哈爾濱工業(yè)大學(xué)計算機網(wǎng)絡(luò)8HITNetwork8v3

QoSControlReferences:ZhengWang,InternetQoS:ArchitecturesandMechanismsforQualityofServices,MorganKaufmann,2001.H.J.ChaoandX.Guo,QualityofServiceControlinHigh-speedNetworks,JohnWiley&Sons,Inc.,2002.J.Wroclawski,“Specificationofthecontrolled-loadnetworkelementservice,”RFC2211,Sept1997.S.Shenker,C.PartridgeandR.Guerin,“Specificationofguaranteedqualityofservice,”RFC2212,Sept1997.IntegratedServicesRecall:

Traditionally,Internethasprovidedbest-effortservice

ToprovidedifferentQoScommitments,IETFdevelopedtheintegratedservicesmodel

Requireresourcereservationforeverydataflow

AflowisadistinguishablestreamofrelatedIPpacketsthatresultsfromasingleuseractivityandrequiresthesameQoS(RFC1633)

AflowisdifferentfromaTCPconnection

Aflowisunidirectional

Therecanbemorethanonereceiverofaflow(multicast)BackgroundfunctionsRoutingReservationManagementagentagentagentAdmissioncontrolRoutingdatabaseTrafficcontroldatabaseForwardingfunctionsClassifier&routeselectionPacketschedulerInputdriverOutputdriver

Theintegratedservicesmodelcomposesofbackgroundfunctionsandforwardingfunctions

Backgroundfunctions:

Reservationprotocol:

UsetoreserveresourcesonroutersandendsystemsforanewflowatagivenlevelofQoS.

Maintainsflow-specificstateinformation.

Updatesthetrafficcontroldatabaseusedbythepacketschedulertodeterminetheserviceprovidedforpacketsofeachflow.

Routingprotocol

Itmaintainsadatabasethatgivesthenexthopaddressforeachdestinationaddress

Admissioncontrol:

TodetermineifarouterhasthenecessaryresourcestoacceptanewflowattherequestedQoS

Thedeterminationisdonebasedonthecurrentlevelofcommitmenttootherreservationsand/orthecurrentloadonthenetwork

Managementagent

Itcanmodifythetrafficcontroldatabaseanddirecttheadmissioncontrolmoduleinordertosettheadmissioncontrolpolicies

Forwardingfunctions:

Packetclassifierandrouteselection:

Toidentifyflowsthataretoreceiveacertainlevelofservice

Toidentifythenexthopaddress

Packetscheduler:

TohandletheforwardingofdifferentpacketflowsinamannerthatensuresthatQoScommitmentsaremet

Managesoneormorequeuesforeachoutputport

Determinestheorderinwhichqueuedpacketsaretransmittedandtheselectionofpacketsfordiscard,ifnecessary

ISserviceisdefinedontwolevels1.Anumberofgeneralclassesofservice,eachofwhichprovidesacertaingeneraltypeofserviceguarantees2.Withineachclass,theserviceforaparticularflowisspecifiedbyanumberofparameters

Requirespacketschedulingandbuffermanagementonaper-flowbasis

Notethatasthenumberofflowsandlinerateincrease,itbecomesverydifficultandcostlyfortherouterstoprovideintegratedservice

Threeserviceclasses:Controlled-loadservice,guaranteedservice,andbesteffortserviceControlledLoad

TrafficShapingandPolicing

Whatandwhyistrafficshapingandtrafficpolicing

LeakyBucketTokenBucketTraffic

TrafficPolicingQuestion:

AconnectionacceptedbyCalladmissioncontrol,it’sQoScanbesatisfied,ifthesourceobeysthetrafficdescriptor.

Whathappensifthetrafficflowviolatestheinitialcontract?

Answer:Thenetworkmaynotmaintainacceptableperformance

Whatcanbedone?

TrafficPolicingisperformedbythenetworktoensurethattheparameterspecifiedbytheuserarebeingcomplied.

TrafficPolicingTheprocessofmonitoringandenforcingthetrafficflow?WhatTrafficPolicingdo?

DiscardthenonconformingtrafficTagthenonconformingtraffic(withlowerpriority)

Providestrafficshaping:Inputbursty.Outputratecontrolled.?Providestrafficpolicing:Ensurethatusersaresendingtrafficwithinspecifiedlimits.ExcesstrafficdiscardedDesignExample

Sendermax.transmissionrateof200Mbps

-Routercapacityis16Mbps

-Applicationgeneratesdatainburstof8Mb,withaburstlengthof40ms,onceeverysecond.DesignExample

Firstmakesuretheroutercanpossiblyhandlethetraffic:

ThendeterminesCfortheleakybucket:

Averagedatarategeneratedbyapplicationis:

Total=8Mb/1s=8Mbps<router’scapacity(16Mbps)

ThendeterminesCfortheleakybucket:LetAbearrivalrate,andTbeburstlength(inseconds),thenC≥max{(totalreceivedintimet)-(totaltxintimet)|?t}=A*t-r*t=(A-r)t=(200-16)*0.04=7.36Mbor0.92MBTokenBucketTrafficShaper

Whyatokenbuckettrafficshaper?

Leakybucket:theoutputrateisconstantwhenthebufferisnotempty;

onlyCBRisallowed.

TokenBucketShaper(Dual-bucketShaper)

2buckets–Onebufferfordata–Onebufferforapooloftokens:tokensaregeneratedataconstantrate

Moreflexible:allowsforsomeburstinessinthetrafficaslongasitisunderacertainlimit

Conformingpacketsarepassedthroughwithoutfurtherdelay

Toprovidecontrolled-loadservice,atokenbucketdeviceisusedforshaping/policingtheincomingtrafficTokenarrivingatraterBucketwithmaximumcapacityequalstobtokensInputbufferTx

Thetokenbucketisdefinedby2parameters:

thetokenarrivalrate,rorρ(inbytespersecond)

thebucketdepth,b(inbytes)

Apacketistransmittedonlyiftokensareavailable;otherwise,itisrejectedorwaitsinthebufferfortokensifinputbufferspaceisavailableThetokenbucketallowstransmissionofaninitialburstoflengthb;thenthetransmissioncontinuesatrateρ.

nomorethanb+ρTbytescanbetransmittedthroughthetokenbucketinanytimeintervalT

TheTokenBucketAlgorithm

–DifferencesfromLeakyBucket:

Allowssomeburstiness(uptobucketsize).Allowsahosttosavetokensforfutureuse.

WidelyimplementedinIPswitch/routers.

Determiningthelengthofthemax-rateburst:

Let:Sbeburstlength;Cbetokencapacity;ρbetokenarrivalrate;MbemaxoutputrateSince:(a)Maxsizeofoutputburst=C+ρSbytes,and(b)butitmustalsoequalsMSbytesHence:C+ρS=MSorS=C/(M?ρ)

TokenBucketShaperDesignExample

Question:

Considerthearrivaltrafficcharacterizedbyatokenbucketwithparametersρ(averagerate)=1Mbps,M(maximumrate)=2Mbps,andC(tokendepth)=100Kb.Whatistheminimumraterthatneedstobeallocatedbyarouterinordertoguaranteeadelaynolargerthan50ms?TokenBucketShaperDesignExample(cont’d)

WeconsidertheworstcasewherethemaximumburstlengthisgivenbyS=C/(M-ρ)

ThenthemaximumaccumulativeamountofarrivaltraffictotherouterisMS=MC/(M-ρ)

WecandrawthearrivalandservicecurveasfollowsTheminimumrateneedstobeallocatedbytherouterinordertoguaranteeadelaynolargerthan50msisjusttheslopeoftheservicecurve.Fromtheabovefigure,wecanseetheslopeisgivenby:Theminimumraterthatneedstobeallocatedbyarouterinordertoguaranteeadelaynolargerthan50ms=1.333Mb/sQoSControl--RSVPResourceReservationRef:1.L.Zhang,S.Deering,D.Estrin,S.ShenkerandD.Zappala,“RSVP:AnewresourceReSerVationprotocol,”IEEENetwork,Vol.7,pp.8-18,Sept1993.2.B.Braden,L.Zhang,S.Berson,S.HerzogandS.Jamin,“ResourceReSerVationprotocol(RSVP)–version1functionalspecification,”RFC2205,InternetEngineeringTaskForce,Oct1997.3.P.PanandH.Schulzrinne,“YESSIR:ASimpleReservationMechanismfortheInternet,”ACMSIGCOMMComputerCommunicationReview,vol.29,no.2,pp.89-101,Apr99.MultimediaontheInternetObjective:

Tosupportnewdistributedapplicationssuchasremotevideo,multimediaconferencing,datadiffusion,andvirtualreality,etc.Characteristicsoftheseapplications:

ApplicationsareverysensitivetotheQualityofServicetheirpacketsreceive

Thebest-effortservicemodelisnotgoodenough

Shouldallowflows,i.e.datatrafficstreams,toreservenetworkresources

Theseapplicationsareoftenmultipoint-to-multipointwithseveralsendersandreceivers

e.g.multipartyconferencingwhereeachparticipantisbothasenderandareceiverofdata

TosupportmulticastingserviceandavarietyofQoS,thenetworkarchitecturerequiresthefollowingcomponents:

FlowSpecification

Describeboththecharacteristicsofthetrafficstreamsentbythesourceandtheservicerequirementsoftheapplication

Ref.:RFC1363,RC1190

Routing

RoutingprotocolsthatsupportQoSandmulticast

ST2+(RFC1819),CoreBasedTree(CBT),Mrouted

ResourceReservation

ToprovideguaranteeQoSforaparticulardataflow,itisnecessarytosetasidecertainresources,suchasbuffer,bandwidth,etc.

i.e.needtocreateandmaintainresourcereservationoneachlinkalongthetransportpath

RSVP(RFC2205)

TransportProtocols

Forsupportingreal-timeapplications

RTP(RFC1889),XTP

AdmissionControl

Asnetworkresourcesarelimited,thenetworkcannotsatisfyallreservationrequests

Anadmissioncontrolmechanismisneededtodeterminewhichreservationrequestsaretobeacceptedandwhichtobedenied

PacketScheduling

Whenanetworkswitchreceivesthepacketsfromanumberofstreams,ithastodecidewhichisthenextpackettobetransmitted

Thepacketschedulerwillactuallydeterminethequalityofservicethatthenetworkcanprovide

E.g.WeightedFairQueuing,Worst-caseWeightedFairQueuing,Real-timeVirtualClockResourceReSerVationProtocol(RSVP)Overview:

ProtocolforresourcereservationontopofIPforreal-timetraffic

RSVPisNOTaroutingprotocol

Routesaredeterminedbytheroutingprotocol

Asimplexprotocol,i.e.reservesresourcesinonlyonedirection(fromsourcetoreceiver)

Bidirectionalresourcereservationrequiresbothendsystemstoinitiateseparatereservations

Receiverinitiatesandmaintainstheresourcereservations

EnablesRSVPtoaccommodateheterogeneousreceiversinamulticastgroup

Eachreceivermayreserveadifferentamountofresources

Notallreceivershavethesameprocessingcapacityforincomingdata

Differentreceiversmayrequiredifferentqualityofservice

E.g.iflayeredencodingisusedforvideosignal

somereceiverswillhaveenoughprocessingpowertodecodelow-resolutionsignalonly

somepathsmayhaveenoughbandwidthforlowresolutionsignalonly

Caterfordynamicnatureofmembershipinmulticastgroups

Reservationmusthencebedynamicsuchthatseparatedynamicreservationsareneededforeachmember

Allowend-userstospecifytheirapplicationneeds

E.g.Inaudioconferencing,usuallyonlyoneperson,oratmostafewpersons,willtalkatthesametime.Hence,itisadequatetoreserveonlyresourcesfromafewsimultaneouslyaudiochannels.

Receivershouldbeabletoswitchbetweenchannels

E.g.Inmultipartyconference,areceivermaywanttowatchoneorafewparticipantsatatimeandwouldliketoswitchamongvariousparticipants.

Hence,receivershouldbeableto

controlwhichdatastreamiscarriedonthereservedresources

switchamongchannels

Reservationsfromdifferentreceivers,i.e.downstreambranchesofthemulticasttree,tothesamesourcecanbemergedasreservationstravelupstreamRSVPArchitectureHostRouterAppli-cationRSVPRSVPprocessRSVPRoutingprocessprocessPolicyPolicycontrolcontrolDataAdmissionAdmissioncontrolcontrolClassi-PacketClassi-PacketfierschedulerfierschedulerDataDataRSVPOperation-Overview

ReceiversuseRSVPtodeliveritsrequesttotheroutersalongthedatastreamspathstowardsthesources

RSVPisusedtonegotiateconnectionparameterswiththerouters

Ifareservationissetup,RSVPisalsoresponsibleformaintainingtherouterandhoststatestoprovidetherequestedservice

TheRSVPprocessineachnodeperformslocalproceduresforreservationsetupandenforcement

Policycontrol:determinesiftheapplicationisallowedtomakethereservation

Infuture,authentication,accesscontrolandaccountingforreservationmayalsobeimplementedbythepolicycontrol

Admissioncontrol:keepstrackofthesystemresourcesanddetermineswhetherthenodehassufficientresourcestosupplytherequestedQoS

TheRSVPdaemonchecksboththepolicycontrolandadmissioncontrolprocedures

Ifeithercheckfails,anerrorisreturnedtotheapplicationthatoriginatetherequest

Ifbothcheckssucceed,theRSVPdaemonsetsparametersinpacketclassifierandpacketschedulertoobtaintherequestedQoS

PacketclassifierdeterminestheQoSclassforeachpacket

PacketschedulerorderspackettransmissiontoachievethepromisedQoSforeachstream

RSVPusestwobasicmessages:PathandResv

Pathmessagesaresentperiodicallyfromthesendertothemulticastaddress

Pathmessageissentfromsourcetoreceiversviathepathsdecidedbytheroutingprotocol

Pathstateisstoredineachnodealongtheway

ContainsatleasttheunicastIPaddressoftheprevioushopnode,whichisusedtoroutetheResvmessageshop-by-hopinthereservedirectionfromthereceivers

Containsthedescriptionofthetrafficcharacteristics,TspecandAdspec,andtheIPaddressofthesource

Info.isusedbythereceiverstofindreservepathtothesenderandtodeterminetheamountofresourcesneedtobereserved

Resvmessagesareusedbythereceiversforsettingupreservations

Containsreservationparameters

Resvmessagestraveltowardthesendersbyfollowingexactlythereverseoftherouteswhichdatapacketswilluse

ResvmessagesaredeliveredtothesenderhostssothatthehostscansetupappropriatetrafficcontrolparametersforthefirsthopPathPathSR1PathR3RxPathResvResvResvResvR2

Reservationmerging

Whentherearemultiplereceivers,theresourceisnotreservedforeachreceiver

TheresourceisshareduptothepointwherethepathstodifferentreceiversdivergePathRx1PathResvPathR3SR1PathPathResvResvRx2ResvR2ResvPathPathResvR4Rx3Resv

RSVPmergesthereservationrequestsfromdifferentreceiversatthepointwheremultiplerequestsconverge

Areservationmovingupstreamwillstopatthepointwherethereisalreadyanexistingreservationthatisequalorgreaterthanthatbeingrequested

ThishelpstoreducetheRSVPtrafficwhentherearemanyreceiversinthemulticasttreeSpecifyingResourceRequirement(RFC2210)Source

ThesourceprovidetheSenderTspectoRSVP

Flowstowardsthereceivers

SenderTspec

Carriesthetrafficspecificationgeneratedbyeachdatasource,i.e.describethetraffictheapplicationexpectstogenerate

Tokenbucketrate

Tokenbucketsize

Peakdatarate

Minimumpacketsize

ThisincludestheapplicationdataandprotocolheadersatoraboveIPlevel

Usedbythenetworknodetocomputethebandwidthoverheadneededtocarrytheflowoveraparticularlink-leveltechnologyandhencetocomputetheamountofbandwidthtobeallocatedtotheflow

MaximumpacketsizeSource/IntermediateNetworkElements

Adspecisgeneratedateitherthesourceortheintermediatenetworkelements

Adspec

Flowstowardsthereceivers

Info.carriedintheAdspecmaybechangedbynetworkelementsalongthepathtothereceiver

Describethepropertiesofthedatapath,i.e.containsinfo.abouttheavailabilityofaspecificQoSandtherequirementsofthesendingapplication

GlobalBreakbit

thisbitissetifarouternotsupportingRSVPisencountered

usuallysetbyanetworkelementthatsupportsRSVPandisawareofthegapinintegratedservicescoverage

usetoinformthereceiverthattheAdspecmaybeinvalid

hopcount

estimatebandwidthavailable(min.ofindividuallinkbandwidthsalongthepath)

min.pathlatency(summationofindividuallinklatencies)

PathMax.TransmissionUnit(MTU):min.ofMTUsofindividuallinkalongthepathReservationandFilteringReceiver

InitiatestheRSVPreservationandtherequestissenttowardstosource

ARSVPreservationrequestconsistsofaflowspecandafilterspec

FlowspeccontainsaReceiver_TspecandRspec

Receiver_Tspec

Describetheleveloftrafficforwhichresourcesshouldbereserved

Specifythebucketrate,bucketsize,peakdatarate,min.andmax.packetsize

Rspec

DescribethelevelofQoSservicedesired

Specifythedesiredbandwidthanddelayguarantees

Usedbypacketscheduler

SpecifytheamountofresourcestobereservedbutNOTwhichdatastreamcanusetheresourcesReservationandFiltering(contd)

Filterspecdefinesthedatastream,i.e.theflow,toreceivetheQoSdefinedbytheflowspec

Usedbypacketclassifier

Thedatastreamusingtheresourcescanbychangedbythereceiverwithoutchangingtheamountofreservedresources

ThisisusedtosupportswitchingbetweendifferentchannelsReservationStylesReservationstyleisasetofoptionsthatspecifieshowthereservedresourcescanbeusedbydifferentdatastreams

Oneoptionspecifiesthereservationclass

Distinctreservations:areservationisforeachsenderineachsession

Sharedreservations:areservationisusedbyasetofsendersthatareknownnottointerferewitheachother

Anotheroptioncontrolstheselectionofsenders

Explicit:specifyalistofselectedsenders

Wildcard:thereservedresourcesareforallsenderstothesession3reservationstyleshavebeendefined:SenderReservationsSelectionExplicitDistinctSharedFixed-Filter(FF)Shared-Explicitstyle(Nonedefined)(SE)StyleWildcard-Filter(WF)StyleWildcard

Wildcard-filter(WF)Style

Asinglereservationiscreatedandissharedbyflowsfromallupstreamsenders

i.e.anypacketsdestinedtothemulticastgroupcanusethereservedresources

Asharedpipewhosesizeisthelargestoftheresourcerequestsforthatlinkfromallreceivers,independentofthenumberofsendersusingit

Suitableforapplicationsinwhichtherearemultipledatasourcesbuttheyareunlikelytotransmitsimultaneously

Symbolicrepresentation:WF(*{Q})

where*representswildcardsenderselectionandQistheflowspec

Fixed-filter(FF)Style

Adistinctreservationrequestiscreatedfordatapacketsfromeachsender

ThetotalreservationonalinkforagivensessionisthetotaloftheFFreservationsforallrequestedsenders

FFreservationsrequestedbydifferentreceivers,butthesamesender,mustbemergedtoshareasinglereservationinagivennode

Symbolicrepresentation:FF(S{Q})

whereSistheselectedsenderandQistheflowspec

FormultipleFFreservation:FF(S1{Q1},S2{Q2},…)

ThetotalreservationisthesumofQ1,Q2,…forallrequestedsenders

Shared-explicit(SE)Style

Asinglereservationiscreatedandissharedbyasetofexplicitsenders

Thesetofsendersisspecifiedbythereceivermakingthereservation

Thereceivercanswitchbetweensendersbyinformingtheintermediatenodes

Thepacketclassifieroftheintermediatewillfilteroffthoseflowsthatarenotselectedbythereceiver

Symbolicrepresentation:SE((S1,S2,…){Q})

whereS1,S2,…aresendersandQistheflowspecNote:

WFandSEareappropriateformulticastapplicationsinwhichapplication-specificconstraintsmakeitunlikelythatmultipledatasourceswilltransmitsimultaneously

e.g.Inaudioconferencing,alimitednumberofpeopletalkatthesametime

EachreceivermightissueaWForSEreservationrequestforacoupleofaudiochannels

FFcreatesindependentreservationsforflowsfromdifferentsenders

MoreappropriateforvideosignalsifvideofromallparticipantsneedtobedisplayedExample:(a)(c)(S1)(R1)Router(R2)(b)(d)(S2,S3)(R3)RouterConfigurationExample(cont’d)

Arouterhastwoincominginterfaces(a)and(b),andtwooutgoinginterfaces(c)and(d)

Threeupstreamsenders:S1,S2andS3

Threedownstreamreceivers:R1,R2andR3

Assumethat(d)isconnectedtoabroadcastLAN,i.e.replicationoccursinthenetwork,andR2andR3arereachedviadifferentnexthoprouters(notshown)

DatapacketsfromeachSiareroutedtobothoutgoinginterfacesExample(cont’d)

Wildcard-Filter(WF)styleSendReserveReceiveWF(*{4B})WF(*{4B})(a)*{4B}(c)WF(*{3B})WF(*{2B})WF(*{4B})(b)*{3B}(d)Example(cont’d)

Fixed-Filter(FF)styleSendReserveReceiveFF(S1{4B})S1{4B}S2{5B}FF(S1{4B},S2{5B})(a)(c)FF(S1{3B},S3{B})FF(S1{B})FF(S2{5B},S3{B})S1{3B}S3{B}(d)(b)Example(cont’d)

Shared-Explicit(SE)styleSendReserveReceiveSE(S1{3B})SE((S1,S2){B})(a)(S1,S2){B}(c)SE((S1,S3){3B})SE(S2{2B})SE((S2,S3){3B})(S1,S2,S3)(b){3B}(d)Example:

Inthepreviousexample,datapacketsfromS1,S2andS3areforwardedtobothoutgoinginterfaces

Here,packetsfromS2andS3areforwardedonlytooutgoinginterface(d)

TheremaybeashorterpathtoR1viasomeotherrouterRouter(S1)(a)(c)(R1)(b)(d)(R2)(S2,S3)(R3)RouterConfigurationExample(cont’d)

Wildcard-Filter(WF)styleSendReserveReceiveWF(*{4B})WF(*{4B})(a)*{4B}(c)WF(*{3B})WF(*{2B})WF(*{3B})(b)*{3B}(d)Scalability

ReservationmergingleadstotheprimaryadvantagesofRSVP–scalability

Largenumberofuserscanbeaddedtoamulticastgroupwithoutincreasingthedatatrafficsignificantly

Asinglephysicalinterfacemayreceivemultiplereservationrequestsfromdifferentnexthopsforthesamesessionandwiththesamefilterspec

RSVPshouldinstallonlyonereservationonthatinterface

Theinstalledreservationshouldhaveaneffectiveflowspecthatisthe"largest”oftheflowspecsrequestedbythedifferentnexthops

Similarly,aResvmessageforwardedtoaprevioushopshouldcarryaflowspecthatisthe"largest"oftheflowspecsrequestedbythedifferentnexthopsRSVPOperation1.Asourcejoiningamulticastgroupwillconsultitsroutingprotocoltoobtaintheroutes.APathmessagecarryingtheTspec,andmayalsoincludestheAdspec,fromthesourcewillbesentdownstream.ThePathmessageisusedtoupdatethePathstateofeachswitchalongthepath.ThePathstateincludes:2.3.

TheincominglinkupstreamtothesourceTheoutgoinglinkdownstreamfromthesourcetothereceiversinthegroupThePathstateisusedtoroutethereservationinthereversedirectionNote:theTspecwillnotbemodifiedbytheswitchonitswayfromthesourcetothereceivers;however,thebreakbitintheAdspecmaybemodifiedbytheswitchifanetworkelementnotsupportingRSVPisencountered

4.Whenapathmessagearrivesaswitch,theswitchwill

Checkstoseeifitalreadyhasthepathstateforthenamedgroup;ifnot,apathstatewillbecreatedObtainstheoutgoinginterface(s)ofthepathmessagefromtheroutingprotocolUpdateitstableofincomingandoutgoinglinksRecordthesourceaddressifthepathmessageindicatesthattheapplicationmayrequireafilteredreservationThepathmessageisforwardedifitisfromanewsourceorthereisachangeinroutes

ExampleH1H5S1S4H4S2S3H2H35.Whenareceiverreceivesthepathmessageandifitwouldliketocreateareservation,aReservationmessage(Resv)whichcarriestheFlowspecwillbeforwardedbacktowardsthesourcesbyreversingthepathsofthepathmessage

henceformingasinktreefromeachreceivertoallthesourcesH1H5S1S4H4S2S3H2H36.Whenaswitchreceivesthereservationmessage

Ifresourcescannotbeallocatedtotherequest,aRSVPResvErrormessagesaresentbacktoallthereceiverandthereservationmessageisdiscarded

Note:areservationrequestmayembodyanumberofrequestsmergedtogether

Ifthereservationisestablished,theinfo.inthereservationmessageisusedtomaintainthereservationstateattheswitchTheswitchwillalsotrytomergetherequestsforthesamemulticastgroupbypruningthosecarryarequestforreservingasmaller,orequal,amountofresourcesthanthepreviousrequestThereservationmessageisforwardedtothenextswitchupstreamifnew(extra)resourcesareneeded

Examples:1.Reservationwithwildcardfiltering???Audioconferencingamong5participantsEachhostbehavesasasourceandreceiverAudiorate:bH2H3R1R2R3H4H1H5

Assumedthattheroutingprotocolhasbuiltamulticastroutingtreefromeachsource

Note:Withwildcardfiltering,theswitcheswillnotrecordthesourceinformation

H1,…,H5allsendpathmessagestoaddressm1

SupposeH1sendsthefirstpathmessagem1:inL1m1:inL7outL2L6outL3L4m1:inL6outL5L7H2H3L2L3R1L6R2L5L7R3L4L1H4H1H5

Next,H5sendspathmessage,creatingmorestateinroutersm1:inL1L6m1:inL7outL1L2L6outL3L4m1:inL5L6outL5L6L7H2H3L2L3R1L6R2L5L7R3L4L1H4H1H5

H2,H3,H4sendpathmessages,completingthepathstatetablesm1:inL1L2L6m1:inL3L4L7outL1L2L6outL3L4L7m1:inL5L6L7outL5L6L7H2H3L2L3R1L6R2L7R3L4L1L5H4H1H5

H1wantstoreceivedatafromallsendersbutonlywantsenoughbandwidthforONEaudiostream

H1sendsthereservationmessage(b,wildcardfilter)upstreamtoallsources

Withwildcardfilter,anysendercanusethereservedbandwidthH2H3L2L3R1L6R2L5L7R3L4L1H4H1H5

Whenarouterreceivesthereservationmessage

itreservesbandwidthbonthedownstreamlinktowardsH1

Whenahostreceivesthereservationmessage

itsetsupappropriatetrafficcontrolparametersforthefirsthopm1:inL1L2L6m1:inL3L4L7outL1(b)L2L6outL3L4L7(b)m1:inL5L6L7outL5L6(b)L7H2bH3L2bL3bbbL4bR1L6R2L7R3L1bL5H4H1H5

WhenH2wantstocreateareservation

H2sendsareservationmessage(b,wildcardfilter)toR1

R1willforwardthemessagetoH1ONLY,asithasforwardedanidenticalrequestoverR2previously

AfterallreceivershavesentRSVPreservationmessages,anamountbofresourceshavebeenreservedovereachofthesevenlinksm1:inL1L2L6m1:inL3L4L7outL1(b)L2(b)L6outL3L4L7(b)m1:inL5L6L7outL5L6(b)L7H2bbH3L2bL3bbbL4bR1L6R2L7R3bL1bL5H4H1H5

Whatifmultiplesenders(e.g.H3,H4andH5)senddataoverthesamelink(e.g.link6)simultaneously?

Arbitraryinterleavingofpackets

L6flowpolicedbyleakybucket:ifH3+H4+H5sendingrateexceedsb,packetlosswilloccurm1:inL1L2L6m1:inL3L4L7outL1(b)L2(b)L6outL3L4L7(b)m1:inL5L6L7outL5L6(b)L7H2bbH3L2bL3bbbL4bR1L6R2L7R3bL1bL5H4H1H5

Considerthesituationwhereeachreceiverrequested2bofbandwidth

2bwouldbereservedoneverylinkeventhoughtho