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1、MultimediaApplicationsMultimediarequirementsStreamingPhoneoverIPRecoveringfromJitterandLossRTPDiff-serv,Int-serv,RSVPApplicationClassesTypicallysensitivetodelay,butcantoleratepacketloss(wouldcauseminorglitchesthatcanbeconcealed)Datacontainsaudioandvideoconten
2、t(“continuousmedia”),threeclassesofapplications:StreamingUnidirectionalReal-TimeInteractiveReal-TimeApplicationClasses(more)StreamingClientsrequestaudio/videofilesfromserversandpipelinereceptionoverthenetworkanddisplayInteractive:usercancontroloperation(simil
3、artoVCR:pause,resume,fastforward,rewind,etc.)Delay:fromclientrequestuntildisplaystartcanbe1to10secondsApplicationClasses(more)UnidirectionalReal-Time:similartoexistingTVandradiostations,butdeliveryonthenetworkNon-interactive,justlisten/viewInteractiveReal-Tim
4、e:PhoneconversationorvideoconferenceMorestringentdelayrequirementthanStreamingandUnidirectionalbecauseofreal-timenatureVideo:<150msecacceptableAudio:<150msecgood,<400msecacceptableChallengesTCP/UDP/IPsuiteprovidesbest-effort,noguaranteesonexpectationorvarianc
5、eofpacketdelayStreamingapplicationsdelayof5to10secondsistypicalandhasbeenacceptable,butperformancedeteriorateiflinksarecongested(transoceanic)Real-TimeInteractiverequirementsondelayanditsjitterhavebeensatisfiedbyover-provisioning(providingplentyofbandwidth),w
6、hatwillhappenwhentheloadincreases?...Challenges(more)MostrouterimplementationsuseonlyFirst-Come-First-Serve(FCFS)packetprocessingandtransmissionschedulingTomitigateimpactof“best-effort”protocols,wecan:UseUDPtoavoidTCPanditsslow-startphase…Buffercontentatclien
7、tandcontrolplaybacktoremedyjitterAdaptcompressionleveltoavailablebandwidthSolutionApproachesinIPNetworksJustaddmorebandwidthandenhancecachingcapabilities(over-provisioning)!Needmajorchangeoftheprotocols:Incorporateresourcereservation(bandwidth,processing,buff
8、ering),andnewschedulingpoliciesSetupservicelevelagreementswithapplications,monitorandenforcetheagreements,chargeaccordinglyNeedmoderatechanges(“DifferentiatedServices”):Usetwotrafficclass
