ETSI EN 300 419 V1.2.1 (2001-07)

Access and Terminals (AT); 2 048 kbit/s digital structured leased lines (D2048S); Connection characteristics

REN/AT-020019

Dostop in terminali (AT) – Digitalni zakupljeni vodi za prenosno hitrost 2.048 kbit/s in za strukturirane signale (D2048S) – Priključitvene značilnosti

General Information

• Status: Published
• Publication Date: 03-Jul-2001
• Technical Committee: AT Digital - AT Digital
• Current Stage: 12 - Completion
• Due Date: 06-Jul-2001
• Completion Date: 04-Jul-2001
• Ref Project: SIST EN 300 419 V1.2.1:2003 - Access and Terminals (AT); 2 048 kbit/s digital structured leased lines (D2048S); Connection characteristics

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Access and Terminals (AT); 2 048 kbit/s digital structured leased lines (D2048S); Connection characteristics33.040.50Vodi, zveze in tokokrogiLines, connections and circuitsICS:Ta slovenski standard je istoveten z:EN 300 419 Version 1.2.1SIST EN 300 419 V1.2.1:2003en01-december-2003SIST EN 300 419 V1.2.1:2003SLOVENSKI
STANDARD



SIST EN 300 419 V1.2.1:2003



ETSIEN300419V1.2.1(2001-07)EuropeanStandard(Telecommunicationsseries)AccessandTerminals(AT);2048kbit/sdigitalstructuredleasedlines(D2048S);ConnectioncharacteristicsSIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)2ReferenceREN/AT-020019Keywordsaccess,digital,leasedline,network,ONP,testing,UNIETSI650RoutedesLuciolesF-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.©EuropeanTelecommunicationsStandardsInstitute2001.Allrightsreserved.SIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)3ContentsIntellectualPropertyRights.5Foreword.5Introduction.61Scope.72References.73Definitionsandabbreviations.83.1Definitions.83.2Abbreviations.94Requirements.94.1Attributes.104.1.1Transferrate.114.1.1.1Leasedlinetiming.114.1.1.2Informationtransferrate.114.1.2Informationtransfersusceptance.114.1.3Structure.114.1.3.1CRC-4.114.1.3.2UseoftheE-bits.124.1.3.3Framesynchronizationanddatatransmissioncapability.124.1.3.3.1Multiframealignment.124.1.3.4UseoftheA-bit.124.1.3.5UseoftheSabits.134.1.4Establishmentofconnection.134.1.5Symmetry.134.1.6Connectionconfiguration.134.1.7Networkperformance.134.1.7.1Transmissiondelay.134.1.7.2Jitter.144.1.7.2.1Jittertoleranceatthenetworkinputport.144.1.7.2.2Maximumjitteratthenetworkoutputport.144.1.7.3Controlledslip.154.1.7.4Error.154.1.7.4.1BringingIntoService(BIS)limits.154.1.7.4.2Performancelevel.154.1.7.5Availability.15AnnexA(normative):Testmethods.16A.1General.16A.1.1Equipmentconnection.16A.1.2Sequenceofperformingthetests.16A.2Testmethods.16A.2.1Informationtransferrate,susceptanceandsymmetry.16A.2.2Delay.17A.2.3Jitter.18A.2.4Errorandslip.19A.2.5Structure.20A.2.5.1OutputstructureandCRC-4generation.20A.2.5.2UseoftheE-bits.21A.2.5.3Framesynchronizationanddatatransmissioncapability.21A.2.5.4Multiframealignment.23AnnexB(normative):Definitionofframestructure.24SIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)4B.1Framestructure.24B.2CRC-4.24B.2.1CRC-4generation.25B.2.2CRC-4monitoring.25AnnexC(informative):Derivationoferrorperformancelimits.26C.1Introduction.26C.2Referenceconnections.26C.2.1Terrestrialconnection.26C.2.2Satelliteconnection.27C.3Errorperformanceobjectives.27C.4Long-termerrorperformance.28AnnexD(informative):Availability.29D.1General.29D.1.1Unavailability.29D.1.2Outageintensity.29D.1.3Meantimebetweenfailures.29D.1.4Meantimetorestoreservice.29D.2Recommendations.29AnnexE(informative):Bibliography.31History.32SIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)5IntellectualPropertyRightsIPRsessentialorpotentiallyessentialtothepresentdocumentmayhavebeendeclaredtoETSI.TheinformationpertainingtotheseessentialIPRs,ifany,ispubliclyavailableforETSImembersandnon-members,andcanbefoundinETSISR000314:"IntellectualPropertyRights(IPRs);Essential,orpotentiallyEssential,IPRsnotifiedtoETSIinrespectofETSIstandards",whichisavailablefromtheETSISecretariat.LatestupdatesareavailableontheETSIWebserver(http://www.etsi.org/ipr).PursuanttotheETSIIPRPolicy,noinvestigation,includingIPRsearches,hasbeencarriedoutbyETSI.NoguaranteecanbegivenastotheexistenceofotherIPRsnotreferencedinETSISR000314(ortheupdatesontheETSIWebserver)whichare,ormaybe,ormaybecome,essentialtothepresentdocument.ForewordThisEuropeanStandard(Telecommunicationsseries)hasbeenproducedbyETSITechnicalCommitteeAccessandTerminals(AT).ThepresentdocumentresultedfromamandatefromtheCommissionoftheEuropeanCommunity(CEC)toprovidestandardsforsupportoftheDirectiveonOpenNetworkProvision(ONP)ofleasedlines(92/44/EEC).Therearetwootherstandardsdirectlyrelatedtothepresentdocument:-EN300418:"AccessandTerminals(AT);2048kbit/sdigitalunstructuredandstructuredleasedlines(D2048UandD2048S);Networkinterfacepresentation";-EN300420:"AccessandTerminals(AT);2048kbit/sdigitalstructuredleasedlines(D2048S);Terminalequipmentinterface".ThepresentdocumentisbasedoninformationfromITU-TRecommendationsandETSIpublicationsandtherelevantdocumentsarequotedwhereappropriate.NationaltranspositiondatesDateofadoptionofthisEN:29June2001DateoflatestannouncementofthisEN(doa):30September2001DateoflatestpublicationofnewNationalStandardorendorsementofthisEN(dop/e):31March2002DateofwithdrawalofanyconflictingNationalStandard(dow):31March2002SIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)6IntroductionTheCouncilDirectiveontheapplicationofONPtoleasedlines(92/44/EEC)concernstheharmonizationofconditionsforopenandefficientaccessto,anduseof,theleasedlinesprovidedoverpublictelecommunicationsnetworks,andtheavailabilitythroughouttheEuropeanUnion(EU)ofaminimumsetofleasedlineswithharmonizedtechnicalcharacteristics.TheconsequenceoftheDirectiveisthattelecommunicationsorganizationswithintheEUshallmakeavailableasetofleasedlinesbetweenpointsinthesecountrieswithspecifiedconnectioncharacteristicsandspecifiedinterfaces.UndertheDirective91/263/EEC,laterreplacedby98/13/EC,terminalequipmentforconnectiontotheseleasedlineswasrequiredtofulfilcertainessentialrequirements.Thepresentdocumenthasbeenproducedtointroducesomenecessarychanges.ITU-TRecommendationI.340forIntegratedServicesDigitalNetwork(ISDN)connectiontypeswasusedasabasisfortheconnectioncharacteristics.ETS300167andITU-TRecommendationsG.704andG.706areusedasthebasisforthestructure.SIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)71ScopeThepresentdocumentspecifiesthetechnicalrequirementsandtestprinciplesforconnectioncharacteristicsofOpenNetworkProvision(ONP)2048kbit/sdigitalstructuredleasedlines.Theleasedlineoperatesat2048kbit/sandprovidesaninformationtransmissioncapability,withoutrestrictiononbinarycontent,of1984kbit/s.Theremaining64kbit/sprovidesan8kHzframingstructureinaccordancewithETS300167andITU-TRecommendationsG.704andG.706.AconnectionispresentedviainterfacesatNetworkTerminationPoints(NTPs)andincludesanyequipmentthatmayprovidetheNTP.Signalsbetweenterminalequipmentsaresubjecttoimpairmentsduringtheirtransferovertheconnection.Thelimitstotheseimpairmentsarestatedinthepresentdocument.Togetherwiththecompanionstandard,EN300418[4]definingthenetworkinterfacepresentation,thepresentdocumentdescribesthetechnicalcharacteristicsoftheleasedlineserviceofferedtotheuser.Thetestsspecifiedinthepresentdocumentcannotbecarriedoutbytheleasedlineprovider,whiletheleasedlineisinservice,i.e.carryingusers'traffic.Thusthetestsaredesignedforbringingintoandreturningintoservice,althoughthereisnoobligationtoperformthesetestseachtimealeasedlineisbroughtintoorreturnedintoservice.However,becausetheconnectionisstructured,theerrorperformancemaybemonitoredbytheleasedlineproviderwhilethelineisinservice.Thepresentdocumentisapplicableforleasedlines,includingparttimeleasedlines,forwhichtheestablishmentorreleasedoesnotrequireanyprotocolexchangeorotherinterventionattheNTP.Thepresentdocumentspecifiesthecompliancetestsfortheconnectionrequirements.Thepresentdocumentdoesnotincludedetailsconcerningtheimplementationofthetests,nordoesitincludeinformationonanyrelevantregulations.2ReferencesThefollowingdocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthepresentdocument.• Referencesareeitherspecific(identifiedbydateofpublicationand/oreditionnumberorversionnumber)ornon-specific.• Foraspecificreference,subsequentrevisionsdonotapply.• Foranon-specificreference,thelatestversionapplies.[1]ITU-TRecommendationO.151(1992):"Errorperformancemeasuringequipmentoperatingattheprimarybitrateandabove".[2]ITU-TRecommendationO.153(1992):"Basicparametersforthemeasurementoferrorperformanceatbitratesbelowtheprimaryrate".[3]ITU-TRecommendationO.171(1997):"Timingjitterandwandermeasuringequipmentfordigitalsystemswhicharebasedontheplesiochronousdigitalhierarchy(PDH)".[4]ETSIEN300418:"AccessandTerminals(AT);2048kbit/sdigitalunstructuredandstructuredleasedlines(D2048UandD2048S);Networkinterfacepresentation".SIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)83Definitionsandabbreviations3.1DefinitionsForthepurposesofthepresentdocument,thefollowingtermsanddefinitionsapply:BackgroundBlockError(BBE):erroredblocknotoccurringaspartofaSeverelyErroredSecond(SES)BBEratio:ratiooferroredblockstototalblocksduringafixedmeasurementintervalexcludingallblocksduringseverelyerroredsecondsandwhiletheleasedlineconnectionisintheunavailablestate(seeITU-TRecommendationG.826)block:setof2048consecutivebitsequivalenttooneSub-MultiFrame(SMF).EachblockismonitoredbymeansofaCyclicRedundancyCheck-4bit(CRC-4)errorcheck.Thelengthofeachblockcorrespondstoaperiodof1msNOTE:ThisdefinitionisrelevantonlytothepresentdocumentandismorespecificthanthegenericdefinitiongiveninITU-TRecommendationG.826.controlledslip:irretrievablelossorgainofasetofconsecutivedigitpositionsinadigitalsignal,inwhichboththemagnitudeandinstantofthatlossorgainarecontrolled,toenablethesignaltoaccordwitharatedifferentfromitsownerroredblock:blockinwhichoneormorebitsareinerror(seeITU-TRecommendationG.826)ErroredSecond(ES):one-secondperiodwithoneormoreerroredblocks(seeITU-TRecommendationG.826)ESratio:ratioofEStototalsecondsduringafixedmeasurementinterval.TheESratioisnotevaluatedwhiletheleasedlineconnectionisintheunavailablestate(seeITU-TRecommendationG.826)erroredSub-MultiFrame:Sub-MultiFrame(SMF)wherethecalculatedCRC-4doesnotcorrespondwiththeCRC-4containedwithinthenextSMF(seeclauseB.2.2)frame:sequenceof256bitsofwhichthefirst8bitsdefinetheframestructure(seeannexB)frameslip:slipofonecompleteframeleasedlines:telecommunicationsfacilitiesprovidedbyapublictelecommunicationsnetworkthatprovidedefinedtransmissioncharacteristicsbetweenNTPsandthatdonotincludeswitchingfunctionsthattheusercancontrol(e.g.on-demandswitching)multiframe:sequenceoftwoSMFscontainingthemultiframealignmentword(seeannexB)NetworkTerminationPoint(NTP):allphysicalconnectionsandtheirtechnicalaccessspecificationswhichformpartofthepublictelecommunicationsnetworkandarenecessaryforaccessto,andefficientcommunicationthrough,thatpublicnetworkPRBS(29-1):PseudoRandomBitSequence(PRBS)(asdefinedinclause2.1ofITU-TRecommendationO.153[2])PRBS(215-1):PRBS(asdefinedinclause2.1ofITU-TRecommendationO.151[1])Sabits:bits4to8(bitsSa4toSa8)inframesnotcontainingtheframealignmentsignal(seeannexB)satellitetransmission:transmissionviaanearthorbitingsatelliteseverelydisturbedperiod:forout-of-servicemeasurements,aseverelydisturbedperiodoccurswhen,overaperiodoftimeequivalenttofourcontiguousblocks,eitherallthecontiguousblocksareaffectedbyahighbiterrordensityof=10-2,oralossofsignalisobserved.Forin-servicemonitoringpurposes,aseverelydisturbedperiodisestimatedbytheoccurrenceoflossofsignalorlossofframealignment(seeITU-TRecommendationG.826)SeverelyErroredSecond(SES):one-secondperiodwhichcontains=805erroredblocksoratleastoneseverelydisturbedperiod(seeITU-TRecommendationG.826)SESratio:ratioofSEStototalsecondsduringafixedmeasurementinterval.TheSESratioisnotevaluatedwhiletheleasedlineconnectionisintheunavailablestate(seeITU-TRecommendationG.826)SIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)9Sub-MultiFrame(SMF):sequenceof8frames,eachof256bits,overwhichtheCRC-4iscalculated(seeannexB)uncontrolledslip:lossorgainofadigitpositionorasetofconsecutivedigitpositionsinadigitalsignal,resultingfromanaberrationofthetimingprocessesassociatedwithtransmissionorswitchingofadigitalsignal,andinwhicheitherthemagnitudeortheinstantofthatlossorgainisnotcontrolledunavailabilityperiod:unavailabilityperiodbeginsattheonsetof10consecutiveSES.These10sareconsideredtobepartoftheunavailabilityperiod.Theunavailabilityperiodendsattheonsetof10consecutivenon-SES.These10sarenotconsideredpartoftheunavailabilityperiodunavailablestate:leasedlineconnectionisintheunavailablestateifanunavailabilityperiodisoccurringinoneorbothdirectionsoftransmission3.2AbbreviationsForthepurposesofthepresentdocument,thefollowingabbreviationsapply:BBEBackgroundBlockErrorBISBringingIntoServiceCRC-4CyclicRedundancyCheck-4bitD2048S2048kbit/sdigitalstructuredONPleasedlineD2048U2048kbit/sdigitalstructuredONPleasedlineEMCElectroMagneticCompatibilityESErroredSecondHDB3HighDensityBipolarcodeoforder3NTPNetworkTerminationPointONPOpenNetworkProvisionppmpartspermillionPRBSPseudoRandomBitSequencePRCPrimaryReferenceClockRAIRemoteAlarmIndicationRXRXisasignalinput(ateithertheleasedlineinterfaceorthetestequipment)SESSeverelyErroredSecondSMFSub-MultiFrameTXTXisasignaloutput(ateithertheleasedlineinterfaceorthetestequipment)UIUnitInterval4RequirementsTheperformanceoftheleasedlineshallcomplywiththeserequirementsonlyiftheconditionsofsupplyofthenetworkequipmentprovidingtheNTParemet(e.g.iftheequipmentisconnectedtoanappropriatepowersupplyonthecustomer'spremises).TheITU-Tattributetechniqueisusedtoexpresstheconnectionrequirements.ThefollowingattributesfromITU-TRecommendationI.140arespecifiedinthepresentdocument:-transferrate;-informationtransfersusceptance;-structure;-establishmentofconnection;-symmetry;-connectionconfiguration;-networkperformance.SIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)10Thefollowingnetworkperformancesub-attributesareconsideredrelevantforthepresentdocument:-transmissiondelay;-jitter;-slip;-error.4.1AttributesTheconnectionattributesaredisplayedintable1.Ineffect,theseattributesdefinetheservicebeingoffered.Thevaluesandtheassociatedcompliancetestscanbefoundinthesubsequentclauses.Table1:ConnectionattributesConnectiontypeattributesValueDescriptionNatureReferenceclauseTransferrateLeasedlinetimingInformationtransferrate2048kbit/s1984kbit/sSee4.1.1.1See4.1.1.2InformationtransfersusceptanceNorestrictiononbinarycontentSee4.1.2StructureFrameintegritySee4.1.3EstablishmentofconnectionWithoutuserinterventionSee4.1.4SymmetrySymmetricalinbothdirectionsSee4.1.5ConnectionconfigurationPoint-to-pointSee4.1.6Networkperformancesub-attributesConnectiontypeattributesValueDescriptionNatureReferenceclauseTransmissiondelayTerrestrialandsatelliteoptionsSee4.1.7.1JitterInputandoutputportsSee4.1.7.2Slip(controlledslip)≤5per24hourperiodSee4.1.7.3Errorparameters(see5.1.7.4)TerrestrialSatelliteEnd-to-endperformanceobjectivesErroredSeconds(ES)ratio<2,000%<3,120%SeverelyErroredSeconds(SES)ratio<0,100%<0,156%BackgroundBlockErrors(BBE)ratio<0,015%<0,023%Performancelevelover24hourperiod(24hourtestlimit)ErroredSeconds(ES)<1645<2592SeverelyErroredSeconds(SES)<68<112BackgroundBlockErrors(BBE)<12732<19933SIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)114.1.1Transferrate4.1.1.1LeasedlinetimingRequirement:Theleasedlineshalleither:a)carryusertimingwithintherange2048kbit/s±50partspermillion(ppm);orb)providetimingthatissynchronoustothenetworktiming;orc)takeusertimingwithintherange2048kbit/s±50ppmfromoneinputandprovidethistimingatbothoutputsoftheleasedline.NOTE1:Incaseb),networktimingistimingthatisderivedfromthesourceorsourcesoftimingthatareusedforthenetwork.Thusthetimingprovidedbytheleasedlinewillbesimilartothatprovidedbyotherdigitalservices.NOTE2:Whenthetiminginbothdirectionsisnotsynchronous,thenumberoftransmittedE-bitsdiffersfromthenumberofreceivedSMFs.Asaconsequence,eithersomevalidE-bitsarelostormeaninglessE-bitsareinserted.Test:Thereisnospecifictest;theleasedlineprovidershalldeclarewhichtypeoftimingtheleasedlineprovidesandthisshallbetakenintoaccountduringthesubsequenttestsdefinedinannexA.4.1.1.2InformationtransferrateRequirement:Theconnectionshallbecapableoftransferringanominalinformationrateof1984kbit/swhichiscontainedwithintheframestructuredefinedfortheleasedline(seeclause4.1.3).Test:ThetestshallbeconductedaccordingtoclauseA.2.1.4.1.2InformationtransfersusceptanceRequirement:Theconnectionshallbecapableoftransferringdigitalinformationwithbitsequenceintegrity,andwithoutrestrictiononbinarycontent,atthenominalrateof1984kbit/swithinthedefinedframestructure(seeclause4.1.3).Test:ThetestshallbeconductedaccordingtoclauseA.2.1.4.1.3StructureThepurposeofthestructureistoallowtheleasedlineprovidertomonitortheerrorperformanceoftheleasedlinesfromNTPtoNTP.TheCRC-4is,therefore,notnecessarilytransmittedtransparentlyfromNTPtoNTP;itmaybeupdatedbytheleasedlineprovidertodeterminethelocationoferrors.InordertoallowtheterminalequipmenttomonitortheintegrityofthepathbetweentheterminalequipmentandtheNTP,theNTPisrequiredtoprovideacorrectCRC-4,andtorespondcorrectlywiththeE-bitsintheeventofanincorrectlyreceivedCRC-4.Requirement:Foreachdirectionoftransmission,theleasedlineshallacceptaninputbitstreamwithaframeandmultiframestructureasdefinedinannexB.Whentheleasedlineinputhastheaboveframestructureandtheconnectionisnotintheunavailablestate,theoutputoftheleasedlineshallalsoconformtotheframeandmultiframestructuredefinedinannexB,withthestructurehavingthesamerelationshiptotheinformationtransferredasattheinput,maintainingtheframestructureintegrity.Test:ThetestshallbeconductedaccordingtoclausesA.2.1andA.2.5.1.4.1.3.1CRC-4Requirement:AteachNTP,theCRC-4bitstransmittedintheoutputbitstreamshallbeasdefinedintablesB.1andB.2foracompleteCRC-4multiframeandshallcorrespondtothedatatransmittedattheoutputoftheleasedlineinterface,(i.e.theCRC-4shallberecalculatedintheequipmentprovidingtheNTP).Test:ThetestshallbeconductedaccordingtoclauseA.2.5.1.SIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)124.1.3.2UseoftheE-bitsRequirement:AteachNTP,theE-bitstransmittedintheoutputbitstreamshallindicateerroredSMFsintheinputbitstreamatthatNTP.OneE-bitineachmultiframeshallbesettobinaryZEROforeacherroredSMFreceivedintheinputbitstream.TheE-bitscorrespondingtonon-erroredSMFsshallbesettobinaryONE.AnydelaybetweenthedetectionofanerroredSMFandthesettingoftheE-bitthatindicatestheerroredSMFshallbelessthan1s.NOTE:TheintentionisthattheCRC-4verification,andtheassociatedgenerationoftheE-bits,willbeperformedintheequipmentthatprovidestheNTPinordertoindicateonlythoseerrorsthathaveoccurredbetweentheterminalequipmentandtheNTPandnotthoseerrorsthathaveoccurredwithinthenetwork.Test:ThetestshallbeconductedaccordingtoclauseA.2.5.2.4.1.3.3FramesynchronizationanddatatransmissioncapabilityRequirement:Theleasedlineshallcontinuetotransparentlytransmitdataintheeventofreceivingoneortwoconsecutiveincorrectframealignmentsignals.Onreceiptof:-threeconsecutiveincorrectframealignmentsignals;or-therebeing=915erroredSMFsoutof1000SMFs,theleasedlineshallconsiderframealignmenttohavebeenlostandinitiateasearchforframealignmentduringwhichtimetheleasedlinemayceasetransparenttransmissionofdata.NOTE:Someimplementationsmayalsoconsiderframealignmenttohavebeenlostintheeventthatbit2inframesnotcontainingtheframealignmentsignalisinerroronthreeconsecutiveoccasions.ThissituationisunlikelytooccurexceptintheeventofhigherrorratesbetweentheterminalequipmentandtheNTP.Framealignmentshallnotbeconsideredashavingbeenregaineduntil:a)forthefirsttime,thepresenceofthecorrectframealignmentsignal;andb)theabsenceoftheframealignmentsignalinthefollowingframedetectedbyverifyingthatbit2ofthebasicframeisabinaryONE;andc)forthesecondtime,thepresenceofthecorrectframealignmentsignalinthenextframe,inwhichcasetransparenttransmissionofthedatashallcommencewithin20msprovidedthatthedatadoesnotcontainanysimulatedframealignmentwords.Test:ThetestshallbeconductedaccordingtoclauseA.2.5.3.4.1.3.3.1MultiframealignmentRequirement:CRC-4multiframealignmentshallbeachievedifatleasttwovalidCRC-4multiframealignmentsignalscanbelocatedwithin8ms(thetimeseparatingtwoCRC-4multiframealignmentsignalsbeing2msoramultipleof2ms).Ifmultiframealignmentcannotbeachievedwithin8msitshallbeassumedthatframealignmentisduetoaspuriousframealignmentsignalandaresearchforframealignmentshallbeinitiated.NOTE:Theresearchforframealignmentshouldbestartedatapointjustafterthelocationoftheassumedspuriousframealignmentsignal.Thiswillusuallyavoidrealignmentontothespuriousframealignmentsignal.Test:ThetestshallbeconductedaccordingtoclauseA.2.5.4.4.1.3.4UseoftheA-bitThereisnorequirementoftheuseoftheA-bitwithinthepresentdocument.ThevalueoftheA-bitisundefinedattheoutputoftheleasedline.SIST EN 300 419 V1.2.1:2003



ETSIETSIEN300419V1.2.1(2001-07)134.1.3.5UseoftheSabitsThereisnorequirementoftheuseoftheSabitswithinthepresentdocument.ThevaluesoftheSabitsareundefinedattheoutputoftheleasedline.4.1.4EstablishmentofconnectionRequirement:EstablishmentorreleaseoftheconnectionshallnotrequireanyprotocolexchangeorotherinterventionattheNTPbytheuser.Test:Bydeclaration.4.1.5SymmetryRequirement:Theconnectionshallbesymmetrical,i.e.eachdirectionoftransmissionshallhavethesameframestructureandinformationtransfercapability.Test:ThetestshallbeconductedaccordingtoclauseA.2.1.4.1.6Connectionconfiguration
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