ETSI EN 300 463 V1.1.2 (2000-06)

Transmission and Multiplexing (TM); Requirements of passive Optical Access Networks (OANs) to provide services up to 2 Mbit/s bearer capacity

REN/TM-01088

Prenos in multipleksiranje (TM) – Zahteve pasivnih optičnih dostopovnih omrežij (OANs) za zagotavljanje storitev do nosilne zmogljivosti 2 Mbit/s

General Information

• Status: Published
• Publication Date: 12-Jun-2000
• Technical Committee: TM 1 - TM Core networks, fibres and cables
• Current Stage: 12 - Completion
• Due Date: 24-Apr-2000
• Completion Date: 13-Jun-2000
• Ref Project: SIST EN 300 463 V1.1.2:2003 - Transmission and Multiplexing (TM); Requirements of passive Optical Access Networks (OANs) to provide services up to 2 Mbit/s bearer capacity

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Transmission and Multiplexing (TM); Requirements of passive Optical Access Networks (OANs) to provide services up to 2 Mbit/s bearer capacity33.040.20Prenosni sistemTransmission systemsICS:Ta slovenski standard je istoveten z:EN 300 463 Version 1.1.2SIST EN 300 463 V1.1.2:2003en01-december-2003SIST EN 300 463 V1.1.2:2003SLOVENSKI
STANDARD



SIST EN 300 463 V1.1.2:2003



ETSIEN300463V1.1.2(2000-06)EuropeanStandard(Telecommunicationsseries)TransmissionandMultiplexing(TM);RequirementsofpassiveOpticalAccessNetworks(OANs)toprovideservicesupto2Mbit/sbearercapacitySIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)2ReferenceREN/TM-01088Keywordsaccess,bearer,network,optical,transmissionETSI650RoutedesLuciolesF-06921SophiaAntipolisCedex-FRANCETel.:[phone]Fax:[phone]SiretN°34862356200017-NAF742CAssociationàbutnonlucratifenregistréeàlaSous-PréfecturedeGrasse(06)N°7803/88ImportantnoticeIndividualcopiesofthepresentdocumentcanbedownloadedfrom:http://www.etsi.orgThepresentdocumentmaybemadeavailableinmorethanoneelectronicversionorinprint.Inanycaseofexistingorperceiveddifferenceincontentsbetweensuchversions,thereferenceversionisthePortableDocumentFormat(PDF).Incaseofdispute,thereferenceshallbetheprintingonETSIprintersofthePDFversionkeptonaspecificnetworkdrivewithinETSISecretariat.Usersofthepresentdocumentshouldbeawarethatthedocumentmaybesubjecttorevisionorchangeofstatus.InformationonthecurrentstatusofthisandotherETSIdocumentsisavailableathttp://www.etsi.org/tb/status/Ifyoufinderrorsinthepresentdocument,sendyourcommentto:[e-mail]opartmaybereproducedexceptasauthorizedbywrittenpermission.Thecopyrightandtheforegoingrestrictionextendtoreproductioninallmedia.©EuropeanTelecommunicationsStandardsInstitute2000.Allrightsreserved.SIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)3ContentsIntellectualPropertyRights.5Foreword.51Scope.62References.63Definitionsandabbreviations.83.1Definitions.83.2Abbreviations.94ConfigurationofanOAN.104.1Topologicalandfunctionalissues.104.2Servicecapability.135ONU.135.1Descriptionoffunctions.135.1.1ONUcoreshell.145.1.2ONUserviceshell.145.1.3ONUcommonshell.145.2ONUdimensions.145.3UsertoNetworkInterfaces(UNIs).155.4ONUpowerconsiderations.166ODN.166.1GeneralODNrequirements.166.2ReachlimitationsandsplitratiosoftheODN.177OLT.177.1Descriptionoffunctions.187.1.1OLTcoreshell.187.1.2OLTserviceshell.197.1.3OLTcommonshell.197.2OLTdimensions.197.3SNIs.208SpecificattributesofOANs.208.1Transmissionmethod.208.2OperatingwavelengthrangeforanOAN.208.2.1SDM.218.2.2TCM.218.2.3WDM.218.2.4FDM.218.3Signaltransferdelay.219Timingandsynchronization.229.1Synchronizationarchitecture.229.2ProtectionandONUtiming.239.3Synchronizationinterfaces.239.3.1Jitterandwandertolerance.239.4Network-sideinterfacesforsynchronousservices.239.4.1Jitterandwandertolerance.239.4.2Jitterandwandergeneration.239.5User-sideinterfacesforsynchronousservices.249.5.1Jitterandwandertolerance.249.5.2Jitterandwandergeneration.249.6Timingrequirementsforasynchronousservices.2410OAM.2410.1GeneralOAMrequirements.24SIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)410.2Lineconfigurationandtesting.2510.3OANoperation.2511SecurityofOANs.2611.1Generalinformation.2611.2Identificationandauthentication.2611.3Accesscontrol.2711.4Accountabilityandaudit.2711.5Accuracy.2711.6Availability.2711.7Dataexchange.2711.8Layersofphysicalsecurity.2811.8.1Physicalsecurityfunction.2811.8.2Transmissionsystemsecurityfunction.2811.8.3Servicesecurityfunction.2912Safety.2913Reliabilityandavailability.2914UpgradeofOANs.3014.1ODNconsiderations.3014.2ONUconsiderations.31AnnexA(informative):RelationshipbetweentypesandclassesforONUs.32AnnexB(informative):AnexamplepowerconsumptionforanOAN.33AnnexC(informative):Signaltransferdelaymeasurementtechnique.35AnnexD(informative):FrameworktocapturetheOAMrequirements.36D.1AnalysisofOAMrequirementsbyfunctionalsub-systems.36D.2Examplesforlinecircuitsupervision.37D.3AnalysisofOAMrequirementsbyfunctionalcategory.38D.3.1Accessandsecurity.38D.3.2Configurationandresourcemanagement.38D.3.3Performancemanagement.39D.3.4Event(alarm)management.40D.3.5Financialaccountingmanagement.41Bibliography.42History.43SIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)5IntellectualPropertyRightsIPRsessentialorpotentiallyessentialtothepresentdocumentmayhavebeendeclaredtoETSI.TheinformationpertainingtotheseessentialIPRs,ifany,ispubliclyavailableforETSImembersandnon-members,andcanbefoundinSR000314:"IntellectualPropertyRights(IPRs);Essential,orpotentiallyEssential,IPRsnotifiedtoETSIinrespectofETSIstandards",whichisavailablefromtheETSISecretariat.LatestupdatesareavailableontheETSIWebserver(http://www.etsi.org/ipr).PursuanttotheETSIIPRPolicy,noinvestigation,includingIPRsearches,hasbeencarriedoutbyETSI.NoguaranteecanbegivenastotheexistenceofotherIPRsnotreferencedinSR000314(ortheupdatesontheETSIWebserver)whichare,ormaybe,ormaybecome,essentialtothepresentdocument.ForewordThisEuropeanStandard(Telecommunicationsseries)hasbeenproducedbyETSITechnicalCommitteeTransmissionandMultiplexing(TM).Thepresentdocumentdescribescosteffectiveandflexibleaccessnetworksusingopticalfibretechnologyandisdesignedtoprovidebothservicestomeetthecurrentdemandsandaninfrastructure,whichisabletosatisfytherequirementsofthefuture.NationaltranspositiondatesDateoflatestannouncementofthisEN(doa):30September2000DateoflatestpublicationofnewNationalStandardorendorsementofthisEN(dop/e):31March2001DateofwithdrawalofanyconflictingNationalStandard(dow):31March2001SIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)61ScopeThepresentdocumentdescribescosteffectiveandflexibleaccessnetworksusingopticalfibretechnology.Thepresentdocumentisdesignedtoprovidebothservicestomeetthecurrentdemandsandaninfrastructure,whichisabletosatisfytherequirementsofthefuture.ThepresentdocumentdescribesthecharacteristicsofanOpticalAccessNetwork(OAN)withthecapabilityoftransportinginteractiveservices,basedon64kbit/sbearercapabilities,betweentheUserNetworkInterface(UNI)andthelocalexchange.ThepresentdocumentconsidersanOANcapableofprovidingbusinessandresidentialcustomerswitharangeofservices(upto2Mbit/s)overapassivesplitopticalnetwork.Distributiveservices(e.g.cabletelevision)areoutsidethescopeofthepresentdocument.TheOANdescribedinthepresentdocumenthasconsideredtherequirementfortheaccessnetworktoadapttothechangingrequirementsofindividualcustomersintermsofcapacity,flexibilityandtypesofservicesofferedwithouttheneedfornetworkoperatorstoprovideservicespecificoverlaynetworks.TheconsideredsystemswithinthepresentdocumentarebasedonTimeDivisionMultipleAccess(TDMA)and/orSubcarrierMultipleAccess(SCMA)methods.Oneandtwofibresystemsaredescribed.ThepresentdocumentconsidersOANswheretheOpticalDistributionNetwork(ODN)isbasedonpoint-to-multipointtreeandbranchoptionsasdescribedinETS300681[4].Thepresentdocumentisnotacompletesystemdefinition.Itidentifiesaspectsthatcanbedefinedwithoutpreventingtransmissioninnovation.2ReferencesThefollowingdocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthepresentdocument.• Referencesareeitherspecific(identifiedbydateofpublication,editionnumber,versionnumber,etc.)ornon-specific.• Foraspecificreference,subsequentrevisionsdonotapply.• Foranon-specificreference,thelatestversionapplies.• Anon-specificreferencetoanETSshallalsobetakentorefertolaterversionspublishedasanENwiththesamenumber.[1]ECSYN287(1990):"Proposalforthecouncildirectiveconcerningtheprotectionofindividualsinrelationtotheprocessingofpersonaldata".[2]ECSYN288(1990):"Proposalforthedirectiveconcerningtheprotectionofpersonaldataandprivacyinthecontextofpublicdigitaltelecommunicationnetworks,inparticulartheintegratedservicesdigitalnetwork(ISDN)andpublicdigitalmobilenetworks".[3]EN60950:"Safetyofinformationtechnologyequipment,includingelectricalbusinessequipment".[4]ETSIETS300681(1996):"TransmissionandMultiplexing(TM);OpticaldistributionnetworkforOpticalAccessNetworks(OANs)".[5]ETSIETS300736:"TransmissionandMultiplexing(TM);OperationandmaintenanceofOpticalAccessNetworks(OANs)".[6]ETSIETR080:"TransmissionandMultiplexing(TM);IntegratedServicesDigitalNetwork(ISDN)basicrateaccess;Digitaltransmissionsystemonmetalliclocallines".[7]ETSIETS300011:"IntegratedServicesDigitalNetwork(ISDN);Primaryrateuser-networkinterface;Layer1specificationandtestprinciples".SIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)7[8]ETSIETS300012:"IntegratedServicesDigitalNetwork(ISDN);Basicuser-networkinterface;Layer1specificationandtestprinciples".[9]ETSIETS300019:"EquipmentEngineering(EE);Environmentalconditionsandenvironmentaltestsfortelecommunicationsequipment".[10]ETSIETS300233:"IntegratedServicesDigitalNetwork(ISDN);AccessdigitalsectionforISDNprimaryrate".[11]ETSIETS300288:"BusinessTeleCommunications(BTC);64kbit/sdigitalunrestrictedleasedlinewithoctetintegrity(D64U);Networkinterfacepresentation".[12]ETSIETS300324:"SignallingProtocolsandSwitching(SPS);VinterfacesatthedigitalLocalExchange(LE);V5.1interfaceforthesupportofAccessNetwork(AN)".[13]ETSIETS300347:"SignallingProtocolsandSwitching(SPS);VinterfacesatthedigitalLocalExchange(LE);V5.2interfaceforthesupportofAccessNetwork(AN)".[14]ETSIEN300376-1:"TelecommunicationsManagementNetwork(TMN);Q3interfaceattheAccessNetwork(AN)forconfigurationmanagementofV5interfacesandassociateduserports;Part1:Q3interfacespecification".[15]ETSIEN300378-1:"TelecommunicationsManagementNetwork(TMN);Q3interfaceattheAccessNetwork(AN)forfaultandperformancemanagementofV5interfacesandassociateduserports;Part1:Q3interfacespecification".[16]ETSIETS300462-2:"TransmissionandMultiplexing(TM);Genericrequirementsforsynchronizationnetworks;Part2:Synchronizationnetworkarchitecture".[17]ETSIETS300462-5:"TransmissionandMultiplexing(TM);Genericrequirementsforsynchronizationnetworks;Part5:TimingcharacteristicsofslaveclockssuitableforoperationinSynchronousDigitalHierarchy(SDH)equipment".[18]ETSIETS300418:"BusinessTeleCommunications(BTC);2048kbit/sdigitalunstructuredandstructuredleasedlines(D2048UandD2048S);Networkinterfacepresentation".[19]ITU-TRecommendationG.703:"Physical/electricalcharacteristicsofhierarchicaldigitalinterfaces".[20]ITU-TRecommendationG.704:"Synchronousframestructuresusedat1544,6312,2048,8488and44736kbit/shierarchicallevels".[21]ITU-TRecommendationG.803:"Architecturesoftransportnetworksbasedonthesynchronousdigitalhierarchy(SDH)".[22]ITU-TRecommendationG.823:"Thecontrolofjitterandwanderwithindigitalnetworkswhicharebasedonthe2048kbit/shierarchy".[23]ITU-TRecommendationG.832:"TransportofSDHelementsonPDHnetworks:Frameandmultiplexingstructures".[24]ITU-TRecommendationI.430:"Basicuser-networkinterface-Layer1specification".[25]ITU-TRecommendationM.3010:"Principlesforatelecommunicationsmanagementnetwork".[26]ECITSEC:"InformationTechnologySecurityCriteria(ITSEC)".[27]ETSIEG201212:"ElectricalSafety;Classificationofinterfacesforequipmenttobeconnectedtotelecommunicationnetworks".SIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)83Definitionsandabbreviations3.1DefinitionsForthepurposesofthepresentdocument,thefollowingdefinitionsapply:accesslink:wholeoftransmissionmeansbetweenagivennetworkinterfaceandasingleuserinterface.TheconceptofaccesslinkisusedinordertoallowafunctionalandproceduraldescriptionandadefinitionofthenetworkrequirementsNOTE1:Theuser-sideandthenetwork-sideoftheaccesslinkarenotidenticalandthereforetheaccesslinkisnotsymmetrical.AdaptationUnit(AU):providesadaptationfunctionsbetweentheOpticalNetworkUnit(ONU)andtheuser-sidediplexworking:bi-directionalcommunicationusingadifferentwavelengthforeachdirectionoftransmissionoverasinglefibreduplexworking:bi-directionalcommunicationusingthesamewavelengthforbothdirectionsoftransmissionoverasinglefibreFieldReplaceableUnit(FRU):lowestlevelofmaintenancespareandwilltypicallybeaplug-incard.ThemodulesofanOpticalLineTermination(OLT)andONUshouldbeFRUsfullaccess:givennootherconnections,anyslotononesideoftheconcentratormaybeconnectedtoanyslotontheothersideoftheconcentratormultiplexingstatic:systemofmultiplexingwheretherelationshipbetweenthepositionofthetributariestothemultiplexedformat(channels)ispredeterminedandfixedmultiplexingdynamic:systemofmultiplexingwheretherelationshipbetweenthepositionofthetributariestothemultiplexedformat(channels)isflexible.Italsoallowsfortributariestobeaggregatedwheretherearemoretributariesthanavailablechannelsandthepossibilitytovarythebandwidthtontimesthecapacityofthechannelsnon-blocking:anyallowableconnectionmaybemadeatanytime,regardlessoftheorderinwhichconnectionsareestablishedorremoved(Anallowableconnectionassumesthattherespectiveslotsarefree)OpticalAccessNetwork(OAN):setofaccesslinkssharingthesamenetwork-sideinterfacesandsupportedbyopticalaccesstransmissionsystemsNOTE2:TheOANmayincludeanumberofODNsconnectedtothesameOLT.OpticalDistributionNetwork(ODN):providestheopticaltransmissionmeansfromtheOLTtowardstheusers,andviceversaOpticalLineTermination(OLT):providesthenetwork-sideinterfaceoftheOANandisconnectedtooneormoreODNsOpticalNetworkUnit(ONU):provides(directlyorremotely)theuser-sideinterfaceoftheOANandisconnectedtotheODNopticalfilter:devicefortheselectionofopticalsignalsatopticalspecificwavelengthsopticalpowersplitter:devicethathasninputswithkoutputs,wheren=1tokandk2passivecomponent:componentpartoftheODNthatdoesnotrequireexternalpower,i.e.fibre,splitter,filterpoint-to-multipoint:transmissionsystem,whichcanhaveoneinputoroutputatoneendwithmultipleinputsoroutputsattheotherendPassiveOpticalNetwork(PON):subsetofanODNandreferstoapoint-to-multipointoptionSpaceDivisionMultiplexing(SDM):bi-directionalmultiplexingusingdifferentfibresforupanddownstreamsignalsSIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)9SubCarrierMultiplexing(SCM):multiplexingmultipleelectricalfrequenciesontoasinglefibreatasinglewavelengthtoprovideanindividualfrequencytoeachmultipointtopointpathserialnumber:referencenumberassignedtoanobject,component,etc.servicechannel:eachbearerserviceisallocatedaservicechannelinthePONsystems.e.g.a64kbit/schanneltosupportthePublicSwitchedTelephoneNetwork(PSTN)ServiceUnit(SU):FRUthatsupportsserviceinterface(ServiceUnit(SU))function(s)simplexworking:communicationwhichusesadifferentfibreforeachdirectionoftransmissionTimeCompressionMultiplexing(TCM):bi-directionalmultiplexingusingdifferenttimeslotsforupanddownstreamsignalsTimeDivisionMultiplexing(TDM):multiplexinginformationontofixedtimerangesTributaryUnit(TU):FRUwithoneormoretributaryinterfacefunctionsWavelengthDivisionMultiplexing(WDM):bi-directionalmultiplexingusingdifferentopticalwavelengthforupanddownstreamsignals3.2AbbreviationsForthepurposesofthepresentdocument,thefollowingabbreviationsapply:ACAlternatingCurrentA/DAnaloguetoDigital(conversion)ANAccessNetworkATMAsynchronousTransferModeAUAdaptationUnitBABasicAccessB-ISDNBroadbandIntegratedServicesDigitalNetworkDCDirectCurrentD/ADigitaltoAnalogue(conversion)D2048S2048kbit/sdigitalstructuredONPleasedlineD2048U2048kbit/sdigitalunstructuredONPleasedlineFDMFrequencyDivisionMultiplexingFITLFibreInTheLoopFRUFieldReplaceableUnitISDNIntegratedServicesDigitalNetworkISDN-BAISDN-BasicAccessITSECInformationTechnologySecurityCriteriaMTBFMeanTimeBetweenFailuresMTTRMeanTimeToRepairNNINetworktoNetworkInterfaceNTNetworkTerminationNT1NetworkTermination1OAMOperationsAdministrationandMaintenanceOANOpticalAccessNetworkODNOpticalDistributionNetworkOLTOpticalLineTerminationONPOpenNetworkProvisionONUOpticalNetworkUnitOSOperationsSystemOSIOpenSystemsInterconnectionOTDROpticalTimeDomainReflectometerPONPassiveOpticalNetworkPOTSPlainOldTelephonyServicesppmpartspermillionPRAPrimaryRateAccessPRCPrimaryReferenceClockPSTNPublicSwitchedTelephoneNetworkSIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)10QANQinterfacefortheAccessNetworkSCMSubCarrierMultiplexingSCMASubCarrierMultipleAccessSDHSynchronousDigitalHierarchySDMSpaceDivisionMultiplexingSNIServiceNodeInterfaceSPFSignallingProcessingFunctionSSUSynchronizationSupplyUnitSUServiceUnitTCMTimeCompressionMultiplexingTDMTimeDivisionMultiplexingTDMATimeDivisionMultipleAccessTUTributaryUnitUIppUnitIntervalspeaktopeakUNIUserNetworkInterfaceVCVirtualContainerVFVoiceFrequencyWDMWavelengthDivisionMultiplexing4ConfigurationofanOANTheconfigurationofanOANisconsideredinthisclause.ItprovidesanintroductiontothedetailedrequirementsofanOAN.NOTE:ThefunctionalarchitectureissuesareunderstudyinETSISubTechnicalCommittee(STC)TM3.4.1TopologicalandfunctionalissuesAconfigurationforanOANisshowninfigure1.AnOANconsistsof:a)oneOLT;b)atleastoneODN;c)atleastoneONU;d)AUs.TheODNprovidestheopticaltransmissionmeansfromtheOLTtowardstheusersandviceversa.ONUsprovidetheuser-sideinterfaceoftheOANandareconnectedtotheODN.ThefunctionscomprisedbytheAUincludeadaptationoftheserviceinterfacingbetweenONUanduser(e.g.conversionofdatacommunicationprotocolsandrates)aswellastransportationoftheserviceoverthelastdropbetweentheONUanduserwhentheseinterfacesdonotcoincide(e.g.NetworkTermination1(NT1)forIntegratedServicesDigitalNetwork,BasicAccess(ISDN-BA)).ThereferencepointsUserNetworkInterface(UNI)andServiceNodeInterface(SNI)aswellastheQ3interfaceshowninfigure1.TheRandSreferencepointsaredescribedinETS300681[4].NOTE:StandardizationworkrelatedtosuchanAUisoutsidethescopeofthepresentdocument.SIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)11AUAccesslinkUsersideNetworksideONUS/RS/RSNIUNIONUODNOLTANSystemManagementQ3LineFigure1:ExampleconfigurationforanOANAfunctionalarchitectureoftheOANinaccordancewiththeprinciplesofITU-TRecommendationG.803[21]isshowninfigure2.ISDN-BAistheadaptedserviceshowninthisarchitecture.TheServiceNodeInterface(SNI)isaccordingtoV5.1;seeETS300324[12].ThemultiplexingoftheuserindividualD-channelsisperformedonahigherlayerandnotshowninthisstructure.ThestructureofDandD*arenotidentical.Althoughanumberofotheroptionsexist(e.g.leasedlines,V5.2,etc.)theyarenotshownonthisdiagram.SIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)12OpticalsectiontrailWavelength1WavelengthnFibreadaptationFibreterminationOpticalterminationE/OAdaptationODNtransmissionprotocolTTPODNtransmissionprotocoltrailPayload/ODNtransmissionprotocoladaptationBCodedringing,hook(+dial)DG.704connection(V5.1)AdaptationsofISDNBAandPOTSintoG.704(forV5.1)G.702terminationAdaptationintoPOTSlinePOTSlineterminationPOTSlineAdaptationintoISDNBAlineISDNBAterminationS/TbusAdaptationterminationS/TbusCopperlineAdaptationtermination(NT1)MediumlayerOpticallayerTransmissionsectionlayerTransmissionpathlayerD*Figure2:ExamplearchitectureconfigurationfortheOANSIST EN 300 463 V1.1.2:2003



ETSIETSIEN300463V1.1.2(2000-06)134.2ServicecapabilityTheOANshallbecapableofsupportingthefollowingservices:a)POTS;b)leasedlines;c)packetdata;d)ISDN-BA;e)ISDNPrimaryRateAccess(ISDN-PRA);f)nx64kbit/s;g)2Mbit/s(structuredorunstructured).5ONUTheONUprovidesanopticalinterfacetowardstheODNandimplementstheinterfacesatthecustomersideoftheOAN.ONUsshallbelocatedonthecustomer'spremises(fibretothehome,fibretotheoffice,fibretothebuilding)orinthefieldaspartoftheopticalaccesssection(fibretothekerb).TheONUprovidesthemeansnecessaryfordeliveringthedifferentservicesthataretobehandledbythesystem.5.1DescriptionoffunctionsFigure3showsafunctionaldescriptionoftheONU.ItisusefulforstandardizationpurposestoconsidertheONUintermsofthreeparts,thesearedefinedas:a)coreshell;b)serviceshell;c)commonshell.Thefunctionalityoftheseshellsisdescribedinsubclauses5.1.1to5.1.3.****CommonshellCoreshellServiceshellODNCustomerServiceinterfacefunctionServiceinterfacefunctionCustomerandservicesMultiplexfunctionTransmissionmultiplexfunctionODNinterfacefunctionOAMf
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