersusingout-of-bandlookupmechanisms(e.g.,DNS)oraprioriknowledge(e.g.,Webisonport80)beforeinitiatingcommunication.SocketprogrammingonIPaddressandportServal:applicationscommunicateoveractivesocketsusingserviceID,enableslatebindingofserviceIDtoaserviceinstances.RethinktheNetworkStackTransportlayerToday’sstackusesafive-tuple<remoteIP,remoteport,localIP,localport,protocol>todemultiplexanincomingpackettoasocket.Theinterfaceaddressescannotchangewithoutdisruptingongoingconnections–lackofmobilityServal:transportprotocolsdealonlywithdatadeliveryacrossoneormoreflows,includingretransmissionandcongestioncontrol;DemuxisattheSALlayerbasedonflowIDRethinktheNetworkStackNetworklayerToday’snetworklayeruseshierarchicalIPaddressingtoefficientlydeliverpackets.Challengedbytheneedforend-hostmobilityinastackwhereupper-layerprotocolsfailwhenaddresseschange.Serval:thenetworklayerunchanged.OverviewRethinktheNetworkStackServalAbstractionTheServalNetworkStackExperimentsReviewGroup-BasedServiceNamingAServalservicename,calledaserviceID,correspondstoagroupofoneormore(possiblychanging)processesofferingthesameservice.ServiceIDServicenamesdonotdictatethegranularityCanbeasingleSSHdaemon,aclusterofprinters,asetofpeersdistributingacommonfileFormatProviderprefixPrefix-basedaggregationandLPMExample:/cs/printerSecuringcommunicationandregistration:Endwithaself-certifyingbitstringExplicitHost-LocalFlowNamingServalprovidesexplicithost-localflownamingthroughflowIDsthatareassignedandexchangedduringconnectionsetup.Benefits:Network-layeroblivious:identifyflowswithoutknowingthenetwork-layeraddress.Mobilityandmultiplepaths:FlowIDshelpidentifyflowsacrossavarietyofdynamicevents,suchasmigration,addresschange,etc.OverviewRethinktheNetworkStackServalAbstractionTheServalNetworkStackExperimentsReviewTheServalNetworkStackSALisinclient,server

andservicerouterTheServalNetworkStackTheuser-spaceservicecontrollerManageserviceresolutionbasedonpoliciesListenforservice-relatedevents,monitorserviceperformance,andcommunicatewithothercontrollersTheServiceAccessLayer(SAL)providesaservice-leveldataplaneresponsibleforconnectingtoservicesthroughforwardingoverservicetables.Onceconnected,theSALmapsthenewflowtoitssocketintheflowtable,ensuringpacketdemultiplexed.ActiveSocketRetainthestandardBSDsocketinterface.AserviceIDisautomaticallyregisteredonacalltobind,andunregisteredonclose,processtermination,ortimeout.Onalocalserviceregistration,thestackupdatesthelocalservicetableandnotifiestheservicecontroller,whichmaynotifyupstreamservicecontrollers.Alocalunregistrationeventtriggerstheremovaloflocalrulesandnotificationoftheservicecontroller.ResolvingaserviceIDtonetworkaddressesisdelegatedtotheSALApplicationsjustcallthesocketinterfaceusingserviceIDsandneverseenetworkaddresses.AService-LevelDataPlaneThefirstpacketofanewconnection(synpacket)oranunconnecteddatagramincludesaserviceIDThestackperformslongestprefixmatching(LPM)ontheserviceIDtoselectarulefromtheservicetable.ActionsFORWARD:IncludeanassociatedsetofoneormoreIPaddressesEitherselectsalladdressesorusesweightedsamplingtoselectoneoftheaddresses.Foreachselecteddestination,thestackpassesapackettothenetworklayerfordelivery.DEMUX:Deliverareceivedpackettoalocalsocket,whenanserviceprocessislisteningontheserviceID.Addedbyanactivesocket’sbindeventActionsDELAY:QueuethepacketandnotifytheservicecontrolleroftheserviceID.allowaruletobeinstalled“on-demand”DROP:DiscardunwantedpacketExample:Connection-lessdatagramcommunicationServicerouter(SR)AclientapplicationinitiatescommunicationonserviceIDX,whichismatchedintheclient’sservicetabletoSR’saddress.Uponreceivingapacket,theSRlooksuptheserviceIDinitsownservicetable;givenaFORWARDrule,itforwardsthepackettotheserver.Attheserver,theDEMUXruledeliversthepackettothesocketofthelisteningapplication.Example:ConnectionestablishmentWhenclientaattemptstoconnecttoserviceX,theclient’sSALassignsalocalflowIDtothesocket,andthenaddsanentryinitsflowtable.ASYNpacketisgeneratedwiththeserviceIDfromtheconnectcall,alongwiththenewflowIDTheSALthenlooksuptherequestedserviceIDinitsservicetable,therequestissenttotheIPaddressbofthedefaultFORWARDruleForwardingcontinuesrecursivelythrougheUntilreachingalisteningserviceendpointsxonhostg,whichthencreatesarespondingsocketwithanewflowID,alsoupdatingitsflowtable.End-hostg’sSYN-ACKresponseincludesitsownaddress,flowIDTheSYN-ACKandallsubsequenttrafficinbothdirectionstraveldirectlybetweentheend-points,bypassingSRsb,cande.Afterthefirstpacket,allremainingpacketscanbedemultiplexedbytheflowtablebasedondestinationflowIDs.AnotherexampleClientaconnectstoserviceXAServiceControlPlaneforExtensibleServiceDiscoveryAserver’scontrollercan“announce”anewserviceinstancetoanupstreamservicecontrollerthat,inturn,disseminatesreachabilityinformationtoalargernetworkofcontrollers.serviceIDscanbeaggregatedbyadministrativeentitiesforscalabilityandresolutioncontrol.Ontheclient,theservicetablewouldhaveFORWARDrulestodirectaSYNpackettoitslocalservicerouter,whichinturndirectstherequestuptheservicerouterhierarchytoreachaserviceinstance.AcontrollerinstallsaDELAYrule,andmatchingpacketsarebufferedwhilethecontrollerresolvestheirserviceIDs.AreturnedmappingisinstalledasaFORWARDruleandthecontrollersignalsthestacktore-matchthedelayedpackets.Multi-homingandmulti-pathingServalcansplitasocket’sdatastreamacrossmultipleflowsestablishedandmaintainedbytheSALondifferentpaths.Onanypacket,eitherhostcanpiggybackalistofotheravailableinterfacesinaSALextensionheader,toenabletheotherhosttocreateadditionalflowsusingasimilarthree-wayhandshake.E.g.,ifS’sSYN-ACKpacketpiggybacksinformationaboutinterfaceaddressa4,Ccouldinitiateasecondflowfroma2toa4.TheSALcanfreelymigrateaflowfromoneaddress,interface,orpathtoanother.Example:Tomigratetheflow,CsendsSanRSYNpacket(for“resynchronize”)withflowIDs<fC1,fS1>andthenewaddressa2.TheserverreturnsanRSYN-ACK,whilewaitingforafinalacknowledgmenttoconfirmthechange.OverviewRethinktheNetworkStackServalAbstractionTheServalNetworkStackExperimentsReviewPerformancePrototypeof28,000linesofCcodeClient-serverthroughputcomparisonwithTCPComparingservicerouterwithIProuterTranslator:allowlegacyhosttocommunicateswithservalhostCaseExperiment:ReplicatedWebServicesFourclientsrunningtheApachebenchmarkgeneraterequeststoaServalwebservicewithanevolvingsetofMongooseserviceinstances.eachclientrequestsa3MBfileandmaintainsanopenwindowof20HTTPrequestsAttime60,twonewserviceinstancesstart,registerwiththeservicerouterAttime120,weforcethefirsttwoserverstogracefullyshutdown,whichcausesthemtoclosetheirlisteningsocketStartanotherserverattime180,CaseExperiment:Back-EndDistributedStorageImplementedadynamicMemcachedsystem.Memcachedprovidesasimplekey-valueGET/SETcachingservice,where“keyspace”partitionsarespreadoveranumberofserversforloadbalancingClientsissuerequestsdirectlytoaserviceID.TheSALthenmapstheserviceIDtoapartitionusingLPMintheservicetable,andultimatelyforwardstherequesttoaresponsibleserverthatlistensonthecommon