RFC 4666 - Signaling System 7 (SS7) Message Transfer Part 3 (MTP3) - User Adaptation Layer (M3UA)

7/31/2019 RFC 4666 - Signaling System 7 (SS7) Message Transfer Part 3 (MTP3) - User Adaptation Layer (M3UA)

1/116

RFC4666-SignalingSystem7(SS7)MessageTransferPart3(MTP3)-UserAdaptationLayer(M3UA)[Docs][txt|pdf][draft-ietf-sigtra...][Diff1][Diff2][IPR][Errata]PROPOSEDSTANDARDErrataExist

NetworkWorkingGroupK.Morneault,Ed.RequestforComments:4666CiscoSystemsObsoletes:3332J.Pastor-Balbas,Ed.Category:StandardsTrackEricssonSeptember2006

SignalingSystem7(SS7)MessageTransferPart3(MTP3)-UserAdaptationLayer(M3UA)

StatusofThisMemo

ThisdocumentspecifiesanInternetstandardstrackprotocolfortheInternetcommunity,andrequestsdiscussionandsuggestionsforimprovements.Pleaserefertothecurrenteditionofthe"InternetOfficialProtocolStandards"(STD1)forthestandardizationstate

andstatusofthisprotocol.Distributionofthismemoisunlimited.

CopyrightNotice

Copyright(C)TheInternetSociety(2006).

Abstract

ThismemodefinesaprotocolforsupportingthetransportofanySS7MTP3-Usersignalling(e.g.,ISUPandSCCPmessages)overIPusingtheservicesoftheStreamControlTransmissionProtocol.Also,provisionismadeforprotocolelementsthatenableaseamlessoperationoftheMTP3-UserpeersintheSS7andIPdomains.This

protocolwouldbeusedbetweenaSignallingGateway(SG)andaMediaGatewayController(MGC)orIP-residentDatabase,orbetweentwoIP-basedapplications.ItisassumedthattheSGreceivesSS7signallingoverastandardSS7interfaceusingtheSS7MessageTransferPart(MTP)toprovidetransport.ThisdocumentobsoletesRFC3332.

Morneault&Pastor-BalbasStandardsTrack[Page1]


2/116

RFC4666SS7MTP3-UserAdaptationLayerSeptember2006

TableofContents

1.Introduction....................................................61.1.Scope......................................................61.2.Terminology................................................61.3.M3UAOverview..............................................91.3.1.ProtocolArchitecture...............................91.3.2.ServicesProvidedbytheM3UALayer................101.3.2.1.SupportfortheTransportofMTP3-UserMessages........................101.3.2.2.NativeManagementFunctions...............111.3.2.3.InterworkingwithMTP3NetworkManagementFunctions......................111.3.2.4.SupportfortheManagementofSCTPAssociationsbetweenthe..................111.3.2.5.SupportfortheManagementofConnectionstoMultipleSGPs..............121.4.FunctionalAreas..........................................121.4.1.SignallingPointCodeRepresentation...............121.4.2.RoutingContextsandRoutingKeys..................14

1.4.2.1.Overview..................................141.4.2.2.RoutingKeyLimitations...................151.4.2.3.ManagingRoutingContextsandRoutingKeys..............................151.4.2.4.MessageDistributionattheSGP...........151.4.2.5.MessageDistributionattheASP...........161.4.3.SS7andM3UAInterworking..........................161.4.3.1.SignallingGatewaySS7Layers.............161.4.3.2.SS7andM3UAInterworkingattheSG.......171.4.3.3.ApplicationServer........................171.4.3.4.IPSPConsiderations.......................181.4.4.RedundancyModels..................................181.4.4.1.ApplicationServerRedundancy.............18

1.4.5.FlowControl.......................................181.4.6.CongestionManagement..............................191.4.7.SCTPStreamMapping................................191.4.8.SCTPClient/ServerModel...........................191.5.SampleConfiguration......................................201.5.1.Example1:ISUPMessageTransport..................201.5.2.Example2:SCCPTransportbetweenIPSPs............211.5.3.Example3:SGPResidentSCCPLayer,withRemoteASP.........................................221.6.DefinitionofM3UABoundaries.............................231.6.1.DefinitionoftheBoundarybetweenM3UAandanMTP3-User.......................................231.6.2.DefinitionoftheBoundarybetweenM3UAandSCTP...23

1.6.3.DefinitionoftheBoundarybetweenM3UAandLayerManagement...................................24

Morneault&Pastor-BalbasStandardsTrack[Page2]RFC4666SS7MTP3-UserAdaptationLayerSeptember2006


3/116

2.Conventions....................................................273.M3UAProtocolElements.........................................283.1.CommonMessageHeader.....................................283.1.1.M3UAProtocolVersion:8bits(unsignedinteger)...283.1.2.MessageClassesandTypes..........................283.1.3.Reserved:8Bits...................................303.1.4.MessageLength:32-Bits(UnsignedInteger).........303.2.Variable-LengthParameterFormat..........................303.3.TransferMessages.........................................333.3.1.PayloadDataMessage(DATA)........................333.4.SS7SignallingNetworkManagement(SSNM)Messages.........363.4.1.DestinationUnavailable(DUNA).....................363.4.2.DestinationAvailable(DAVA).......................393.4.3.DestinationStateAudit(DAUD).....................403.4.4.SignallingCongestion(SCON).......................403.4.5.DestinationUserPartUnavailable(DUPU)...........433.4.6.DestinationRestricted(DRST)......................453.5.ASPStateMaintenance(ASPSM)Messages....................453.5.1.ASPUp.............................................453.5.2.ASPUpAcknowledgement(ASPUpAck)................463.5.3.ASPDown...........................................473.5.4.ASPDownAcknowledgement(ASPDownAck)............483.5.5.Heartbeat(BEAT)...................................483.5.6.HeartbeatAcknowledgement(BEATAck)...............49

3.6.RoutingKeyManagement(RKM)Messages[Optional]..........493.6.1.RegistrationRequest(REGREQ).....................493.6.2.RegistrationResponse(REGRSP)....................543.6.3.DeregistrationRequest(DEREGREQ).................563.6.4.DeregistrationResponse(DEREGRSP)................573.7.ASPTrafficMaintenance(ASPTM)Messages..................593.7.1.ASPActive.........................................593.7.2.ASPActiveAcknowledgement(ASPActiveAck)........603.7.3.ASPInactive.......................................613.7.4.ASPInactiveAcknowledgement(ASPInactiveAck)....623.8.Management(MGMT)Messages................................633.8.1.Error..............................................633.8.2.Notify.............................................67

4.Procedures.....................................................704.1.ProcedurestoSupporttheM3UA-User.......................704.1.1.ReceiptofPrimitivesfromtheM3UA-User...........704.2.ReceiptofPrimitivesfromtheLayerManagement...........714.2.1.ReceiptofM3UAPeerManagementMessages...........724.3.ASandASP/IPSPStateMaintenance.........................734.3.1.ASP/IPSPStates....................................744.3.2.ASStates..........................................764.3.3.M3UAManagementProceduresforPrimitives..........784.3.4.ASPMProceduresforPeer-to-PeerMessages..........794.3.4.1.ASPUpProcedures.........................79


4.3.4.2.ASP-DownProcedures.......................814.3.4.3.ASPActiveProcedures.....................824.3.4.4.ASPInactiveProcedures...................864.3.4.5.NotifyProcedures.........................88


4/116

4.3.4.6.HeartbeatProcedures......................894.4.RoutingKeyManagementProcedures[Optional]..............904.4.1.Registration.......................................904.4.2.Deregistration.....................................924.4.3.IPSPConsiderations(REG/DEREG)....................934.5.ProcedurestoSupporttheAvailabilityorCongestionStatusofSS7Destination......................934.5.1.AtanSGP..........................................934.5.2.AtanASP..........................................944.5.2.1.SingleSGConfigurations..................944.5.2.2.MultipleSGConfigurations................944.5.3.ASPAuditing.......................................944.6.MTP3Restart..............................................964.7.NIFNotAvailable.........................................974.8.M3UAVersionControl......................................974.9.M3UATermination..........................................975.ExamplesofM3UAProcedures....................................985.1.EstablishmentofAssociationandTrafficbetweenSGPsandASPs.............................................985.1.1.SingleASPinanApplicationServer("1+0"sparing),NoRegistration..........................985.1.1.1.SingleASPinanApplicationServer("1+0"Sparing),NoRegistration...985.1.1.2.SingleASPinApplicationServer

("1+0"Sparing),DynamicRegistration.....995.1.1.3.SingleASPinMultipleApplicationServers(Eachwith"1+0"Sparing),DynamicRegistration(Case1-MultipleRegistrationRequests)........1005.1.1.4.SingleASPinMultipleApplicationServers(eachwith"1+0"sparing),DynamicRegistration(Case2-SingleRegistrationRequest)...........1015.1.2.TwoASPsinApplicationServer("1+1"Sparing)....1025.1.3.TwoASPsinanApplicationServer("1+1"Sparing,LoadsharingCase)........................1035.1.4.ThreeASPsinanApplicationServer("n+k"

Sparing,LoadsharingCase)........................1045.2.ASPTrafficFailoverExamples............................1055.2.1.1+1Sparing,WithdrawalofASP,BackupOverride...1055.2.2.1+1Sparing,BackupOverride......................1055.2.3.n+kSparing,LoadsharingCase,WithdrawalofASP..1065.3.NormalWithdrawalofanASPfromanApplicationServer...1065.4.AuditingExamples........................................107


5.4.1.SGState:Uncongested/Available...................1075.4.2.SGState:Congested(CongestionLevel=2)/Available.........................................1075.4.3.SGState:Unknown/Available.......................1075.4.4.SGState:Unavailable.............................1085.5.M3UA/MTP3-UserBoundaryExamples.........................1085.5.1.AtanASP.........................................1085.5.1.1.SupportforMTP-TRANSFER


5/116

PrimitivesattheASP....................1085.5.2.AtanSGP.........................................1095.5.2.1.SupportforMTP-TRANSFERRequestPrimitiveattheSGP.....................1095.5.2.2.SupportforMTP-TRANSFERIndicationPrimitiveattheSGP..........1105.5.2.3.SupportforMTP-PAUSE,MTP-RESUME,MTP-STATUSIndicationPrimitives...............................1105.6.ExamplesforIPSPCommunication..........................1125.6.1.SingleExchange...................................1125.6.2.DoubleExchange...................................1136.SecurityConsiderations.......................................1137.IANAConsiderations...........................................1147.1.SCTPPayloadProtocolIdentifier.........................1147.2.M3UAPortNumber.........................................1147.3.M3UAProtocolExtensions.................................1147.3.1.IETF-DefinedMessageClasses......................1157.3.2.IETFDefinedMessageTypes........................1157.3.3.IETF-DefinedParameterExtension..................1158.Acknowledgements..............................................1159.DocumentContributors.........................................11610.References...................................................11610.1.NormativeReferences....................................116

10.2.InformativeReferences..................................117AppendixA.......................................................119A.1.SignallingNetworkArchitecture.............................119A.2.RedundancyModels...........................................121A.2.1.ApplicationServerRedundancy........................121A.2.2.SignallingGatewayRedundancy........................122


1.Introduction

ThismemodefinesaprotocolforsupportingthetransportofanySS7MTP3-Usersignalling(e.g.,ISUPandSCCPmessages)overIPusingtheservicesoftheStreamControlTransmissionProtocol[18].Also,provisionismadeforprotocolelementsthatenableaseamlessoperationoftheMTP3-UserpeersintheSS7andIPdomains.ThisprotocolwouldbeusedbetweenaSignallingGateway(SG)andaMediaGatewayController(MGC)orIP-residentDatabase[12],orbetweentwoIP-basedapplications.

1.1.Scope


6/116

ThereisaneedforSwitchedCircuitNetwork(SCN)signallingprotocoldeliveryfromanSS7SignallingGateway(SG)toaMediaGatewayController(MGC)orIP-residentDatabaseasdescribedintheFrameworkArchitectureforSignallingTransport[12].Thedeliverymechanismshouldmeetthefollowingcriteria:

*SupportforthetransferofallSS7MTP3-UserPartmessages(e.g.,ISUP[1,2,3],SCCP[4,5,6],TUP[13],etc.)*SupportfortheseamlessoperationofMTP3-Userprotocolpeers*SupportforthemanagementofSCTPtransportassociationsandtrafficbetweenanSGandoneormoreMGCsorIP-residentDatabases*SupportforMGCorIP-residentdatabaseprocessfailoverandloadsharing*Supportfortheasynchronousreportingofstatuschangestomanagement

Insimplistictransportterms,theSGwillterminateSS7MTP2andMTP3protocollayers[7,8,9]anddeliverISUP,SCCP,and/oranyotherMTP3-Userprotocolmessages,aswellascertainMTPnetworkmanagementevents,overSCTPtransportassociationstoMTP3-UserpeersinMGCsorIP-residentdatabases.

1.2.Terminology

ApplicationServer(AS)-AlogicalentityservingaspecificRoutingKey.AnexampleofanApplicationServerisavirtualswitchelementhandlingallcallprocessingforasignallingrelation,identifiedbyanSS7DPC/OPC.Anotherexampleisavirtualdatabaseelement,handlingallHLRtransactionsforaparticularSS7SIO/DPC/OPCcombination.TheAScontainsasetofoneormoreuniqueApplicationServerProcesses,ofwhichoneormoreisnormallyactivelyprocessingtraffic.Notethatthereisa1:1relationshipbetweenanASandaRoutingKey.


ApplicationServerProcess(ASP)-AprocessinstanceofanApplicationServer.AnApplicationServerProcessservesasanactiveorbackupprocessofanApplicationServer(e.g.,partofadistributedvirtualswitchordatabase).ExamplesofASPsareprocesses(orprocessinstances)ofMGCs,IPSCPs,orIPHLRs.AnASPcontainsanSCTPendpointandmaybeconfiguredtoprocess

signallingtrafficwithinmorethanoneApplicationServer.

Association-AnassociationreferstoanSCTPassociation.TheassociationprovidesthetransportforthedeliveryofMTP3-UserprotocoldataunitsandM3UAadaptationlayerpeermessages.

IPServerProcess(IPSP)-AprocessinstanceofanIP-basedapplication.AnIPSPisessentiallythesameasanASP,exceptthatitusesM3UAinapoint-to-pointfashion.Conceptually,anIPSPdoesnotusetheservicesofaSignallingGatewaynode.


7/116

Failover-ThecapabilitytoreroutesignallingtrafficasrequiredtoanalternateApplicationServerProcess,orgroupofASPs,withinanApplicationServerintheeventoffailureorunavailabilityofacurrentlyusedApplicationServerProcess.FailoveralsoappliesuponthereturntoserviceofapreviouslyunavailableApplicationServerProcess.

Host-Thecomputingplatformthattheprocess(SGP,ASPorIPSP)isrunningon.

LayerManagement-LayerManagementisanodalfunctionthathandlestheinputsandoutputsbetweentheM3UAlayerandalocalmanagemententity.

Linkset-Anumberofsignallinglinksthatdirectlyinterconnecttwosignallingpoints,whichareusedasamodule.

MTP-TheMessageTransferPartoftheSS7protocol.

MTP3-MTPLevel3,thesignallingnetworklayerofSS7.

MTP3-User-AnyprotocolnormallyusingtheservicesoftheSS7MTP3(e.g.,ISUP,SCCP,TUP,etc.).

NetworkAppearance-TheNetworkAppearanceisaM3UAlocalreferencesharedbySGandAS(typicallyaninteger)that,togetherwithanSignalingPointCode,uniquelyidentifiesanSS7nodebyindicatingthespecificSS7networktowhichitbelongs.ItcanbeusedtodistinguishbetweensignallingtrafficassociatedwithdifferentnetworksbeingsentbetweentheSGandtheASPoveracommonSCTPassociation.AnexamplescenarioiswhereanSGappearsasan



elementinmultipleseparatenationalSS7networksandthesameSignalingPointCodevaluemaybereusedindifferentnetworks.

NetworkByteOrder-Mostsignificantbytefirst,a.k.aBigEndian.RoutingKey-ARoutingKeydescribesasetofSS7parametersandparametervaluesthatuniquelydefinetherangeofsignallingtraffictobehandledbyaparticularApplicationServer.ParameterswithintheRoutingKeycannotextendacrossmorethanasingleSignallingPointManagementCluster.

RoutingContext-AvaluethatuniquelyidentifiesaRoutingKey.RoutingContextvaluesareconfiguredeitherusingaconfigurationmanagementinterface,orbyusingtheroutingkeymanagementproceduresdefinedinthisdocument.

SignalingEndPoint(SEP)-AnodeintheSS7networkassociatedwithanoriginatingorterminatinglocalexchange(switch)oragatewayexchange.

SignallingGatewayProcess(SGP)-AprocessinstanceofaSignalling


8/116

Gateway.Itservesasanactive,backup,load-sharing,orbroadcastprocessofaSignallingGateway.

SignallingGateway(SG)-AnSGisasignalingagentthatreceives/sendsSCNnativesignalingattheedgeoftheIPnetwork[12].AnSGappearstotheSS7networkasanSS7SignallingPoint.AnSGcontainsasetofoneormoreuniqueSignallingGatewayProcesses,ofwhichoneormoreisnormallyactivelyprocessingtraffic.WhereanSGcontainsmorethanoneSGP,theSGisalogicalentity,andthecontainedSGPsareassumedtobecoordinatedintoasinglemanagementviewtotheSS7networkandtothesupportedApplicationServers.

SignallingProcess-AprocessinstancethatusesM3UAtocommunicatewithothersignallingprocesses.AnASP,anSGP,andanIPSPareallsignallingprocesses.

SignallingPointManagementCluster(SPMC)-ThecompletesetofApplicationServersrepresentedtotheSS7networkunderasingleMTPentity(SignallingPoint)inonespecificNetworkAppearance.SPMCsareusedtoaggregatetheavailability,congestion,anduserpartstatusofanMTPentity(SignallingPoint)thatisdistributedintheIPdomain,forthepurposeofsupportingMTP3managementprocedurestowardstheSS7network.Insomecases,theSGitselfmayalsobea

memberoftheSPMC.Inthiscase,theSGavailability/congestion/User_PartstatusshouldalsobetakenintoaccountwhenconsideringanysupportingMTP3managementactions.


SignalingTransferPoint(STP)-AnodeintheSS7networkthat

providesnetworkaccessandperformsmessagerouting,screeningandtransferofsignalingmessages.

Stream-AnSCTPstream;aunidirectionallogicalchannelestablishedfromoneSCTPendpointtoanotherassociatedSCTPendpoint,withinwhichallusermessagesaredeliveredin-sequenceexceptforthosesubmittedtotheunordereddeliveryservice.

1.3.M3UAOverview

1.3.1.ProtocolArchitecture

TheframeworkarchitecturethathasbeendefinedforSCNsignalling

transportoverIP[12]usesmultiplecomponents,includingacommonsignallingtransportprotocolandanadaptationmoduletosupporttheservicesexpectedbyaparticularSCNsignallingprotocolfromitsunderlyingprotocollayer.

Withintheframeworkarchitecture,thisdocumentdefinesanMTP3-UseradaptationmodulesuitableforsupportingthetransferofmessagesofanyprotocollayerthatisidentifiedtotheMTPLevel3asanMTPUser.ThelistoftheseprotocollayersincludesbutisnotlimitedtoISDNUserPart(ISUP)[1,2,3],SignallingConnectionControlPart


9/116

(SCCP)[4,5,6],andTelephoneUserPart(TUP)[13].TCAP[14,15,16]orRANAP[16]messagesaretransferredtransparentlybytheM3UAprotocolasSCCPpayload,astheyareSCCP-Userprotocols.

ItisrecommendedthatM3UAusetheservicesoftheStreamControlTransmissionProtocol(SCTP)[18]astheunderlyingreliablecommonsignallingtransportprotocol.ThisistotakeadvantageofvariousSCTPfeatures,suchas:

-Explicitpacket-orienteddelivery(notstream-oriented)-Sequenceddeliveryofusermessageswithinmultiplestreams,withanoptionfororder-of-arrivaldeliveryofindividualusermessages-OptionalmultiplexingofusermessagesintoSCTPdatagrams-Network-levelfaulttolerancethroughsupportofmulti-homingateitherorbothendsofanassociation-Resistancetofloodingandmasqueradeattacks-DatasegmentationtoconformtodiscoveredpathMTUsize

Undercertainscenarios,suchasback-to-backconnectionswithoutredundancyrequirements,theSCTPfunctionsabovemightnotbearequirement,andTCPMAYbeusedastheunderlyingcommontransportprotocol.


1.3.2.ServicesProvidedbytheM3UALayer

TheM3UALayeratanASPorIPSPprovidestheequivalentsetofprimitivesatitsupperlayertotheMTP3-UsersasprovidedbytheMTPLevel3toitslocalMTP3-UsersatanSS7SEP.Inthisway,the

ISUPand/orSCCPlayeratanASPorIPSPisunawarethattheexpectedMTP3servicesareofferedremotelyfromanMTP3LayeratanSGP,andnotbyalocalMTP3layer.TheMTP3layeratanSGPmayalsobeunawarethatitslocalusersareactuallyremoteuserpartsoverM3UA.Ineffect,theM3UAextendsaccesstotheMTP3layerservicestoaremoteIP-basedapplication.TheM3UAlayerdoesnotitselfprovidetheMTP3services.However,inthecasewhereanASPisconnectedtomorethanoneSG,theM3UAlayeratanASPshouldmaintainthestatusofconfiguredSS7destinationsandroutemessagesaccordingtotheavailabilityandcongestionstatusoftheroutestothesedestinationsviaeachSG.

TheM3UAlayermayalsobeusedforpoint-to-pointsignallingbetween

twoIPServerProcesses(IPSPs).Inthiscase,theM3UAlayerprovidesthesamesetofprimitivesandservicesatitsupperlayerastheMTP3.However,inthiscasetheexpectedMTP3servicesarenotofferedremotelyfromanSGP.TheMTP3servicesareprovided,buttheprocedurestosupporttheseservicesareasubsetoftheMTP3procedures,duetothesimplifiedpoint-to-pointnatureoftheIPSP-to-IPSPrelationship.

1.3.2.1.SupportfortheTransportofMTP3-UserMessages


10/116

TheM3UAlayerprovidesthetransportofMTP-TRANSFERprimitivesacrossanestablishedSCTPassociationbetweenanSGPandanASPorbetweenIPSPs.

AtanASP,inthecasewhereadestinationisreachableviamultipleSGPs,theM3UAlayermustalsochooseviawhichSGPthemessageistoberoutedorsupportloadbalancingacrosstheSGPs,therebyminimizingmissequencing.

TheM3UAlayerdoesnotimposea272-octetsignallinginformationfield(SIF)lengthlimitasspecifiedbytheSS7MTPLevel2protocol[7,8,9].LargerinformationblockscanbeaccommodateddirectlybyM3UA/SCTP,withouttheneedforanupperlayersegmentation/re-assemblyprocedureasspecifiedinrecentSCCPorISUPversions.However,inthecontextofanSG,themaximum272-octetblocksizemustbefollowedwheninterworkingtoaSS7networkthatdoesnotsupportthetransferoflargerinformationblockstothefinaldestination.ThisavoidspotentialISUPorSCCPfragmentationrequirementsattheSGPs.TheprovisioningandconfigurationoftheSS7networkdeterminestherestrictionplacedonthemaximumblock



size.Someconfigurations(e.g.,BroadbandMTP[19,20,22])maypermitlargerblocksizes.

1.3.2.2.NativeManagementFunctions

TheM3UAlayerprovidesthecapabilitytoindicateerrorsassociatedwithreceivedM3UAmessagesandtonotify,asappropriate,localmanagementand/orthepeerM3UA.

1.3.2.3.InterworkingwithMTP3NetworkManagementFunctions

AttheSGP,theM3UAlayerprovidesinterworkingwithMTP3managementfunctionstosupportseamlessoperationoftheuserSCNsignallingapplicationsintheSS7andIPdomains.Thisincludes

-providinganindicationtoMTP3-UsersatanASPthatadestinationintheSS7networkisnotreachable;

-providinganindicationtoMTP3-UsersatanASPthatadestinationintheSS7networkisnowreachable;

-providinganindicationtoMTP3-UsersatanASPthatmessagestoa

destinationintheSS7networkareexperiencingSS7congestion;

-providinganindicationtotheM3UAlayeratanASPthattheroutestoadestinationintheSS7networkarerestricted;and

-providinganindicationtoMTP3-UsersatanASPthataMTP3-Userpeerisunavailable.

TheM3UAlayeratanASPkeepsthestateoftheroutestoremoteSS7destinationsandmayinitiateanauditoftheavailabilityandthe


11/116

restrictedorthecongestedstateofremoteSS7destinations.ThisinformationisrequestedfromtheM3UAlayerattheSGP.

TheM3UAlayeratanASPmayalsoindicatetotheSGthattheM3UAlayeritselfortheASPortheASP'sHostiscongested.

1.3.2.4.SupportfortheManagementofSCTPAssociationsbetweentheSGPandASPs

TheM3UAlayerattheSGPmaintainstheavailabilitystateofallconfiguredremoteASPs,tomanagetheSCTPAssociationsandthetrafficbetweentheM3UApeers.Also,theactive/inactiveandcongestionstateofremoteASPsismaintained.

TheM3UAlayerMAYbeinstructedbylocalmanagementtoestablishanSCTPassociationtoapeerM3UAnode.Thiscanbeachievedusingthe


M-SCTP_ESTABLISHprimitives(seeSection1.6.3foradescriptionofmanagementprimitives)torequest,indicate,andconfirmtheestablishmentofanSCTPassociationwithapeerM3UAnode.InordertoavoidredundantSCTPassociationsbetweentwoM3UApeers,oneside(client)SHOULDbedesignatedtoestablishtheSCTPassociation,orM3UAconfigurationinformationmaintainedtodetectredundantassociations(e.g.,viaknowledgeoftheexpectedlocalandremoteSCTPendpointaddresses).

LocalmanagementMAYrequestfromtheM3UAlayerthestatusoftheunderlyingSCTPassociationsusingtheM-SCTP_STATUSrequestandconfirmprimitives.Also,theM3UAMAYautonomouslyinformlocalmanagementofthereasonforthereleaseofanSCTPassociation,

determinedeitherlocallywithintheM3UAlayerorbyaprimitivefromtheSCTP.

Also,theM3UAlayerMAYinformthelocalmanagementofthechangeinstatusofanASPorAS.ThisMAYbeachievedusingtheM-ASP_STATUSrequestorM-AS_STATUSrequestprimitives.

1.3.2.5.SupportfortheManagementofConnectionstoMultipleSGPs

AsshowninFigure1,anASPmaybeconnectedtomultipleSGPs.Insuchacase,aparticularSS7destinationmaybereachableviamorethanoneSGPand/orSG;i.e.,viamorethanoneroute.AsMTP3usersonlymaintainstatusonadestinationandnotonaroutebasis,the

M3UAlayermustmaintainthestatus(availability,restriction,and/orcongestionofroutetodestination)oftheindividualroutes,derivetheoverallavailabilityorcongestionstatusofthedestinationfromthestatusoftheindividualroutes,andinformtheMTP3usersofthisderivedstatuswheneveritchanges.

1.4.FunctionalAreas

1.4.1.SignallingPointCodeRepresentation


12/116

Forexample,withinanSS7network,aSignallingGatewaymightbechargedwithrepresentingasetofnodesintheIPdomainintotheSS7networkforroutingpurposes.TheSGitself,asasignallingpointintheSS7network,mightalsobeaddressablewithanSS7PointCodeforMTP3Managementpurposes.TheSGPointCodemightalsobeusedforaddressinganylocalMTP3-UsersattheSGsuchasalocalSCCPlayer.


AnSGmaybelogicallypartitionedtooperateinmultipleSS7networkappearances.Insuchacase,theSGcouldbeaddressablewithaPointCodeineachnetworkappearance,anditrepresentsasetofnodesintheIPdomainintoeachSS7network.AliasPointCodes[8]

mayalsobeusedwithinanSGnetworkappearance.

WhereanSGcontainsmorethanoneSGP,theMTP3routeset,SPMC,andremoteAS/ASPstatesofeachSGPSHOULDbecoordinatedacrossalltheSGPs.ReroutingoftrafficbetweentheSGPsMAYalsobesupported.

ApplicationServerscanberepresentedunderthesamePointCodeoftheSG,undertheirownindividualPointCodes,orgroupedwithotherApplicationServersforPointCodepreservationpurposes.AsinglePointCodemaybeusedtorepresenttheSGandalltheApplicationServerstogether,ifdesired.

IfanASPorgroupofASPsisavailabletotheSS7networkviamore

thanoneSG,eachwithitsownPointCode,theASP(s)willtypicallyberepresentedbyaPointCodethatisseparatefromanySGPointCode.Thisallows,forexample,theseSGstobeviewedfromtheSS7networkas"STPs",eachhavinganongoing"route"tothesameASP(s).UnderfailureconditionswheretheASP(s)become(s)unavailablefromoneoftheSGs,thisapproachenablesMTP3routemanagementmessagingbetweentheSGandSS7network,allowingsimpleSS7reroutingthroughanalternateSGwithoutchangingtheDestinationPointCodeAddressofSS7traffictotheASP(s).

WhereaparticularAScanbereachedviamorethanoneSGP,thecorrespondingRoutingKeysintheSGPsshouldbeidentical.(Note:ItispossiblefortheSGPRoutingKeyconfigurationdatatobe

temporarilyoutofsyncduringconfigurationupdates).

+--------+||+------------+SG1+--------------++-------+|SS7links|"STP"|IPnetwork|----|SEP+---++--------++---/\|or||*|ASPs||STP+---++--------++---\/+-------+||||----


13/116

+------------+SG2+--------------+|"STP"|+--------+

Figure1.ExamplewithmatedSGs

*Note:SG-to-SGcommunication(i.e.,"C-links")isrecommendedforcarriergradenetworks,usinganMTP3linksetoran


equivalent,toallowreroutingbetweentheSGsintheeventofroutefailures.WhereSGPsareused,inter-SGPcommunicationmightbeused.Inter-SGPprotocolisoutsideofthescopeofthisdocument.

Thefollowingexampleshowsasignallinggatewaypartitionedintotwonetworkappearances.

SG+-------++---------------+|SEP+--------------|SS7Ntwk.|M3UA|----+-------+SS7links|"A"||/\|__________|+-----------+ASPs||||\/+-------+|SS7Ntwk.||----|SEP+--------------+"B"||+-------++---------------+

Figure2.Examplewithmultiplenetwork

1.4.2.RoutingContextsandRoutingKeys

1.4.2.1.Overview

ThedistributionofSS7messagesbetweentheSGPandtheApplicationServersisdeterminedbytheRoutingKeysandtheirassociatedRoutingContexts.ARoutingKeyisessentiallyasetofSS7parametersusedtofilterSS7messages,whereastheRoutingContextparameterisa4-octetvalue(integer)thatisassociatedtothatRoutingKeyina1:1relationship.TheRoutingContextthereforecanbeviewedasanindexintoasendingnode'sMessageDistributionTablecontainingtheRoutingKeyentries.

PossibleSS7address/routinginformationthatcompriseaRoutingKey

entryincludes,forexample,theOPC,DPC,andSIOfoundintheMTP3routinglabel.SomeexampleRoutingKeysare:theDPCalone,theDPC/OPCcombination,ortheDPC/OPC/SIcombination.TheparticularinformationusedtodefineanM3UARoutingKeyisapplicationandnetworkdependent,andnoneoftheaboveexamplesaremandated.

AnApplicationServerProcessmaybeconfiguredtoprocesssignallingtrafficrelatedtomorethanoneApplicationServer,overasingleSCTPAssociation.InASPActiveandASPInactivemanagementmessages,thesignallingtraffictobestartedorstoppedis


14/116

discriminatedbytheRoutingContextparameter.AtanASP,theRoutingContextparameteruniquelyidentifiestherangeofsignallingtrafficassociatedwitheachApplicationServerthattheASPisconfiguredtoreceive.


1.4.2.2.RoutingKeyLimitations

RoutingKeysSHOULDbeuniqueinthesensethateachreceivedSS7signallingmessageSHOULDhaveafullorpartialmatchtoasingleroutingresult.AnexampleofapartialmatchwouldbeadefaultRoutingKeythatwouldbetheresultiftherearenootherRoutingKeystowhichthemessagebelongs.ItisnotnecessaryfortheparameterrangevalueswithinaparticularRoutingKeytobecontiguous.

1.4.2.3.ManagingRoutingContextsandRoutingKeys

TherearetwowaystoprovisionaRoutingKeyatanSGP.ARoutingKeymaybeconfiguredstaticallyusinganimplementationdependentmanagementinterface,ordynamicallyusingtheM3UARoutingKeyregistrationprocedure.

WhenusingamanagementinterfacetoconfigureRoutingKeys,themessagedistributionfunctionwithintheSGPisnotlimitedtothesetofparametersdefinedinthisdocument.Otherimplementation-dependentdistributionalgorithmsmaybeused.

1.4.2.4.MessageDistributionattheSGP

TodirectmessagesreceivedfromtheSS7MTP3networktothe

appropriateIPdestination,theSGPmustperformamessagedistributionfunctionusinginformationfromthereceivedMTP3-Usermessage.

Tosupportthismessagedistribution,theSGPmight,forexample,maintaintheequivalentofanetworkaddresstranslationtable,mappingincomingSS7messageinformationtoanApplicationServerforaparticularapplicationandrangeoftraffic.ThiscouldbeaccomplishedbycomparingelementsoftheincomingSS7messagetocurrentlydefinedRoutingKeysintheSGP.

TheseRoutingKeyscouldinturnmapdirectlytoanApplicationServerthatisenabledbyoneormoreASPs.TheseASPsprovide

dynamicstatusinformationregardingtheiravailability,traffic-handlingcapabilityandcongestiontotheSGPusingvariousmanagementmessagesdefinedintheM3UAprotocol.

ThelistofASPsinanASisassumedtobedynamic,takingintoaccounttheavailability,traffic-handlingcapability,andcongestionstatusoftheindividualASPsinthelist,aswellasconfigurationchangesandpossiblefailovermechanisms.


15/116


Normally,oneormoreASPsareactive(i.e.,currentlyprocessingtraffic)intheAS,butincertainfailureandtransitioncasesitispossiblethattheremaybenoactiveASPavailable.Broadcast,loadsharing,andbackupscenariosaresupported.

WhenthereisnomatchingRoutingKeyentryforanincomingSS7message,adefaulttreatmentMAYbespecified.PossiblesolutionsaretoprovideadefaultApplicationServerattheSGPthatdirectsallunallocatedtraffictoa(setof)defaultASPs,ortodropthemessageandprovideanotificationtolayermanagement.Thetreatmentofunallocatedtrafficisimplementationdependent.

1.4.2.5.MessageDistributionattheASP

TheASPmustchooseanSGPtodirectamessagetotheSS7network.ThisisaccomplishedbyobservingtheDestinationPointCode(and

possiblyotherelementsoftheoutgoingmessage,suchastheSLSvalue).TheASPmustalsotakeintoaccountwhethertherelatedRoutingContextisactiveornot(seeSection4.3.4.3).

ImplementationNote:Wheremorethanoneroute(orSGP)ispossibleforroutingtotheSS7network,theASPcould,forexample,maintainadynamictableofavailableSGProutesfortheSS7destinations,takingintoaccounttheSS7destinationavailability/restricted/congestionstatusreceivedfromtheSGP(s),theavailabilitystatusoftheindividualSGPs,andconfigurationchangesandfailovermechanisms.Thereis,however,noM3UAmessagingtomanagethestatusofanSGP(e.g.,SGP-Up/Down/Active/Inactivemessaging).

WheneveranSCTPassociationtoanSGPexists,theSGPisassumedtobereadyforthepurposesofrespondingtoM3UAASPSMmessages(refertoSection3).

1.4.3.SS7andM3UAInterworking

InthecaseofSS7andM3UAinterworking,theM3UAadaptationlayerisdesignedtoprovideanextensionoftheMTP3-defineduserprimitives.

1.4.3.1.SignallingGatewaySS7Layers

TheSGisresponsibleforterminatingMTPLevel3oftheSS7protocol,andofferinganIP-basedextensiontoitsusers.



16/116


FromanSS7perspective,itisexpectedthattheSignallingGatewaytransmitsandreceivesSS7MessageSignallingUnits(MSUs)overastandardSS7networkinterface,usingtheSS7MessageTransferPart(MTP)[7,8,9].

AsastandardSS7networkinterface,theuseofMTPLevel2signallinglinksisnottheonlypossibility.ATM-basedHighSpeedLinkscanalsobeusedwiththeservicesoftheSignallingATMAdaptationLayer(SAAL)[19,20].

Note:ItisalsopossibleforIP-basedinterfacestobepresent,usingtheservicesoftheMTP2-UserAdaptationLayer(M2UA)[24]orM2PA[25].

ThesecouldbeterminatedataSignallingTransferPoint(STP)orSignallingEndPoint(SEP).UsingtheservicesofMTP3,theSGcouldbecapableofcommunicatingwithremoteSS7SEPsinaquasi-associatedfashion,whereSTPsmaybepresentintheSS7pathbetweentheSEPandtheSG.

1.4.3.2.SS7andM3UAInterworkingattheSG

TheSGPprovidesafunctionalinterworkingoftransportfunctionsbetweentheSS7networkandtheIPnetworkbyalsosupportingtheM3UAadaptationlayer.ItallowsthetransferofMTP3-UsersignallingmessagestoandfromanIP-basedApplicationServerProcesswherethepeerMTP3-Userprotocollayerexists.

ForSS7userpartmanagement,itisrequiredthattheMTP3-UserprotocolsatASPsreceiveindicationsofSS7signallingpointavailability,SS7networkcongestion,andremoteUserPartunavailability,aswouldbeexpectedinanSS7SEPnode.Toaccomplishthis,theMTP-PAUSE,MTP-RESUME,andMTP-STATUSindication

primitivesreceivedattheMTP3upperlayerinterfaceattheSGneedtobepropagatedtotheremoteMTP3-UserlowerlayerinterfaceattheASP.

MTP3managementmessages(suchasTFPsorTFAsreceivedfromtheSS7network)MUSTNOTbeencapsulatedasDatamessagePayloadDataandsenteitherfromSGtoASPorfromASPtoSG.TheSGMUSTterminatethesemessagesandgenerateM3UAmessages,asappropriate.

1.4.3.3.ApplicationServer

AclusterofapplicationserversisresponsibleforprovidingtheoverallsupportforoneormoreSS7upperlayers.FromanSS7

standpoint,aSignallingPointManagementCluster(SPMC)providescompletesupportfortheupperlayerserviceforagivenpointcode.



17/116

Asanexample,anSPMCprovidingMGCcapabilitiescouldprovidecompletesupportforISUP(andanyotherMTP3userlocatedatthepointcodeoftheSPMC)foragivenpointcode.

InthecasewhereanASPisconnectedtomorethanoneSGP,theM3UAlayermustmaintainthestatusofconfiguredSS7destinationsandroutemessagesaccordingtotheavailability/congestion/restrictedstatusoftheroutestotheseSS7destinations.

1.4.3.4.IPSPConsiderations

SinceIPSPsuseM3UAinapoint-to-pointfashion,thereisnoconceptofroutingofmessagesbeyondtheremoteend.Therefore,SS7andM3UAinterworkingisnotnecessaryforthismodel.

1.4.4.RedundancyModels

1.4.4.1ApplicationServerRedundancy

AllMTP3-Usermessages(e.g.,ISUP,SCCP)thatmatchaprovisionedRoutingKeyatanSGParemappedtoanApplicationServer.

TheApplicationServeristhesetofallASPsassociatedwithaspecificRoutingKey.EachASPinthissetmaybeactive,inactive,

orunavailable.ActiveASPshandletraffic;inactiveASPsmightbeusedwhenactiveASPsbecomeunavailable.

Thefailovermodelsupportsan"n+k"redundancymodel,where"n"ASPsistheminimumnumberofredundantASPsrequiredtohandletrafficand"k"ASPsareavailabletotakeoverforafailedorunavailableASP.TrafficSHOULDbesentafter"n"ASPsareactive."k"ASPsMAYbeeitheractiveatthesametimeas"n"orkeptinactiveuntilneededduetoafailedorunavailableASP.

A"1+1"active/backupredundancyisasubsetofthismodel.Asimplex"1+0"modelisalsosupportedasasubset,withnoASPredundancy.

1.4.5.FlowControl

LocalManagementatanASPmaywishtostoptrafficacrossanSCTPassociationtotemporarilyremovetheassociationfromserviceortoperformtestingandmaintenanceactivity.ThefunctioncouldoptionallybeusedtocontrolthestartoftrafficontoanewlyavailableSCTPassociation.


1.4.6.CongestionManagement

TheM3UAlayerisinformedoflocalandIPnetworkcongestionbymeansofanimplementation-dependentfunction(e.g.,an


18/116

implementation-dependentindicationfromtheSCTPofIPnetworkcongestion).

AtanASPorIPSP,theM3UAlayerindicatesIPnetworkcongestiontolocalMTP3-UsersbymeansofanMTP-STATUSprimitive,aspercurrentMTP3procedures,toinvokeappropriateupper-layerresponses.

WhenanSGdeterminesthatthetransportofSS7messagestoaSignallingPointManagementCluster(SPMC)isencounteringIPnetworkcongestion,theSGMAYtriggerSS7MTP3TransferControlledmanagementmessagestooriginatingSS7nodes,perthecongestionproceduresoftherelevantMTP3standard.ThetriggeringofSS7MTP3ManagementmessagesfromanSGisanimplementation-dependentfunction.

TheM3UAlayeratanASPorIPSPMAYindicatelocalcongestiontoanM3UApeerwithanSCONmessage.WhenanSGreceivesacongestionmessage(SCON)fromanASPandtheSGdeterminesthatanSPMCisnowencounteringcongestion,itMAYtriggerSS7MTP3TransferControlledmanagementmessagestoconcernedSS7destinationsaccordingtocongestionproceduresoftherelevantMTP3standard.

1.4.7.SCTPStreamMapping

TheM3UAlayeratboththeSGPandASPalsosupportstheassignmentofsignallingtrafficintostreamswithinanSCTPassociation.TrafficthatrequiressequencingSHOULDbeassignedtothesamestream.Toaccomplishthis,MTP3-Usertrafficmaybeassignedtoindividualstreamsbasedon,forexample,theSLSvalueintheMTP3RoutingLabel,subjectofcoursetothemaximumnumberofstreamssupportedbytheunderlyingSCTPassociation.

Thefollowingrulesapply(seeSection3.1.2):

1.TheDATAmessageMUSTNOTbesentonstream0.2.TheASPSM,MGMT,RKMclassesSHOULDbesentonstream0(otherthanBEAT,BEATACKandNTFYmessages).

3.TheSSNM,ASPTMclassesandBEAT,BEATACKandNTFYmessagescanbesentonanystream.

1.4.8.SCTPClient/ServerModel

ItisrecommendedthattheSGPandASPbeabletosupportbothclientandserveroperation.ThepeerendpointsusingM3UASHOULDbe


configuredsothatonealwaystakesontheroleofclientandtheothertheroleofserverforinitiatingSCTPassociations.ThedefaultorientationwouldbefortheSGPtotakeontheroleofserverwhiletheASPistheclient.Inthiscase,ASPsSHOULDinitiatetheSCTPassociationtotheSGP.

InthecaseofIPSPtoIPSPcommunication,thepeerendpointsusingM3UASHOULDbeconfiguredsothatonealwaystakesontheroleof


19/116

clientandtheothertheroleofserverforinitiatingSCTPassociations.

TheSCTPandTCPRegisteredUserPortNumberAssignmentforM3UAis2905.

1.5.SampleConfiguration

1.5.1.Example1:ISUPMessageTransport

********SS7*****************IP*********SEP*---------*SGP*--------*ASP**********************************

+------++---------------++------+|ISUP||(NIF)||ISUP|+------++------++------++------+|MTP3||MTP3||M3UA||M3UA|+------|+------+-+------++------+|MTP2||MTP2||SCTP||SCTP|+------++------++------++------+|L1||L1||IP||IP|+------++------++------++------+|_______________||______________|

SEP-SS7SignallingEndPointSCTP-StreamControlTransmissionProtocolNIF-NodalInterworkingFunction

Inthisexample,theSGPprovidesanimplementation-dependentnodalinterworkingfunction(NIF)thatallowstheMGCtoexchangeSS7signallingmessageswiththeSS7-basedSEP.TheNIFwithintheSGPservesastheinterfacewithintheSGPbetweentheMTP3andM3UA.ThisnodalinterworkingfunctionhasnovisiblepeerprotocolwitheithertheMGCorSEP.Italsoprovidesnetworkstatusinformationtooneorbothsidesofthenetwork.

ForinternalSGPmodelingpurposes,attheNIFlevel,SS7signallingmessagesthataredestinedtotheMGCarereceivedasMTP-TRANSFERindicationprimitivesfromtheMTPLevel3upperlayerinterface,


translatedtoMTP-TRANSFERrequestprimitives,andsenttothelocalM3UA-residentmessagedistributionfunctionforongoingroutingto

thefinalIPdestination.MessagesreceivedfromthelocalM3UAnetworkaddresstranslationandmappingfunctionasMTP-TRANSFERindicationprimitivesaresenttotheMTPLevel3upper-layerinterfaceasMTP-TRANSFERrequestprimitivesforongoingMTPLevel3routingtoanSS7SEP.ForthepurposesofprovidingSS7networkstatusinformation,theNIFalsodeliversMTP-PAUSE,MTP-RESUME,andMTP-STATUSindicationprimitivesreceivedfromtheMTPLevel3upper-layerinterfacetothelocalM3UA-residentmanagementfunction.Inaddition,asanimplementationandnetworkoption,restricteddestinationsarecommunicatedfromMTPnetworkmanagementtothe


20/116

localM3UA-residentmanagementfunction.

1.5.2.Example2:SCCPTransportbetweenIPSPs

********IP*********IPSP**IPSP*****************

+------++------+|SCCP-||SCCP-||User||User|+------++------+|SCCP||SCCP|+------++------+|M3UA||M3UA|+------++------+|SCTP||SCTP|+------++------+|IP||IP|+------++------+|________________|

ThisexampleshowsanarchitecturewherenoSignallingGatewayisused.Inthisexample,SCCPmessagesareexchangeddirectlybetween

twoIP-residentIPSPswithresidentSCCP-Userprotocolinstances,suchasRANAPorTCAP.SS7networkinterworkingisnotrequired;therefore,thereisnoMTP3networkmanagementstatusinformationfortheSCCPandSCCP-Userprotocolstoconsider.AnyMTP-PAUSE,MTP-RESUME,orMTP-STATUSindicationsfromtheM3UAlayertotheSCCPlayershouldconsiderthestatusoftheSCTPAssociationandunderlyingIPnetworkandanycongestioninformationreceivedfromtheremotesite.


1.5.3.Example3:SGPResidentSCCPLayer,withRemoteASP

********SS7*****************IP*********SEP*---------**--------***or**SGP**ASP**STP*****

*********************************

+------++---------------++------+|SCCP-||SCCP||SCCP-||User|+---------------+|User|+------+|_____|+------+|SCCP||||||SCCP|+------++------+-+------++------+|MTP3||MTP3||M3UA||M3UA|+------|+------++------++------+


21/116

|MTP2||MTP2||SCTP||SCTP|+------++------++------++------+|L1||L1||IP||IP|+------++------++------++------+|_______________||______________|

STP-SS7SignallingTransferPoint

Inthisexample,theSGPcontainsaninstanceoftheSS7SCCPprotocollayerthatmay,forexample,performtheSCCPGlobalTitleTranslation(GTT)functionformessageslogicallyaddressedtotheSGSCCP.IftheresultofaGTTforanSCCPmessageyieldsanSS7DPCorDPC/SSNaddressofanSCCPpeerlocatedintheIPdomain,theresultingMTP-TRANSFERrequestprimitiveissenttothelocalM3UA-residentnetworkaddresstranslationandmappingfunctionforongoingroutingtothefinalIPdestination.

Similarly,theSCCPinstanceinanSGPcanperformtheSCCPGTTserviceformessageslogicallyaddressedtoitfromSCCPpeersintheIPdomain.Inthiscase,MTP-TRANSFERindicationprimitivesaresentfromthelocalM3UA-residentnetworkaddresstranslationandmappingfunctiontotheSCCPforGTT.IftheresultoftheGTTyieldstheaddressofanSCCPpeerintheSS7network,thentheresultingMTP-TRANSFERrequestprimitiveisgiventotheMTP3fordeliverytoan

SS7-residentnode.

ItispossiblethattheaboveSCCPGTTattheSGPcouldyieldtheaddressofanSCCPpeerintheIPdomain,andthattheresultingMTP-TRANSFERrequestprimitivewouldbesentbacktotheM3UAlayerfordeliverytoanIPdestination.



ForinternalSGPmodelingpurposes,thismaybeaccomplishedwiththeuseofanimplementation-dependentnodalinterworkingfunctionwithintheSGPthateffectivelysitsbelowtheSCCPandroutesMTP-TRANSFERrequest/indicationmessagesto/fromboththeMTP3andtheM3UAlayer,basedontheSS7DPCorDPC/SIaddressinformation.ThisnodalinterworkingfunctionhasnovisiblepeerprotocolwitheithertheASPorSEP.

NotethattheservicesandinterfaceprovidedbytheM3UAlayerarethesameasinExample1andthatthefunctionstakingplaceinthe

SCCPentityaretransparenttotheM3UAlayer.TheSCCPprotocolfunctionsarenotreproducedintheM3UAprotocol.

1.6.DefinitionofM3UABoundaries

ThissectionprovidesadefinitionoftheboundariesoftheM3UAprotocol.TheyconsistofSCTP,LayerManagement,andtheMTP3-User.

+-----------+|MTP3-User|


22/116

+-----------+||+-----------++------------+|M3UA|-----|LayerMgmt|+-----------++------------+||+-----------+|SCTP|+-----------+

1.6.1.DefinitionoftheBoundarybetweenM3UAandanMTP3-User

FromITUQ.701[7]:

MTP-TRANSFERrequestMTP-TRANSFERindicationMTP-PAUSEindicationMTP-RESUMEindicationMTP-STATUSindication

1.6.2.DefinitionoftheBoundarybetweenM3UAandSCTP

Anexampleoftheupper-layerprimitivesprovidedbytheSCTPareprovidedinReference[18],Section10.


1.6.3.DefinitionoftheBoundarybetweenM3UAandLayerManagement

M-SCTP_ESTABLISHrequestDirection:LM->M3UAPurpose:LMrequeststhatASPestablishanSCTPassociationwithitspeer.

M-SCTP_ESTABLISHconfirmDirection:M3UA->LMPurpose:ASPconfirmstoLMthatithasestablishedanSCTPassociationwithitspeer.

M-SCTP_ESTABLISHindicationDirection:M3UA->LM

Purpose:M3UAinformsLMthataremoteASPhasestablishedanSCTPassociation.

M-SCTP_RELEASErequestDirection:LM->M3UAPurpose:LMrequeststhatASPreleaseanSCTPassociationwithitspeer.

M-SCTP_RELEASEconfirmDirection:M3UA->LM


23/116

Purpose:ASPconfirmstoLMthatithasreleasedSCTPassociationwithitspeer.

M-SCTP_RELEASEindicationDirection:M3UA->LMPurpose:M3UAinformsLMthataremoteASPhasreleasedanSCTPAssociationorthattheSCTPassociationhasfailed.

M-SCTP_RESTARTindicationDirection:M3UA->LMPurpose:M3UAinformsLMthatanSCTPrestartindicationhasbeenreceived.

M-SCTP_STATUSrequestDirection:LM->M3UAPurpose:LMrequeststhatM3UAreportthestatusofanSCTPassociation.

M-SCTP_STATUSconfirmDirection:M3UA->LMPurpose:M3UArespondswiththestatusofanSCTPassociation.


M-SCTPSTATUSindicationDirection:M3UA->LMPurpose:M3UAreportsthestatusofanSCTPassociation.

M-ASP_STATUSrequest

Direction:LM->M3UAPurpose:LMrequeststhatM3UAreportthestatusofalocalorremoteASP.

M-ASP_STATUSconfirmDirection:M3UA->LMPurpose:M3UAreportsthestatusoflocalorremoteASP.

M-AS_STATUSrequestDirection:LM->M3UAPurpose:LMrequeststhatM3UAreportthestatusofanAS.

M-AS_STATUSconfirm

Direction:M3UA->LMPurpose:M3UAreportsthestatusofanAS.

M-NOTIFYindicationDirection:M3UA->LMPurpose:M3UAreportsthatithasreceivedaNotifymessagefromitspeer.

M-ERRORindicationDirection:M3UA->LM


24/116

Purpose:M3UAreportsthatithasreceivedanErrormessagefromitspeerorthatalocaloperationhasbeenunsuccessful.

M-ASP_UPrequestDirection:LM->M3UAPurpose:LMrequeststhatASPstartitsoperationandsendanASPUpmessagetoitspeer.

M-ASP_UPconfirmDirection:M3UA->LMPurpose:ASPreportsthatithasreceivedanASPUPAckmessagefromitspeer.

M-ASP_UPindicationDirection:M3UA->LMPurpose:M3UAreportsthatithassuccessfullyprocessedanincomingASPUpmessagefromitspeer.



M-ASP_DOWNrequestDirection:LM->M3UAPurpose:LMrequeststhatASPstopitsoperationandsendanASPDownmessagetoitspeer.

M-ASP_DOWNconfirmDirection:M3UA->LMPurpose:ASPreportsthatithasreceivedanASPDownAckmessagefromitspeer.

M-ASP_DOWNindicationDirection:M3UA->LMPurpose:M3UAreportsthatithassuccessfullyprocessedanincomingASPDownmessagefromitspeer,ortheSCTPassociationhasbeenlost/reset.

M-ASP_ACTIVErequestDirection:LM->M3UAPurpose:LMrequeststhatASPsendanASPActivemessagetoitspeer.

M-ASP_ACTIVEconfirmDirection:M3UA->LM

Purpose:ASPreportsthatithasreceivedanASPActiveAckmessagefromitspeer.

M-ASP_ACTIVEindicationDirection:M3UA->LMPurpose:M3UAreportsthatithassuccessfullyprocessedanincomingASPActivemessagefromitspeer.

M-ASP_INACTIVErequestDirection:LM->M3UA


25/116

Purpose:LMrequeststhatASPsendanASPInactivemessagetoitspeer.

M-ASP_INACTIVEconfirmDirection:LM->M3UAPurpose:ASPreportsthatithasreceivedanASPInactiveAckmessagefromitspeer.

M-ASP_INACTIVEindicationDirection:M3UA->LMPurpose:M3UAreportsthatithassuccessfullyprocessedanincomingASPInactivemessagefromitspeer.

M-AS_ACTIVEindicationDirection:M3UA->LMPurpose:M3UAreportsthatanAShasmovedtotheAS-ACTIVEstate.


M-AS_INACTIVEindicationDirection:M3UA->LMPurpose:M3UAreportsthatanAShasmovedtotheAS-INACTIVEstate.

M-AS_DOWNindicationDirection:M3UA->LMPurpose:M3UAreportsthatanAShasmovedtotheAS-DOWNstate.

IfdynamicregistrationofRKissupportedbytheM3UAlayer,thelayerMAYsupportthefollowingadditionalprimitives:

M-RK_REGrequestDirection:LM->M3UA

Purpose:LMrequeststhatASPregisterRK(s)withitspeerbysendinganREGREQmessage

M-RK_REGconfirmDirection:M3UA->LMPurpose:ASPreportsthatithasreceivedREGRSPmessagewitharegistrationstatusofsuccessfulfromitspeer.

M-RK_REGindicationDirection:M3UA->LMPurpose:M3UAinformsLMthatithassuccessfullyprocessedanincomingREGREQmessage.

M-RK_DEREGrequestDirection:LM->M3UAPurpose:LMrequeststhatASPderegisterRK(s)withitspeerbysendingaDEREGREQmessage.

M-RK_DEREGconfirmDirection:M3UA->LMPurpose:ASPreportsthatithasreceivedDEREGREQmessagewithaderegistrationstatusofsuccessfulfromitspeer.


26/116

M-RK_DEREGindicationDirection:M3UA->LMPurpose:M3UAinformsLMthatithassuccessfullyprocessedanincomingDEREGREQfromitspeer.

2.Conventions

Inthisdocument,thekeywordsMUST,MUSTNOT,REQUIRED,SHALL,SHALLNOT,SHOULD,SHOULDNOT,RECOMMENDED,NOTRECOMMENDED,MAY,andOPTIONALaretobeinterpretedasdescribedin[21].


3.M3UAProtocolElements

ThegeneralM3UAmessageformatincludesaCommonMessageHeaderfollowedbyzeroormoreparametersasdefinedbytheMessageType.

Forforwardcompatibility,allMessageTypesmayhaveattachedparametersevenifnonearespecifiedinthisversion.

3.1.CommonMessageHeader

TheprotocolmessagesforMTP3-UserAdaptationrequireamessageheaderthatcontainstheadaptationlayerversion,themessagetype,andmessagelength.

012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Version|Reserved|MessageClass|MessageType|

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|MessageLength|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\//

AllfieldsinanM3UAmessageMUSTbetransmittedinnetworkbyteorder,unlessotherwisestated.

3.1.1.M3UAProtocolVersion:8bits(unsignedinteger)

TheversionfieldcontainstheversionoftheM3UAadaptationlayer.

Thesupportedversionsareasfollows:

1Release1.0

3.1.2.MessageClassesandTypes

ThefollowinglistcontainsthevalidMessageClasses:

MessageClass:8bits(unsignedinteger)


27/116

ThefollowinglistcontainsthevalidMessageTypeClasses:

0Management(MGMT)Messages1TransferMessages2SS7SignallingNetworkManagement(SSNM)Messages3ASPStateMaintenance(ASPSM)Messages4ASPTrafficMaintenance(ASPTM)Messages5ReservedforOtherSIGTRANAdaptationLayers


6ReservedforOtherSIGTRANAdaptationLayers7ReservedforOtherSIGTRANAdaptationLayers8ReservedforOtherSIGTRANAdaptationLayers9RoutingKeyManagement(RKM)Messages10to127ReservedbytheIETF128to255ReservedforIETF-DefinedMessageClassextensions

MessageType:8bits(unsignedinteger)

Thefollowinglistcontainsthemessagetypesforthedefinedmessages.

Management(MGMT)Messages(seeSection3.8)

0Error(ERR)1Notify(NTFY)2to127ReservedbytheIETF128to255ReservedforIETF-DefinedMGMTextensions

TransferMessages(seeSection3.3)

0Reserved1PayloadData(DATA)2to127ReservedbytheIETF128to255ReservedforIETF-DefinedTransferextensions

SS7SignallingNetworkManagement(SSNM)Messages(seeSection3.4)

0Reserved1DestinationUnavailable(DUNA)2DestinationAvailable(DAVA)3DestinationStateAudit(DAUD)4SignallingCongestion(SCON)

5DestinationUserPartUnavailable(DUPU)6DestinationRestricted(DRST)7to127ReservedbytheIETF128to255ReservedforIETF-DefinedSSNMextensions

ASPStateMaintenance(ASPSM)Messages(seeSection3.5)

0Reserved1ASPUp(ASPUP)2ASPDown(ASPDN)


28/116

3Heartbeat(BEAT)4ASPUpAcknowledgement(ASPUPACK)5ASPDownAcknowledgement(ASPDNACK)6HeartbeatAcknowledgement(BEATACK)


7to127ReservedbytheIETF128to255ReservedforIETF-DefinedASPSMextensions

ASPTrafficMaintenance(ASPTM)Messages(seeSection3.7)

0Reserved1ASPActive(ASPAC)2ASPInactive(ASPIA)3ASPActiveAcknowledgement(ASPACACK)4ASPInactiveAcknowledgement(ASPIAACK)5to127ReservedbytheIETF128to255ReservedforIETF-DefinedASPTMextensions

RoutingKeyManagement(RKM)Messages(seeSection3.6)

0Reserved1RegistrationRequest(REGREQ)2RegistrationResponse(REGRSP)3DeregistrationRequest(DEREGREQ)4DeregistrationResponse(DEREGRSP)5to127ReservedbytheIETF128to255ReservedforIETF-DefinedRKMextensions

3.1.3.Reserved:8Bits

TheReservedfieldSHOULDbesettoall'0'sandignoredbythereceiver.

3.1.4.MessageLength:32-Bits(UnsignedInteger)

TheMessageLengthdefinesthelengthofthemessageinoctets,includingtheCommonHeader.TheMessageLengthMUSTincludeparameterpaddingoctets,ifthereareany.

Note:AreceiverSHOULDacceptthemessagewhetherornotthefinalparameterpaddingisincludedinthemessagelength.

3.2.Variable-LengthParameterFormat

M3UAmessagesconsistofaCommonHeaderfollowedbyzeroormorevariable-lengthparameters,asdefinedbythemessagetype.AlltheparameterscontainedinamessagearedefinedinaTagLength-Valueformat,asshownbelow.


29/116


012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|ParameterTag|ParameterLength|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/ParameterValue/\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Wheremorethanoneparameterisincludedinamessage,theparametersmaybeinanyorder,exceptwhereexplicitlymandated.AreceiverSHOULDaccepttheparametersinanyorder.

Unlessexplicitlystatedorshowninamessageformatdiagram,onlyoneparameterofthesametypeisallowedinamessage.

ParameterTag:16bits(unsignedinteger)

TheTagfieldisa16-bitidentifierofthetypeofparameter.Ittakesavalueof0to65534.Commonparametersusedbyadaptationlayersareintherangeof0x00to0x3f.M3UA-specificparametershaveTagsintherange0x0200to0x02ff.TheparameterTagsdefinedareasfollows:

CommonParameters.TheseTLVparametersarecommonacrossthedifferentadaptationlayers:

ParameterNameParameterID

==========================Reserved0x0000NotUsedinM3UA0x0001NotUsedinM3UA0x0002NotUsedinM3UA0x0003INFOString0x0004NotUsedinM3UA0x0005RoutingContext0x0006DiagnosticInformation0x0007NotUsedinM3UA0x0008HeartbeatData0x0009NotUsedinM3UA0x000aTrafficModeType0x000b

ErrorCode0x000cStatus0x000dNotUsedinM3UA0x000eNotUsedinM3UA0x000fNotUsedinM3UA0x0010ASPIdentifier0x0011



30/116


AffectedPointCode0x0012CorrelationID0x0013

M3UA-Specificparameters.TheseTLVparametersarespecifictotheM3UAprotocol:

NetworkAppearance0x0200Reserved0x0201Reserved0x0202Reserved0x0203User/Cause0x0204CongestionIndications0x0205ConcernedDestination0x0206RoutingKey0x0207RegistrationResult0x0208DeregistrationResult0x0209LocalRoutingKeyIdentifier0x020aDestinationPointCode0x020bServiceIndicators0x020cReserved0x020d

OriginatingPointCodeList0x020eReserved0x020fProtocolData0x0210Reserved0x0211RegistrationStatus0x0212DeregistrationStatus0x0213ReservedbytheIETF0x0214to0xffff

Thevalueof65535isreservedforIETF-definedextensions.ValuesotherthanthosedefinedinspecificparameterdescriptionsarereservedforusebytheIETF.AnRFCisrequiredtomakeuseofparametervalues"ReservedbytheIETF".

ParameterLength:16bits(unsignedinteger)

TheParameterLengthfieldcontainsthesizeoftheparameterinoctets,includingtheParameterTag,ParameterLength,andParameterValuefields.Thus,aparameterwithazero-lengthParameterValuefieldwouldhaveaLengthfieldof4.TheParameterLengthdoesnotincludeanypaddingoctets.Iftheparametercontainssubparameters,theParameterLengthfieldwillincludealltheoctetsofeachsubparameter,includingsubparameterpaddingoctets(ifthereareany).

ParameterValue:variablelength

TheParameterValuefieldcontainstheactualinformationtobetransferredintheparameter.



31/116

Thetotallengthofaparameter(includingTag,ParameterLength,andValuefields)MUSTbeamultipleof4octets.Ifthelengthoftheparameterisnotamultipleof4octets,thesenderpadstheParameterattheend(i.e.,aftertheParameterValuefield)withallzerooctets.ThelengthofthepaddingisNOTincludedintheparameterlengthfield.AsenderMUSTNOTpadwithmorethan3octets.ThereceiverMUSTignorethepaddingoctets.

3.3.TransferMessages

ThefollowingsectiondescribestheTransfermessagesandparametercontents.

3.3.1.PayloadDataMessage(DATA)

TheDATAmessagecontainstheSS7MTP3-Userprotocoldata,whichisanMTP-TRANSFERprimitive,includingthecompleteMTP3RoutingLabel.TheDATAmessagecontainsthefollowingvariable-lengthparameters:

NetworkAppearanceOptionalRoutingContextConditionalProtocolDataMandatoryCorrelationIdOptional

ThefollowingformatMUSTbeusedfortheDataMessage:

012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0200|Length=8|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|NetworkAppearance|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0006|Length=8|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|RoutingContext|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

|Tag=0x0210|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/ProtocolData/\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0013|Length=8|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|CorrelationId|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


NetworkAppearance:32bits(unsignedinteger)

TheNetworkAppearanceparameteridentifiestheSS7networkcontextforthemessageandimplicitlyidentifiestheSS7Point


32/116

Codeformatused,theSS7NetworkIndicatorvalue,andtheMTP3andpossiblytheMTP3-Userprotocoltype/variant/versionusedwithinthespecificSS7network.WhereanSGoperatesinthecontextofasingleSS7network,orifindividualSCTPassociationsarededicatedtoeachSS7networkcontext,theNetworkAppearanceparameterisnotrequired.Inothercases,theparametermaybeconfiguredtobepresentfortheuseofthereceiver.

TheNetworkAppearanceparametervalueisoflocalsignificanceonly,coordinatedbetweentheSGPandASP.Therefore,inthecasewhereanASPisconnectedtomorethanoneSGP,thesameSS7networkcontextmaybeidentifiedbydifferentNetworkAppearancevalues,dependingonwhichSGPamessageisbeingtransmitted/received.

WheretheoptionalNetworkAppearanceparameterispresent,itMUSTbethefirstparameterinthemessage,asitdefinestheformatoftheProtocolDatafield.

IMPLEMENTATIONNOTE:Forsimplicityofconfiguration,itmaybedesirabletousethesameNAvalueacrossallnodessharingaparticularnetworkcontext.

RoutingContext:32bits(unsignedinteger)

TheRoutingContextparametercontainstheRoutingContextvalueassociatedwiththeDATAmessage.WhereaRoutingKeyhasnotbeencoordinatedbetweentheSGPandASP,sendingofRoutingContextisnotrequired.WheremultipleRoutingKeysandRoutingContextsareusedacrossacommonassociation,theRoutingContextMUSTbesenttoidentifythetrafficflow,assistingintheinternaldistributionofDatamessages.

ProtocolData:variablelength

TheProtocolDataparametercontainstheoriginalSS7MTP3

message,includingtheServiceInformationOctetandRoutingLabel.


TheProtocolDataparametercontainsthefollowingfields:

ServiceIndicatorNetworkIndicatorMessagePriority

DestinationPointCodeOriginatingPointCode


33/116

SignallingLinkSelectionCode(SLS)

UserProtocolData,whichincludes

MTP3-Userprotocolelements(e.g.,ISUP,SCCP,orTUPparameters)

TheProtocolDataparameterisencodedasfollows:

012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|OriginatingPointCode|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|DestinationPointCode|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|SI|NI|MP|SLS|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/UserProtocolData/\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

OriginatingPointCode:32bits(unsignedinteger)

DestinationPointCode:32bits(unsignedinteger)

TheOriginatingandDestinationPointCodefieldscontainstheOPCandDPCfromtheroutinglabeloftheoriginalSS7messageinNetworkByteOrder,justifiedtotheleastsignificantbit.Unusedbitsarecoded`0'.

ServiceIndicator:8bits(unsignedinteger)

TheServiceIndicatorfieldcontainstheSIfieldfromtheoriginalSS7messagejustifiedtotheleastsignificantbit.Unusedbitsare

coded`0'.


NetworkIndicator:8bits(unsignedinteger)

TheNetworkIndicatorcontainstheNIfieldfromtheoriginalSS7messagejustifiedtotheleastsignificantbit.Unusedbitsarecoded`0'.

MessagePriority:8bits(unsignedinteger)

TheMessagePriorityfieldcontainstheMPbits(ifany)fromtheoriginalSS7message,bothforANSI-styleandTTC-style[26]messageprioritybits.TheMPbitsarealignedtotheleastsignificantbit.Unusedbitsarecoded`0'.


34/116

SignallingLinkSelection:8bits(unsignedinteger)

TheSignallingLinkSelectionfieldcontainstheSLSbitsfromtheroutinglabeloftheoriginalSS7messagejustifiedtotheleastsignificantbitandinNetworkByteOrder.Unusedbitsarecoded`0'.

UserProtocolData:variable-lengthoctetstring

TheUserProtocolDatafieldcontainsanoctetstringofMTP-UserinformationfromtheoriginalSS7message,startingwiththefirstoctetoftheoriginalSS7messagefollowingtheRoutingLabel[7][8][26].

CorrelationId:32bits(unsignedinteger)

TheCorrelationIdparameteruniquelyidentifiestheMSUcarriedintheProtocolDatawithinanAS.ThisCorrelationIdparameterisassignedbythesendingM3UA.

3.4.SS7SignallingNetworkManagement(SSNM)Messages

3.4.1.DestinationUnavailable(DUNA)

TheDUNAmessageissentfromanSGPinanSGtoallconcernedASPstoindicatethattheSGhasdeterminedthatoneormoreSS7destinationsareunreachable.ItisalsosentbyanSGPinresponsetoamessagefromtheASPtoanunreachableSS7destination.Asanimplementationoption,theSGmaysuppressthesendingofsubsequent"response"DUNAmessagesregardingacertainunreachableSS7destinationforacertainperiodtogivetheremotesidetimetoreact.IfthereisnoalternaterouteviaanotherSG,theMTP3-UserattheASPisexpectedtostoptraffictotheaffecteddestinationviatheSGasperthedefinedMTP3-Userprocedures.


TheDUNAmessagecontainsthefollowingparameters:

NetworkAppearanceOptionalRoutingContextConditionalAffectedPointCodeMandatoryINFOStringOptional

TheformatforDUNAMessageparametersisasfollows:

012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0200|Length=8|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|NetworkAppearance|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


35/116

|Tag=0x0006|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/RoutingContext/\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0012|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Mask|AffectedPC1|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/.../\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Mask|AffectedPCn|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0004|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/INFOString/\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

NetworkAppearance:32-bitunsignedinteger

ThedescriptionofNetworkAppearanceinSection3.3.1applies,withtheexceptionthatNetworkAppearancedoesnothavetobethefirstparameterinthismessage.



RoutingContext:nx32bits(unsignedinteger)

TheconditionalRoutingContextparametercontainstheRoutingContextvaluesassociatedwiththeDUNAmessage.WhereaRoutingKeyhasnotbeencoordinatedbetweentheSGPandASP,sendingofRoutingContextisnotrequired.WheremultipleRoutingKeysandRoutingContextsareusedacrossacommonassociation,theRoutingContext(s)MUSTbesenttoidentifytheconcernedtrafficflowsforwhichtheDUNAmessageapplies,assistinginoutgoingtrafficmanagementandinternaldistributionofMTP-PAUSEindicationsto

MTP3-Usersatthereceiver.

AffectedPointCode:nx32bits

TheAffectedPointCodeparametercontainsalistofAffectedDestinationPointCodefields,eachathree-octetparametertoallowfor14-,16-,and24-bitbinaryformattedSS7PointCodes.AffectedPointCodesthatarelessthan24bitsarepaddedonthelefttothe24-bitboundary.TheencodingisshownbelowforANSIandITUPointCodeexamples.


36/116

ANSI24-bitPointCode

012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Mask|Network|Cluster|Member|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

|MSB-----------------------------------------LSB|

ITU14-bitPointCode

012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Mask|0000000000|Zone|Region|SP|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

|MSB--------------------LSB|

ItisoptionaltosendanAffectedPointCodeparameterwithmorethanoneAffectedPC,butitismandatorytoreceiveit.IncludingmultipleAffectedPCsmaybeusefulwhenreceiptofan

MTP3managementmessageoralinkseteventsimultaneouslyaffectstheavailabilitystatusofalistofdestinationsatanSG.


Mask:8bits(unsignedinteger)

TheMaskfieldcanbeusedtoidentifyacontiguousrangeofAffectedDestinationPointCodes.IdentifyingacontiguousrangeofAffectedDPCsmaybeusefulwhenreceiptofanMTP3managementmessageoralinkseteventsimultaneouslyaffectstheavailabilitystatusofaseriesofdestinationsatanSG.

TheMaskparameterisanintegerrepresentingabitmaskthatcanbeappliedtotherelatedAffectedPCfield.ThebitmaskidentifieshowmanybitsoftheAffectedPCfieldaresignificantandwhichareeffectively"wildcarded".Forexample,amaskof"8"indicatesthatthelasteightbitsofthePCare"wildcarded".ForanANSI24-bitAffectedPC,thisisequivalenttosignalling

thatallPCsinanANSIClusterareunavailable.Amaskof"3"indicatesthatthelastthreebitsofthePCare"wildcarded".Fora14-bitITUAffectedPC,thisisequivalenttosignalingthatanITURegionisunavailable.Amaskvalueequal(orgreaterthan)thenumberofbitsinthePCindicatesthattheentirenetworkappearanceisaffected;thisisusedtoindicatenetworkisolationtotheASP.

INFOString:variablelength


37/116

TheoptionalINFOStringparametercancarryanymeaningfulUTF-8[10]characterstringalongwiththemessage.LengthoftheINFOStringparameterisfrom0to255octets.Noproceduresarepresentlyidentifiedforitsuse,buttheINFOStringMAYbeusedfordebuggingpurposes.AnINFOStringwithazero-lengthparameterisnotconsideredanerror(azerolengthparameterisoneinwhichtheLengthfieldintheTLVwillbesetto4).

3.4.2.DestinationAvailable(DAVA)

TheDAVAmessageissentfromanSGPtoallconcernedASPstoindicatethattheSGhasdeterminedthatoneormoreSS7destinationsarenowreachable(andnotrestricted),orinresponsetoaDAUDmessage,ifappropriate.IftheASPM3UAlayerpreviouslyhadnoroutestotheaffecteddestinations,theASPMTP3-Userprotocolisinformedandmaynowresumetraffictotheaffecteddestination.TheASPM3UAlayernowroutestheMTP3-usertrafficthroughtheSGinitiatingtheDAVAmessage.


TheDAVAmessagecontainsthefollowingparameters:

NetworkAppearanceOptionalRoutingContextConditionalAffectedPointCodeMandatory

INFOStringOptional

TheformatanddescriptionoftheNetworkAppearance,RoutingContext,AffectedPointCode,andINFOStringparametersarethesameasfortheDUNAmessage(SeeSection3.4.1).

3.4.3.DestinationStateAudit(DAUD)

TheDAUDmessageMAYbesentfromtheASPtotheSGPtoaudittheavailability/congestionstateofSS7routesfromtheSGtooneormoreaffecteddestinations.

TheDAUDmessagecontainsthefollowingparameters:


TheformatanddescriptionofDAUDMessageparametersarethesameasfortheDUNAmessage(SeeSection3.4.1).

Itisrecommendedthatduringnormaloperation(traffichandling)the


38/116

maskfieldoftheAffectedPointCodeparameterintheDAUDmessagebekepttoazerovalueinordertoavoidSGoverloading.

3.4.4.SignallingCongestion(SCON)

TheSCONmessagecanbesentfromanSGPtoallconcernedASPstoindicatethatanSGhasdeterminedthatthereiscongestionintheSS7networktooneormoredestinations,ortoanASPinresponsetoaDATAorDAUDmessage,asappropriate.ForsomeMTPprotocolvariants(e.g.,ANSIMTP)theSCONmessagemaybesentwhentheSS7congestionlevelchanges.TheSCONmessageMAYalsobesentfromtheM3UAlayerofanASPtoanM3UApeer,indicatingthatthecongestionleveloftheM3UAlayerortheASPhaschanged.

IMPLEMENTATIONNOTE:AnM3UAnodemaymaintainatimertocontrolcongestionnotificationvalidity,ifdesired.Thistimerwillbeusefulincaseswherethepeernodefailstoindicatecongestionabatement.



TheSCONmessagecontainsthefollowingparameters:

NetworkAppearanceOptionalRoutingContextConditionalAffectedPointCodeMandatoryConcernedDestinationOptionalCongestionIndicationsOptionalINFOStringOptional

TheformatforSCONMessageparametersisasfollows:

012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0200|Length=8|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|NetworkAppearance|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0006|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/RoutingContext/

\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0012|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Mask|AffectedPC1|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/.../\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


39/116

|Mask|AffectedPCn|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0206|Length=8|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|reserved|ConcernedDPC|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0205|Length=8|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Reserved|Cong.Level|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0004|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/INFOString/\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


TheformatanddescriptionoftheNetworkAppearance,RoutingContext,AffectedPointCode,andINFOStringparametersarethesameasfortheDUNAmessage(seeSection3.4.1).

TheAffectedPointCodeparametercanbeusedtoindicatecongestionofmultipledestinationsorrangesofdestinations.

ConcernedDestination:32bits

TheoptionalConcernedDestinationparameterisonlyusediftheSCONmessageissentfromanASPtotheSGP.ItcontainsthepointcodeoftheoriginatorofthemessagethattriggeredtheSCONmessage.TheConcernedDestinationparametercontainsone

ConcernedDestinationPointCodefield,athree-octetparametertoallowfor14-,16-,and24-bitbinaryformattedSS7PointCodes.AConcernedPointCodethatislessthan24bitsispaddedonthelefttothe24-bitboundary.AnyresultingTransferControlled(TFC)messagefromtheSGissenttotheConcernedPointCodeusingthesingleAffectedDPCcontainedintheSCONmessagetopopulatethe(affected)DestinationfieldoftheTFCmessage

CongestedIndications:32bits

TheoptionalCongestionIndicationsparametercontainsaCongestionLevelfield.ThisoptionalparameterisusedtocommunicatecongestionlevelsinnationalMTPnetworkswith

multiplecongestionthresholds,suchasinANSIMTP3.ForMTPcongestionmethodswithoutmultiplecongestionlevels(e.g.,theITUinternationalmethod)theparameterisnotincluded.

CongestionLevelfield:8bits(unsignedinteger)

TheCongestionLevelfield,associatedwithalloftheAffectedDPC(s)intheAffectedDestinationsparameter,containsoneofthefollowingvalues:


40/116

0NoCongestionorUndefined1CongestionLevel12CongestionLevel23CongestionLevel3

ThecongestionlevelsaredefinedinthecongestionmethodintheappropriatenationalMTPrecommendations[7,8].


3.4.5.DestinationUserPartUnavailable(DUPU)

TheDUPUmessageisusedbyanSGPtoinformconcernedASPsthataremotepeerMTP3-UserPart(e.g.,ISUPorSCCP)atanSS7nodeis

unavailable.

TheDUPUmessagecontainsthefollowingparameters:

NetworkAppearanceOptionalRoutingContextConditionalAffectedPointCodeMandatoryUser/CauseMandatoryINFOStringOptional

TheformatforDUPUmessageparametersisasfollows:

0123

01234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0200|Length=8|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|NetworkAppearance|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0006|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/RoutingContext/\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0012|Length=8|

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Mask=0|AffectedPC|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0204|Length=8|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Cause|User|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0004|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\


41/116

/INFOString/\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


User/Cause:32bits

TheUnavailabilityCauseandMTP3-UserIdentityfields,associatedwiththeAffectedPCintheAffectedPointCodeparameter,areencodedasfollows:

UnavailabilityCausefield:16bits(unsignedinteger)

TheUnavailabilityCauseparameterprovidesthereasonfortheunavailabilityoftheMTP3-User.ThevalidvaluesfortheUnavailabilityCauseparameterareshowninthefollowingtable.ThevaluesagreewiththoseprovidedintheSS7MTP3UserPartUnavailablemessage.DependingontheMTP3protocolusedintheNetworkAppearance,additionalvaluesmaybeused;thespecificationoftherelevantMTP3protocolvariant/versionrecommendationisdefinitive.

0Unknown1UnequippedRemoteUser2InaccessibleRemoteUser

MTP3-UserIdentityfield:16bits(unsignedinteger)

TheMTP3-UserIdentitydescribesthespecificMTP3-Userthatisunavailable(e.g.,ISUP,SCCP,etc.).SomeofthevalidvaluesfortheMTP3-UserIdentityareshownbelow.ThevaluesalignwiththoseprovidedintheSS7MTP3UserPartUnavailablemessageandServiceIndicator.DependingontheMTP3protocolvariant/versionusedintheNetworkAppearance,additionalvaluesmaybeused.TherelevantMTP3protocolvariant/versionrecommendationisdefinitive.

0to2Reserved3SCCP

4TUP5ISUP6to8Reserved9BroadbandISUP10SatelliteISUP11Reserved12AALtype2Signalling13BearerIndependentCallControl(BICC)14GatewayControlProtocol15Reserved


42/116

TheformatanddescriptionoftheAffectedPointCodeparameterarethesameasfortheDUNAmessage(seeSection3.4.1.)exceptthattheMaskfieldisnotusedandonlyasingleAffectedDPCis


included.RangesandlistsofAffectedDPCscannotbesignaledinaDUPUmessage,butthisisconsistentwithUPUoperationintheSS7network.TheAffectedDestinationsparameterinanMTP3UserPartUnavailablemessage(UPU)receivedbyanSGPfromtheSS7networkcontainsonlyonedestination.

TheformatanddescriptionoftheNetworkAppearance,RoutingContext,andINFOStringparametersarethesameasfortheDUNAmessage(seeSection3.4.1).

3.4.6.DestinationRestricted(DRST)

TheDRSTmessageisoptionallysentfromtheSGPtoallconcernedASPstoindicatethattheSGhasdeterminedthatoneormoreSS7destinationsarenowrestrictedfromthepointofviewoftheSG,orinresponsetoaDAUDmessage,ifappropriate.TheM3UAlayerattheASPisexpectedtosendtraffictotheaffecteddestinationviaanalternateSGwitharouteofequalpriority,butonlyifsuchanalternaterouteexistsandisavailable.IftheaffecteddestinationiscurrentlyconsideredunavailablebytheASP,TheMTP3-Usershouldbeinformedthattraffictotheaffecteddestinationcanberesumed.Inthiscase,theM3UAlayershouldroutethetrafficthroughtheSGinitiatingtheDRSTmessage.

ThismessageisoptionalfortheSGtosend,anditisoptional

fortheASPtoactonanyinformationreceivedinthemessage.Itisforuseinthe"STP"casedescribedinSection1.4.1.

TheDRSTmessagecontainsthefollowingparameters:


TheformatanddescriptionoftheNetworkAppearance,RoutingContext,AffectedPointCode,andINFOStringparametersarethesameasfortheDUNAmessage(seeSection3.4.1).

3.5.ASPStateMaintenance(ASPSM)Messages

3.5.1.ASPUp

TheASPUpmessageisusedtoindicatetoaremoteM3UApeerthattheadaptationlayerisreadytoreceiveanyASPSM/ASPTMmessagesforallRoutingKeysthattheASPisconfiguredtoserve.


43/116


TheASPUpmessagecontainsthefollowingparameters:

ASPIdentifierOptionalINFOStringOptional

TheformatforASPUpmessageparametersisasfollows:

012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0011|Length=8|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|ASPIdentifier|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0004|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

\\/INFOString/\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

ASPIdentifier:32-bitunsignedinteger

TheoptionalASPIdentifierparametercontainsauniquevaluethatislocallysignificantamongtheASPsthatsupportanAS.TheSGPshouldsavetheASPIdentifiertobeused,ifnecessary,withtheNotifymessage(seeSection3.8.2).

TheformatanddescriptionoftheoptionalINFOStringparameter

arethesameasfortheDUNAmessage(seeSection3.4.1).

3.5.2.ASPUpAcknowledgement(ASPUpAck)

TheASPUPAckmessageisusedtoacknowledgeanASPUpmessagereceivedfromaremoteM3UApeer.

TheASPUpAckmessagecontainsthefollowingparameters:

ASPIdentifierOptionalINFOStringOptional



44/116


TheformatforASPUpAckmessageparametersisasfollows:

012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0011|Length=8|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|ASPIdentifier|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0004|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/INFOString/\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

TheoptionalASPIdentifierparameterisspecificallyusefulforIPSPcommunication.Inthatcase,theIPSPansweringtheASPUpmessageMAYincludeitsownASPIdentifiervalue.

TheformatanddescriptionoftheoptionalINFOStringparameterarethesameasfortheDUNAmessage(seeSection3.4.1).TheINFOStringinanASPUpAckmessageisindependentfromtheINFOStringintheASPUpmessage(i.e.,itdoesnothavetoechobacktheINFOStringreceived).

3.5.3.ASPDown

TheASPDownmessageisusedtoindicatetoaremoteM3UApeerthattheadaptationlayerisNOTreadytoreceiveDATA,SSNM,RKM,orASPTMmessages.

TheASPDownmessagecontainsthefollowingparameter:

INFOStringOptional

TheformatfortheASPDownmessageparametersisasfollows:

012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0004|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/INFOString/\\

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



45/116

TheformatanddescriptionoftheoptionalINFOStringparameterarethesameasfortheDUNAmessage(seeSection3.4.1).

3.5.4.ASPDownAcknowledgement(ASPDownAck)

TheASPDownAckmessageisusedtoacknowledgeanASPDownmessagereceivedfromaremoteM3UApeer.

TheASPDownAckmessagecontainsthefollowingparameter:

INFOStringOptional

TheformatfortheASPDownAckmessageparametersisasfollows:

012301234567890123456789012345678901+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|Tag=0x0004|Length|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\\/INFOString/\\+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

TheformatanddescriptionoftheoptionalINFOStringparameterarethesameasfortheDUNAmessage(SeeSection3.4.1).

TheINFOStringinanASPDownAckmessageisindependentfromtheINFOStringintheASPDownmessage(i.e.,itdoesnothavetoechobacktheINFOStringreceived).

3.5.5.Heartbeat(BEAT)

TheBEATmessageisoptionallyusedtoensurethattheM3UApeersarestillavailabletoeachother.Itisre

RFC 4666 - Signaling System 7 (SS7) Message Transfer Part 3 (MTP3) - User Adaptation Layer (M3UA)

Documents

Transcript of RFC 4666 - Signaling System 7 (SS7) Message Transfer Part 3 (MTP3) - User Adaptation Layer (M3UA)