DIFFSERV—THE SCALABLE END-TO-END QUALITY OF SERVICE MODEL模型

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1、WHITEPAPERDIFFSERV—THESCALABLEEND-TO-ENDQUALITYOFSERVICEMODELLastUpdated:August2005TheInternetischangingeveryaspectofourlives—business,entertainment,education,andmore.BusinessesusetheInternetandWeb-relatedtechnologiestoestablishIntranetsandExtranetsthathelpstreamlinebusinessprocessesandde

2、velopnewbusinessmodels.BehindallthissuccessistheunderlyingfabricoftheInternet:theInternetProtocol(IP).IPwasdesignedtoprovidebest-effortservicefordeliveryofdatapacketsandtorunacrossvirtuallyanynetworktransmissionmediaandsystemplatform.TheincreasingpopularityofIPhasshiftedtheparadigmfrom“IP

3、overeverything,”to“everythingoverIP.”Inordertomanagethemultitudeofapplicationssuchasstreamingvideo,VoiceoverIP(VoIP),e-commerce,EnterpriseResourcePlanning(ERP),andothers,anetworkrequiresQualityofService(QoS)inadditiontobest-effortservice.Differentapplicationshavevaryingneedsfordelay,delay

4、variation(jitter),bandwidth,packetloss,andavailability.TheseparametersformthebasisofQoS.TheIPnetworkshouldbedesignedtoprovidetherequisiteQoStoapplications.Forexample,VoIPrequiresverylowjitter,aone-waydelayintheorderof150millisecondsandguaranteedbandwidthintherangeof8Kbps->64Kbps,dependent

5、onthecodecused.Inanotherexample,afiletransferapplication,basedonftp,doesnotsufferfromjitter,whilepacketlosswillbehighlydetrimentaltothethroughput.Tofacilitatetrueend-to-endQoSonanIP-network,theInternetEngineeringTaskForce(IETF)hasdefinedtwomodels:IntegratedServices(IntServ)andDifferentiat

6、edServices(DiffServ).IntServfollowsthesignaled-QoSmodel,wheretheend-hostssignaltheirQoSneedstothenetwork,whileDiffServworksontheprovisioned-QoSmodel,wherenetworkelementsaresetuptoservicemultipleclassesoftrafficwith®varyingQoSrequirements.Bothmodelscanbedrivenoffapolicybase,usingtheCoPS(Co

7、mmonopenPolicyServer)protocol.CiscoIOSSoftwaresupportsboththeIntServandDiffServmodelsofQoS,alongwithanoptionalCoPS-clientfunctionality.AllcontentsareCopyright©1992–2006CiscoSystems,Inc.Allrightsreserved.ImportantNoticesandPrivacyStatement.Page1of18IntServprovidesfor