DifferentiatedTreatmentofInternetTrafficABROADBANDINTERNETTECHNICALADVISORYGROUP

TECHNICALWORKINGGROUPREPORT

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October2015

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AbouttheBITAG

TheBroadbandInternetTechnicalAdvisoryGroup(BITAG)isanon-profit,multi-stakeholderorganizationfocusedonbringingtogetherengineersandtechnologistsinaTechnicalWorkingGroup(TWG)todevelopconsensusonbroadbandnetworkmanagementpracticesandotherrelatedtechnicalissuesthatcanaffectusers’Internetexperience,includingtheimpacttoandfromapplications,contentanddevicesthatutilizetheInternet.

TheBITAG’smissionincludes:(a)educatingpolicymakersonsuchtechnicalissues;(b)addressingspecifictechnicalmattersinanefforttominimizerelatedpolicydisputes;and(c)servingasasoundingboardfornewideasandnetworkmanagementpractices.SpecificTWGfunctionsalsomayinclude:(i)identifying“bestpractices”bybroadbandprovidersandotherentities;(ii)interpretingandapplying“safeharbor”practices;(iii)otherwiseprovidingtechnicalguidancetoindustryandtothepublic;and/or(iv)issuingadvisoryopinionsonthetechnicalissuesgermanetotheTWG’smissionthatmayunderliedisputesconcerningbroadbandnetworkmanagementpractices.

TheBITAGTechnicalWorkingGroupanditsindividualCommitteesmakedecisionsthroughaconsensusprocess,withthecorrespondinglevelsofagreementrepresentedonthecoverofeachreport.EachTWGRepresentativeworkstowardsachievingconsensusaroundrecommendationstheirrespectiveorganizationssupport,althoughevenatthehighestlevelofagreement,BITAGconsensusdoesnotrequirethatallTWGmemberorganizationsagreewitheachandeverysentenceofadocument.TheChairofeachTWGCommitteedeterminesifconsensushasbeenreached.InthecasethereisdisagreementwithinaCommitteeastowhetherthereisconsensus,BITAGhasavotingprocesswithwhichvariouslevelsofagreementmaybemoreformallyachievedandindicated.FormoreinformationpleaseseetheBITAGTechnicalWorkingGroupManual,availableontheBITAGwebsiteatwww.bitag.org.

BITAGTWGreportsfocusprimarilyontechnicalissues,especiallythosewiththepotentialtobeconstruedasanti-competitive,discriminatory,orotherwisemotivatedbynon-technicalfactors.Whilethereportsmaytouchonabroadrangeofquestionsassociatedwithaparticularnetworkmanagementpractice,thereportsarenotintendedtoaddressoranalyzeinacomprehensivefashiontheeconomic,legal,regulatoryorpublicpolicyissuesthatthepracticemayraise.BITAGwelcomespubliccomment.Pleasefeelfreetosubmitcommentsinwritingviaemailatcomments@bitag.org.

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ExecutiveSummaryTheInternetiscomposedofinterconnectednetworks,eachhavingitsownarchitectureandtechnicalcharacteristics.Thedatatransmittedacrossthesenetworksisformattedaspacketscontaininginformationpayloadsencapsulatedwithinoneormoreheaders,whichinturnprovidetheinformationneededbynetworkstodeliverthepacketstotheirdestinations.Asthesepacketstravelacrossnetworks,theycontendwithotherpacketsfornetworkresources.Contentioncanoccuratanypointwheretwoormorepacketscancompeteforaresourceatthesametime.Thesimplestwaytohandlesuchrequestswouldbeonafirstcome,firstservedbasis(alsoknownasFirstInFirstOut,orFIFO).Inpractice,however,networkoperatorsmakemanyexceptionstoFIFO,usingthepacketheaderinformationtoclassifypacketsintoflowsandtreatingthoseflowsdifferently,forexamplerearrangingtheorderorthetimingwithwhichpacketsaresent,orsendingthemalongdifferentnetworkpaths.

DifferentiatedtreatmentofInternetAccessServicetraffichasbeenasubjectofdebateandregulatoryscrutiny.InFebruary2015,theFederalCommunicationsCommission(FCC)adoptedOpenInternetrulesthataddresspaidprioritizationaswellasothertopics[1].Thisreporttouchesonabroadrangeofquestionsassociatedwithdifferentiation,butisnotintendedtoaddressoranalyzetheeconomic,legal,regulatory,orpublicpolicyissuesthatthedifferentiatedtreatmentofInternetaccessservicetrafficmayraise,focusinginsteadonthetechnicalissues.

TheabilitytotreattrafficdifferentiallyhasbeenbuiltintoInternetprotocolsfromthebeginning.ThespecificationsforbothIPv4andIPv6haveincludedfieldstosupporttrafficdifferentiationsincetheirinception(initiallyIPv4’sTypeofServiceorToSfield)toindicatetoroutersthequalityofservicedesired,intermsofqueuingprecedenceandroutingparametersarounddelay,rate,andreliability.ThiswaschangedtomoregenericservicedescriptionswiththedefinitionoftheDifferentiatedServicesField,andimplementedinIPv4andIPv6.Notably,trafficdifferentiationinthissensehasnotbeenimplementedinmulti-providerenvironments,althoughitisextensivelyusedwithinspecificnetworks.Endtoenddeployment wouldrequiretheharmonizationandcooperationofalargenumber,ifnotall,oftherelevantnetworkoperators.

Initsbroadestsense,trafficdifferentiationincludesanytechniquethatclassifiesandappliespotentiallydifferenttreatmenttotwoormoretrafficflowscontendingforresourcesonanetwork(aflowbeingagroupofpacketsthatshareacommonsetofproperties).Differentiatedtreatmentofnetworktrafficisatwo-partprocess:(1)trafficisclassifiedintotrafficstreams,and(2)aprescribedsetofactionsisappliedtoeachstream.Thistreatmentmaydeterminetheorderinwhichroutersandswitchessendpacketsfromdifferentflowsacrossthelink,therateoftransmissionofagivenflow,orevenwhethercertainpacketsaresentatall.

Whilethetechniquesusedfortrafficdifferentiationoverlapwiththoseusedtomanagecongestion,differentiationhasabroaderpurposethatincludesmeetingservicelevelagreement(SLA)guaranteesandselectingpathsfortrafficfromdifferentapplications,amongotherthings.Differentiatedtreatmentoftrafficcanalsocontributebothtothe

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efficiencyofanetworkandtothepredictabilityofthemannerinwhichnetworkresourcesareshared.

Differentiationcanbecomplex,andacommonvocabularyiskey.Thisreportusestheterms“differentiatedtreatment”or“differentiation,”asopposedto“prioritization”whenreferringtothefullrangeoftreatmentsthatmaybeappliedtotrafficflows.Thetechnicaldefinitionof“prioritization”isnarrowandgenerallyappliesonlytocertainscheduling,dropping,andmarkingtechniques.Thisreportuses“differentiation”inamuchbroadersense,includingmostofthewaysinwhichpacketsmaybetreateddifferentlyfromeachotherwhileenroutetotheirrespectivedestinationsacrossoneormorenetworks.Thescopeofdifferentiationinthisreportencompassestheclassictechniquesofscheduling,shapingandqueuemanagementbywhichpacketsareprocessedatanetworknode,andalsoincludesthetechniquesbywhichtrafficflowsaresegregatedorforwardedontodifferentphysicalorlogicalnetworkpathswheretheymayencountergreaterorlesserpropagationdelaysorcontentionforresources.

ThisreportaddressesdifferentiationappliedtotrafficonInternetaccessservices,aswellastheimpactstoInternetaccessserviceswhendifferentiationisappliedtoothertrafficcarriedoverthesamenetwork.Trafficformass-marketInternetaccessservicesisoftencarriedoveracommoninfrastructurewithtrafficassociatedwithotherIPservices,aswellasthenetworkmanagementtrafficusedtocontroldevicesandreportstatusfromthem.SincedifferentialtreatmentofothernetworktraffichasthepotentialtoaffecttheperformanceofInternetaccessservices,itisconsideredhere.

ThesubjectiveexperienceperceivedbytheuserofanetworkedapplicationisknownasQualityofExperience,orQoE,andthefactorsthatcontributetoQoEvarysignificantlyfromoneapplicationtothenext.Incontrast,QualityofService,orQoS,describestheperformanceofanetworkserviceusingobjectivemetricssuchasthroughput,delay,delayvariation,andloss.TherelationshipbetweenQoSandQoEishighlydependentonthetypeofapplication,butvariationsinQoShavebeenmappedtocorrespondingvariationsinQoEforanumberofapplications.ItispossibletouseknowledgeabouttherelationshipsbetweennetworkperformanceparametersandtheireffectsonQoEtoattempttooptimizetheperformanceofnetworkflowsfortheirintendedapplications.DifferentiationisoftenalsousedtoaddressimpairmentstoQoS.

Broadbandnetworksusedifferentnetworkarchitecturesandaccesstechnologies.Severalofthesenetworkarchitectureshavedevelopedtotakeadvantageofexistingaccessinfrastructurethatwasoriginallydeployedforotherservices–forexample,telephoneserviceovertwistedcopperpairsorvideoovercoaxialcable.Othernetworksweredevelopedtomeetspecificneeds,suchasformobilityorforaccessinremoteruralareas.Inmanycases,differencesinnetworkdesigncanbetracedtothedifferentcharacteristicsoftheaccesstechnologyused.Accesstechnologiescanrequiredifferentapproachestodifferentiationoftraffic.

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Observations.FromtheanalysismadeinthisreportandthecombinedexperienceofitsmemberswhenitcomestothedifferentiatedtreatmentofInternettraffic,theBITAGTechnicalWorkingGroupmakesthefollowingobservations:

• TCPcausesrecurringmomentarycongestion.WhenTCPtransfersalargefile,suchasvideocontentoralargewebpage,itpracticallyguaranteesthatitwillcreaterecurringmomentarycongestionatsomepointinitsnetworkpath.Thiseffectexistsbydesign,anditcannotnecessarilybeeliminatedbyincreasingcapacity.Giventhesametrafficload,however,theseverityofthemomentarycongestionshoulddecreasewithincreasedcapacity.

• Anominallevelofpacketdiscardisnormal.PacketdiscardoccursbydesignintheInternet.ProtocolssuchasTCPusepacketdiscardasameansofdetectingcongestion,respondingbyreducingtheamountofdataoutstandingandwithitself-inducedcongestiononthetransmissionpath.Ratherthanbeinganimpairment,packetdiscardservesasanimportantsignalingmechanismthatkeepscongestionincheck.

• Theabsenceofdifferentiationdoesnotimplycomparablebehavioramongapplications.

Intheabsenceofdifferentiation,theunderlyingprotocolsusedontheInternetdonotnecessarilygiveeachapplicationcomparablebandwidth.Forexample:

§ TCPtendstoshareavailablecapacity(althoughnotnecessarilyequally)betweencompetingconnections.However,someapplicationsusemanyconnectionsatoncewhileotherapplicationsonlyuseoneconnection.

§ SomeapplicationsusingRTP/UDPorothertransportprotocolsbalancetransmissionrateagainstexperiencedlossandlatency,reducingthecapacityavailabletocompetingapplications.

• DifferentiatedtreatmentcanproduceanetimprovementinQualityofExperience(QoE).

Whendifferentiatedtreatmentisappliedwithanawarenessoftherequirementsfordifferenttypesoftraffic,itbecomespossibletocreateabenefitwithoutanoffsettingloss.Forexample,somedifferentiationtechniquesimprovetheperformanceorqualityofexperience(QoE)forparticularapplicationsorclassesofapplicationswithoutnegativelyimpactingtheQoEforotherapplicationsorclassesofapplications.Theuseanddevelopmentofthesetechniqueshasvalue.

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• Accesstechnologiesdifferintheircapabilitiesandcharacteristics.

Specificarchitecturesandaccesstechnologieshaveuniquecharacteristicswhichareaddressedusingdifferenttechniquesfordifferentiatedtreatment.

• Securityoftraffichasattimesbeendowngradedtofacilitatedifferentiationtechniques.

Encryptedtrafficisontheriseandithasimplicationsforcurrentdifferentiationtechniques.Inresponsetothisincrease,somesatelliteandin-flightnetworkoperatorshavedeployeddifferentiationmechanismsthatdowngradesecuritypropertiesofsomeconnectionstoaccomplishdifferentiation.Theresultingriskstothesecurityandprivacyofenduserscanbesignificant,anddifferentiationviaobservableinformationsuchasportsandtrafficheuristicsismorecompatiblewithsecurity.

Recommendations.TheBITAGTechnicalWorkingGroupalsohasthefollowingrecommendations:

• Networkoperatorsshoulddiscloseinformationondifferentialtreatmentoftraffic.

Inpreviousreports,BITAGhasrecommendedtransparencywithrespecttoanumberofaspectsofnetworkmanagement.BITAGcontinuestorecommendtransparencywhenitcomestothepracticesusedtoimplementthedifferentialtreatmentofInternettraffic.

Specificallywithrespecttoconsumer-facingservicessuchasmass-marketInternetaccess,networkoperatorsshoulddisclosetheuseoftrafficdifferentiationpracticesthatimpactanenduser’sInternetaccessservice.Thedisclosureshouldbereadilyaccessibletothepublic(e.g.viaawebpage)anddescribethepracticewithitsimpacttoendusersandexpectedbenefitsintermsmeaningfultoendusers.ThedisclosureshouldincludeanydifferentiationamongstInternettrafficandshoulddisclosetheextentandmannerinwhichotherservicesofferedoverthesameenduseraccessfacilities(forexamplevideoservices)mayaffecttheperformanceoftheInternetaccessservice.

• NetworkoperatorsandASPsshouldbeencouragedtoimplementefficientandadaptivenetworkresourcemanagementpractices.

InapreviousreportBITAGrecommendedthatASPsandCDNsimplementefficientandadaptivenetworkresourcemanagementpractices;wereiteratethatrecommendationhere,extendingittonetworkoperators.Examplesofsuchpracticesmighttargettheminimizationoflatencyandvariationinlatencyinducedinnetworkequipment,ensuringsufficientbandwidthforexpected

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trafficloads,andtheuseofqueuemanagementtechniquestomanageresourcecontentionissues.

• QualityofServicemetricsshouldbeinterpretedinthecontextofQualityofExperience.

CommonQualityofServicemetrics,oftenincludedincommercialservicelevelagreements,includecapacity,delay,delayvariation,andlossrate,amongotherthings.Fromtheviewpointoftheenduserapplication,thesemetricstradeoffagainsteachotherandmustbeconsideredinthecontextofQualityofExperience.Forexample,sinceTCPCongestionControlandadaptivecodecsdependonlosstoinfernetworkbehavior,activelytryingtoreducelosstozeroleadstounintendedconsequences.Ontheotherhand,non-negligiblelossratesoftendirectlyreducetheuser'sQualityofExperience.Hence,suchmetricsshouldbeinterpretedinthecontextofimprovinguserexperience.

• Networkoperatorsshouldnotdowngrade,interferewith,orblockuser-selectedsecurityinordertoapplydifferentiatedtreatment.

Networkoperatorsshouldrefrainfrompreventingusersfromapplyingover-the-topencryptionorothersecuritymechanismswithoutuserknowledgeandconsent.Networksshouldnotinterferewith,modify,ordropsecurityparametersrequestedbyanendpointtoapplydifferentiatedtreatment.Giventhepotentialforpossibleexposureofsensitive,confidential,andproprietaryinformation,priornoticeshouldbegiventoendusersoftrafficdifferentiationfeaturesthataffectsecuritypropertiestransmittedbyendpoints.

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TableofContents1 Introduction 1

2 DifferentiationinIPnetworks 22.1 Historyandevolutionofdifferentiationmethods 32.2 Differentiatedtreatmentandallocationofresources 42.3 QualityofExperience(QoE)andQualityofService(QoS) 52.4 ContributorstoQoS 62.4.1 Delay 72.4.2 PacketdiscardandTransmissionControlProtocol(TCP)CongestionControl 72.4.3 Fragmentation 8

3 Differentiationtechniques 83.1 Layerednetworkmodel 83.2 Classification 103.3 Applicationofservicepolicies 113.3.1 TrafficMarkings 113.3.2 ServicePolicies 11

4 Differentiationinaccessnetworkarchitectures 124.1 Telcofixedbroadbandnetworkarchitectures 134.2 Cableoperatornetworkarchitectures 154.3 SatelliteInternet 164.4 Mobile(3GPP)architecture 184.5 Fixedwirelessnetworkarchitecture 204.5.1 MiddleMile 204.5.2 LastMile 21

4.6 WirelessLANPublicHotspotNetworks 214.7 NetworkFunctionVirtualization(NFV) 22

5 Examples 235.1 Interactiveservicedifferentiation 235.1.1 EffectsofcarriergradeinteractivevoiceonInternetaccessservices 235.1.2 Managingtheimpactofstreamingvideoonothertraffic 25

5.2 TransmissionControlProtocol(TCP)performanceoptimizations 255.3 User-defineddifferentiatedtreatment 275.4 Differentiationinthepresenceofsecuretraffic 27

6 Observations 286.1 TCPcausesrecurringmomentarycongestion 286.2 Anominallevelofpacketdiscardisnormal 28

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6.3 Theabsenceofdifferentiationdoesnotimplycomparablebehavioramongapplications 286.4 DifferentiatedtreatmentcanproduceanetgaininQualityofExperience(QoE) 286.5 Accesstechnologiesdifferintheircapabilitiesandcharacteristics 296.6 Securityoftraffichasattimesbeendowngradedtofacilitatedifferentiationtechniques 29

7 Recommendations 297.1 Networkoperatorsshoulddiscloseinformationondifferentialtreatmentoftraffic. 297.2 NetworkoperatorsandASPsshouldbeencouragedtoimplementefficientandadaptivenetworkresourcemanagementpractices 307.3 QualityofServicemetricsshouldbeinterpretedinthecontextofQualityofExperience 307.4 Networkoperatorsshouldnotdowngrade,interferewith,orblockuser-selectedsecurityinordertoapplydifferentiatedtreatment. 30

8 References 31

9 Glossaryofterms 37

10 DocumentContributorsandReviewers 39

11 Appendix:Standards,StandardsOrganizations,andIndustryReferences 40

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1 IntroductionTheInternetiscomposedofinterconnectednetworks,eachhavingitsownarchitectureandtechnicalcharacteristics.Thedatatransmittedacrossthesenetworksisformattedintopackets,whicharecomposedofinformationpayloadsencapsulatedwithinoneormoreheaders,whichinturnprovidetheinformationneededbynetworkstodeliverthepacketstotheirdestinations.Asthesepacketstravelacrossnetworks,theycontendwithotherpacketsfornetworkresources.Contentioncanoccuratanypointwheretwoormorepacketscancompeteforaresourceatthesametime–forexample,atanetworkswitchwheretrafficfrommultipleinputportsisforwardedtoacommonoutputport.Thesimplestwaytohandlesuchrequestswouldbeonafirstcome,firstservedbasis(alsoknownasFirstInFirstOut,orFIFO).Inpractice,however,networkoperatorsmakemanyexceptionstoFIFO,usingthepacketheaderinformationtoclassifypacketsintoflowsandtreatingthoseflowsdifferently,forexamplerearrangingtheorderand/orthetimingwithwhichpacketsaresent,orsendingthemalongdifferentnetworkpaths.Such“differentiatedtreatment”ofnetworktrafficisthesubjectofthisreport.

DifferentiatedtreatmentofInternetAccessServicetraffichasbeenasubjectofdebateandregulatoryscrutiny.InFebruary2015,theFederalCommunicationsCommission(FCC)adoptedOpenInternetrulesthataddresspaidprioritizationaswellasothertopics[1].Thisreporttouchesonabroadrangeofquestionsassociatedwithdifferentiation,butisnotintendedtoaddressoranalyzetheeconomic,legal,regulatory,orpublicpolicyissuesthatthedifferentiatedtreatmentofInternetaccessservicetrafficmayraise,focusinginsteadonthetechnicalissues.

Differentiationcanbeacomplextopic,andacommonvocabularyisimportant.Thisreportusestheterms“differentiatedtreatment”or“differentiation”asopposedto“prioritization”whenreferringtothefullrangeoftreatmentsthatmaybeappliedtotrafficflows.“Prioritization”hasanarrowertechnicaldefinitionthatappliesonlytocertainscheduling,dropping,andmarkingtechniques.Thisreportuses“differentiation”inabroadersense,includingmostofthewaysinwhichpacketsmaybetreateddifferentlyfromeachotherwhileenroutetotheirrespectivedestinationsacrossoneormorenetworks.Thescopeofdifferentiationinthisreportencompassestheclassictechniquesofscheduling,shaping,andqueuemanagementbywhichpacketsareprocessedatanetworknode,andalsoincludesthetechniquesbywhichtrafficflowsaresegregatedand/orforwardedontodifferentphysicalorlogicalnetworkpathswheretheymayencountergreaterorlesserpropagationdelaysorcontentionforresources.

ThisreportaddressesdifferentiationappliedtotrafficonInternetaccessservices,1aswellastheimpactstoInternetaccessserviceswhendifferentiationisappliedtoothertrafficcarriedoverthesamenetwork.Trafficformass-marketInternetaccessservicesisoften1TheseservicesarelargelyanalogoustoBroadbandInternetAccessServices(BIAS)intherecentOpenInternetReportandOrderpublishedbytheFCC[1].TheFCCOrderusestheterm“non-BIASdataservices”torefertoservicesthatshare“lastmile”connectionswithBIASyetarenotBIAS.NotethatalthoughtheFCCemphasizeslastmileconnectionsattimesinitsReportandOrder,thisreportaddressesdifferentiatedtreatmentatanypointinthenetwork.

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carriedoveracommoninfrastructurewithtrafficassociatedwithotherIPservices,aswellasthenetworkmanagementtrafficusedtocontroldevicesandreportstatusfromthem.SincedifferentialtreatmentofothernetworktraffichasthepotentialtoaffecttheperformanceofInternetaccessservices,itisconsideredhere.

Thereportisorganizedasfollows:Section2givesanoverviewofhowandwhydifferentiatedtreatmentoftrafficexistsincurrentnetworks,reviewsthehistoryofdifferentiation,anddiscussesthepotentialimpactsoftrafficdifferentiationintermsofbothQualityofService(QoS)andQualityofExperience(QoE).Section3addressesthetechniquesusedtodifferentiatetraffic,andSection4showshowthesetechniquesareappliedindifferentaccessnetworkarchitectures.Section5illustratestheimpactofthesetechniqueswithanumberofexamplesofnetworkpracticesassociatedwithtrafficdifferentiation.Section6providesanumberofobservations,andSection7providesrecommendations.Inaddition,thereportincludesreferencesandaglossary,aswellasanappendixlistingrelevantstandards.

2 DifferentiationinIPnetworksInitsbroadestsense,trafficdifferentiationincludesanytechniquethatclassifiesandappliespotentiallydifferenttreatmenttotwoormoretrafficflows(groupsofpacketsthatsharecommonproperties[2])contendingforresourcesonanetwork.Differentiatedtreatmentofnetworktrafficisatwo-partprocess:(1)trafficisclassifiedintotrafficstreams,and(2)aprescribedsetofactionsisappliedtoeachstream.Thistreatmentmaydeterminetheorderinwhichroutersandswitchessendpacketsfromdifferentflowsacrossthelink,therateoftransmissionofagivenflow,orevenwhethercertainpacketsaresentatall.

Whilethetechniquesusedfortrafficdifferentiationoverlapwiththoseusedtomanagecongestion[3],differentiationhasabroaderpurposethanjustcongestionmanagement.Differentiationisusedtodealwithimpairmentsduetocongestion.Itisalsousedtoensurethatservicelevelagreement(SLA)guaranteesaremet.Differentiationcanbeusedtoschedulepacketsortoselectapaththatminimizesdelayfordelay-sensitiveapplications,selectapaththatexperienceslowcorruptionofbitsforloss-sensitiveapplications,orevenselectapaththatkeepsthetrafficonthenetworkoftheproviderofferingaguaranteedSLA.

Differentiatedtreatmentoftrafficispracticedinnearlyeveryprovidernetwork.Someofthemanyreasonsfortrafficdifferentiationare:

● Networkoperatorsroutinelyuseshapingtolimiteachcustomer’straffictotheirpurchasedrate,anduseschedulingtomanagetrafficfromdifferentcustomersattimesofcongestion.SinceInternetaccessservicesaretypicallyofferedatavarietyofrates,bothshapingandschedulingmayusedifferentparametersfordifferentcustomers.

● Manynetworkscarryamixoftraffic,includingcustomertrafficandtrafficwhosepurposeissolelynetworkcontrolormanagement,suchasroutingprotocol

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messagesordeviceconfigurationupdates.Networkoperatorstypicallyprioritizecontrolandmanagementtrafficaboveothertraffictoensuretimelydelivery,whichinsomecasescanbenecessaryforthestabilityofthenetwork.

● ManynetworkoperatorsoffermultipleIP-basedservicestoconsumersoveracommonaccesslink.AtypicalcombinationofservicesincludesInternetaccess,IPTV,andcarriergradevoice,frequentlyreferredtoas“tripleplay.”TrafficforthevoiceandvideoservicesmaybedifferentiatedtoensurethateachserviceisdeliveredtothecustomerwithitsrequiredQualityofExperience(QoE,seeSection2.3).

● Manynetworkscarrytrafficforavarietyofbusinessservicesinadditiontotheconsumerservicesnotedabove.Businessconnectivityservices,suchasCarrierEthernet,aretypicallysoldwithanassociatedservicelevelagreement(SLA)thatspecifiestheservicerequirementsforsomeorallofthetrafficcarriedbytheservice.TrafficfortheseservicesisdifferentiatedtoenableitsdeliverywithintheQoSparameterssetbytheSLA.

● Mobileaccessnetworkshavetodealwithconstantlychangingcapacityandcongestionconditionsbasedonthemobilityoftheircustomers.Thesenetworksdifferentiateservicestoensureproperbalanceofsignaling,voiceanddatatoensuretheproperexperienceforeachaspectofthenetwork.

2.1 HistoryandevolutionofdifferentiationmethodsTheabilitytotreattrafficdifferentiallyhasbeenbuiltintoInternetprotocolsfromthebeginning.TheIPv4protocol,firstspecifiedfortheDefenseAdvancedResearchProjectsAgency(DARPA)in1981[4],isstillthedominantprotocolintheInternettoday–althoughthereisanincreasingmovementtoIPv6asthenumberofassignableIPv4addressesdwindles[5,6,7].EverypacketsentacrosstheInternetuseseitherIPv4orIPv6toprovideend-to-endaddressingandotherinformation.ThespecificationsforbothIPv4andIPv6haveincludedfieldstosupporttrafficdifferentiationsincetheirinception,providingasetofcontrolbitsintheInternetProtocolheader(initiallytheTypeofServiceorToSfield)toindicatetosystemsenroute,includingrouters,middleboxes,andthedestinationhost,thequalityofservicedesired[8].Originally,theToSfieldwasdescribedintermsofprecedence,latency,throughput,andreliabilityrequirements[8].Withthedefinitionofthedifferentiatedservicesarchitecture[9],theToSfieldwasredefinedtoincludeadifferentiatedservicescodepoint(DSCP)whosevaluesweredefinedintermsofthelocalizeddifferentiatedtreatment(or“per-hopbehavior”)requestedofroutersinthenetworkpath.

OneexampleoftrafficdifferentiationfromtheearlydaysoftheInternet(the1980s)concernedinteractivetrafficfromremoteloginsessions.Thistrafficwasgivenpriorityoverothertraffictoimprovetheperceivedperformanceoftheinteractivesession[10].ItisworthnotingthattheoriginalbackboneoftheInternet(theARPAnet)hadlongdistancelinksthatranat56kb/s,andthatatthetime,persistentcongestionwaswidespread[11,12].

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EarlynetworkingstandardsrecommendedthatapplicationsonhostcomputerssendingtrafficshouldspecifythecorrectsettingoftheToSfield,andthatroutersshouldrespectthissetting(eitherbyprocessingitorbypassingittothedatalinkcontrollayer)[13,14,8].Thisdesignputthesendinghost,andnottherouter(oritsoperator)incontrolofselectingwhatsortoftraffictreatmentthepacketswouldreceive.TheDifferentiatedServicesArchitecturemakesthesameassumption,althoughitallowsthenetworktooverridethesetting[9].

TheinclusionoftheToScontrolfieldintheIPheaderallowedthatfieldtobeactedonbycontemporaryrouters,which(atleastintheory)onlyexaminedfieldswithinthatheader.Newerrouters,however,regularlylookatportnumbersintheTransmissionControlProtocol(TCP)orUserDatagramProtocol(UDP)headertoclassify,andsometimesdifferentiatebetweentrafficfromdifferentapplications(frequentlyduetosecuritypolicies).2However,thereisnoguaranteethatapplicationswilluseportnumbersintheexpectedway,orindeedthatportfieldswillalwaysbepresentintheheader.IntheincreasinglyencryptedInternet,eventhebasicassumptionofthevisibilityofthosefieldsmaybesuspect[19].Asaresult,routersthatlookintohigherlayerheadersaretakingadvantageofacommonconvention,butnotafeatureassuredbythearchitecture.

Whiletheyhavebeenusedinspecificnetworks,suchasUSNavySPAWARandinindividualpublicandprivatenetworks,theIPv4ToSfieldandtheIPv4/IPv6DSCP,havenotbeendeployedorusedacrossnetworkinterconnectsforbothengineeringandeconomicreasons[20],andwouldrequiretheharmonizationandcooperationoftherelevantnetworkoperators.ProposalstothatendarebeingdiscussedintheIETF,however[21].

2.2 DifferentiatedtreatmentandallocationofresourcesDifferentiatedtreatmentoftrafficcanaffectthemannerinwhichnetworkresourcesareshared.Differentmethodsofsharingresourcesmightaffect:

• Theamountoftimethateachsenderissending,• Theamountofdatathateachsendersends(intermsofpacketsorbits),or• Theaveragerateofeachsession.

Itisalsopossibletoshareresourcesatdifferentlevelsofaggregation,includingforexample:

• Individualflows,forexampleasdefinedbytheir5-tuple(seeSection3.2),• Allflowsassociatedwiththesameserviceanduser,or• Allflowsassociatedwiththesameuserregardlessofservice.

2TheInternetCorporationforAssignedNamesandNumbers(ICANN),undercontractbytheNationalTelecommunications&InformationAdministration(NTIA)toperformtheInternetAssignedNumbersAuthority(IANA)functions,maintainsaregistryof“wellknown”portnumbersassociatedwithdifferentapplications[15].TransmissionControlProtocol(TCP)andUserDatagramProtocol(UDP)aretwoofthecoreprotocolsintheInternetProtocolsuite,withTCPbeingtheprotocolthatmanymajorInternetapplicationsrelyon[16,17,18],seealsoSec.3.1and5.2.

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Theliteratureincludessignificantdiscussionofnetworkresourceallocationamongapplicationsandtransportprotocols[22,23].TCPandsimilartransportprotocolstendtoshareavailablecapacity(althoughnotnecessarilyequally)betweencompetingconnections.Intheabsenceofschedulingorotherdifferentiationtechniques,however,thissharingofcapacitymaybeskewedbytheapplicationssendingtrafficoverTCP.Forexample,evenifweassumethateachTCPconnectionreceivesaroughlyequalshareofcapacity,anapplicationthatopensmanyconnectionswillreceivemuchmorecapacitythananapplicationopeningasingleconnection.Inaddition,notalltransportsorapplicationssharecapacityinthesameway;forexample,voiceandvideoapplicationsusingRTP/UDPtransportwilloftenbalancetransmissionrateagainstexperiencedlossandlatency,reducingthecapacityavailabletocompetingapplications.

2.3 QualityofExperience(QoE)andQualityofService(QoS)CustomersofInternetaccessservicesusethoseservicesforabroadrangeofapplications.However,customersrarelynoticetheunderlyingtransferofdataacrossthenetworkthatenablestheseactivities,exceptwhenaperformanceissuecausesaperceptiblereductioninqualityintheapplicationtheyareusing.ThesubjectiveexperienceperceivedbysomeoneusinganapplicationisknownasQualityofExperience,orQoE[24].QoEhasanumberofcontributingelements,includingnetworkperformance,theplatformusedbythecustomer,andtheapplicationitself.

ThesubjectivefactorsthatcontributetoQoEvarysignificantlyfromoneapplicationtothenext.Forvoicecommunications,contributingfactorsincludewhetherthereceivedvoiceisgarbledormissinginplaces,whetherthespeaker’sechoisaudible,andhowmuchdelayisintroducedbythecombinationofcommunicationschannel,applicationandequipment[25].Forstreamingvideo,factorsincludewhetherblockingorotherartifactscorruptthereceivedvideo,whetheritfreezesorstutters,theamountoftimebeforeplaybackbeginsandthequalityofthesourcecontentincludingitsencodingalgorithmandencodedbitrate[26].TheQoEassociatedwithawebbrowsingapplicationmaybeaffectedbythespeedatwhichpagesloadandwhetherallofthecontentisreceivedcorrectly.Someapplicationsmayexhibitmultiplebehaviorssimultaneously(e.g.videoinsideabrowsingsession)andthiscanmakeQoEdifficulttoassess.QoEcanbemeasuredandquantifiedforagivenapplicationandsetofconditions(forinstance,byuseofMeanOpinionScores[27]),butthespecificmeasurementmethodsvaryfromoneapplicationtoanother[28,29].

ArelatedconceptthatisfrequentlyconfusedwithQoEisQualityofService,orQoS.3WhileQoEdescribessubjectiveuserexperience,QoSdescribestheperformanceofanetworkserviceusingobjectivemetricssuchasthroughput,delay,delayvariation,andloss[33].VariationsinQoShavebeenmappedtocorrespondingvariationsinQoEforanumberofapplications[34,35].ThecontributionsmadetoQoEbyspecificnetworkperformanceparametersarehighlydependentonthetypeofapplication.Forexample,two-way3ContributingtotheconfusionisthefactthatbeforethetermQoEcameintogeneraluseinanetworkingcontext,QoS(andvariationssuchasPQoS)wascommonlyusedtodescribebothnetworkperformanceandsubjectiveuserexperience[29,30,31,32].

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interactivevoicecommunicationissensitivetoroundtripdelayanddelayvariation,butthethroughputrequiredisordersofmagnitudelowerthantypicalbroadbandservicerates.Conversely,videostreamingQoEissensitivetopacketlossandvariationsinthroughputbelowathresholdrate,butlesssensitivetodelayvariationorroundtripdelay.Videostreamingalsoaccountsforthemajorityofcurrentthroughputrequirementsonatypicalbroadbandservice.

Figure1showsageneralizedshapefortherelationshipbetweenQoSimpairmentandtheQoEforanapplication[36].ThecurveshowsthreeregionsofvaryingdegreesofQoSimpairment.Thefirstregion(QoSimpairmentlessthanx1)denotesarangeinwhichtheimpairmenthasnodiscernibleeffectonQoE.Thesizeofregion1,whichmaybezeroinsomecasesandsignificantinothers,dependsontheimpairmentandtheapplication.Forexample,intheabsenceofotherimpairments,aone-waydelayofupto150msecfromthespeaker’smouthtothelistener’searhasnodiscernibleeffectoninteractivevoiceQoE[37].Inthesecondregion(QoSimpairmentbetweenx1andx2),increasingQoSimpairmentcorrespondstodecreasingQoE.Inthethirdregion(QoSimpairmentgreaterthanx2)theQoEissopoorthatmostusersconsideritunacceptableandmaystopusingtheapplication.Thevalueofx2isdependentontheimpairment,theapplication,andusertolerance.

Figure1:GeneralshapeofthemappingcurvebetweenQoSandQoE[36]

ItispossibletouseknowledgeabouttherelationshipsbetweennetworkperformanceparametersandtheireffectsonQoEtooptimizetheperformanceofnetworkflowsfortheirintendedapplications.Inmanycases,differentiatingbetweenflowscanimprovetheQoEforsomeapplicationswithoutmateriallydegradingtheQoEforotherapplications.Section5describesanumberofexamplesofthistypeofoptimization.

2.4 ContributorstoQoSThenetworkcontributorstoQoSdiscussedbelowhaveadirectbearingondifferentiatedtreatmentoftraffic.Othercontributors,suchaspacketcorruptionorreordering,affect

Excellent

QoS Impairment

Poor

x1 x2

1

2

3

QoE

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networkperformancebutonlyhaveanindirectbearingondifferentiation(e.g.,reorderedpacketsincreasingdelay).

2.4.1 DelayDelaysacrossthenetworkderivefromfourbasiccomponents[38]:

• Serializationdelay:theamountoftimeittakestosendapacketonacommunicationslink.Serializationdelayforapacketiscalculatedasthelengthofthepacketdividedbytherateofthelink.

• Processingdelay:theamountoftimerequiredtocalculatehowtoforwardthepacketwithinarouterorswitch.

• Propagationdelay:theamountoftimeittakespacketstotravelthephysicalnetworkpathfromsourcetodestination.Thisiscalculatedasthedistancetraveleddividedbythespeedofpropagationinthetransmissionmedium.

• Queuingdelay:occurswhenpacketsmustwaitinabufferbeforebeingtransmitted.

Serializationandprocessingdelaysdonotusuallychangesignificantlyduetodifferentiation,althoughtheyareaffectedbythenumberofhopsinanetworkpath.Propagationdelaycanbeaffectedbythechoiceofnetworkpath,andqueuingdelaycanbeaffectedsignificantlybydifferentiatedtreatment.

Delayischaracterizedbymedianoraveragelatencyandbyvariationinlatency(alsoknownas“jitter”).Queuingdelayisusuallythelargestcontributortojitter.Jittermaybeincreasedbytechniquesinwhichatechnologyqueuesseveralpackets(introducingmomentarydelay)andthensendstheminaburst.ExamplesexistinIEEE802.11WLANandDOCSIStechnologies.

2.4.2 PacketdiscardandTransmissionControlProtocol(TCP)CongestionControl

Whenapacketarrivesatabuffer,itmaybeprocessedimmediately(iftheresourcefedbythebufferisavailable),bufferedforlaterprocessing,ordiscarded.Inthesimplestcase,packetsarediscardedwhenthebufferhasnoroomfornewtraffic(“taildrop”).MoresophisticatedalgorithmsdiscardpacketsbeforethebufferisfulltosignalcongestiontoTCP[39].Somealgorithmsalsodifferentiatebasedonthedropprecedencemarkedinpacketheaders(Section3.2),discardingsomepacketsmoreaggressivelythanothers[40].

PacketdiscardisfundamentaltothedesignoftheprotocolssupportingtheInternettoday.TCPprobesforavailablecapacitybycontinuouslyincreasingtheamountofdataplacedonthenetworkuntilitdetectslostpackets,whichitinterpretsascongestion.4Upondetectingcongestiontheprotocoldecreasestheamountofoutstandingdatabeforeitonceagain

4NodesinthenetworkpathcanalsosignalcongestiontoTCPexplicitlyusingbitsintheTCPheader[41]–however,packetdiscardisusedtoimplicitlysignalcongestioninmostcases.

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startsprobingforcapacity.Ratherthannecessarilybeinganimpairment,packetdiscardcanserveasanimportantsignalingmechanismthatkeepscongestionincheck.

2.4.3 FragmentationPacketfragmentationinIPv4occurswhenahostattemptstosendpacketsthatarelargerthanthemaximumpacketsize(knownasMaximumTransmissionUnit,orMTU)thatcanbeprocessedbyanetworksegment[42].Whenapacketlargerthanthesegment’sMTUarrives,itmaybesubdividedintotwoormorepacketsbeforebeingforwarded,ordroppedincaseswhenfragmentationisnotdesired.

Fragmentationcancauseadditionallatency(asareceivermustbufferandreassemblepackets),additionalCPUutilization,andadditionalmemoryusageorpacketlosswhenbuffersareexhausted.Whenpacketsarefragmented,onlytheinitialfragmenthastheTCP/UDPportnumber,anddifferentiatedtreatmentthatdependsontheportnumberforclassification(Section3.2)maynotwork[42].

3 DifferentiationtechniquesDifferentiatedtreatmentofnetworktrafficisatwo-partprocess:(1)trafficisclassifiedintotrafficstreams,and(2)aprescribedsetofactionsisappliedtoeachstream.Theclassificationrulesandtheactionrulesarecombinedtoformservicepolicyrules[43].

3.1 LayerednetworkmodelTounderstandhowdifferentiationisperformed,ithelpstofirsthaveabackgroundunderstandingofthelayerednetworkmodelusedtodescribehownetworksoperate,assomedifferentiationtechniquesareimplementedatdifferentlayers.Whileanumberofdifferentmodelsexist,eachusestheconceptof“layers”toabstractawaytheinternalstructureandtechnologyofanetwork,aswellasgroupcommonfunctionstogether.Thisreportusesthe5-layerTCP/IPmodel[44]asshowninFigure2below.

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Figure2:5-layermodeloftheInternetandIPPacketElements[44]

Layer1–PhysicalLayer.Thephysicallayerconveysthebitstreamonthetransmissionmedia(fiber,copper,radiowave)attheelectricalandmechanicallevel–convertedtoelectricalimpulses,lightwaves,orradiosignals.

Layer2–DataLinkLayer.Thedatalinklayerencompassesthetechnologiesandprotocolsusedtosendtrafficacrossasub-network,or“link.”5Atthelowestlevel,linklayerprotocolsmanageaccesstothephysicalmediaandencodetrafficintoframessuchasEthernetframes,FrameRelayframes,orATMcells[44].Theseprotocolsaresometimesdesignedinconjunctionwithaspecificphysicallayer,suchasIEEE802.11orDOCSIS.Linklayerprotocolsalsosupportclassificationandmarkingtofacilitatescheduling,shaping,andotherdifferentiationfunctionsthatmayoccurinthenodesthatperformswitchingwithinalink.

Insomenetworkarchitectures,multipleprotocolsmayoperatebetweenthephysicallayerandtheInternetlayer.ExamplesofthisareMPLSandtheuseofEthernetMACoverATMandPPPoEoverEthernetMAC[46,47,48].

Layer3–InternetLayer.TheInternetlayerdeliverspacketsacrosstheend-to-endnetworkfromsourceendpointtodestinationendpoint.TheInternetProtocol(IPv4orIPv6)atthislayersupportsend-to-endaddressing,aswellasclassificationandmarking.Routersperformscheduling,shaping,andpolicingaswellasroutingatthislayer.

Layer4–TransportLayer.Atthetransportlayer,theInternettransportprotocol(typicallyTCPorUDP)deliversaflowofpacketsacrossthenetworkwithcharacteristicsdeterminedbytheprotocolused.TCPprovidesend-to-endflowidentification,packet

5TheIETFusestheterm“link”forasub-networkinwhichtrafficflowsbetweentwoormoreIPinterfaces[45].Inthiscontext,a“link”canincludemultiplephysicalsegmentsaswellasswitcheswheretrafficmaybedifferentiated.

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sequencing,errorrecovery,andflowcontrolforreliabledatatransfer[17].UDPprovidesflowidentificationanderrorcorrection[18].

Layer5–ApplicationLayer.Theapplicationlayerrepresentsallthefunctionsthatareperformedbytheapplicationendpoints(e.g.clientandserver)tomanageapplication-to-applicationlevelcommunication,suchascontrollingthetransferofalargefile.Oneexampleisthehypertexttransferprotocol(HTTP),theprotocolforthetransmissionofwebpages[49].Otherexamplesincludethefiletransferprotocol(FTP),theDynamicHostConfigurationProtocol(DHCP),andtheemailprotocolsPOP,IMAPandSMTP[50,51,52,53,54].

3.2 ClassificationTrafficclassificationcanbeperformedinmostlayersofthenetworkmodel,thoughtheavailableclassificationelementsdifferateachlayer.ClassificationbelowtheApplicationlayer(Layer5)usespatternanalysisonelementswithinpacketheaders.ClassificationattheApplicationlayermayusepatternanalysisorother,morecomplextechniques.

• Layer2.TrafficisoftenclassifiedatLayer2inconvergednetworksthatdelivermultipleservicessuchashigh-speedInternetaccessserviceandcarriergradevoice.ClassificationcanbeperformedusinganyelementintheLayer2frameheaderssuchasMACaddress,virtualLAN(VLAN)tags,andmultiprotocollabelswitching(MPLS)labels.

• Layer3and4classificationisperformedontheelementsintheIP(Internetlayer)andTCP/UDP(Transportlayer)packetheaders.TheIPpacketheaderincludesIPaddresses(sourceanddestination),typeofservice(TOS),andprotocol(TCPorUDP).TheTCPandUDPheadersbothcontainsourceanddestinationportnumbersthatcanbeusedtoidentifycertainapplications.FiveelementsintheInternetlayerandTransportlayerheaders(IPsourceanddestinationaddresses,protocol,andTCP/UDPsourceanddestinationportnumbers)arereferredtoasthe"5-tuple,"andtheyuniquelyidentifyaconnectionorflowbetweentwoapplicationlayerentities[55].Theterm“IPflow”isoftenusedtorefertoallthepacketsthathavethesame5-tuple.

• Layer5.ApplicationlayerclassificationisperformedonelementsabovetheTransportlayer,includingthehigherlayerheadersandthedatapayload.Unencryptedtrafficcanbeclassifiedthroughpatternmatchingand/ormoreadvancedtechniques.Manyapplicationsusestandardprotocolssuchashypertexttransferprotocol(HTTP),sessioninitiationprotocol(SIP),andfiletransferprotocol(FTP)aspartoftheircommunicationsandexposeelementsthatcanbeusedforclassification[49,56,50].ClassificationatLayer5issometimesreferredtoas"DeepPacketInspection."Encryptiongenerallyinterfereswithattemptstoperformpatternanalysisordeeppacketinspectionatthislayer[57].

Trafficthatisencryptedorthatdoesnotusestandardprotocolsmaystillbeclassifiableusingsignature-orheuristic-basedtechniques.Heuristicanalysis

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involvesinspectingalargesetoftrafficforbehaviorpatterns[58,59].Itisoftenpossibletoinferthetypeoftrafficbyexamininghowmanyendpointsaretalkingtoeachother.Forexample,encryptedVoIPtrafficcansometimesbeclassifiedbylookingforIPflowsbothtoandfrommanyend-pointscommunicatingtoasoft-switch,combinedwithnumericalanalysisthatexaminestheflowratesandpacketpayloadsizes[60].Malicioustrafficmayalsobeinferredbylookingforamany-to-oneIP-flowrelationship[61].

3.3 ApplicationofservicepoliciesAftertraffichasbeenclassified,certainservicepoliciescanbeapplied.Inaddition,packetsmaybemarkedsothatotherprocessesornetworknodescanapplytheassignedservicepoliciesmorereadily.

3.3.1 TrafficMarkingsTrafficcanbemarkedatLayer2andLayer3ofthenetworkmodelbysettingorchangingsomeelementinoneoftheheaders.

• Layer2Marking(DataLinkLayer).ThecommonlyusedLayer2technologiessuchasATM,FrameRelay,andEthernetallincludeoptionsformarkingtheLayer2frameorpacket[62,63].ATMandFrameRelaybothincludeafieldintheirheadersthatcanbeusedtoindicatewhetherthecellorframecanbedroppedduringperiodsofcongestion.TheIEEE802.1QstandarddefinespriorityandVLANfields,bothofwhichcanbeusedtomarkEthernetframes[64].

• Layer3Marking(InternetLayer).AtLayer3theIPheaderhasfieldsthatcanbeusedtomarktraffic.TheIPheaderhasafieldthatcanbeusedtoindicateeitherType-of-Service(TOS)orusedtospecifyadiffservcodepoint(DSCP)intendedtoindicateadesiredper-hopbehavior[9].

3.3.2 ServicePoliciesOnceapackethasbeenclassified,itcanbetreatedaccordingtotheassignedservicepolicy.Servicepoliciesincludeschedulingpolicies(e.g.,queuing,shaping,dropping)aswellasroutingdecisions,suchaswhategressporttouseonthenetworkelementorwhetherthepacketiseligibletobecached.

3.3.2.1 SchedulingPoliciesWhenthereiscontentionforanetworkresource,forexampletheegressportonanetworkelementsuchasarouterorswitchorforaccesstoasharedmedium,thenetworkelementmayuseaschedulingalgorithmtodeterminetheorderinwhichpacketsaretransmitted.Manyschedulingalgorithmsfallintooneofthreecategories:1)priorityscheduling[65],whichscheduleshigherprioritytrafficbeforelowerprioritytraffic;2)rate-basedscheduling(suchasround-robinscheduling[66]orweightedfairqueuing[67]),whichallocatesresourcestoisolatetheeffectsofdifferentflowsoneachother;or3)deadlinescheduling[68],whichlimitsthemaximumtimeallowedbeforeapacketiseithertransmittedordiscarded.

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Theabovealgorithmsarenotmutuallyexclusiveandcanbeusedincombinationwitheachother.Forexample,anetworkprovidermightusearate-basedschemetoseparateusersfromeachotherinasharedaccessregime,andthenuseprioritywithineachsharetoalloweachusertofavortheirlatency-sensitivetrafficrelativetoothertraffic.Inaddition,somenetworkelementssupportmorespecializedschedulingalgorithmsthanthosedescribedhere.

3.3.2.2 TrafficshapingTrafficshapingistheprocessthatanetworkmightusetolimittheratethatasender(i.e.,adevice,application,user)cansendtrafficonaparticularlink[69].Anoperatormayuseatrafficshaperforexample,toimplementbandwidthlimitations;tolimittherateatwhichtrafficbursts(avertingunnecessarydelayandloss),ortocontroltheeffectsofbufferbloat[70].Shapingofdifferentflowstodifferentparametersimplementsdifferentiatedtreatment.

Thereareseveralmechanismsthatproviderscanusetoshapetraffic;eachofthesemechanismshasdifferentcharacteristics.Someofthesemechanismslimitaflowtoacertainaveragerate.Othermechanismsallowasendertoperiodically“burst”(i.e.,sendtrafficatahigherrateforaperiodoftimebeforetheyareshapedtoalowersustainedrate).Thesemechanismscanincludeleakybucket,tokenbucket,andcompositeshaping(whichcombinesleakyandtokenbucketshaping)[71].

3.3.2.3 ResourcereservationResourcereservationisatechniqueappropriateforapplicationsthatrequireaminimumlevelofnetworkresourcesinordertofunctionadequately.Resourcescanbestaticallyconfiguredtoreservethemforcertainusersorapplicationtraffic,orresourcereservationandassociatedadmissioncontrol(denyingorgrantingapplicationrequestsforspecialtreatmentofcertainflowsbasedonavailabilityofnetworkresources)canbedonedynamically[72,73].

3.3.2.4 RoutingpoliciesInadditiontopacketschedulingpolicies,classificationcanbeusedbyanetworknodetoassistroutingdecisions.Thenode,whichmaybeconnectedtomultiplenetworks,canattempttooptimizetheQoEforcertaintrafficbyforwardingittoapathwithQoScharacteristicsthatmaybealignedwiththetraffic’srequirementssuchaslowerlatency,lowerround-triptime,lesscongestion,etc.

4 DifferentiationinaccessnetworkarchitecturesDifferentiationtechniquesaremostoftendeployedintheaccessandaggregationnetworksthatoperateclosetoendusers.Differentiationcanmakemoreofadifferenceinthelowerspeednetworksegmentsnearthenetworkedgethataggregatesmallernumbersofflows,becauseinthesesegmentstherelativeeffectofeachflowonotherflowsismagnifiedcomparedtothehighlyaggregatedsegmentsinthenetworkcore.Whendifferentiationis

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usedinthecoreitfrequentlytakestheformofroutingalongengineeredpaths.Thissectionfocusesonthearchitecturesandaccesstechnologiesdeployednearthenetworkedge.

Broadbandnetworkshavebeendeployedwithanumberofdifferentnetworkarchitecturesandaccesstypes.Severalofthesenetworktypeshavedevelopedtotakeadvantageofexistingaccessinfrastructurethatwasoriginallydeployedforotherservices–forexample,telephoneserviceovertwistedcopperpairsorvideoovercoaxialcable.Othernetworksweredevelopedtomeetspecificneeds,suchasformobilityorforaccessinremoteruralareas.Mostbroadbandnetworksareengineeredtosupportmultipleservicessharingcommoninfrastructure.Whilethedesignsdiffer,theyareconceptuallysimilartothedegreethattheyaredesignedtomeetsimilarrequirements.Eachoftheunderlyingbroadbandaccessnetworksprovidesameanstoisolateservicesfromoneanotheratthelinklayer(Layer2)bycreatinglogicalchannels.InDOCSIScablenetworksthelogicalchannelsarecalledserviceflows,intelconetworkstheyarecalledVLANs,andin3GPPmobilenetworkstheyarecalledbearerchannels.Eachbroadbandaccesstechnologyincludesthecapabilitiesto:

● Classifyandmaptraffictotheassignedlogicalchannel.

● Limittherateatwhichtrafficisdeliveredoverthelogicalchannel.● Controlhowtrafficineachlogicalchannelisdeliveredrelativetootherchannels

whencontentionoccurs.

Inmanycases,networkdesigncanbetracedtothecharacteristicsoftheaccesstechnologyused.Specificaccesstechnologiescanpresentuniquechallengesthatrequiredifferentapproachestodifferentiationoftrafficsentovertheaccesslink,asdocumentedinthefollowingsections.

4.1 TelcofixedbroadbandnetworkarchitecturesTelecombroadbandnetworkstracetheirheritagetothetelephonenetworksthatdeliveredanalogvoiceserviceovertwistedcopperwirepairs(or“loops”)tohouseholdsacrossthedevelopedworldformuchofthetwentiethcentury.DigitalSubscriberLoop(DSL)technologywasdevelopedtosupportbroadbanddataservicesoverthesesamecopperloops.WhileopticalfiberhasbeenincreasinglydeployedintheaccessnetworkandmaximumDSLspeedshaveincreasedbyordersofmagnitude,inmanycasescopperloopsstilldeliverdataoverthelastlinktotheconsumer.Theevolutionfromvoicetodatanetworksandthephysicalchallengesimposedbythecopperloopenvironmenthaveeachinfluencedhowtelcobroadbandnetworkarchitectureshaveevolved.

TheBroadbandForum(BBF)hasspecifiedarchitecturesforbroadbandaccessthroughaseriesoftechnicalreports[74,75].ArepresentativearchitecturefortheMulti-ServiceAccessNetworkisshowninFigure3below.Inthefigure,trafficistransportedoveraregionalaccessnetworkbetweenthenetwork’sinterconnectioninterfacetoothernetworks(interfaceA10)andtheinterfacestocustomerequipment(interfaceT).ThepointsatwhichtrafficmaybedifferentiatedcanbeexaminedbytracingthepathofInternetaccesstrafficsentfromothernetworkstothesubscriber.Thistraffic,sourcedbya

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serverinaremotenetwork,istransportedacrosstheremotenetworkandpossiblyoneormoreintermediatetransportnetworks(labeledNSP2)beforearrivingattheinterconnectionpointA10forthedestinationnetwork.ThetrafficentersandistransportedacrosstheregionalIPnetworkattheIPlayer(Layer3).Atnodesintheregionalnetwork,thetrafficisaggregatedwithInternetaccesstrafficdestinedforothersubscribersandmaybescheduledalongwithtrafficassociatedwithotherIPservices,usingDSCPmarkingsorothermeansofclassificationtodeterminethedifferentiatedtreatmentprovidedduringscheduling.

Figure3:BroadbandMulti-ServiceReferenceModel[74]

AnodecalledtheBroadbandNetworkGateway(BNG)providestheprimaryinterfacebetweentheIP-basednetworksontheleftandtheLayer2network–socalledbecausewithfewexceptions,thenodeswithinthisnetworkignoreanypacketinformationabovetheLayer2(e.g.,Ethernet)header–extendingtothesubscriberontheright.TheBNGmayalsoprovideper-subscribershapingtoenforceeachsubscriber’sservicerate,andschedulingtoenforcepolicybetweensubscribers.Finally,theBNGmayisolateeachsubscriber’sInternetaccesstrafficintoaseparateVLANfortransportacrosstheaccessnetwork(notethattherearevariationsinhowisolationisimplementedbydifferentnetworkoperators,includingisolationbysubscriberandisolationbytypeofservice).

TheMulti-ServiceAccessNetworksupportsavarietyofIPservicesinadditiontoInternetaccess,includingresidentialservicessuchasIPTVandvoice.Trafficfortheseservicesmaycomefromnetworkproviders(NSP2)orapplicationproviders(ASP1)acrossA10asIPtraffic,or(forservicessuchasLayer2businessconnectivity),fromanothernetworkprovider(labeledNSP1)asEthernetorotherLayer2traffic.ThistrafficmaybemultiplexedwithInternetaccesstrafficintheregionaloraccessnetworkasshown,andmaybescheduledalongsideInternetaccesstraffictogeneratethedesiredQoSforeachservice.

ThelastlinksusedinthesenetworkstoreachthecustomertypicallyrunovereithertwistedcopperpairsknownasDigitalSubscriberLoops(DSL)oropticalfibers,whichmaybeeithersharedbetweenmultiplecustomersasPassiveOpticalNetworks(PON)or

IP Network

OLT

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dedicatedtoasinglecustomer.Eachaccessmediumhasdifferentcharacteristics,someofwhichlendthemselvestospecificdifferentiationtechniques:

● DigitalSubscriberLoop(DSL).DSLtechnologyisusedtoprovidebroadbandaccessacrosstwistedpaircopperloops.Dependingonthenetworkdesign,DSLtechnologyandlooplength,thecapacityavailableacrosstheDSLlinkmayrangefromonetohundredsofmegabitspersecond(Mbps).Ofparticularinterestarelinksthatprovidecapacityontheorderof20to40Mbps,whichishighenoughtosupportbothIPTVandInternetaccessservices,butwhichmaynotsupportbothservicesconcurrentlyattheirmaximumexpectedrates.Undertheseconditions,IPTVtrafficmaybeprioritizedtopreventinterruptionofvideoprogrammingwhentheDSLlinkbecomescongested[76].

● OpticalFiber.TheopticalfibersoverwhichPassiveOpticalNetworks(PONs)transmitcancarrygigabitspersecond.However,PONscanbesharedby32ormorecustomers,soshapingandscheduling(frequentlyperformedattheBNG)enforcepolicyinthedownstreamdirection.Intheupstreamdirection,onlyonecustomeronthePONcantransmitdataatanygiventime.Thespecificationforgrantingupstreamallocationsincludesprovisionsfordifferentialtreatmentincludingweighting,prioritization,andguaranteedbandwidth[77].

4.2 CableoperatornetworkarchitecturesCablenetworkswereoriginallydeployedtodelivertelevisionservicestosubscribersovercoaxialcables.Startinginthe1990s,thesenetworksevolvedtosupporttwo-waydatacommunicationandhavesinceseenseveralgenerationsoftheDataOverCableServiceInterfaceSpecifications(DOCSIS)standardsthatspecifyhowbroadbandaccessservicesareprovidedtoresidentialandsmall-to-mediumbusinesscustomers[78].Aswithtelecomnetworks,thearchitecturesofmodernHybridFiber/Coaxial(HFC)cablenetworkshavebeeninfluencedbothbytheirhistoryandbythemixofservicestheyoffer.

Asinglecablesystemtypicallyservesametropolitanarea,includingoutlyingcommunities.AnexampleofacablesystemisshowninFigure4below.Inatypicalcablesystem,ahubsitemightprovideservicetoanareaconsistingof10,000to20,000households.Thehubsiteconnectsahybridfiber-coaxportionofthecablenetwork(the“AccessNetwork”)totheregionaldatanetworkviatheCableModemTerminationSystem(CMTS),whichconnectsIPservicestocustomers'cablemodems[79].6

6Insomecablesystems,someoralloftheaccessnetworkisdeployedusingEthernetPassiveOpticalNetwork(EPON)technologyinsteadofHFC.CableLabsDOCSISProvisioningofEPON(DPoE)specificationsallowEPONdevicestomimicthefunctionalityofaDOCSISCMTSandcablemodem.

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Figure4:ExampleCableSystem

Intheaccessnetwork,cablespectrumisdividedintochannelsasspecifiedbyDOCSIS,whichinturnaregroupedintoServiceGroups[79].EachServiceGroupconsistsofasetofupstreamanddownstreamDOCSISchannelswhosetotalcapacityissharedbyanumberofcablemodems.Eachcablemodemtypicallyservesonecustomer.AsingleCMTSsupportsdozensofServiceGroups,witheachServiceGroupprovidingservicetodozensofcustomers.ThetotalcapacityofeachServiceGroupcanbemanagedtoprovidethedesiredperformancetothecustomersservedbythatgroup.ServicesareshapedandscheduledintheCMTS,andbandwidthforspecificservicesmaybereservedtoenforcepolicy,managecontention,andprovideeachservice’sQoS.InDOCSIS,servicesareconfiguredusingServiceFlows,whichareuni-directional(upstreamordownstream)logicalchannelsbetweenaCMTSandacablemodem[79].EachcablemodemcansupportadozenormoreServiceFlows,thoughforbasicresidentialbroadbandserviceonlytwoareconfigured(oneupstreamandonedownstream).EachServiceFlowisconfiguredwithaQoSusingcontrolsthatincluderateshaperparameters,reservedrateandtrafficpriority,allowingservicestobeoptimizedforapplicationssuchasdigitalphoneserviceorbusinessservicelevelagreements(SLAs).IPpacketsareclassifiedintoServiceFlowsbyclassifiersinthecablemodem(forupstreamflows)ortheCMTS(fordownstreamflows)[79].

OneexampleofservicedifferentiationincablesystemsisthehostingofpublicWLANhotspotsinresidentialgateways,asdescribedinSection4.6.

4.3 SatelliteInternetSatelliteisusedbyavarietyofServiceProviderstodeliverbroadbandservicesthatincludeInternetaccessservice,voice,video,andenterprisebusinessapplications.Whileoftenusedasasecondaryoptiontoterrestrialbroadbandwhenaddressingchallengedserviceareas,itisalsousedbyanumberofprovidersastheprimaryoptionindeliveryofbroadbandservices[80,81,82].Theuseofsatellitefacesanumberofuniquechallengeswhencomparedtoterrestrialalternatives.Thisstemsfromthesignificantpropagationdelaysof

Hub

Head-end

Hub

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IXP

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GeosynchronousEarthOrbit(GEO)satellitesandthevariablepropagationdelaysandlossinherenttoLow-EarthOrbit(LEO)satellites[83].Giventheimplicationsofhighandvariablelatency,linkimpairments,asymmetryandpacketloss,trafficdifferentiationplaysakeyroleinmaximizingtheusabilityofsatelliteindeliveringbroadbandservices.

Figure5:Satelliteaccessarchitecture[84]

Whiletrafficdifferentiationmaybeperformedatbothbasestationandremotesites,thefocalpointisatthebasestationwheretrafficflowsaremultiplexedtothesatelliteuplink.BothbasestationandremotesitespossesstheQoScapabilitiesofatraditionalIProuter(classification,marking,scheduling,shaping),withaddedrequirementsforcross-layercommunicationwithdata-link(layer2)andphysical(layer1)layers.Duetotheuniquereceiveconditionsofeachremoteterminal(clearsky,rainfade,interference),bandwidthresourceswillvarypersite;therebycompromisingefficientutilizationofthereturnlinkandanymeaningfulenforcementofqualityofservice(QoS)servicelevelagreements(SLAs).Toaddressthisissue,dynamicbandwidthallocationschemesuseafeedbackloopfromremotesitestobasestationstocommunicatethestatusofbandwidthdemandandtheconditionsofthesatelliteinterface.Withsuchinformationavailable,thebasestationisabletoassignbandwidthtoitsmultiplexedtrafficflowsinamoredeterministicmanner.

AnadditionalmethodinwhichsatellitearchitecturesfacilitatetrafficdifferentiationisthroughtheuseofPerformanceEnhancingProxies(PEPs)withsplitconnectioncapabilities.PEPshavebeenusedtoimprovetheperformanceofprotocolsacrossnetworkswithsuboptimallinkorsubnetworkcharacteristics[85].PEPshavenoinherentlayerrestrictionsandmaybeimplementedinisolationorthroughcross-layercoordinationinordertoachieveholisticperformanceimprovements.SatellitenetworkshaveusedavarietyofPEPssuchasTCPcompression/acceleration,HTTPcompression/acceleration,Link-layercompression,HTTPcaching,andTCPspoofing[85,86].Inthecontextoftrafficdifferentiation,TCPPEPsmaybeusedtogiveprioritytourgent,interactiveconnectionswhilelowerpriorityconnectionswouldyieldbandwidthresourcesbyslowingorbeingsuspendedwhenbandwidthcongestionarises.Thisprocessmaybeperformedbysteering

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TCPconnections,baseduponDSCPclassifier,totheTCPPEPwheretheymaybecompressedand/oraccelerated.AllotherTCPconnectionsfollowthenormaldatapathandarenotaffectedbytheTCPPEP.

4.4 Mobile(3GPP)architectureLiketheirfixedtelcocounterparts,mobilenetworkshaveevolvedfromvoice-onlytoarichmixofdataandvoiceservicesonthenetwork.Mobilenetworks,however,faceanumberofuniquechallengestodeliveryacrosstheradioaccessnetwork,includingbutnotlimitedto:rapidlychangingperformanceasausermoveswithinacell;theneedtohandusersoverfromonecelltoanother;finitespectrumandinterferencefromothercells;andaggregatecapacitylimitationsthatconstantlychangeasusersmove,amongotherthings.

TheThirdGenerationPartnershipProject(3GPP)andotherorganizationshavespecifiedsophisticatedQoSmechanismstocopewiththedynamicmobileenvironment[87].ThisreportfocusesontheLTE(andLTE-A)specificationsdevelopedbythe3GPP,asthesespecificationsenabledthefirstend-to-endall-IPmobilenetworks,aresupportedbymostmobilenetworkoperators,andprovidethearchitectureformostcurrentandnearfuturemobilenetworks[88,89].

Figure6:LTEArchitecture[90,91]

Figure6showsasimplifiedversionofthe3GPPLTEarchitecture.Inthisarchitecture,trafficistransportedbetweenasubscriber’suserequipment(UE)andremoteendpointsacrosstheEvolvedPacketSystem(EPS),whichincludestheEvolvedNode-B(eNB)basestation,theServingGateway(S-GW),andthePacketDataNetworkGateway(PDNGW).LTEnetworkstypicallyhavemanyeNBsandS-GWstoservemobileusers,andmultiplePDNGWinterfacestoothernetworksthroughwhichtrafficmayberouted,dependingonwhetherthetrafficisassociatedwithInternetaccess,voiceservice,oradifferentservicesuchasabusinessVPN.

Evolved Packet System (EPS)

Evolved Packet Core (EPC)Evolved UTRAN(E-UTRAN)

eNB

eNB

eNB

UE

UE

PDN GW

UE

UE

UES-GW

MME PCRF

Packet Data Networks

EPS Bearer 1EPS Bearer 2EPS Bearer 3

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LTEusesEPSbearers(threeofwhichareshowninFigure6)toisolateanddifferentiatebetweenservicesacrosstheEPS[92].AnEPSbearerisaconnectionsetupbetweenauserequipmentandaninterfacelinkingaPDNGWtoanexternalnetwork,andisidentifiedbythreecharacteristics:theuserequipmentatoneend;thePDNGWinterfaceattheotherend;andaQoSprofilethatidentifiestheperformanceobjectivesassociatedwiththetraffic.TheQoSprofilecontainsseveralparametersincludingtheQoSClassIndicator(QCI),whichdefinesanumberofQoS-relatedcharacteristicsforthebearerasshowninTable1.

Table1:StandardizedQCItypes[92]

MultiplenodesintheEvolvedPacketSystemplayaroleinimplementingQoSandpolicymanagement:

● ThePolicyandChargingRulesFunction(PCRF)usesavailablenetworkinformationandoperator-configuredpoliciestocreateservicesession-levelpolicydecisions[93].

● ThePolicyandChargingEnforcementFunction(PCEF)locatedinthePDNGWenforcesthepolicydecisionsforwardedfromthePCRFbyestablishingbearers,mappingservicedataflowstobearers,andperformingtrafficpolicingandshaping[93].

● BoththeeNBandtheuserequipmentmayallocatebandwidthandscheduletrafficusingtheparametersassociatedwitheachbearer.

Mobilenetworkshavealwaysreliedontightperformancerequirementsinthebackhaulnetworksthattransporttrafficbetweencellularbasestationsandthenodesthatmakeupthemobilecore.Asthosebackhaulnetworkshavemigratedfromtimedivisionmultiplexing(TDM)/synchronousopticalnetworking(SONET)toIPpacketnetworks,differentiationtechniqueshavebeenkeytoensuringthatthemosttimesensitivetrafficistransportedwithminimumdelay.

Industrystandardsprovideguidancefornetworkoperatorsimplementingmobilebackhaul[94,95].Onestandarddefinesuptofourclassesofservicewithincreasinglystringentperformancerequirementstoenablebearertrafficwithtime-sensitiveQCIstobescheduledfirstoverEthernet-basedservices[94].Anotherprovidessupportformultipleclassesofservice,includingtheclassesidentifiedbythefirststandard,overMPLS

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networks[95].Whenthesestandardsareused,bearersaremappedbasedonQCIvalueintotheappropriateclassofserviceandthenscheduledwithinthebackhaulnetworktoachievethenecessaryperformance.

4.5 Fixedwirelessnetworkarchitecture

Fixedwirelessaccessnetworksfrequentlyserveruralareasthatarecharacterizedbylongdistancesbetweensubscribersandlackofhigh-speedwiredcommunicationsinfrastructure.Asaresult,thesenetworksfrequentlymakeuseofmultiplewirelesslinks,bothinthe“lastmile”usedtoreachthesubscriberandinthe“middlemile”backhaulandaggregationlinksthatsendtrafficbetweentowers.Theselinksaresubjecttocapacitylimitsandperformancevariationbasedonthespectrumusedandatmosphericconditions.

Figure7:Examplefixedwirelessaccessnetworkarchitecture

Figure7showsanexamplefixedwirelessaccessnetwork.Inthefigure,downstreamtrafficisclassifiedandanydifferentiatedtreatmentisappliedattheedgerouterontheleftwherethewirelessInternetserviceprovider(WISP)networkinterconnectstoothernetworks.Routersateachrelaytowermayscheduletrafficasnecessary,andper-serviceshapingtosubscriberserviceratesistypicallyperformedataccessnodetowerssuchastheonesshownontheright.MostWISPsprovidebusiness-gradeInternetaccessservicesinadditiontoconsumer-gradeservices,andsomeofferbusinessconnectivityservicesaswell.

4.5.1 MiddleMile

Mostmiddle-milelinksinWISPnetworksuse5GHzunlicensedspectrum,whichwithmodernequipmentcandeliver100to200Mbpsoverdistancesof20milesormore[96]andwhichmakeitfeasibletodeployservicetoremoteandsparselypopulatedareas.Asdemandforcapacityhasgrown,WISPshavebeguntodeployfibermiddle-mileconnectionswheretheyareavailable,supplementedwithmicrowavebackhaulsinlicensedspectrumincoreareas.Shortrange,gigabitcapacityradiosusingunlicensed24GHzspectrumhavealsobecomepopularforshortbackhaullinks[97].

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Despitetheincreasedcapacityofthemiddle-mileoptionsavailabletoWISPs,exponentialincreasesindemandcontinuetostraincapacitylimits.ThishasledtoariseintheuseofpacketprocessingsystemsbyWISPs,toshapenetworkflowsandmoreefficientlyusecapacityinoverloadedbackhauls[98].End-userdatacantraverseadaisy-chainofmultiplemiddle-milemicrowaveconnectionsbeforereachingafiberbackhaul.Inthisenvironment,differentiatedtreatmentcanenabledeliveryofserviceswithpredictablejitterandlatency.

4.5.2 LastMileThe“lastmile”linksinaWISParetypicallypoint-to-multipointlinksinwhichonetowerservesmultiplesubscribers.Atypicalunlicensedaccesspointhasavariablecapacitythatdependsonspectruminterferencelevels,channelsizes,distanceofcustomersfromtheaccesspointandpropagationcharacteristicsofthespectrumutilized.Underreal-worldconditions,amodernfixedwirelessaccesspointwith20Mhzofclearspectrummayhaveacapacityofupto50Mbps[99].Withoutdifferentiatedtreatment,asmallnumberofhighbandwidthvideostreamscanconsumemostofthecapacityoftheaccesspoint,leadingtodegradedservicefortherestoftheendusers.ConfiguringratelimitsonflowssuchasvideostreamsisonetoolusedbyWISPstoensuretheaccesspointapproachesbutneverreachesthepointofoverloadwithoutblockingservices.Thisallowsforasignificantincreaseinoversubscriptionlevelswithoutanoticeabledecreaseinperformancetotheenduser[100].ForWISPcustomersinremoteareaswithlimitedalternatives,thisisoneofthefewwaystoprovideaqualityuserexperiencewithoutupgradingeverysegmentbetweentheend-userandthenetworkcore.

4.6 WirelessLANPublicHotspotNetworksWirelessLocalAreaNetworks(WLANs)basedonIEEE802.11radiotechnologyarefrequentlyusedtoprovidewirelessbroadbandaccesstousersathomes,enterprises,andvenuessuchasrestaurants,stores,andairports.TheseWLANscangenerallybeconsideredasanextensionofanyofthenetworkarchitecturesdiscussedabove.Fromadifferentiationandsubscriberviewpoint,theycanbecategorizedinseveralways:

• HomeWLANsaregenerallyconsideredprivate(althoughmanyhavelittleornosecurity,theyarestillintendedonlyforusebymembersandguestsofthehousehold).WiththeexceptionofthesharedWLANtechnologiesdiscussedbelow,theyarenotconsideredfurther.

• Venue-basedWLANsandpublichotspotsmaybedesignedforlargerpopulationsandmayimplementpoliciestopreventmisuse,including:isolationofdevicessothattheycannotcommunicatedirectlywitheachotherontheWLANtopreventLAN-basedattacks(althoughdevicesthatneedtocommunicatecanstilldosothroughtheIPlayer);andlimitingindividualusers’ratestopreventanyoneuserfrommonopolizingtheavailableWLANbandwidth.Someofthesevenuesalsooffermultipletiersofserviceshapedtodifferentrates.

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Ofparticularinterestarepublichotspotnetworkswithmultiplegeographiclocationsandcentralizedmanagement,suchasthoseoperatedbyfixedandmobilenetworkprovidersandover-the-top(OTT)WLANnetworkoperators[101,102].Inanumberofthesenetworks,subscribersusein-homewirelessroutersthatsupportseparatelogicalWLANs–oneWLANforthesubscriber’sprivateuseandasecondWLANforuseasapublichotspot.AbroadbandnetworkprovidercaneithermanagethehotspotasanextensionoftheirnetworkorcontractwithanOTTWLANprovidertomanagetheservice.Conversely,anOTTWLANprovidercanmanageahotspotwithorwithoutcoordinatingwiththesubscriber’sbroadbandprovider.Whenthebroadbandproviderisinvolvedinmanagingthehotspot,themanagementdomaincoversboththeWLANnetworkanditsupstreamconnectivity–otherwise,themanagementdomainonlycoverstheWLANnetwork.Dependingonthescopeofthehotspotoperator’smanagementdomain,thefollowingoptionsmaybeavailabletodifferentiatethetreatmentofpublicWLANtrafficcomparedtothesubscriber’sprivatetraffic:

• WithintheWLAN,publictrafficcanbescheduledandshapedsothatitdoesnotimpactthesubscriber’straffic.

• Intheuplink,publictrafficcanbeisolatedfromthesubscriber’strafficinaseparatelogicalbroadbandconnection,withafirewallbetweentheWLANs.

• Inthebroadbandnetwork,publictrafficcanbeexcludedsothatitdoesnotcountagainstsubscriberusagelimits.

InafullymanagedsolutiontheoperatormaychoosetoapplydifferentiationtechniquesapplicabletotheaccessnetworktechnologyusedalongwiththoseavailableintheWLANspecifications.InasolutionwheretheoperatoronlymanagestheWLANnetworkdevice,onlyWLANspecificdifferentiationtechniquesareavailabletotheoperator.ThedifferentiationtechniquesmaybeusedtoisolatepublictrafficfromsubscribertrafficthatisusingtheWLAN,aswellasaidingintheseamlesshandoverbetweenWLANsandcellularnetworks.

4.7 NetworkFunctionVirtualization(NFV)NetworkoperatorsarebeginningtodeployNetworkFunctionVirtualization(NFV)intheabovearchitecturestomakethemmoreflexibleandresponsivetochangingbusinessandtechnicalrequirements.NFVallowsnetworkoperatorstoimplementfunctionsassoftwareinvirtualmachinesusingcommoditizedhardware,insteadofindedicatedhardwareappliances.NFVhardwareisoftendeployedindatacenters,centralofficesorotherlocationswherepooledresourcescanbemanagedandorchestrated;however,somenetworkoperatorsarealsoexperimentingwithhostingnetworkfunctionsinlightweight“containers”(aloweroverheadalternativetovirtualmachines)andinsmallerhardwareresourcesdistributedattheedgeofthenetwork.

NFVhasseveralimplicationsforthedifferentiatedtreatmentofInternettraffic:

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• Virtualizationofnetworkfunctionsmakesitpossibletodeployandmodifythesefunctionsmuchmoreflexiblyinresponsetonewserviceofferingsandrequirements.Forexample,virtualizedtrafficshapersorfirewallscanbedeployedinthelogicalpathswheretheyareneededwithoutphysicallydeployingnewhardwareacrossthenetworkperimeter.

• NFVcanfacilitatenewservicesthatmaybeimpracticalwithconventionalapproaches.Forexample,byvirtualizingtheroutingandnetworkaddresstranslation(NAT)functionsinresidentialgateways,networkoperatorshavebettervisibilityofflowstooptimizefeaturessuchasparentalcontrolofchildren’sonlineactivities.

• Conversely,NFVhasthepotentialtodegradeperformancebyintroducingadditionallatencyorjitterinthephysicalpath.Forexample,trafficflowsmayneedtobe“steered”throughasequenceofnetworkfunctions;ifthosefunctionsarehostedatdistantnetworklocations,thelatencyofthoseflowsmaysuffer.StandardsbodiesandthebroadernetworkingresearchcommunityareactivelyexploringtheperformanceandsecurityofNFV,aswellasdesigningarchitecturesandalgorithmsforimprovedmanagementandorchestration[103].

• Sincevirtualmachinescanbeisolated,NFVallowsnetworkoperatorstohostfunctionsthataredeployedandmanagedbythirdparties.Forexample,acontentprovidermightperformCDNfunctionssuchascachingorserverselectiononthenetworkprovider’sNFVinfrastructure,improvingperformanceforthatcontent.

5 ExamplesNetworkoperatorsoftendelivermultipleservicessuchasInternetaccessplusotherIP-based,non-Internetservicesoveracommoninfrastructure.Theexamplesinthissectionillustratemultipleservicesbeingdeliveredovercommoninfrastructureeachwiththeirowndeliveryrequirementsusingthedifferentiationtechniquesdescribedearlierinthisreport.

5.1 InteractiveservicedifferentiationInteractiveapplicationsandservicesoftenhavestringentdeliveryrequirementstomeettheinteractivenatureoftheapplicationorservice.Exampleapplicationsorservicesincludevoiceandvideo.

5.1.1 EffectsofcarriergradeinteractivevoiceonInternetaccessservices

Interactivevoiceisareal-timeapplicationthatrequireslownetworkdelayandjitterinordertoprovideagoodQoEtotheuser[104].Whilejitterbufferscancompensateforalimitedamountofjitter,theyaddtotheaverageend-to-enddelay,whichinturnplacesmorestringentrequirementsonthenetwork’scontributiontoend-to-enddelay.Hencethe

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engineeringofcarriergradevoiceservicesseekstominimizebothdelayandjitterinthenetwork.

Carriergradevoiceservicescommonlyrelyonacombinationof“connectionadmissioncontrol”(allowingnewcallsonlyiftherearesufficientnetworkresources)andbandwidthreservation.CarriergradevoicetrafficmayalsobeprioritizedandscheduledaheadoftrafficforInternetaccessservicesonnetworkscarryingbothtypesoftraffic.

3GPPmobilenetworksandsomefixednetworksusetheIPMultimediaSubsystem(IMS)forcalladmissioncontrolandbandwidthreservation[105].TheIMScreatesnewvoicebearers,differentiatedbythe5-tuple(Section3.2),andscheduledviaacombinationofresourceadmissioncontrolandpriority.IMSallows3rd-partyvoiceproviderstorequestdifferentiationandQoSformobileroamingusers.Morecommonly,3rd-partyvoiceprovidersmarkpacketswithadifferentiatedservicescodepointrequestingappropriatetreatment[9].

Cablenetworks(Section4.2)usePacketCable™[106]forthecalladmissioncontrolandbandwidthreservation.SimilartohowIMSworks,PacketCabledynamicallycreatesserviceflowsfortheadmittedcalls.Thedynamicserviceflowsaredifferentiatedbythe5-tuple,assignedbandwidthandpriority,andscheduled.

Telconetworks(Section4.1)useEthernetVLANs,andIPDSCPmarkings,andprioritycodepointstoisolate,schedule,androutecarriergradevoicetraffic.

Carriergradevoicetraffic,whichistransportedoverUDP,isdifferentiatedprimarilytomitigatedegradationinitsQoEinconvergednetworks,causedbyTCPtrafficcompetingforresources.BecauseTCPtendstofillupthequeuefeedingacongestedlink,itincreasesthedelayandjitterexperiencedbyalltrafficinthesamequeue–whichincludesvoicetrafficifitisnotdifferentiated.TherearetwofundamentalapproachestoimprovingvoiceQoE,bothofwhichremovethevoicetrafficfromthequeueusedbyTCPtraffic.Oneapproachistodivertvoicetraffictoanothernetworkpathengineeredtothepurpose,andtheotheristoqueuevoicetrafficseparatelyandscheduleitbeforeTCPtraffic.NeitheroftheseapproachesdegradesQoEfortheTCPtraffic:

• Ifvoicetrafficisdivertedtoanotherpath,theTCPtrafficbenefitsinthatitnolongercompeteswiththevoicetraffic.

• IfvoiceisprioritizedoverTCPtraffic,theTCPtrafficmaintainsthesameQoEasitwouldwithoutprioritization.Thisistruebecauseboththecapacityusedbyvoicetraffic(sentoverUDP,whichdoesnotchangerateinresponsetocongestion)andtheoverallcapacityofthenetworklinksareindependentofwhetherornotthevoicetrafficisprioritized.SimplesubtractionshowsthattheremainingcapacityavailableforTCPtraffic–thatis,thedifferencebetweentheoverallcapacityandthecapacityusedbyvoice–isalsoindependentofwhetherornotthevoicetrafficisprioritized.TheonlyobservabledifferenceintheQoEoftheTCPtrafficisanincreaseindelayvariationrelativetotheoptimaldelay.IftheincreaseisrelativelysmallTCPperformancewillnotbeadverselyaffected.SinceTCPisinsensitiveto

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moderateamountsofrelativedelayvariation,itsQoEisnotaffectedbytheprioritizationofthevoicetraffic.

Ineithercase,differentiationcanprovideasignificantbenefittotheQoEforvoicetrafficwithoutdegradingtheQoEfortheTCPtraffic.

5.1.2 ManagingtheimpactofstreamingvideoonothertrafficAtypicalvideostream,assentbyaserver,consistsofaseriesoflargeburstsoftraffic,or“chunks,”whereeachchunkconsistsofmultiplepacketstransmittedasquicklyaspossible.Sequentialchunksareseparatedbytimeperiodsthatcanspanseconds[107].Thetransmissionrateforeachchunkismuchhigherthantheaveragerateoftheencodedstream,whichisafunctionoftheaveragechunksizeandthetimebetweenchunks.7Thevideoclientbuffersthechunksandthenplaysthemoutattheencodedrate.

Whenachunkfromavideostreamarrivesatabottlenecklink,itcancausesignificantdelayandjitterforothertrafficsharingthesamelink,causingseveredegradationintheQoEoftime-sensitiveapplicationssuchasinteractivevoice.Thisproblemcanbemitigatedviaatechniqueknownaspacing[110],inwhichthevideostreamisdifferentiatedandtrafficshapedtoarateequaltoorgreaterthanthestream’saveragerate,butstilllowerthanthebottlenecklink’srate.Pacingspacesoutthevideopacketsintime,allowingothertrafficinbetweenthechunksandindoingsomayreducethelatencyandjitterexperiencedbyothertraffic.Sincethefirstpacketineachchunkisnotdelayed,theneteffectofpacingonstreamingvideoistodelivervideopacketstothereceiveratamoreconsistentratewithoutcreatinganyadditionaldelayinvideoplayback.Ineffect,networkpacingperformsthesame“smoothing”functioninthereceivedvideocontentthatthereceivebufferinthevideoclientwouldhaveperformedhadthechunksbeenreceivedindiscretehighspeedbursts,sotheQoEforthestreamingvideomaybemaintainedbecausethecontentineachchunkisstillreceivedbeforethedecoderneedsit.

PacingisanexampleofdifferentiatedtreatmentthatisimplementedinmobilenetworksandthatactsonthetrafficwithinInternetaccessservices.Itmayalsobeimplementedbythesendingserviceorapplication,reducingtheneedfordifferentiationinthenetwork.Asnotedabove,thistechniquecanimprovetheQoEforothertrafficwithoutdegradingtheQoEforOTTvideostreams.

5.2 TransmissionControlProtocol(TCP)performanceoptimizationsTransmissionControlProtocol(TCP)isthedominanttransportprotocolusedintheInternet.Theprotocolisdesignedtodelivertrafficreliablyfromoneendpointtoanother,asquicklyasthenetworkwillallow[17].Undercertainnetworkandtrafficconditionshowever,theprotocolcanperformpoorlyandcanevencontributeunnecessarilytonetworkcongestion.Twokeyelementsoftheprotocol’sdesignare:7Mostmodernover-the-topvideostreamsuseadaptiveratetechnology:theserverofferseachvideoatmultiplebitrates,andreceiversrequestthebestratesupportedbythenetwork,switchingbetweenratesmid-flowifnecessarytoavoidstalling[108,109].

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• TCPprovidesreliabledeliverybyhavingthereceiveracknowledgereceiptoftrafficfromthesender.Ifnoacknowledgementisreceivedwithinsometimeframe,thesenderwillassumethattheunacknowledgedpacketislostandwillretransmitit.Thesendermayalsoreducethenumberofunacknowledgedpacketsitsendsintothenetworkbasedontheassumptionthatthelosswasduetocongestion.

• TCPadaptstoavailablecapacity,increasingtheamountoftrafficitsendsuntilitdetectscongestion.Oneconsequenceofthisisthatwhenthereisenoughtraffictosend,TCPvirtuallyguaranteesthatitwillcreaterecurringmomentarycongestionatsomepointinitsnetworkpath[111].Thiseffectexistsbydesign,anditcannotnecessarilybeeliminatedbyincreasingcapacity.8

Whenthereisalargeamountofupstreamtraffic–especiallyinnetworkswithasymmetricspeedsandcapabilities(e.g.,mobile,satellite)–upstreamcongestionfromoneormoreTCPflowscancauseacknowledgementsassociatedwithdownstreamflowstobedropped.Thisdegradesperformanceandmayaddtocongestioninthedownstreamdirection,becausedownstreamtrafficthatwassentandreceivedmustnowbesentagain.Italsocausesamultiplicativeeffectinthatoneupstreamflowcandegradetheperformanceofmanydownstreamflows[112].

Satelliteandcellularnetworkscommonlyprioritizeemptyacknowledgements(i.e.,packetsthatincludetheacknowledgementflagbutnodata)tomitigatetheaboveissues[113].Emptyacknowledgementsareshortpacketsthatcreateonlyminimaldelayforothertrafficiftheyareprioritized,sothisuseofprioritizationeitherdoesnoharm(whenthereisnocongestion)orresultsinanetperformancegain(whencongestionispresent).Somehomeroutersalsoallowuserstoprioritizeoutgoingacknowledgements[114].

AnotherTCPperformanceoptimizationcommonlyusedisinthetransitionbetweendissimilarnetworks.Forexample,amobilenetworkincludesaradioaccesslinkwithhighlatencyandmoderatepacketloss(someofwhichisduetotransmissionerrorsratherthancongestion),whichinterconnectswithwirednetworkshavinglowlatencyandlowloss.Inthisenvironment,aclient(inthehighlatency/moderatelossenvironment)canstruggletogetaTCPconnectionuptospeed,whichaffectsapplicationperformance.Networkbasedtechniquesareoftenalsousedtomitigatethis.Forexample,aproxymayconvertfromaTCPmodelsuitableforlow-loss/low-latencynetworkstoonesuitableformoderate-loss/highlatencynetworks[115,116].9Usingthismodel,themobilenetworkmaybemoreefficientasitspendslesstimetransitioninginandoutofidlestates.Theend-useralsoachievesafasterpage-loadtimeinwebapplications.

8 Increasingcapacitywillgivemorebandwidthtocompetingflows,butTCPflows–bydesign–willsendasfastastheyareableuntilthenewincreasedcapacitypathiscongested.Giventhesametrafficload,however,theseverityofthemomentarycongestionshoulddecreasewithincreasedcapacity. 9 Thistechniqueofdifferentiationiscommonlyusedinmobilenetworks.Theoptimizationdevicerecognizeswhichflowswillbenefitfromahigherinitialburst(e.g.web)versusonesthatwillnot(e.g.long-formvideo).Thedevicethenproxiestheflowstobeoptimized,usingaTCPcongestionmodelsuchasTCP‘cubic’or‘TCPreno’ontheInternetside,andacongestionmodelsuchasTCP‘Westwood+’(whichismoreoptimizedforlong-latency,moderatelossenvironments)ontheaccessside.Formoreinformationsee[116].

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5.3 User-defineddifferentiatedtreatmentRecentexperimentationsuggestspossibletrendstowardsnetworkdifferentiationthatisconfigurablebyusers.Forexample,participatorynetworking(PANE)allowsthenetworktoexposeaconfigurationAPItousers,applicationsandendhosts,potentiallyallowingthesesystemstospecifyschedulingorotherdifferentiationparameters[117].PANE’suser-facingAPIexposesabstractionsthatallowusersandapplicationstomakerequestsforguaranteedminimumbandwidth,ortoprefer(oravoid)networkpathsthathavespecifiedperformanceproperties.Forexample,theusermightroutebulktrafficthroughapacketshaperduringbusyhours,oravoidcertainpartsofthenetwork.TherearealsonetworkcontrollersthatconfigureQoSusingapplication-describedrequirementsandadatabaseofnetworkstate[118],aswellascontrollersthatcanperformapplicationclassificationandautomaticallyassignapplicationtrafficflowstotheappropriatetrafficclasses[119].

5.4 DifferentiationinthepresenceofsecuretrafficSecuredtrafficthatusesencryptedtransportprotocols(e.g.,TLS)toprotecttheconfidentialityandintegrityofthecommunicationsessionnecessarilyobfuscatesthepayloadofpackets.Becauseofthis,classificationislimitedtoeitheranexplicitcontrolmechanism(e.g.,IMS)orheaderfieldsthatfalloutsidetheencryptedpayload(e.g.,DSCP,SNI[120],IP,protocolnumber).EncryptedtraffichasbecomeincreasinglyprevalentonthewebandthelargerInternetinrecentyears[121].

Somesatelliteandin-flightnetworkoperatorshavedeployedproxysystemsthatallowdifferentiationofencryptedtraffic.Theydothisbybreakingtheend-to-endencryptionprincipleinfavoroftwoencryptedsegments,orinsomecaseswithonesegmentbeingunencryptedentirely.Examplesofthesesystemsinclude:

• SatelliteoperatorViaSathasdevelopedamodifiedversionoftheChromebrowserthatdecryptstrafficinsidetheirnetwork,inordertooptimizeperformance[122].

• Toimproveperformanceonretailin-flightWLANnetworkaccess,thenetworksprovidedbyGogoInflightInternet,foraperiodoftime,dynamicallyforgedTLScertificatesinordertoshapetrafficorblockhigh-bandwidthusessuchasvideostreaming(duetopopularoutcry,thispracticewasceasedshortlyafterdiscovery)[123].

Ineachofthesecases,thenetworkproviderhasmadeadecisiontotradesecurityforperformanceinordertodifferentiatebetweendifferentdataflows,andserveasaman-in-the-middleforanotherwisesecurecommunication.Asanadditionalbyproducttheygenerallyweakenthesecurityoftheconnectionagainstothermoremaliciousattackers.Forexample,intheGogocase,theprovidermandatedthattheuserdisregardcertificateauthenticationwarnings.ThiswouldhaveappliedindistinguishablybothtothosecertificatesgeneratedbyGogoaswellasthosemadebyanattackerelsewhereonthenetwork.Theriskstothesecurityandprivacyofenduserscanbesignificant.

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6 ObservationsFromtheanalysismadeinthisreportandthecombinedexperienceofitsmemberswhenitcomestothedifferentiatedtreatmentofInternettraffic,theBITAGTechnicalWorkingGroupmakesthefollowingobservations.

6.1 TCPcausesrecurringmomentarycongestionAsmentionedinSections2.4.2and5.2,whenTCPtransfersalargefile,suchasvideocontentoralargewebpage,itpracticallyguaranteesthatitwillcreaterecurringmomentarycongestionatsomepointinitsnetworkpath[111].Thiseffectexistsbydesign,anditcannotnecessarilybeeliminatedbyincreasingcapacity.Giventhesametrafficload,however,theseverityofthemomentarycongestionshoulddecreasewithincreasedcapacity.

6.2 AnominallevelofpacketdiscardisnormalAsmentionedinSections2.4.2and5.2,packetdiscardoccursbydesignintheInternet.ProtocolssuchasTCPusepacketdiscardasameansofdetectingcongestion,respondingbyreducingtheamountofdataoutstandingandwithitself-inducedcongestiononthetransmissionpath.Ratherthanbeinganimpairment,packetdiscardservesasanimportantsignalingmechanismthatkeepscongestionincheck.

6.3 Theabsenceofdifferentiationdoesnotimplycomparablebehavioramongapplications

AsdiscussedinSections5.1and5.2,intheabsenceofdifferentiation,theunderlyingprotocolsusedontheInternetdonotnecessarilygiveeachapplicationcomparablebandwidth.Forexample:

• TCPtendstoshareavailablecapacity(althoughnotnecessarilyequally)betweencompetingconnections.However,someapplicationsusemanyconnectionsatoncewhileotherapplicationsonlyuseoneconnection.

• SomeapplicationsusingRTP/UDPorothertransportprotocolsbalancetransmissionrateagainstexperiencedlossandlatency,reducingthecapacityavailabletocompetingapplications.

6.4 DifferentiatedtreatmentcanproduceanetgaininQualityofExperience(QoE)

AsintroducedintheSection2discussionontherelationshipbetweenQoSandQoEandlaterinSection5.1,whendifferentiatedtreatmentisappliedwithanawarenessoftherequirementsfordifferenttypesoftraffic,itbecomespossibletocreateabenefitwithoutanoffsettingloss.Forexample,somedifferentiationtechniquesimprovetheQualityofService(QoS)orQualityofExperience(QoE)forparticularapplicationsor

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classesofapplicationswithoutnegativelyimpactingtheQoEforotherapplicationsorclassesofapplications.Theuseanddevelopmentofthesetechniqueshasvalue.

6.5 AccesstechnologiesdifferintheircapabilitiesandcharacteristicsSpecificarchitecturesandaccesstechnologieshaveuniquecharacteristicsthatareaddressedusingdifferenttechniquesfordifferentiatedtreatment.Section4describeshowdifferentiationisaccomplishedinvariousaccessnetworkarchitectures.

6.6 Securityoftraffichasattimesbeendowngradedtofacilitatedifferentiationtechniques

AsdiscussedinSection5.4,encryptedtrafficisontheriseandithasimplicationsforcurrentdifferentiationtechniques.Inresponsetothisincrease,somesatelliteandin-flightnetworkoperatorshavedeployeddifferentiationmechanismsthatdowngradesecuritypropertiesofsomeconnectionstoaccomplishdifferentiation.Theresultingriskstothesecurityandprivacyofenduserscanbesignificant,anddifferentiationviaobservableinformationsuchasportsandtrafficheuristicsismorecompatiblewithsecurity.

7 RecommendationsThissectionofthereportpresentsrecommendationsoftheBITAGTechnicalWorkingGroup(TWG).

7.1 Networkoperatorsshoulddiscloseinformationondifferentialtreatmentoftraffic.Inpreviousreports,BITAGhasrecommendedtransparencywithrespecttoanumberofaspectsofnetworkmanagement[124,3,125,126,127,128].BITAGcontinuestorecommendtransparencywhenitcomestothepracticesusedtoimplementthedifferentialtreatmentofInternettraffic.

Specificallywithrespecttoconsumer-facingservicessuchasmass-marketInternetaccess,networkoperatorsshoulddisclosetheuseoftrafficdifferentiationpracticesthatimpactanenduser’sInternetaccessservice.Thedisclosureshouldbereadilyaccessibletothepublic(e.g.viaawebpage)anddescribethepracticewithitsimpacttoendusersandexpectedbenefitsintermsmeaningfultoendusers.ThedisclosureshouldincludeanydifferentiationamongstInternettrafficandshoulddisclosetheextentandmannerinwhichotherservicesofferedoverthesameenduseraccessfacilities(forexamplevideoservices)mayaffecttheperformanceoftheInternetaccessservice.

30

7.2 NetworkoperatorsandASPsshouldbeencouragedtoimplementefficientandadaptivenetworkresourcemanagementpracticesInapreviousreportBITAGrecommendedthatASPsandCDNsimplementefficientandadaptivenetworkresourcemanagementpractices[3];wereiteratethatrecommendationhere,toincludenetworkoperators.Examplesofsuchpracticesmighttargettheminimizationoflatencyandvariationinlatencyinducedinnetworkequipment,ensuringsufficientbandwidthforexpectedtrafficloads,andtheuseofqueuemanagementtechniquestomanageresourcecontentionissues.

7.3 QualityofServicemetricsshouldbeinterpretedinthecontextofQualityofExperienceCommonQualityofServicemetrics,oftenincludedincommercialservicelevelagreements,includethroughput,delay,delayvariation,andloss,amongotherthings.AsnotedinSection2.3and6.4,fromtheviewpointoftheenduserapplication,thesemetricstradeoffagainsteachotherandmustbeconsideredinthecontextofQualityofExperience.Forexample,sinceTCPCongestionControlandadaptiveapplicationsdependonlosstoinfernetworkbehavior,activelytryingtoreducelosstozeroleadstounintendedconsequences.Ontheotherhand,non-negligiblelossratesoftendirectlyreducetheuser'sQualityofExperience.Hence,suchmetricsshouldbeinterpretedinthecontextofimprovinguserexperience.

7.4 Networkoperatorsshouldnotdowngrade,interferewith,orblockuser-selectedsecurityinordertoapplydifferentiatedtreatment.Networkoperatorsshouldrefrainfrompreventingusersfromapplyingover-the-topencryptionorothersecuritymechanismswithoutuserknowledgeandconsent.Networksshouldnotinterferewith,modify,ordropsecurityparametersrequestedbyanendpointtoapplydifferentiatedtreatment.Giventhepotentialforpossibleexposureofsensitive,confidential,andproprietaryinformation,priornoticeshouldbegiventoendusersoftrafficdifferentiationfeaturesthataffectsecuritypropertiestransmittedbyendpoints.(SeeSection5.4)

31

8 References[1]FederalCommunicationsCommission,“IntheMatterofProtectingandPromotingtheOpenInternet,”FCC15-

24A1,February26,2015.https://apps.fcc.gov/edocs_public/attachmatch/FCC-15-24A1.pdf.[2]J.Lennox,“Connection-OrientedMediaTransportovertheTransportLayerSecurity(TLS)Protocolinthe

SessionDescriptionProtocol(SDP),”RFC5472,July2006,https://tools.ietf.org/html/rfc4572.[3]BroadbandInternetTechnicalAdvisoryGroup(BITAG),Real-timeNetworkManagementofInternetCongestion,

October2013,http://www.bitag.org/documents/BITAG_-_Congestion_Management_Report.pdf.[4]InformationSciencesInstitute,UniversityofSouthernCalifornia,“InternetProtocol,DARPAInternetProgram

ProtocolSpecification,”RFC791,September1981,https://tools.ietf.org/html/rfc791.[5]G.Huston,IPv4AddressReport,August2,2015,http://www.potaroo.net/tools/ipv4/.[6]TheHostingNews,ColoGuardOffersIPv6AddressesasIPv4AddressesareExhausted,July31,2015,

http://www.thehostingnews.com/cologuard-offers-ipv6-addresses-as-ipv4-addresses-are-exhausted.html(lastvisitedSept.3,2015).

[7]Cisco,6Lab,IPv6AdoptionMaps,http://6lab.cisco.com/ciscolive(lastvisitedSept.3,2015).[8]P.Almquist,“TypeofServiceintheInternetProtocolSuite,”RFC1349,July1992,

https://tools.ietf.org/html/rfc1349.[9]K.Nichols,S.Blake,F.Baker,D.Black,“DefinitionoftheDifferentiatedServicesField(DSField)intheIPv4and

IPv6Headers,”RFC2474,December1998,https://tools.ietf.org/html/rfc2474.[10]Mills,D.L.TheFuzzball.Proc.ACMSIGCOMM88Symposium(PaloAltoCA,August1988),115-122.[11]ComputerHistoryMuseum,InternetHistory,1980s,1986,

http://www.computerhistory.org/internet_history/internet_history_80s.html(lastvisitedSept.3,2015).[12]J.Nagle,CongestionControlinIP/TCPInternetworks,RFC896,January1986,

https://tools.ietf.org/html/rfc896.[13]R.Braden,“RequirementsforInternetHosts–CommunicationLayers,”RFC1122,October1989,

https://tools.ietf.org/html/rfc1122.[14]R.Braden,“RequirementsforInternetHosts–ApplicationandSupport,”RFC1123,October1989,

https://tools.ietf.org/html/rfc1123.[15]InternetAssignedNumbersAuthority(IANA),ServiceNameandTransportProtocolPortNumberRegistry,

July2015,http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml.

[16]A.L.Russell,OSI:TheInternetthatwasn’t,HowTCP/IPeclipsedtheOpenSystemsInterconnectionstandardstobecometheglobalprotocolforcomputernetworking,IEEESpectrum,July30,2013,http://spectrum.ieee.org/computing/networks/osi-the-internet-that-wasnt(lastvisitedSept.3,2015).

[17]InformationSciencesInstitute,UniversityofSouthernCalifornia,“TransmissionControlProtocol,DARPAInternetProgramProtocolSpecification,”RFC793,Sept.1981,https://tools.ietf.org/html/rfc793.

[18]J.Postel,UserDatagramProtocol,RFC768,Aug.1980,https://tools.ietf.org/html/rfc768.[19]S.Kent,“IPEncapsulatingSecurityPayload(ESP),”RFC4303,December2005,

https://www.ietf.org/rfc/rfc4303.txt.[20]Huston,Geoff,"QualityofService-FactorFiction?"TheInternetProtocolJournal3,no.1(2000):30.Accessed

July29,2015.http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_3-1/ipj_3-1.pdf.[21]R.GeibandD.Black,"Diffservinterconnectionclassesandpractice",InternetDraft,July1,2015,

https://tools.ietf.org/html/draft-ietf-tsvwg-diffserv-intercon.[22]N.Lynch,N.Griffeth,M.Fischer,andL.Guibas,“ProbabilisticAnalysisofaNetworkResourceAllocation

Algorithm,”JournalofInformationandControl,vol.68,Issue1-3,Jan/Feb/March1986,pp.47-85,availableathttp://www.sciencedirect.com/science/article/pii/S0019995886800286.

[23]K.NahrstedtandR.Steinmetz,“ResourceManagementinMultimediaNetworkedSystems,”1994,TechnicalReports(CIS),Paper331,availableathttp://repository.upenn.edu/cis_reports/331.

[24]Kilkki,K.,“QualityofExperienceinCommunicationsEcosystem,”JournalofUniversalComputerScience,vol.

32

14,no.5,pp.615-624,March2008.[25]A.Charny,J.Bennet,K.Benson,J.Boudec,A.Chiu,W.Courtney,S.Davari,V.Firoiu,C.Kalmanek,K.

Ramakrishnan,“SupplementalInformationfortheNewDefinitionoftheEFPHB(ExpeditedForwardingPer-HopBehavior),”RFC3247,March2002,https://tools.ietf.org/html/rfc3247.

[26]R.K.P.Mok,E.W.W.Chan,andR.K.CChang,”MeasuringthequalityofexperienceofHTTPvideostreaming,”Conference:Proceedingsofthe12thIFIP/IEEEInternationalSymposiumonIntegratedNetworkManagement,IM2011,Dublin,Ireland,23-27May2011.

[27]InternationalTelecommunicationUnion,StandardizationSector(ITU-T),“MeanOpinionScore(MOS)terminology,”RecommendationP.800.1,July2006,https://www.itu.int/rec/T-REC-P.800.1-200303-S/en.

[28]J.Babiarz,K.Chan,andF.Baker,“ConfigurationGuidelinesforDiffServServiceClasses,”RFC4594,August2006,https://tools.ietf.org/html/rfc4594.

[29]InternationalTelecommunicationUnion,StandardizationSector(ITU-T),“End-usermultimediaQoScategories,”RecommendationG.1010,November2001.

[30]A.Bouch,A.Kuchinsky,N.Bhatti,“QualityisintheEyeoftheBeholder:MeetingUsers'RequirementsforInternetQualityofService,”ProceedingsoftheSIGCHIconferenceonHumanFactorsinComputingSystems(CHI'00),pp.297-304,April2000.

[31]InternationalTelecommunicationUnion,StandardizationSector(ITU-T),“Definitionsoftermsrelatedtoqualityofservice,”RecommendationE.800,September2008,http://www.itu.int/rec/T-REC-G.1010-200111-I.

[32]H.Koumaras,A.Kourtis,D.Martakos,andJ.Lauterjung,“QuantifiedPQoSassessmentbasedonfastestimationofthespatialandtemporalactivitylevel,”MultimediaToolsandApplications,vol.34,issue3,pp.355-374,September2007.

[33]R.Beuran,M.Ivanovici,B.Dobinson,N.Davies,andP.Thompson,“NetworkQualityofServiceMeasurementSystemforApplicationRequirementsEvaluation,”InternationalSymposiumonPerformanceEvaluationofComputerandTelecommunicationSystems,SPECTS’03,Montreal,Canada,July20-24,2003,pp.380-387,https://ivanovic.web.cern.ch/ivanovic/articles/qos_measurement.pdf.

[34]W.Cherif,A.Kentini,D.Negru,andM.Sidibe,"A_PSQA:PESQ-likenon-intrusivetoolforQoEpredictioninVoIPservices,"2012IEEEInternationalConferenceonCommunications(ICC),vol.,no.,pp.2124,2128,10-15June2012.

[35]D.Hernando,J.E.L.deVergara,D.Madrigal,andF.Mata,"EvaluatingqualityofexperienceinIPTVservicesusingMPEGframelossrate,"2013InternationalConferenceonSmartCommunicationsinNetworkTechnologies(SaCoNeT),vol.03,no.,pp.1,5,17-19June2013.

[36]M.Fiedler,T.Hossfeld,andP.Tran-Gia,"Agenericquantitativerelationshipbetweenqualityofexperienceandqualityofservice,"IEEENetwork,vol.24,no.2,pp.36,41,March-April2010.

[37]InternationalTelecommunicationUnion(ITU),TelecommunicationStandardizationSector,Series:TransmissionSystemsandMedia,DigitalSystemsandNetworks,OneWayTransmissionTime,May2003,ITUG.114,https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.114-200305-I!!PDF-E&type=items.

[38]Cisco,UnderstandingDelayinPacketVoiceNetworks,February2,2006,http://www.cisco.com/c/en/us/support/docs/voice/voice-quality/5125-delay-details.html(lastvisitedSept.3,2015).

[39]F.BakerandG.Fairhurst,IETFRecommendationsRegardingActiveQueueManagement,RFC7567,July2015,https://tools.ietf.org/html/rfc7567.

[40]J.Heinanen,F.Baker,W.Weiss,andJ.Wroclawski,AssuredForwardingPHBGroup,RFC2597,June1999,https://tools.ietf.org/html/rfc2597.

[41]K.Ramakrishnan,S.Floyd,andD.Black,“TheAdditionofExplicitCongestionNotification(ECN)toIP,”RFC3168,Sept.2001,https://tools.ietf.org/html/rfc3168.

[42]InformationSciencesInstitute–UniversityofSouthernCalifornia,“InternetProtocol:DARPAInternetProgramProtocolSpecification,”RFC791,Sept.1981,https://tools.ietf.org/html/rfc791.

[43]K.Chan,R.Sahita,S.Hahn,andK.McCloghrie,“DifferentiatedServicesQualityofServicePolicyInformationBase,”RFC3317,March2003,https://tools.ietf.org/html/rfc3317.

33

[44]R.Braden,“RequirementsforInternetHosts–CommunicationsLayers,”RFC1122,Oct.1989,https://tools.ietf.org/html/rfc1122.

[45]E.Meyer,“ConversationswithSteverCrocker(UCLA),”RFC49,April25,1970,https://tools.ietf.org/html/rfc49.

[46]E.Rosen,A.Viswanathan,andR.Callon,“MultiprotocolLabelSwitchingArchitecture,”RFC3031,Jan.2001,https://tools.ietf.org/html/rfc3031.

[47]D.GrossmanandJ.Heinanen,“MultiprotocolEncapsulationoverATMAdaptationLayer5,”RFC2684,Sept.1999,https://tools.ietf.org/html/rfc2684.

[48]L.Mamakos,K.Lidl,J.Evarts,D.Carrel,D.Simone,andR.Wheeler,“AmethodfortransmittingPPPoverEthernet(PPPoE),”RFC2516,Feb.1999,https://tools.ietf.org/html/rfc2516.

[49]R.Fielding,J.Gettys,J.Mogul,H.Frystyk,L.Masinter,P.Leach,andT.Berners-Lee,“HypertextTransferProtocol--HTTP/1.1,”RFC2616,June1999,https://tools.ietf.org/html/rfc2616.

[50]J.PostelandJ.Reynolds,“FileTransferProtocol(FTP),”RFC959,Oct.1985,https://tools.ietf.org/html/rfc959.[51]R.Droms,“DynamicHostConfiguration,”RFC2131,March1997,https://tools.ietf.org/html/rfc2131.[52]J.MyersandM.Rose,“PostOfficeProtocol–Version3,”RFC1939,May1996,

https://tools.ietf.org/html/rfc1939.[53]M.Crispin,“InternetMessageAccessProtocol–Version4rev1,”RFC3501,March2003,

https://tools.ietf.org/html/rfc3501.[54]J.Klensin,“SimpleMailTransferProtocol,”RFC5321,Oct.2008,https://tools.ietf.org/html/rfc5321.[55]M.Bagnulo,P.Mathews,andI.vanBiejnum,“StatefulNAT64:NetworkAddressandProtocolTranslationfrom

IPv6ClientstoIPv4Servers,”RFC6146,April2011,https://tools.ietf.org/html/rfc6146[56]J.Rosenberg,H.Schulzrinne,G.Camarillo,A.Johnston,J.Peterson,R.Sparks,M.Handley,andE.Schooler,“SIP:

SessionInitiationProtocol,”RFC3261,June2002,https://tools.ietf.org/html/rfc3261.[57]MichaelHibberd,“Encryption:WillitbethedeathofDPI?”,Feb.13,2012,Telecoms.com,

http://telecoms.com/39718/encryption-will-it-be-the-death-of-dpi/(lastvisitedSep.3,2015).[58]A.W.MooreandK.Papagiannaki,“TowardtheAccurateIdentificationofNetworkApplications,”Passiveand

ActiveMeasurementConference(PAM),2001,https://www.cl.cam.ac.uk/~awm22/publications/moore2005toward.pdf

[59]W.JohnandS.Tafvelin,“HeuristicstoClassifyInternetBackboneTrafficbasedonConnectionPatterns,”http://www.sjalander.com/wolfgang/publications/John_ICOIN08_CR.pdf.

[60]C.Wright,F.Monrose,andG.Masson,“OnInferringApplicationProtocolBehaviorsinEncryptedNetworkTraffic,”JournalofMachineLearningResearch(JMLR):SpecialissueonMachineLearningforComputerSecurity,volume7,pp.2745-2769,2006,availableathttp://www.jmlr.org/papers/volume7/wright06a/wright06a.pdf.

[61]A.SeewaldandW.Gansterer,“Onthedetectionandidentificationofbotnets,”Feb.2010,http://www.researchgate.net/profile/Wilfried_Gansterer/publication/220614106_On_the_detection_and_identification_of_botnets/links/0deec518cacaeb6574000000.pdf.

[62]C.BrownandAMalis,“MultiprotocolInterconnectoverFrameRelay,”RFC2427,September1998,https://tools.ietf.org/html/rfc2427.

[63]C.Hornig,“AStandardfortheTransmissionofIPDatagramsoverEthernetNetworks,”RFC894,April1984,https://tools.ietf.org/html/rfc894.

[64]IEEEStandardsAssociation,IEEEStandardforLocalandmetropolitanareanetworks–BridgesandBridgedNetworks,IEEEStd802.1Q-2014,http://standards.ieee.org/getieee802/download/802-1Q-2014.pdf.

[65]R.G.Miller,PriorityQueues,TheAnnalsofMathematicalStatistics,v31,number1(1960),pp.86-103,availableathttp://projecteuclid.org/download/pdf_1/euclid.aoms/1177705990.

[66]P.J.Rasch,“AQueueingTheoryStudyofRound-RobinSchedulingofTime-SharedComputerSystems,JournaloftheACM,v17Issue1,Jan.1970,pp.131-145,availableathttp://dl.acm.org/citation.cfm?id=321569?.

[67]A.K.,ParekhandR.G.Gallager,"Ageneralizedprocessorsharingapproachtoflowcontrolinintegratedservicesnetworks:Thesingle-nodecase,"IEEE/ACMTransactionsonNetworking1993,v1,issue3,pp.344-357,

34

availableathttp://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=234856.[68]W.H.HesselinkandR.M.Tol,“FormalFeasibilityConditionsforEarliestDeadlineFirstScheduling,1994,

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.55.8609.[69]S.Blake,D.Black,M.Carlson,E.Davies,Z.Wang,andW.Weiss,“AnArchitectureforDifferentiatedServices,”

RFC2475,Dec.1998,https://tools.ietf.org/html/rfc2475.[70]CeroWRT,CeroWRTOverview,http://www.bufferbloat.net/projects/cerowrt(lastvisitedonSept.3,2015).[71]G.R.Ash,TrafficEngineeringandQoSOptimizationofIntegratedVoice&DataNetworks,AppendixA.4.1.1and

A4.1.2LeakyBucketAlgorithmandTokenBucketAlgorithm,p.417-418,Nov.3,2006,MorganKaufman[72]R.Braden,L.Zhang,S.Berson,S.Herzog,andS.Jamin,“ResourceReSerVationProtocol(RSVP),”RFC2205,

Sept.1997,https://tools.ietf.org/html/rfc2205.[73]R.Braden,D.Clark,andS.Shenker,“IntegratedServicesintheInternetArchitecture:anOverview,”RFC1633,

June1994,https://tools.ietf.org/html/rfc1633.[74]DSLForum,TR-144:BroadbandMulti-ServiceArchitecture&FrameworkRequirements,TechnicalReport,

August2007,https://www.broadband-forum.org/technical/download/TR-144.pdf.[75]BroadbandForum,TR-145:Multi-serviceBroadbandNetworkFunctionalModulesandArchitecture,Technical

Report,November2012,https://www.broadband-forum.org/technical/download/TR-145.pdf.[76]AT&T,BroadbandInformation:InformationabouttheNetworkPractices,PerformanceCharacteristics&

CommercialTermsofAT&T’sMassMarketBroadbandInternetAccessServices,http://www.att.com/gen/public-affairs?pid=20879(lastvisitedSept.3,2015).

[77]InternationalTelecommunicationsUnion,Gigabit-capablepassiveopticalnetworks(G-PON):Transmissionconvergencelayerspecification,RecommendationG.984.3,January2014,https://www.itu.int/rec/T-REC-G.984.3-201401-I/en.

[78]CableLabs,SpecificationsLibrary,http://www.cablelabs.com/specs/(lastvisitedSept.3,2015).[79]CableLabs,Data-over-CableServiceInterfaceSpecificationsDOCSIS3.0,MACandUpperLayerProtocols

InterfaceSpecification,CM-SP-MULPIv30.0-I28-150827,availableathttp://www.cablelabs.com/wp-content/uploads/specdocs/CM-SP-MULPIv3.0-I28-150827.pdf.

[80]HughesNet,AboutHughesNet,http://www.hughesnet.com//company(lastvisitedSept.3,2015).[81]DISH,AboutDish:CompanyInfo,http://about.dish.com/company-info(lastvisitedSept.3,2015).[82]Exede,WhatisExede,http://www.exede.com/what-is-exede/,(lastvisitedSept.3,2015).[83]BruceR.Elbert,TheSatelliteCommunicationsApplicationsHandbook,ArtechHouse,pg.24,Jan.1,2004.[84]EuropeanTelecommunicationsStandardsInstitute,DigitalVideoBroadcasting(DVB);Secondgeneration

framingstructure,channelcodingandmodulationsystemsforBroadcasting,InteractiveServices,NewsGatheringandotherbroadbandsatelliteapplications(DVB-S2),ETSIEN302307V1.2.1(2009-08),http://www.etsi.org/deliver/etsi_en/302300_302399/302307/01.02.01_60/en_302307v010201p.pdf.

[85]J.Border,M.Kojo,J.Griner,G.Montenegro,Z.Shelby,“PerformanceEnhancingProxiesIntendedtoMitigateLink-RelatedDegradations,”RFC3135,June2001,https://tools.ietf.org/html/rfc3135.

[86]H.Balakrishan,V.N.Padmanabhan,G.Fairhurst,andM.Sooriyabandara,“TCPPerformanceImplicationsofNetworkPathAsymmetry,”RFC3449,Dec.2002,https://tools.ietf.org/html/rfc3449.

[87]The3rdGenerationPartnershipProject(3GPP),About3GPP,2015,http://www.3gpp.org/about-3gpp/about-3gpp(lastvisitedSept.3,2015).

[88]NextGenerationMobileNetwork(NMGN)Alliance,NextGenerationMobileNetworks:BeyondHSPA&EVDO,WhitePaper,December2006,http://ngmn.org/uploads/media/Next_Generation_Mobile_Networks_Beyond_HSPA_EVDO_web.pdf.

[89]F.Firmin,TheEvolvedPacketCore,3GPP,http://www.3gpp.org/technologies/keywords-acronyms/100-the-evolved-packet-core(lastvisitedSept.3,2015)

[90]M.Nohrborg,LTEOverview,3GPP,http://www.3gpp.org/technologies/keywords-acronyms/98-lte(lastvisitedSept.3,2015).

[91]ChristopherCox,AnIntroductiontoLTE:LTE,LTE-Advanced,SAEand4GMobileCommunications,pp.36-

35

37,JohnWiley&Sons2012.[92]3rdGenerationPartnershipProject(3GPP),PolicyandChargingControlArchitecture,3GPPTS23.203,

http://www.3gpp.org/DynaReport/23203.htm.[93]3GPP,ETSIpolicyandchargingcontrolarchitecture—3GPPTS23.203v.12.9.0release

12,http://www.etsi.org/deliver/etsi_ts/123200_123299/123203/12.09.00_60/ts_123203v120900p.pdf.[94]MetroEthernetForum,MEF22.1:MobileBackhaulPhase2,January2012,

http://www.mef.net/PDF_Documents/technical-specifications/MEF_22.1.pdf.[95]BroadbandForum,TR-221:TechnicalSpecificationsforMPLSinMobileBackhaulNetworks,October2011,

https://www.broadband-forum.org/technical/download/TR-221.pdf.[96]Mimosa,WhisperInternet,http://mimosa.co/home/Products/docs/case-studies/wisper-isp.html(lastvisited

Sept.3,2015).[97]UbiquitiNetworks,AirFiber24:24GHzPoint-to-PointGigabitRadio,

https://www.ubnt.com/airfiber/airfiber24/(lastvisitedSept.3,2015).[98]Reuters,ProceraDeployedbyMultipleRuralWirelessInternetServiceProviders,PressRelease,Oct.22,2012,

availableathttp://www.reuters.com/article/2012/10/22/idUS75943+22-Oct-2012+MW20121022.[99]UbiquitiNetworks,RocketACBaseStation,Datasheet,availableat

http://dl.ubnt.com/datasheets/RocketAC/Rocket5ac_DS.pdf.[100]Juniper.net,HierarchicalRateLimitsOverview,

https://www.juniper.net/techpubs/en_US/junose10.3/information-products/topic-collections/policy-management/policy-mgm-rate-limit-hierarchical.html(lastvisitedSept.3,2015).

[101]AT&T,AT&TWifiandHotspots,https://www.wireless.att.com/businesscenter/solutions/wireless-laptop/wifi-hotspots.jsp(lastvisitedSept.3,2015).

[102]CableWifi(BrightHouse,Cox,Optimum,TimeWarnerCable,Comcast),http://www.cablewifi.com/(lastvisitedSept.3,2015).

[103]EuropeanTelecommunicationsStandardsInstitute(ETSI),NetworkFunctionsVirtualisation:NFVinETSI,http://www.etsi.org/technologies-clusters/technologies/nfv(lastvisitedonSept.3,2015).

[104]InternationalTelecommunicationsUnion,StandardizationSector(ITU-T),“One-waytransmissiontime,”RecommendationG.114,May2003,https://www.itu.int/rec/T-REC-G.114/en.

[105]3GPP,IPMultimediasubsystem(stage2),Specificationdetail,http://www.3gpp.org/DynaReport/23228.htm(lastvisitedSept.3,2015).

[106]CableLabs,PacketCableTechnicalReport,MultimediaArchitectureFramework,Oct.29,2009,http://www.cablelabs.com/wp-content/uploads/specdocs/PKT-TR-MM-ARCH-V03-091029.pdf.

[107]R.Pantos,“HTTPLiveStreaming,”April15,2015,draft-pantos-http-live-streaming-16,https://datatracker.ietf.org/doc/draft-pantos-http-live-streaming/.

[108]InternationalOrganizationforStandardization(ISO),AdaptiveStreamingoverHTTP(DASH),ISO/IEC23009-1:2014,https://www.iso.org/obp/ui/#iso:std:iso-iec:23009:-1:ed-2:v1:en.

[109]Apple,HTTPLivestreamingOverview,https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/StreamingMediaGuide/Introduction/Introduction.html(lastvisitedSept.3,2015).

[110]Tellabs,MobileVideoOptimizationConceptandBenefits,WhitePaper,2011,http://s3.amazonaws.com/zanran_storage/www.tellabs.com/ContentPages/2438991029.pdf.

[111]C.Bastien,T.Klieber,J.Livingood,J.Mills,andR.Woundy,“Comcast’sProtocol-AgnosticCongestionManagementSystem,”RFC6057,December2010,https://tools.ietf.org/html/rfc6057.

[112]D.J.Leith,P.Clifford,“TCPFairnessin802.11eWLANs,”http://www.hamilton.ie/peterc/downloads/wicom05tcpfairness.pdf(lastvisitedSept.3,2015).

[113]Z.Sun,SatelliteNetworking:PrinciplesandProtocols,Dec.13,2005,WileyandSons.[114]Trendnet.com,AC3200TriBandWirelessRouter,

http://www.trendnet.com/products/proddetail.asp?prod=100_TEW-828DRU(lastvisitedSept.3,2015).[115]S.Mascolo,C.Casetti,M.Gerla,M.Y.Sanadidi,andR.Wang,TCPWestwood:BandwidthEstimationfor

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EnhancedTransportoverWirelessLinks,ACMSigmobileJuly2001,pp.287-297,http://cpham.perso.univ-pau.fr/TCP/2001-mobicom-0.pdf.

[116]C.Casetti,M.Gerla,S.Mascolo,M.Y.Sanadidi,andR.Wang,TCPWestwood:End-to-EndCongestionControlforWired/WirelessNetworks,WirelessNetworksv.8,2002,pp.467-479,http://netlab.cs.ucla.edu/publication/download/41/Wn_02.pdf.

[117]BrownUniversity,ParticipatoryNetworking:Auser-levelAPIforSDNs,http://pane.cs.brown.edu/(lastvisitedSept.3,2015).

[118]W.Kim,P.Sharma,J.Lee,S.Banerjee,J.Tourrilhes,S.Lee,andP.Yalagandula,“AutomatedandScalableQoSControlforNetworkConvergence,”2010,availableathttps://www.usenix.org/event/inmwren10/tech/full_papers/Kim.pdf.

[119]GeorgiaTech,FlowQoS:ProvidingPer-FlowQualityofServiceforBroadbandAccessNetworks,http://flowqos.noise.gatech.edu/(lastvisitedSept.3,2015).

[120]D.Eastlake,“TransportLayerSecurity(TLS)Extensions:ExtensionDefinitions,”RFC6066,January2011,availableathttps://tools.ietf.org/html/rfc6066.

[121]Finley,Klint,“EncryptedWebTrafficMorethanDoublesAfterNSARevelations,”Wired(May16,2014),availableathttp://www.wired.com/2014/05/sandvine-report/.

[122]P.Lepeska,“TrustedProxyandtheCostofBits,”IETF90HTTPWGpresentation,availableathttps://www.ietf.org/proceedings/90/slides/slides-90-httpbis-6.pdf(lastvisitedSept.3,2015).

[123]A.Kingsley-Hughes,“Gogoin-flightWi-FiservingspoofedSSLcertificates,”ZDNetJanuary5,2015,http://www.zdnet.com/article/gogo-in-flight-wi-fi-serving-spoofed-ssl-certificates/(lastvisitedSept.3,2015).

[124]BroadbandInternetTechnicalAdvisoryGroup(BITAG),VoIPImpairment,Failure,andRestrictions,May2014,availableathttp://www.bitag.org/documents/BITAG_-_VoIP_Impairment,_Failure,_and_Restrictions_Report.pdf.

[125]BroadbandInternetTechnicalAdvisoryGroup(BITAG),PortBlocking,Aug.2013,availableathttp://www.bitag.org/documents/Port-Blocking.pdf.

[126]BroadbandInternetTechnicalAdvisoryGroup(BITAG),SNMPReflectedAmplificationDDoSAttackMitigation,Aug.2012,availableathttp://www.bitag.org/documents/SNMP-Reflected-Amplification-DDoS-Attack-Mitigation.pdf.

[127]BroadbandInternetTechnicalAdvisoryGroup(BITAG),ImplicationsofLargeScaleNetworkAddressTranslation(NAT),Mar.2012,availableathttp://www.bitag.org/documents/BITAG_TWG_Report-Large_Scale_NAT.pdf.

[128]BroadbandInternetTechnicalAdvisoryGroup(BITAG),IPv6AAAADNSWhitelisting,Sept.2011,availableathttp://www.bitag.org/documents/BITAG_TWG_Report-DNS_Whitelisting.pdf.

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9 GlossaryoftermsAlldefinitionsoftermsaresolelyforthepurposesofthisreport,andmanyareadaptedfrompublicationsoftheInternetEngineeringTaskForce(www.ietf.org).Readersshouldbeawarethatanumberoftermshavealternatedefinitions,particularlywhenusedindifferentornon-networkingcontexts.

Admissioncontrol:Decisionsthatdeterminewhichflowsareallowedtobegin,basedonavailableresources.

Application:Aprogramthatoriginatesorreceivesdata.

Bottleneck:Thelinkornodeinanetworkpathwheredemandishighestrelativetocapacity.

Bursty:Atrafficflowisburstyifitsvolumechangesrapidlyovertime.

Capacity:Thecapacityofalinkisthenumberofbitspersecondthatitcantransmit.Thecapacityofarouteristhenumberofpacketsorbytespersecondthatitcantransmit.

Classification:Thecategorizationoftrafficbasedonidentifyingcharacteristics.

Congestion:Theeffectuponnetworkperformanceduringtimeperiodsinwhichinstantaneousdemandexceedscapacity

Deadlinescheduling:Aschedulingalgorithminwhicheachpacketismarkedoningresswithamaximumperiodoftimeitmaybedelayed(a"deadline"),andthequeuingsystemeitherensuresthepacket’stransmissionwithinthatintervalordropsthepacket.

Demand:Thevolumeoftrafficthatispresentedtoalinkatagivenpointintime,typicallymeasuredinbitspersecond.

Differentiatedtreatment,Differentiation:Theapplicationofatrafficpolicybasedonclassificationofthetraffictoaclassoftrafficsuchasasession,aggregateofsessions,orothertrafficflow.Examplesofsuchpoliciesincluderesourceallocation,schedulingalgorithms,dropprecedence,androuting.

DifferentiatedServicesArchitecture(alsoDiffserv):AnarchitectureforthedifferentiatedhandlingofIPtraffic.PrimarilydescribedinRFC2474andRFC2475.

Dropprecedence:ExamplesofthisincludeFrameRelayDiscardEligibility,ATMCellLossPriority,theIP“AssuredForwarding”service,ora“lessthanbesteffort”service.Insuchcases,includedintheservicelevelagreementisanunderstandingthataspecifiedsubsetoftraffic(thatexceedingsomerate,orperhapsallofit)ismorelikelytobedroppedthanothertraffic.

Flow:Agroupofpacketsthatshareacommonsetofproperties.

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InternetAccessService:Inthisdocumentweusetheterm'internetaccessservice'torefertoamassmarketservicethatprovidestheabilitytotransmitandreceivedatatotheglobaladdressspaceassociatedwiththeInternet.

Mark:Tosetspecificbitsofapacketheader(seemarking)tospecificvalues.

Marking:Specificbitsofapacketheaderthatindicatetheclassificationofapacketorthatindicatecongestion.

NetworkOperator:Abusinessthatoperatesoneormorecommunicationsnetworks.Thenetworksmayincludeaccessnetworksthatinterconnectdirectlywithretailcustomers,othernetworktypessuchastransportnetworksorcontentdeliverynetworks,oralloftheabove.Inthecaseofaccessnetworks,thenetworkoperatormayalsoactasanISP,offeringInternetservicestocustomers.ThenetworkoperatormayalsoactasanNSP,offeringtransportorothernetworkservicestoothernetworkoperators.

Over-the-top(OTT):AnapplicationortrafficflowthatiscarriedoveranInternetaccessservice.

Policing:Thedroppingorreclassificationofpacketsthatexceedthemaximumcapacityallocatedtoaflow.

Prioritization:Theapplicationofatrafficpolicythatprefersoneormoreclassesoftrafficoveroneormoreotherclassesoftraffic.Thismaybeinactualtrafficsequence,indropprobability,orothermechanisms.

QualityofExperience(QoE):Thesubjectivequalityofanetworkedapplicationasperceivedbytheuser.

QualityofService(QoS):theamountofimpairmentexperiencedbytrafficduringitstransmissionacrossoneormorenetworks.QoSisexpressedintermsofdelay,delayvariation,packetloss,andotherobjectivemetrics.

Scheduling:Thereorderingorothertreatmentofpacketsaccordingtoanalgorithm.

ServiceLevelAgreement(SLA):Acontractualagreementbetweennetworkoperatorsorbetweenusersandnetworkoperatorsthatdelineatesaspectsoftheservice,oftenincludingtheupstreamanddownstreambitratesattheboundarybetweentheoperators’networks,themaximumdelayacrossanoperator’snetwork,sometimesthemaximumproportionofpacketstobedroppedorotherQoScharacteristics,andsometimesspecificationsofpayments.

Trafficshaping:Ratelimitingofflowsinanetwork.

Packet:Aformattedunitofdatacarriedbyapacket-switchednetwork.Apacketconsistsofoneormoreheaderscontainingcontrolinformationandapayloadcontaininguserdata.

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10 DocumentContributorsandReviewers

- FredBaker,Cisco- StevenBauer,MassachusettsInstituteofTechnology(MIT)- RichardBennett,AmericanEnterpriseInstitute- DonBowman,Sandvine- LilyChen,Verizon- kcclaffy,UniversityofCalifornia,SanDiego;CenterforAppliedInternetData

Analysis(CAIDA)- DavidClark,MassachusettsInstituteofTechnology(MIT)- DavidCooper,Level3- AmoghDhamdhere,UniversityofCalifornia,SanDiego;CenterforApplied

InternetDataAnalysis(CAIDA)- AmieElcan,CenturyLink- MichaelFargano,CenturyLink- NickFeamster,PrincetonUniversity- JosephLorenzoHall,CenterforDemocracy&Technology(CDT)- KevinKleinsmith,UnionWireless- KenKo,ADTRAN- GaryLangille,EchoStar- MattLarsen,Vistabeam- JasonLivingood,Comcast- PatrickMcManus,Mozilla- ChrisMorrow,Google- BarbaraStark,AT&T- MatthewTooley,NationalCableandTelecommunicationsAssociation(NCTA)- JasonWeil,TimeWarnerCable- GregWhite,CableLabs- DavidWinner,CharterCommunications

*BITAGwouldliketothankProfessorMarvinSirbuofCarnegieMellonUniversityforhispresentationregardingthestructureandcompositionofdifferenttypesofaccessnetworks.

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11 Appendix:Standards,StandardsOrganizations,andIndustryReferences

Avarietyofstandardsorganizationsandindustryallianceshavepublishedstandards,technicalreferences,informationaldocuments,andbestpracticesthatarerelevanttothetopicofdifferentiatedtreatment.Someofthemostprominentandinfluentialoftheseorganizationsandtheirpublicationsarelistedinthissection.Inaddition,somecorporationshavecreatedtechnologiesthatarewidelyusedandaresometimesconsidered“defacto”standards.Alistofsomeoftheseisalsoincluded.

● InternetEngineeringTaskForce(IETF):TheIETFproducestechnicaldocumentsthatinfluencethewaypeopledesign,use,andmanagetheInternet(www.ietf.org).Relevantpublicationsinclude:

○ InternetProtocol[RFC791]:DefinesIPv4headerformats.ThevariouselementsoftheIPv4header(e.g.,sourceIPv4address,destinationIPv4address,typeofservice)canbeusedforclassificationoftraffic(xrefto5.1.1).

○ InternetProtocol,Version6(IPv6)Specification[RFC2460]:DefinesIPv6headerformats.ThevariouselementsoftheIPv6header(e.g.,sourceIPv6address,destinationIPv6address,trafficclass,flowlabel)canbeusedforclassificationoftraffic(xrefto5.1.1).

○ DefinitionoftheDifferentiatedServicesField(DSField)intheIPv4andIPv6Headers[RFC2474]:DefinesthelayoutoftheIPv4typeofserviceheaderfieldandIPv6trafficclassheaderfield,andabasesetofpacketforwardingtreatments,orper-hopbehaviors,thatcanbeusedforscheduling(xrefto5.1.2).

○ Additionalper-hopbehaviors,includingAssuredForwarding[RFC2597]andExpeditedForwarding[RFC3246/3247],thatcanbeusedforscheduling(xrefto5.1.2).

○ Comcast'sProtocol-AgnosticCongestionManagementSystem[RFC6057]:DescribesComcast’scongestionmanagementsystemthatwasdeployedDecember31,2008.Thisisusedforschedulingtraffic(xrefto5.1.2),butnotethatitthisisnotastandard.

○ MultiprotocolLabelSwitchingArchitecture[RFC3031]:DescribestheMPLSarchitecturecommonlyusedincurrentDSLandPONaccessnetworks,beyondthefirstmile,andisusedforservicelevelagreement(SLA)assuranceinserviceprovidernetworks.

○ ResourceReSerVationProtocol(RSVP,RFC2205):aprotocoldesignedforsoftreservationofbandwidthwithinanetwork.Reservationis“soft”inthesensethatwhileitensuresbandwidthisavailablewhenthesubjecttrafficflowispresent,itisavailableforothertrafficwhenthesubjecttrafficflowisnotordoesnotuseitall.RSVPisalsousedforthemanagementofSLA-sensitiveMPLSLSPs.

○ IntegratedServicesintheInternetArchitecture[(RFC1633]):thearchitecturethatdefinesRealTimevs.Elasticapplications,andtheirrequirements.

● InstituteofElectricalandElectronicsEngineers-StandardsAssociation(IEEE-SA):TheIEEE-SAdrivesthefunctionality,capabilitiesandinteroperabilityofawiderangeofproductsandservices(standards.ieee.org).Someofthemostrelevant(todifferentiation)workinggroupsinsideIEEE-SAinclude802.1(HigherLayerLANProtocolsWorkingGroup),EthernetWorkingGroup(802.3),802.11(WirelessLANWorkingGroup),andBroadbandWirelessAccessWorkingGroup(802.16).Therearemanyotherworkinggroupsthatincludeeffortsonsuchtopicsasresilientpacketrings,wirelesscoexistence,mobilebroadband,andpowerlinenetworking(notan802workinggroup).

○ IEEEStandardforLocalandMetropolitanAreaNetworks:OverviewandArchitecture[IEEE802]:ContainsdescriptionsoftheIEEE802®standardspublishedbytheIEEEforframe-baseddatanetworksaswellasareferencemodel(RM)forprotocolstandards.

○ IEEEStandardforEthernet[IEEE802.3]:RelevantpartsdefineEthernet,includingphysicallayerprotocols(e.g.,10BASE-,100BASE-[FastEthernet],1000BASE-[GigabitEthernet],EthernetintheFirstMile[EFM]),andtheformatoftheMediaAccessControl(MAC)frame,commonlycalledtheEthernetframe.ThevariouselementsoftheMACframe(includes

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sourceanddestinationMACaddresses,Ethertype,andextensionsdefinedinotherIEEEstandards)canbeusedforclassificationoftraffic(xrefto5.1.1).

○ IEEEStandardforLocalandMetropolitanAreaNetworks–MediaAccessControl(MAC)BridgesandVirtualBridgedLocalAreaNetworks[IEEE802.1Q]:RelevantaspectsofthisstandardarethatitdefinesVLANTagextensions,whichincludetheVLANIDandPriorityCodePoint(PCP).Bothofthesefieldsareusefulforclassification(xrefto5.1.1),withtheEthernetPriorityusedprimarilytodetermineschedulingbehavior(xrefto5.1.2)andtheVLANIDusedprimarilytodeterminerouting(xrefto5.1.3).

○ IEEEStandardforLocalandMetropolitanAreaNetworks–vMediaAccessControl(MAC)Bridges[IEEE802.1D]:RelevantaspectsofthisstandarddescribebridgingbehaviorbasedonthePriorityCodePointintheVLANTag.

○ Part11:WirelessLANMediumAccessControl(MAC)andPhysicalLayer(PHY)Specifications[IEEE802.11]:Relevantaspectsofthisstandardarethatitdefinesseveralphysicallayerprotocolscommonlyreferredtoas“802.11a,”“802.11b,”“802.11g,”and“802.11n,”anddefinestheMACframesandQoSmechanismsforthesephysicallayers.

○ IEEEStandardforServiceInteroperabilityinEthernetPassiveOpticalNetworks(SIEPON)[P1904.1]:Thisstandarddescribesthesystem-levelrequirementsneededtoensureservice-level,multi-vendorinteroperabilityofEthernetPassiveOpticalNetwork(EPON)equipment.ThespecificationscomplementtheexistingIEEE802.3andIEEE802.1standards,whichensuretheinteroperabilityatthePhysicalLayer(PHY)andDataLinkLayer.Includedinthisspecificationare:● EPONsystem-levelinteroperabilityspecificationscoveringequipmentfunctionality,

trafficengineering,andservice-levelqualityofservice/classofservice(QoS/CoS)mechanisms;

● Managementspecificationscoveringequipmentmanagement,servicemanagement,andEPONpower-savingmechanism.

● BroadbandForum(BBF):TheBBFdevelopsmulti-servicebroadbandnetworkingspecifications

addressinginteroperability,architectureandmanagement(www.broadband-forum.org).ThisorganizationhasastrongfocusonDSLandPONISPaccessnetworksandproviders.TheformerATMForum,IP/MPLSForum,MFAForumandMPLS&FrameRelayAllianceorganizationshaveallmergedwithBBF,andalloftheseorganizations’publicationsarenowavailablefromtheBBFwebsite.

○ MigrationtoEthernet-BasedBroadbandAggregation[TR-101Issue2]:DescribesanEthernet(attheMAClayer)architectureforDSLandPONaccessnetworks.Thisdescribesanaccessandaggregationnetworkarchitecture(xref5.1.3)includingbasicmethodstosupportclassification,schedulingandotherdifferentiationtechniques.

○ Multi-serviceBroadbandNetworkFunctionalModulesandArchitecture[TR-145]:ExtendstheTR-101architecturetosupportmultipleservicesandnetworkinterfaces.

○ UsingGPONAccessinthecontextofTR-101[TR-156]:ExtendsTR-101toGPON.○ UsingEPONintheContextofTR-101[TR-200]:ExtendsTR-101toEPON.○ MultiprotocolLabelSwitching(MPLS)standards:MPLSwasoriginallydefinedbyIETF,but

muchsubsequentworkwasdoneintheIP/MPLSForum,whichhassincemergedwithBBF.

● InternationalTelecommunicationsUnion-TelecommunicationStandardizationSector(ITU-T):ITU-TisthetelecommunicationsstandardssectoroftheITU,whichistheUnitedNationsspecializedagencyforinformationandcommunicationtechnologies.

○ Asymmetricdigitalsubscriberline(ADSL)transceiversADSL:[ITU-TG.992.1],Asymmetricdigitalsubscriberlinetransceivers2(ADSL2)[ITU-TG.992.3],Veryhighspeeddigitalsubscriberlinetransceivers(VDSL)[ITU-TG.993.1],Veryhighspeeddigitalsubscriberlinetransceivers2(VDSL2)[ITU-TG.993.2]:DefinethevariousDSLphysicallayertechnologiesovercoppertwistedpair(phonelines).

○ BroadbandPassiveOpticalNetwork(BPON)fortelecommunicationsAccessnetworks[ITU-TG.983],

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○ Gigabit-capablePassiveOpticalNetworks(GPON)[ITU-TG.984]:DefinetheBPONandGPONphysicallayertechnologies

○ JSeries:ITU-TofficiallynamedtheCableLabs’DOCSISspecificationsasstandardsthroughseveralofitsJSeriespublications.DOCSIS1.0wasJ.112AnnexB(1998),DOCSIS1.1isJ.112AnnexB(2001),DOCSIS2.0isJ.122,andDOCSIS3.0isJ.222.

● CableLabs:○ DOCSIS1.0-AsetofeightspecificationsthatdefinethefirstversionoftheDataOverCable

ServiceInterfaceSpecification(DOCSIS).ThesespecificationsdescriberequirementsforCableModems(CMs)andCableModemTerminationSystems(CMTSs)toprovidebasicbroadbandIPconnectivityoverthehybridfibercoaxcablenetwork,includingpermodemrateshaping,linkencryption,andnetworkmanagementfunctions.

○ DOCSIS1.1-AsetofthreespecificationsthatextendDOCSIS1.0inordertoprovideQualityofServicecontrols,aPublicKeyInfrastructurebasedCMauthenticationandCMfirmwarevalidationmechanism,andenhancednetworkmanagementtools.

○ DOCSIS2.0-AsetofthreespecificationsthatextendDOCSIS1.1withanewupstreamphysicallayertechnologythatprovidesa3xincreaseinupstreamchannelcapacity,andoptionalsupportofIPv6management.

○ DOCSIS3.0-AsetoffivespecificationsthatextendDOCSIS2.0withsupportforchannelbondingtoincreasecapacitytoover200Mbpsintheupstreamandover1Gbpsinthedownstream,andfullIPv6support.

○ DOCSIS3.1-AsetoffivespecificationsthatextendDOCSIS3.0withanewupstreamanddownstreamphysicallayerenablingmulti-Gbpsserviceinbothdirections,aswellasActiveQueueManagementandhierarchicalQualityofService.

○ DOCSISProvisioningofEPON,version1.0(DPoEv1.0)–AsetofninespecificationsdescribingthetranslationofDOCSISprovisioningprocedurestoprovisionandmanageEthernetPassiveOpticalNetworksviaIPv4.AcomprehensivesetofextendedOAMmessagesisdefinedtoallowtheOpticalLineTerminal(OLT)toprovisionandmanageOpticalNetworkUnits(ONUs).ThespecificationsalsodescribethedevicerequirementsforsupportingIPhighspeeddataandEthernetPrivateLine(EPL)MetroEthernetservicemodelsinanMSOenvironment.

○ DOCSISProvisioningofEPON,version2.0(DPoEv2.0)–AcollectionofninespecificationsthatextendDPoEv1.0specifications,includesmanagementusingIPv6,multicastservices,andnetworksynchronization.ThesupportofcommercialservicesisexpandedtoincludeVirtualPrivateLANandTreeservices,asdefinedbytheMetroEthernetForum.

● Wi-FiAlliance(WFA):WFAisanindustryalliancethathascreatedIEEE802.11implementationprofilesanddevelopedcertificationprogramsforthesame.“Wi-Fi”isitsregisteredtrademarkbrand.

○ Wi-FiCERTIFIED™ninboth2.4and5GHz,andWi-FiCERTIFIED™acin5GHz:CertificationprogramsandimplementationprofilesofferedbyWFAforphysicallayerwirelesstechnologiesbasedontheIEEE802.11standard.TheformerWi-FiCERTIFIEDain5GHzandWi-FiCERTIFIEDb/gin2.4GHzarenolongeravailable.

○ Passpoint™:Certificationprogramandspecification(developedwithGSMAandtheWirelessBroadbandAlliance)thatenablesSIMandnon-SIMmobiledevicestodiscover,selectandconnecttoWi-Finetworkswithoutuserintervention.AlsoknownasHotspot2.0.

○ •WMM®(Wi-FiMultimedia™):CertificationprogramandimplementationprofileforIEEE802.11QualityofService(QoS)mechanisms.

● Widely-usedProprietaryTechnologies(primarilyCisco,Juniper,Motorola,andAlcatel-Lucent)○ Cisco’sNetflow,JuniperSflow○ MotorolaCanopy