SIST EN 301 141-1 V2.1.1:2005

• Abstract:

  To clearify following items: 1) B-channel selection, 2) usage of STATUS/ENQUIRY message, 3) call collision.

• Status: Published
• Publication Date: 31-Dec-2004
• ICS: 33.080 - Integrated Services Digital Network (ISDN)
• Technical Committee: SPN - Services and Protocols for Networks
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Jan-2005
• Due Date: 01-Jan-2005
• Completion Date: 01-Jan-2005
• Ref Project: ETSI EN 301 141-1 V2.1.1 (2000-11) - Integrated Services Digital Network (ISDN); Narrowband Multi-service Delivery System (NMDS); Part 1: NMDS interface specification

SIST EN 301 141-1 V2.1.1:2005 is the Slovenian adoption of ETSI EN 301 141-1 Version 2.1.1, published by SIST. It specifies the NMDS interface for carrying existing Public Switched Telephone Network (PSTN) and Integrated Services Digital Network-Basic Access (ISDN-BA) services over an ISDN-BA digital subscriber line, for implementers, operators, and test teams working on the network termination side and the local exchange side.

What does SIST EN 301 141-1 V2.1.1:2005 specify?

SIST EN 301 141-1 V2.1.1:2005 defines the requirements for the Narrowband Multi-service Delivery System (NMDS). The standard covers direct connection to a Local Exchange (LE) through a Network Termination Node (NTN), and it also notes an optional access-network arrangement in Annex D.

The document is organized around the NMDS description, layer 1, layer 2, layer 3, maintenance functions, and B-channel selection. Its annexes give examples, background, protocol context, and functional impacts.

Annex	What it covers
Annex A	Examples of B-channel selection
Annex B	Background and motivation for NMDS
Annex C	The PSTN protocol adopted for NMDS
Annex D	Relationship between direct NMDS access and access-network support
Annex E	Reasons for the new information element values
Annex F	Permanent activation of the basic access digital section
Annex G	Remote equipment functional requirements
Annex H	Supplementary services usable at the NMDS

What are the key requirements of SIST EN 301 141-1 V2.1.1:2005?

SIST EN 301 141-1 V2.1.1:2005 focuses on how NMDS must behave so that PSTN and ISDN-BA ports appear to the user as if they were directly connected to the LE. In practice, this means the NTN, the PSTN-Gateway, and the LE have to coordinate signalling, channel choice, and maintenance status in a controlled way.

Layer 1 and powering

The NMDS layer 1 uses ISDN-BA layer 1. The digital section protocol is kept unchanged, and the NTN must allow activation from the ISDN UNI and from the network side.

The NTN always sends the ACT bit set toward the network once layer 1 is active. This matters because it keeps the digital section available for the PSTN and avoids unwanted deactivation during recovery actions.

Layer 2 and TEI handling

The PSTN-Gateway uses a single permanently activated data link with a fixed Data Link Connection Identifier (DLCI) arrangement. The LE keeps its normal layer 2 behaviour, but the PSTN-Gateway uses a restricted state machine and does not support broadcast data link or TEI management procedures.

This design makes the PSTN side predictable and keeps the gateway simple. It also means implementers must provision the TEI for each gateway line consistently.

Layer 3, maintenance, and call handling

The PSTN network layer follows ETS 300 324-1 clause 13, but the PSTN port blocking and restart procedures do not apply to NMDS. The standard also adds MAINTENANCESTATUS and MAINTENANCESTATUSENQUIRY messages for checking whether a PSTN-Gateway or the ISDN UNI is in the expected state.

The LE initiates the maintenance-status procedure, waits for the reply, and uses timer Tm for retry and error handling. That gives operators a defined way to check port presence and synchronisation without changing call state.

B-channel selection

The B-channel is selected through the Layer 3 address (L3addr) field. The LE is responsible for selecting the B-channel for PSTN calls, and the NTN changes its connection to match the valid L3addr it receives.

This is the core mechanism that resolves call collision and channel choice. For call-related messages, the selected B-channel stays indicated in L3addr until the call is cleared.

What terms does SIST EN 301 141-1 V2.1.1:2005 define?

• Narrowband Multi-service Delivery System (NMDS) - A system that provides network access directly to the LE or via an Access Network to support existing PSTN and ISDN services over an ISDN-BA digital subscriber line.
• Network Termination Node (NTN) - The functional group on the user side of the digital section that supports an ISDN-BA port and/or one or more PSTN ports.
• Network Termination Type 2 (NT2)** - The NTN function that multiplexes and demultiplexes PSTN and ISDN layer 2 traffic over the D-channel and relays layer 3 messages for B-channel switching.
• PSTN-Gateway - The NTN functional group that terminates the PSTN interface.
• T reference point* - The access point between the network termination of the digital section and the NTN functional group.
• L3addr - The Layer 3 address field used to indicate the selected B-channel or, in maintenance procedures, that the address is not relevant.
• DLCI - Data Link Connection Identifier, used here for the permanent PSTN-Gateway data link.

Who uses SIST EN 301 141-1 V2.1.1:2005?

SIST EN 301 141-1 V2.1.1:2005 is used by telecommunications equipment manufacturers, network operators, and service providers who implement NMDS equipment. It is also used by conformance test teams and specification writers who need to verify layer 1, layer 2, layer 3, maintenance, and B-channel selection behaviour.

In practice, it helps with designing NTNs, PSTN-Gateways, LE-side support, and test cases for call establishment, clearing, and maintenance status.

What changed in SIST EN 301 141-1 V2.1.1:2005 from the previous edition?

The document history lists version 1.2.2 and version 2.1.1. The scope of this version says it clarifies B-channel selection, the use of STATUS/ENQUIRY messages, and call collision.

Which standards are used with SIST EN 301 141-1 V2.1.1:2005?

The standard relies on these named references and companion parts:

• ETR 080 - Provides the ISDN basic rate access digital transmission system context.
• ETS 300 012-1 - Gives the ISDN basic user-network interface layer 1 specification.
• ETS 300 324-1 - Supplies the V5.1 PSTN protocol, including the layer 3 call-control basis that NMDS modifies.
• ETS 300 347-1 - Provides the coding background for the information elements used in V5 specifications.
• ETS 300 402-2 - Gives the DSS1 layer 2 protocol basis used by NMDS with restrictions.
• ITU-T I.412 - Defines ISDN user-network interface structures and access capabilities.
• ITU-T M.3603 and ITU-T M.3602 - Provide maintenance-principle context for ISDN basic rate access and subscriber installations.
• ETS 300 297 - Gives the access digital section for ISDN basic access.
• EN 301 141-2 - Provides the PICS proformas for this NMDS series.

What does the SIST EN 301 141-1 V2.1.1:2005 document contain?

The standard contains the NMDS functional description, layer 1, layer 2, layer 3, maintenance, and B-channel selection procedures. It includes message definitions and state-machine changes, plus example figures and tables for TEI allocation, maintenance coding, and B-channel switching.

The annexes add worked examples for call setup and clearing, explain why the new information element values were chosen, and show how supplementary services and remote-equipment architectures relate to NMDS use. That makes the document useful both for implementation and for conformance testing.

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Integrated Services Digital Network (ISDN); Narrowband Multi-service Delivery System (NMDS); Part 1: NMDS interface specification33.080Digitalno omrežje z integriranimi storitvami (ISDN)Integrated Services Digital Network (ISDN)ICS:Ta slovenski standard je istoveten z:EN 301 141-1 Version 2.1.1SIST EN 301 141-1 V2.1.1:2005en01-januar-2005SIST EN 301 141-1 V2.1.1:2005SLOVENSKI
STANDARD
ETSIEN301141-1V2.1.1(2000-11)EuropeanStandard(Telecommunicationsseries)IntegratedServicesDigitalNetwork(ISDN);NarrowbandMulti-serviceDeliverySystem(NMDS);Part1:NMDSinterfacespecificationSIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)2ReferenceREN/SPAN-09103-1Keywordsaccess,basic,ISDN,NMDS,PSTNETSI650RoutedesLuciolesF-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 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)3ContentsIntellectualPropertyRights.5Foreword.5Introduction.51Scope.62References.63Definitionsandabbreviations.73.1Definitions.73.2Abbreviations.74Generaldescription.85Layer1functions.85.1PoweringAspects.95.1.1Poweravailablefromthetransmissionsystem.95.1.2NMDSbehaviourunderpowerfailconditions.96Layer2functions.106.1Overview.106.2PSTN-GWlayer2statemachinemodifications.116.3PSTNlayer2activation.117Layer3functionsandmessagedefinitions.127.1General.127.2Errorhandling.127.3Maintenancefunctions.127.3.1ThenewSTATUSENQUIRYandSTATUSmessages.137.3.1.1PSTNmaintenancemessages.137.3.1.1.1TheMAINTENANCESTATUSENQUIRYmessageforPSTNmaintenance.137.3.1.1.2TheMAINTENANCESTATUSmessageforPSTNmaintenance.137.3.1.2ISDNmaintenancemessages.147.3.1.2.1TheMAINTENANCESTATUSENQUIRYmessageforISDNmaintenance.157.3.1.2.2TheMAINTENANCESTATUSmessageforISDNmaintenance.157.3.2Maintenancestatusprocedure.167.3.2.1Normaloperation.167.3.2.2Exceptionalprocedures.167.3.2.2.1NTN.177.3.2.2.2LE.177.3.2.3TimerTmdefinition.178B-channelselectionprocedure.188.1Introduction.188.2B-channelselection.188.2.1LEFunctionality.188.2.1.1GeneralRequirements.188.2.1.1.1HandlingofvalidL3addrvalues.188.2.1.1.2HandlingofinvalidL3addrvalues.198.2.1.2SpecificRequirementsforPSTNCalls.198.2.2NTNFunctionality.198.2.2.1Generalrequirements.198.2.2.2SpecificRequirementsforPSTNCalls.20SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)4AnnexA(informative):B-channelselection.21A.1General.21A.2Outgoingcalls(NTNtoLE).21A.3Callclearing.22A.4Incomingcalls(LEtoNTN).22A.5PSTN-GWparkedstate.23A.6Clearingfromparkedstate.24A.7Outgoingcalls(NTNtoLE)withdelayedB-channelselection.25AnnexB(informative):BackgroundandmotivationforNMDS.26B.1Transparentsupplementaryserviceoperation.26B.2Operationalbenefits.26AnnexC(informative):ThePSTNprotocoladoptedfortheNMDS.27C.1TheV5PSTNprotocol.27AnnexD(informative):TherelationshipbetweenadirectlyconnectedNMDSandonesupportedviaanaccessnetwork.28D.1Introduction.28AnnexE(informative):Thereasonsforthenewinformationelementvalueschosen.32E.1General.32E.2SpecificcodingrulesforinformationelementsintheV5specifications.32E.3SpecificcodesusedfortheSTATUSENQUIRYinformationelementsforNMDS.32E.4SpecificcodesusedfortheSTATUSinformationelementsforNMDS.32AnnexF(informative):Permanentactivationofbasicaccessdigitalsection.33AnnexG(informative):Remoteequipment-functionalrequirements.34AnnexH(informative):SupplementaryservicesuseableattheNMDS.37H.1ApplicabilityofPSTNsupplementaryservices.37H.2ApplicabilityofISDNsupplementaryservices.37Bibliography.38History.39SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)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)hasbeenproducedbyETSITechnicalCommitteeServicesandProtocolsforAdvancedNetworks(SPAN).Thepresentdocumentispart1ofamulti-partdeliverablecoveringtheIntegratedServicesDigitalNetwork(ISDN);NarrowbandMulti-serviceDeliverySystem(NMDS),asidentifiedbelow:Part1:"NMDSinterfacespecification";Part2:"ProtocolImplementationConformanceStatement(PICS)proformaspecification";Part3:"TestSuiteStructureandTestPurposes(TSS&TP)specificationfortheuser";Part4:"AbstractTestSuite(ATS)andpartialProtocolImplementationeXtraInformationforTesting(PIXIT)proformaspecificationfortheuser".NationaltranspositiondatesDateofadoptionofthisEN:27October2000DateoflatestannouncementofthisEN(doa):31January2001DateoflatestpublicationofnewNationalStandardorendorsementofthisEN(dop/e):31July2001DateofwithdrawalofanyconflictingNationalStandard(dow):31July2001IntroductionThepresentdocumentspecifiestheprovisionofPublicSwitchedTelephoneNetwork(PSTN)servicesoveranexistingIntegratedServicesDigitalNetwork-BasicAccess(ISDN-BA)digitalsubscriberline(DSL).TodayPSTNterminals-normaltelephones-canbeconnectedtotheS/T-interfaceviaaTerminalAdapter(TA)withthesupportofservicesthatcanbemappedatafeasiblecostfromISDN(principallythebasiccallservices).SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)61ScopeThepresentstandarddefinesrequirementstosupporttheNarrowbandMulti-serviceDeliverySystem(NMDS)whichprovidesinterfacesconnectedviaaNetworkTerminationNode(NTN)toaLocalExchange(LE),inordertosupportexistingPSTNandISDNservicesoveranexistingISDN-BasicAccessdigitalsubscriberline(DSL).TheNarrowbandMulti-ServiceDeliverySystem(NMDS)mayalsobeconnectedviaaV5interfaceAccessNetwork(AN)toaLocalExchange(LE)inordertoprovideexistingPSTNandISDNservices.ThisoptionalarrangementisdescribedinannexDwhichidentifiestwoalternativemethodstoprovidethesameoverallfunctionality.Thepresentdocumentalsocontainsrequirementswhichrelatetothefunctionalityofa(new)NetworkTerminationNode(NTN)forsupportingbothPublicSwitchedTelephoneNetwork(PSTN)accessandIntegratedServicesDigitalNetwork-BasicAccess(ISDN-BA)S/Treferencepointinterfacesoverasingle(digitalsection)transmissionsystemasusedforexistingISDN-BA.TheNTNencompassesNT2-like(notedNT2*)functionality,physicalPSTNuserport(s)andPSTNprotocolfunctionality.AnNMDSimplementationmaycontainoneISDN-BAportand/oralimitednumberofPSTNports.TypicallyoneortwoPSTNportswouldbesupported.InordertomaintainanevolutionarypathforPSTNservices,thenationalV5PSTNprotocolmappingisassumedtoexistandformsanintegralpartofthisspecification.NOTE:Itisanunderlyingprincipleofthepresentdocumentthat,whereverpracticable,stepsmaybetakentominimizethecostoftheNTN,subjecttomaintainingtherequiredfunctionality.2ReferencesThefollowingdocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthepresentdocument.• Referencesareeitherspecific(identifiedbydateofpublication,editionnumber,versionnumber,etc.)ornon-specific.• Foraspecificreference,subsequentrevisionsdonotapply.• Foranon-specificreference,thelatestversionapplies.• Anon-specificreferencetoanETSshallalsobetakentorefertolaterversionspublishedasanENwiththesamenumber.[1]ETSIETR080(1996):"TransmissionandMultiplexing(TM);IntegratedServicesDigitalNetwork(ISDN)basicrateaccess;Digitaltransmissionsystemonmetalliclocallines".[2]ETSIETS300012-1(1996):"IntegratedServicesDigitalNetwork(ISDN);BasicUser-NetworkInterface(UNI);Part1:Layer1specification".[3]ETSIETS300324-1(1994):"VinterfacesatthedigitalLocalExchange(LE);V5.1interfaceforthesupportofAccessNetwork(AN);Part1:V5.1interfacespecification".[4]ETSIETS300347-1(1994):"VinterfacesatthedigitalLocalExchange(LE);V5.2interfaceforthesupportofAccessNetwork(AN);Part1:V5.2interfacespecification".[5]ETSIETS300402-2:"IntegratedServicesDigitalNetwork(ISDN);DigitalSubscriberSignallingSystemNo.one(DSS1)protocol;Datalinklayer;Part2:Generalprotocolspecification[ITU-TRecommendationQ.921(1993),modified]".[6]ITU-TRecommendationI.412(1988):"ISDNuser-networkinterfaces-Interfacestructuresandaccesscapabilities".SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)7[7]ETSIEN301141-2(V1.2):"IntegratedServicesDigitalNetwork(ISDN);NarrowbandMulti-serviceDeliverySystem(NMDS);Part2:ProtocolImplementationConformanceStatement(PICS)proformaspecification".[8]ITU-TRecommendationM.3603(1992):"ApplicationofmaintenanceprinciplestoISDNbasicrateaccess".[9]ITU-TRecommendationM.3602(1992):"ApplicationofmaintenanceprinciplestoISDNsubscriberinstallations".[10]ETSIETS300297(1995):"IntegratedServicesDigitalNetwork(ISDN);AccessdigitalsectionforISDNbasicaccess".3Definitionsandabbreviations3.1DefinitionsForthepurposesofthepresentdocument,thefollowingtermsanddefinitionsapply:NarrowbandMulti-serviceDeliverySystem:systemthatprovidesaninterfacetothenetworkdirectlytotheLEorviaanANtosupportexistingPSTNandISDNservicesoveranISDN-BADSL.NetworkTerminationNode:functionalgroupontheusersideofthedigitalsection(NMDSinterfacenotedT*referencepoint)thatincludesfunctionalitytosupportanISDN-BAportand/oroneormorePSTNports.NetworkTerminationType2*:functionalgroupwithintheNTNwhich,attheusersideoftheT*referencepoint,performsthePSTNlayer2andtheISDNlayer2multiplexinganddemultiplexingovertheDchannel,andonlyinterprets(andthenrelays)thelayer3messagestoswitchtheBchannelstotheISDNaccessandthePSTNGatewaysasinstructedbythesignallingmessages.PSTN-Gateway:functionalgroupwithintheNTNwhichterminatesthePSTNinterfaceattheNTN.T*referencepoint:referencepointwhichprovidesaccesstotheNMDS,betweenthenetworkterminationofthedigitalsection(NT1)andtheNetworkTerminationNodefunctionalgroup.V1*referencepoint:V1referencepointwiththeadditionofPSTNfunctionalityrequiredtosupporttheNMDS.3.2AbbreviationsForthepurposesofthepresentdocument,thefollowingabbreviationsapply:ANAccessNetworkBCCBearerChannelControlCPECustomerPremisesEquipmentDLCIDataLinkConnectionIdentifierDSLDigitalSubscriberLineDTMFDualToneMulti-FrequencyISDNIntegratedServicesDigitalNetworkISDN-BAIntegratedServicesDigitalNetwork-BasicAccessLELocalExchangeNMDSNarrowbandMulti-serviceDeliverySystemNTNetworkTerminationNT1NTtype1(seeETR080[1])NT2*NetworkTerminationType2*(seethedefinitioninsubclause3.1above)NTNNetworkTerminationNodeNWKNetworkLayerPSTNPublicSwitchedTelephoneNetworkPSTN-GWPSTNGatewaySAPIServiceAccessPointIdentifierTATerminalAdapterSIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)8TETerminalEquipmentTEITerminalEndpointIdentifierUNIUserNetworkInterface4GeneraldescriptionThepurposeoftheNMDSistosupportbothISDN-BAandoneormorePSTNuserportsinthesamemannersuchthattheyappeartotheuserasiftheyweredirectlyconnectedtotheLE.ThesupportofISDN-BAuserportsutilizesthesametypeoffunctionsasusedbyanNT1definedinETR080[1],whilstPSTNuserportsaresupportedusingthesamePSTNprotocolasdefinedintheV5.1interfacestandardETS300324-1[3]withsomemodifications.TheLEisserviceresponsibleforandcontrolsthetones(voicemessagesetc.)sentandreceivedovertheNMDS.Seefigure1forthefunctionalarchitectureofNMDS.PSTNUserPortUNIISDN-BADSLNTNCallControlLEISDNUserPortnationalPSTNprotocolISDNlayer2mngmntFigure1:GeneralNMDSfunctionaldiagramTheNarrowbandMulti-serviceDeliverySystem(NMDS)isdefinedattheT*referencepointandthecomplementaryV1*referencepointasshowninfigure2.OnanyNMDS,theLEmaysupportupto10PSTN(analogue)linesandtheNTNmayprovideupto10PSTN(analogue)accessports.TheprovisionofPSTNandISDNaccessportsintheLErequiresabilateralagreementbetweentheuserandtheserviceprovideratsubscriptiontime.5Layer1functions• StructureThegeneralaccessstructureisdescribedinITU-TRecommendationI.412[6].TheaccessstructureforISDN-BAinITU-TRecommendationI.412[6]isvalidalsoforthePSTNapplication.Thelayer1transportingthefullNMDSfunctionalityfromtheNTNtotheLEshallbeanISDN-BAlayer1.• ISDN-BADigitalSectionInordertopermittransparentoperationviaanAN,thereshallbenochangestotheISDN-BAdigitalsectionlayer1protocols.• ISDN-BAUNILayer1attheISDN-BAUNIshallbeinaccordancewithETS300012-1[2].• ActivationProcedures-NTNTheNTNshallpermitlayer1activationfromtheISDNUNIandlayer1activation/deactivationfromthenetwork.InordertokeeptheNTNsimple,thePSTNgatewayshallnotrequire"userside"activationprocedures.SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)9TheNTNshallalsoallowthedigitalsectiontobeactivatedregardlessoftheelectricalconditionsprevailingattheISDNUNIandPSTNport.Oncethelayer1isactivatedtheNTNshallalwaystransmittheACTbitsetto1towardsthenetwork.ThisistopreventthepossibilityoftheLE/ANdeactivatingthedigitalsectionaspartoftherecoveryactionsresultingfromanISDNUNIerror.(DetailsoftheACTbitcanbefoundinETR080[1]annexAfigureA.3andsubclauseA.8.3.2.2.Itspurposeistoindicatereadinessforlayer2.)• LE/ANThenetworkshallmaintainthedigitalsectioninapermanentlyactivatedstatewheneverthePSTNprotocolsaretobesupported.Thepermanentactivationofthedigitalsectionmayinterferewithcertainmaintenanceoperationsnormallyprovidedovertheembeddedoperationschannel.TheLEshallbeabletodetecttheactivationstateoftheISDNUNIwhichwouldhaveprevailedifthePSTNportshadnotbeenpresent,usingamessage-basedmaintenancemechanismatlayer3(seesubclause7.3.1.2).• DiagnosticsTheNTNshallsupportfullISDNlayer1diagnosticloopcapability.NT2*LTPSTN-GWZNTNETV*ISDNbasicaccessdigitalsection1LEorANETS300297[10]Rec.M.3603[8]S/TAccessconnectionelementRec.M.3602[9]Customerequipment2B+D(2B1Q/4B3T)ISDNbasicaccesstransmissionsystemNT1T*ETS300012-1[2]NOTE:Thefunctionalityandlayoutshowninfigure2canonlybeoneparticularexampleandisnotrepresentativeofallarchitectureswhereNMDScanbeapplied.InactualimplementationstheNT1functionalgroupislikelytobephysicallyintegratedinanequipmentrealizingtheNTNfunctionality.Figure2:AnexampleofanNMDSscenarioforNMDS5.1PoweringAspects5.1.1PoweravailablefromthetransmissionsystemThepoweravailableforNMDSsupportistheactualpowerbudgetprovidedbytheexistingISDN-BAdigitalsection.AdditionalpowerisexpectedtobeprovidedlocallytotheNTN.WhatmayhappenunderlocalpowerfailconditionswithrespecttoNTNuserportsisdescribedbelow.HencetherearenodeviationsfromtherequirementsspecifiedintheISDN-BAstandardsinordertosupportNMDS.5.1.2NMDSbehaviourunderpowerfailconditionsTheISDN-BAUNIstandard(ETS300012-1[2])describesapotentialrequirementthatadesignatedinstrumentmaybemadeavailableonanS/TInterface.Ifthisdesignatedinstrumentisavailable,thenitshallbecapableof(atleast)makingemergencytelephonecalls.SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)10ForthePSTN,thesituationisnotmandatedonaEuropeanwidebasisanddependsuponnationallyagreedregulationswhichareoutsidethescopeofthepresentdocument.TheNMDSmaybecomprisedofoneormorePSTNports,potentiallyaswellasanISDN-BAport.Henceitisnotpossibletodefineinastandardmandatorybehaviourunderpower-failconditions.Whatismorerelevantisthatmanufacturersareabletoadequatelydefinetheirsystem'sbehaviourunderpowerfailureconditions.Forthisreason,aclausehasbeeninsertedintotheProtocolImplementationConformanceStatement(PICS)document,EN301141-2[7],wheresuchbehaviourmaybeexplained.6Layer2functions6.1OverviewThelayer2usedwithintheNMDSsystem,usedforbothPSTNandISDN-BAservices,shallbeinaccordancewithETS300402-2[5]butwiththefollowingrestrictions.TheLElayer2statemachineshallbeasperETS300402-2[5].ThePSTNgatewaylayer2statemachineshallbeasdefinedinsubclause6.2ofthepresentdocument,providingarestrictedfunctionalityversionofthestatemachineinETS300402-2[5].ThePSTNgatewayshalluseasinglepermanentlyactivateddatalinkwithafixedDataLinkConnectionIdentifier(DLCI)forallcommunicationwiththenetwork.TheDLCIshallconsistofaPSTNTerminalEndpointIdentifier(TEI)allocatedfromtheautomaticTEIvalues(i.e.64-126)andServiceAccessPointIdentifier(SAPI)setequalto0.TEIvalues117to126shallbereservedforPSTNusewhenNMDSisimplementedonanaccess.ThefirstPSTNgatewaytobefittedshalluseTEI126andbeidentifiedasLine1.TEIvalues117to125arereservedforfurtherPSTNgateways,lines2to10,asshowninthetable1.Table1:AllocationofTEItoPSTNportsTEIvalueLinenumber12611252124312341225121612071198118911710ThePSTNgatewayshallnotsupportthebroadcastdatalink,orTEImanagementprocedures,andshallnotinitiatelayer2establishment,i.e.theDL_ESTABLISH_REQUESTprimitiveintheTEIassignedstateshallnotbesupported.OntheISDNport,point-to-point(i.e.TEI0)orpoint-to-multipointproceduresmaybesupportedusingthefullISDNTEIassignmentproceduresascurrentlydefined.TheseincludeTEIassignmentandremovalprocedures.However,somepreviouslyavailablevaluesarenowreserved(seetable1).ItisexpectedthatsomeimplementationsmayprovideadditionalPSTN-GWseitherasseparateequipmentconnectedtotheS/TInterfaceorasfurtherintegratedentities.IneachcasetheTEIallocationsshallcomplywiththoseshownintable1.TheTEIassociatedwitheachexternalPSTN-GWshallbepreprovisioned.SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)116.2PSTN-GWlayer2statemachinemodificationsThemodificationsrequiredtotheBAlayer2statemachineforthePSTN-GWarespecifiedbelowasalistofdifferencestothestatemachinecontainedinannexDofETS300402-2[5].Deletestates1,2,3,5.0,5.2and6.Deletethefollowinginputevents:-DL-ESTABLISH-REQUEST;-DL-RELEASE-REQUEST;-DL-UNITDATA-REQUEST;-UIFRAMEINQUEUE;-MDL-ASSIGN-REQUEST;-MDL-REMOVE-REQUEST;-MDL-ERROR-RESPONSE;-T203TIME-OUT.Renumberstate4,andallreferencestoit,tostate9;renamethestateto"LINKNOTESTABLISHED".Deleteallinstancesofthefollowingoutputeventsreplacingtheeventwith"-"ifitwastheonlyactionassociatedwiththeinputevent/statecombinationunderconsideration:-DISCUIQUEUE;-STARTT203;-STOPT203;-RESTARTT203;-MDL-ERR-IND(allvariants);-DL-UNIT-DATA-IND.Replaceallinstancesof"DISCIandUIQUEUES"with"DISCIQUEUE".Forinputevent"T200TIME-OUT"instates7.0throughtostate7.3deletethe"either"option.Forinputevent"T200TIME-OUT;RC
ETSIETSIEN301141-1V2.1.1(2000-11)127Layer3functionsandmessagedefinitions7.1GeneralThePSTNnetworklayer(NWK)protocolshallbeinaccordancewithETS300324-1[3]clause13subjecttothefollowingmodificationsandrestrictions.• TheNTNshallbeconsideredasimplementingtheANpartsthroughoutETS300324-1[3]clause13.• ThePSTNcallcontrolproceduresofETS300324-1[3]shallbeused.However,thePSTNPortblockingandthePSTNRestartproceduresdefinedinETS300324-1[3]donotapplytotheNMDS.HencethefollowingeventsdescribedinETS300324-1[3]PSTNfunctionalstatemachines(clause13)arenotapplicable:MDU-CRTL(portblocked),MDU-CTRL(portunblocked),MDU-CTL(restartrequest)MDU-CTRL(restartcomplete).ItresultsthatthestatesAN0,AN6,LE0andLE6definedinETS300324-1[3](subclauses13.2.1.1and13.2.1.2)fortheV5.1interfacearenotusedbytheNMDSstatemachine.• ThemeaninganddefinitionoftheL3addrfield(ETS300324-1[3]subclause13.4.3)ismodifiedtosupporttheB-channelselectionfunctionasdescribedinclause8ofthepresentdocument.• ThepresentdocumentprovidesadditionstothemessageformatsandprocedurestothosefoundinETS300324-1[3].Thesearedocumentedinsubclause7.3.Theydefineanddescribenewmaintenancestatusenquiryprocedures.• Theprotocoldiscriminatorvaluefortheadditionalmessagesdefinedinthepresentdocument(i.e.MAINTENANCESTATUSandMAINTENANCESTATUSENQUIRY)shallbethesameasforETS300324-1[3],i.e.48H.TheNTNshallsupportthenationalPSTNrequirementsforallapplicablesignals(includingcollisions).AlltonesandannouncementsgeneratedbythenetworkshallbepassedasinbandsignallingtransparentlyovertheB-channeltothecustomer.IntheeventofnoB-channelbeingavailablethentheproceedindicationshallnotbegiventothecustomeruntilachannelbecomesavailablei.e.theproceedindicationshallnotbegeneratedbythePSTN-GW.DTMFdialleddigitsshallbepassedtransparentlyovertheB-channeltothenetwork.ThenationalPSTNmappingsarebeyondthescopeofthepresentdocument.7.2ErrorhandlingTheLEshallsupportthefullerrorhandlingproceduresdefinedinETS300324-1[3]clause13,relatingtotheV5.1PSTNprotocolwithadditionalrequirementsasindicatedinthepresentdocument.TheNTNshallsupportthefullerrorhandlingproceduresasdefinedinETS300324-1[3]clause13fortheAN,relatingtotheV5.1PSTNprotocolwithadditionalrequirementsasindicatedinthepresentdocument.Inaddition,incaseofaPSTNlayer2failure,ifaPSTNcallisestablished,thiscallisreleasedbytheLE.Uponsuccessfulre-establishmentofthePSTNlayer2,theLEshallsendaDISCONNECTCOMPLETEmessagetotheNTNandgointothe"Nullstate(LE1)"inordertoensuresynchronizationoftheNTNPSTNGWandtheLEstatemachines.NOTE:Callreleasemaycauseanetworkclearingmessagewithacause#27,destinationoutoforder,or#41,temporaryfailure,andthelocationfieldsetto'publicnetworkservingtheremoteuser',tobesenttowardstheexchangeservingtheremoteuser.7.3MaintenancefunctionsThisclausedefinesthemechanismfortheLEtobeabletodetermineifcustomerequipmentisconnectedtothePSTN-GWandtodeterminethesynchronizationstatusoftheS/Tinterface.Thesupportofthe(ISDNandPSTN)maintenancemechanismsbytheLEandNTNisoptional.ItshallusetheLayer3STATUSandSTATUSENQUIRYmessagesasdefinedinETS300324-1[3]subclause13.4,exceptthattheStateandCauseinformationelementsalreadydefinedfortheSTATUSarechangedtooptionalandonlyoneofthenewvariablelengthinformationelementsdefinedbelowshallbeincludedinaSTATUSmessage.SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)137.3.1ThenewSTATUSENQUIRYandSTATUSmessagesThenewSTATUSENQUIRYandSTATUSmessagesandtheirassociatedproceduresshallfollowthosedefinedinETS300324-1[3],withthefollowingadditions:• theStateandCauseinformationelementsshallnotbeincludedintheSTATUSmessage;• newinformationelementsaredefinedfortheSTATUSandSTATUSENQUIRYmessages.ThenewmessagesshallhereafterinthepresentdocumentbereferredtoasMAINTENANCESTATUSandMAINTENANCESTATUSENQUIRYmessagestodifferentiatethemfromthoseusedaspartofthestandardPSTNProtocolprocedures.7.3.1.1PSTNmaintenancemessagesTheMAINTENANCESTATUSENQUIRYandMAINTENANCESTATUSmessagesforthePSTN-GWstatusshallbesentusingtheTEIwhichisallocatedtothatgateway(seetable1).7.3.1.1.1TheMAINTENANCESTATUSENQUIRYmessageforPSTNmaintenanceTable2:ThePSTNgatewayMAINTENANCESTATUSENQUIRYmessageBit87654321ProtocolDiscriminatorLayer3Address(note)1Layer3Address(lower)(note)MessageType11010000PSTNgatewaystatusrequestinformationelementidentifierNOTE:Thelayer3addressshallbecodedas"Layer3addressnotrelevantincurrentmessage"accordingtosubclause8.2.7.3.1.1.2TheMAINTENANCESTATUSmessageforPSTNmaintenanceThismessageshallbesentonreceiptofaMAINTENANCESTATUSENQUIRYmessagefromtheLE.TheMAINTENANCESTATUSmessagecarriesanewvariablelengthoptionalinformationelementinthedirectionNTN-LE.SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)14Table3:ThePSTNgatewayMAINTENANCESTATUSmessageBit87654321ProtocolDiscriminatorLayer3Address1Layer3Address(Lower)MessageType00011110PSTNgatewaystatusresponseinformationelementidentifier00000001Informationelementlength1ext.STGWNOTE1:Thelayer3Addressshallbecodedas"Layer3addressnotrelevantincurrentmessage"accordingtosubclause8.2.STGWdefinesthestatusoftheaddressedPSTN-GW(CPEpresenceindicator).ThecodingoftheSTGWfieldshallbeaccordingtotable4.Table4:CodingoftheSTGWfieldBitsMeaning76543210000000NoCPEpresent0000001CPEconnected0000010TestUnavailableNOTE:Allothervaluesarereserved.NOTE2:ThemethodfordetectingthatCPEisconnectedisnotspecifiedhereandwilldependuponthePSTNarchitectureused.7.3.1.2ISDNmaintenancemessagesTheMAINTENANCESTATUSENQUIRYandMAINTENANCESTATUSmessagesfortheISDNUNIstatusshallbesentusingTEI126.SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)157.3.1.2.1TheMAINTENANCESTATUSENQUIRYmessageforISDNmaintenanceTable5:TheMAINTENANCEISDNUNISTATUSENQUIRYmessageBit87654321ProtocolDiscriminatorLayer3Address(note)1Layer3Address(lower)(note)MessageType11010001ISDNUNIstatusrequestinformationelementidentifierNOTE:Thelayer3Addressshallbecodedas"Layer3addressnotrelevantincurrentmessage"accordingtosubclause8.2.7.3.1.2.2TheMAINTENANCESTATUSmessageforISDNmaintenanceThismessageshallbesentinresponsetothereceiptofaMAINTENANCESTATUSENQUIRYmessagefromthenetworkcontainingtheISDNUNIstatusenquiryinformationelement.TheMAINTENANCESTATUSmessagecarriesanewvariablelengthinformationelementinthedirectionNTN-LE.Table6:TheMAINTENANCEISDNUNISTATUSmessageBit87654321ProtocolDiscriminatorLayer3Address(note)1Layer3Address(Lower)(note)MessageType00011111ISDNUNIstatusresponseinformationelementidentifier00000001Informationelementlength1ext.STUNINOTE:Thelayer3addressshallbecodedas"Layer3addressnotrelevantincurrentmessage"accordingtosubclause8.2.SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)16STUNIdefineswhethertheS/TInterfaceofanyparticularISDN-BAisactive(i.e.INFO3hasbeenreceived).ThecodingoftheSTUNIfieldshallbeaccordingtotable7.Table7:CodingoftheSTUNIfieldBitsMeaning76543210000000NoS/TInterfacesynchronizationonISDN-BAuserport0000001S/TInterfacesynchronizationonISDN-BAuserport0000010TestUnavailableNOTE:Allothervaluesarereserved.7.3.2Maintenancestatusprocedure7.3.2.1NormaloperationTheMaintenancestatusenquiryprocedureshallonlybeinitiatedbytheLE.ThisprocedureapplieswhentheLEwantstocheckthemaintenancestatusofagivenuserport(e.g.aPSTNgatewayoranISDNUNI)intheNTN.NostatechangeshalloccurintheLEandNTNuponperformingthemaintenancestatusenquiryprocedure.OnreceiptofaMDU-maintenance_request,theLEshallsendaMAINTENANCESTATUSENQUIRYmessageandstarttimerTm.TheLayer3addressoftheMAINTENANCESTATUSENQUIRYmessageshallbesetto7FFFh.TheMAINTENANCESTATUSENQUIRYmessageshallbecodedeitherasinsubclause7.3.1.1.1wheretheLEwantstocheckthemaintenancestatusofaPSTNgateway,orasinsubclause7.3.1.2.1wheretheLEwantstocheckthemaintenancestatusofanISDNUNI.UponreceiptofaMAINTENANCESTATUSENQUIRYmessagefromtheLE,theNTNshallrespondtotheLEwiththeappropriateMAINTENANCESTATUSmessagewiththeL3Addr=7FFFh.TheMAINTENANCESTATUSmessageshallbecodedeitherasinsubclause7.3.1.1.2wheretheMAINTENANCESTATUSENQUIRYcontainedaPSTNgatewaystatusrequestIE,orasinsubclause7.3.1.2.2wheretheMAINTENANCESTATUSENQUIRYcontainedanISDNUNIstatusrequestIE.TheLEhavingreceivedtheMAINTENANCESTATUSmessageshallstoptimerTmandshallreporttheresultinternallyusingtheMDU-maintenance_response,andremaininthesamestate.IftimerTmexpires:• thefirsttime,theMAINTENANCESTATUSENQUIRYmessageshallbere-sent,andtimerTmshallberestarted;• thesecondtimeaninternalerrorindicationshallbegeneratedandnostatechangeshalloccur.7.3.2.2ExceptionalproceduresThisclausedescribestheexceptionalproceduresinrelationtothemessagecontentwiththeexceptionoftheL3addrIE.TheL3addrIEisusedwithintheB-channelselectionprocedureasdescribedinclause8.SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)177.3.2.2.1NTNInrelationtotheSTATUSENQUIRYmessagetheNTNshallimplementtheANexceptionproceduresdefinedinETS300324-1[3]withtheexceptionthatthemessagecontentvalidationshallbeextendedtosupportMAINTENANCESTATUSENQUIRYmessages,i.e.ETS300324-1[3]table10isextendedasshownintable8.MessageType:STATUSENQUIRYDirection:LEtoANTable8:STATUSENQUIRYmessagecontentInformationelementReferenceDirectionTypeLengthProtocoldiscriminator[3]13.4.2LEtoANM1L3addr[3]13.4.3LEtoANM2Messagetype[3]13.4.4LEtoANM1ISDNUNIstatusrequest7.3.1.2.1LEtoANC1PSTNgatewaystatusrequest7.3.1.1.1LEtoANC1NOTE:InthecaseofMAINTENANCESTATUSENQUIRYmessages,oneandonlyoneconditionalinformationelementshallbecontainedinthemessageandshallbehandledasmandatoryinformationelement.7.3.2.2.2LEInrelationtotheSTATUSmessagetheLEshallimplementtheLEexceptionproceduresdefinedinETS300324-1[3]withtheexceptionthatthemessagecontentvalidationshallbeextendedtosupportMAINTENANCESTATUSmessages,i.e.ETS300324-1[3]table9isextendedasshownintable9below.MessageType:STATUSDirection:ANtoLETable9:STATUSmessagecontentInformationelementReferenceDirectionTypeLengthProtocoldiscriminator[3]13.4.2ANtoLEM1L3addr[3]13.4.3ANtoLEM2Messagetype[3]13.4.4ANtoLEM1State[3]13.4.6.3ANtoLEC11Cause[3]13.4.7.9ANtoLEC13to5ISDNUNIstatusresponse7.3.1.2.2LEtoANC21PSTNgatewaystatusresponse7.3.1.1.2LEtoANC31NOTE:OnesetofconditionalelementsC1,C2orC3shallbecontainedinthemessageandshallbehandledasmandatoryinformationelement(s).InthecaseofMAINTENANCESTATUSmessagesthesetshallbeC2orC3.7.3.2.3TimerTmdefinitionTheadditionaltimerTm(seetable10below)isapplicableintheLEfortheMaintenancestatusenquiryprocedure.Table10:TimerTmbehaviourTimernumberTimeoutvalueStateCauseforstartNormalstopAtthefirstexpiryAtthesecondexpiryCrossreferenceTm10sAnyMaintenanceSTATUSENQUIRYsentReceivingofSTATUSfromANindicatingresponsetomaintenanceSTATUSENQUIRYRepeatMaintenanceSTATUSENQUIRYandrestartoftimerTmMDU-error_indication7.3.2.1SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)188B-channelselectionprocedure8.1IntroductionTheB-channelsoftheaccessareacommonresourceforboththeISDN-BAandthePSTNports.TohandletheselectionofB-channelforthePSTNportuse,anewmechanismhasbeendefined(seesubclause8.2).TheoperationoftheB-channelselectionproceduresisshowninexampleswithinannexA.8.2B-channelselectionThisclausedescribesthemechanismbywhichtheLEindicatestowhichbearerchanneltheselectedPSTN-GWshallconnectforanyparticularcall.ThisisadeparturefromtheV5.1recommendationETS300324-1[3]andcanonlyfunctionbecausetheNMDSallowsonlyonePSTNlayer3perlayertwo(addressedviaTEIs).Thelayer3address(L3addr)fieldintheV5PSTNProtocolmessagesshallbeusedtoindicatethebearerchannelasintable11.Table11:B-channelselectionviaL3addrL3ADDRB-channelL3addr=0noB-channelselectedorthattheNTNshallreleasetheB-channelL3addr=1B1selectedL3addr=2B2selectedL3addr=nBnSelected(thegeneralcase)(note)L3addr=7FFFhLayer3addressnotrelevantincurrentmessage(e.g.usedinMAINTENANCESTATUSandMAINTENANCESTATUSENQUIRYmessages)Allothervaluesarereserved.NOTE:Ingeneralthisapplies,althoughforNMDSthereareonlytwoB-channelsavailable.8.2.1LEFunctionality8.2.1.1GeneralRequirementsTheLEshallberesponsiblefortheB-channelselectionandshallnotchangedirectlybetweenthetwoB-channelsduringaPSTNcall.TheselectedB-channelshallbeindicatedintheL3addrfieldofallcallrelatedmessagessentbetweenLEandNTN.TheLEshallusetheL3addrvalue7FFFhwhensendingMAINTENANCESTATUSENQUIRYmessagesdescribedinsubclause7.3.8.2.1.1.1HandlingofvalidL3addrvaluesUponreceiptofaPSTNProtocolmessagewithavalidL3addr(seetable11)theLEshallperformoneofthefollowingactionsdependentonthemessageandL3addrvalue.a)IftheLEreceivesanESTABLISHmessagewithaL3addrthatisnot0itshallignoreanddiscardthemessage.NOTE:TheLEmaygenerateaninternalerrorindication.b)IftheLEreceivesanESTABLISHmessagewithL3addrof0itshallbeacceptedandhandledinaccordancewithclause8.2.1.2.c)IftheLEreceivesamessage(otherthanESTABLISH)withaL3addrof0,1,or2itshallcomparetheL3addrvaluewiththatexpected(i.e.thecurrentallocatedvalueforthecalltakingintoaccountthepossibilityofmessagecrossovers).IfthereceivedvalueisnotasexpectedthentheLEshallclearthecallusingthenormalcallclearingprocedures,ensuringanyconnectedB-channelisreleased.Ifthereceivedvalueisasexpected(againmakingallowanceforcrossovers)thenthemessageshallbehandledinaccordancewithclause8.2.1.2.SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)19d)IftheLEreceivesamessage(otherthanESTABLISH)withaL3addrof7FFFhthentheLEshallperformeither(i)or(ii)below:i.TreatthevalueoftheL3addrasvalid,makenochangesinrelationtoitsB-channelallocationatthispoint,andcontinuewiththeprocessingofthemessageinthenormalmannerthroughthePSTNprotocolandbeyond(e.g.tocallcontrolormaintenancefunctions).ThisprocessingmayresultinthereleaseoftheB-channel(e.g.iftheLEreceivesaDISCONNECTorDISCONNECTCOMPLETEmessagewithL3addr=7FFFh).IfthemessageisnotamaintenancemessagetheLEshallclearthecallusingthenormalcallclearingprocedures,ensuringanyconnectedB-channelisreleased.OtherwisetheLEshallmakenochangesinrelationtoitsB-channelallocation.8.2.1.1.2HandlingofinvalidL3addrvaluesIftheLEreceivesamessagewithareservedvalueofL3addrthentheLEshallperformoneofthefollowingoptions:a.ignorethemessageandgenerateaninternalerrorindication;b.treattheL3addrvalueasunexpectedandclearthecallusingthenormalcallclearingprocedures,ensuringanyconnectedB-channelisreleased.8.2.1.2SpecificRequirementsforPSTNCallsTheLEshallperformthegeneralrequirementsofclause8.2.1.1beforegoingontothespecificrequirementsdescribedinthisclause.OnreceiptofanESTABLISHmessagefromtheNTN,theLEshallperformeitheroption(a)oroption(b)below:a)selecttheB-channeltobeusedandindicateitusingtheL3addrwhenreturningtheESTABLISHACKNOWLEDGEmessagetotheNTN.b)selecttheB-channeltobeusedandindicateitusingtheL3addrwhenreturningtheESTABLISHACKNOWLEDGEmessagetotheNTN,oralternativelyifselectionisnotcurrentlypossibleindicatenoB-channelselectedintheL3addrwhenreturningtheESTABLISHACKNOWLEDGEmessagetotheNTN.TheB-channelshallbereleasedbytheLEwhenreceivingtheDISCONNECTCOMPLETEmessagefromtheNTNorwhentheLEsendstheDISCONNECTmessageortheDISCONNECTCOMPLETEmessage(L3addrshallbesetto0bytheLE).PriortosendinganESTABLISHmessagetotheNTNtheLEshalldeterminetheB-channeltobeusedandindicatethisintheL3addrfieldoftheESTABLISHmessage.Forallothermessages,eitheronreceiptorpriortobeingsent,thepointsofselectionandreleaseofB-channelsbytheLEduringacallshallbeinaccordancewithNationalorOperatorrequirementssubjecttotherequirementsofthisstandard.ExamplesaregiveninAnnexA.8.2.2NTNFunctionality8.2.2.1GeneralrequirementsUponreceivinganymessagewithaTEIidentifyingaPSTNport,wheretheL3addrinthemessageisvalid(i.e.isnotareservedvalueandisnotequalto7FFFh),theNTNshallchangetheconnectiontomatchtheL3addrinthemessage.Theonlyexceptiontothisiswherethereceivedmessage(e.g.DISCONNECTorDISCONNECTCOMPLETE)resultsintheNTNenteringtheidlestatewhereuponitshallreleasetheB-channelindependentoftheL3addrinthereceivedmessage.TheNTNshallnotregardchangingbetweenB-channelsasaninvalidrequest.IftheNTNreceivesamessagewithareservedvalueofL3addrthenitshallaccordingtotheL3addrhandlingprocedures(ETS300324-1[3]subclause13.5.2.2)ignorethemessage,generateaninternalerrorindicationandsendaSTATUSmessagetotheLEwiththeL3addrreceived,theStateinformationelementindicatingthecurrentstateandtheCauseinformationelementindicatingcause"L3addresserror".SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)20IftheNTNreceivesamessagewithaL3addrof7FFFhthentheNTNshalltreatthevalueoftheL3addrasvalid,makenochangesinrelationtoitsB-channelallocationatthispoint,andcontinuewiththeprocessingofthemessageinthenormalmannerthroughthePSTNprotocolandbeyond(e.g.tocallcontrolormaintenancefunctions).ThisprocessingmayresultinthereleaseoftheB-channel(e.g.iftheNTNreceivesaDISCONNECTorDISCONNECTCOMPLETEmessagewithL3addr=7FFFh).WhensendingamessagetotheLEtheNTNshallsetthevalueoftheL3addrdependingonthemessagetype.ForMAINTENANCESTATUSmessagestheL3addrshallbesetto7FFFh.ForcallcontrolrelatedmessagestheL3addrshallbesettoindicatethecurrentlyallocatedB-channel,or0whennoB-channelisallocated.(ForexampletheL3addrshallalwaysbe0whensendinganESTABLISHmessageoraDISCONNECTCOMPLETEmessage.ExamplesofvalidactionsoftheNTNareshownintable12.Table12:NTNB-channelconnectionCurrentConnectionReceivedL3addrNewConnectionPort1,B-channel10Port1,NochannelPort2,B-channel21Port2,B-channel1Port1,Nochannel2Port1,B-channel28.2.2.2SpecificRequirementsforPSTNCallsAnESTABLISHmessagesentbytheNTNcannotcontainaB-channelallocation,sincenoallocationhasbeenmadebytheLEatthispointintime.Inthiscase,thevalueL3addr=0shallbesenttoindicatethisfact.IftheNTNreceivesanESTABLISHmessageoranESTABLISHACKmessagewhichcontainsthevalueL3addr=0thentheNTNshallfollowtherequirementsoftheNationalPSTNProtocolassociatedwithreceiptofthemessagebutshallnotconnectaB-channel.Atalatertimeamessagemaybesentwithanon-zeroL3addr,inwhichcasetheB-channelreferredtoshallbeselected.SIST EN 301 141-1 V2.1.1:2005

ETSIETSIEN301141-1V2.1.1(2000-11)21AnnexA(informative):B-channelselectionA.1GeneralThisannexprovidesexamplesofhowtheB-channelselectionprocedurefortheNMDSapplicationmaybeappliedwithinaNationalPSTNProtocol.A.2Outgoingcalls(NTNtoLE)AnoffhookgeneratedbytheusershallcausetheL3addrtobesetto"noB-channelselected"intheESTABLISHmessagesenttotheLE.B-channelselectionintheLEshallbeperformedandtheselectedB-channelreturnedintheL3addrfieldintheESTABLISHACKmessagetoNTN(seefigureA.1).TheselectedB-channelshallbeshownintheL3addrofallsignallinguntilthecalliscleared.ESTABLISHESTABLISHACKestablishindicationestablishacknowledgeoffhookL3addr=0(noB-channelselected)L3addr=1ifB-channelB1wasselected,otherwise=2forB2.NTNLEcallcontrolTerminalPSTNLE4LE3LE1AN1AN5AN2FigureA.1:Outgoi
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