ITU-T H.248.11 (11 2002) (英) Gateway control proto

INTERNATIONALTELECOMMUNICATIONUNIONITU-TH.248.11TELECOMMUNICATIONSTANDARDIZATIONSECTOROFITU(11/2002)SERIESH:AUDIOVISUALANDMULTIMEDIASYSTEMSInfrastructureofaudiovisualservices–CommunicationproceduresGatewaycontrolprotocol:MediagatewayoverloadcontrolpackageITU-TRecommendationH.248.11ITU-TH-SERIESRECOMMENDATIONSAUDIOVISUALANDMULTIMEDIASYSTEMSCHARACTERISTICSOFVISUALTELEPHONESYSTEMSH.100–H.199INFRASTRUCTUREOFAUDIOVISUALSERVICESGeneralH.200–H.219TransmissionmultiplexingandsynchronizationH.220–H.229SystemsaspectsH.230–H.239CommunicationproceduresH.240–H.259CodingofmovingvideoH.260–H.279RelatedsystemsaspectsH.280–H.299SYSTEMSANDTERMINALEQUIPMENTFORAUDIOVISUALSERVICESH.300–H.399SUPPLEMENTARYSERVICESFORMULTIMEDIAH.450–H.499MOBILITYANDCOLLABORATIONPROCEDURESOverviewofMobilityandCollaboration,definitions,protocolsandproceduresH.500–H.509MobilityforH-SeriesmultimediasystemsandservicesH.510–H.519MobilemultimediacollaborationapplicationsandservicesH.520–H.529SecurityformobilemultimediasystemsandservicesH.530–H.539SecurityformobilemultimediacollaborationapplicationsandservicesH.540–H.549MobilityinterworkingproceduresH.550–H.559Mobilemultimediacollaborationinter-workingproceduresH.560–H.569Forfurtherdetails,pleaserefertothelistofITU-TRecommendations.ITU-TRec.H.248.11(11/2002)iITU-TRecommendationH.248.11Gatewaycontrolprotocol:MediagatewayoverloadcontrolpackageSummaryThisRecommendationdescribesapackageforMediaGateway(MG)OverloadControlforusewiththeH.248.1GatewayControlProtocol.ItservestoprotectanMGfromprocessingoverloadthatpreventsthetimelyexecutionofH.248.1transactions.Insummary,inthisRecommendation,overloadprotectionisachievedasfollows:1)AnMG(orvirtualMG)detectsthatitisinoverloadandnotifiesitsMediaGatewayController(MGC)ofthatfactwheneveritreceivesanADDcommand.2)TheMGCadaptivelythrottlestherateitsetsupcallsusingthatMG(orvirtualMG)tomaximizetheMG'seffectivethroughputwhilstboundingitsresponsetimes.Itdoesthisbythrottlingtherateatwhichtransactionsthatset-upnewcallsorthatnewcalllegsaresenttotheoverloadedMG,soastocausetherateofoverloadnotificationstheMGCreceivesfromtheoverloadedMG(orvirtualMG)toconvergetoasuitablylowlevel.AseparateinstanceoftheoverloadcontrolshallbeinitiatedatanMGCforeachofitsdependentMGs(orvirtualMGs)thatisoverloaded.Theseseparateinstancesshouldrunindependently(thatis,theydonotexplicitlyexchangeinformation).Theiroverloadcontrolparametersshallbeseparatelyconfigurable,forexample,bymeansofaproprietarymanagementinterface,ortheuseofSNMPtoinvokeconfigurationfunctions.ThemostgeneraloverloadscenariothecontrolcanhandleiswhereoneormoreMGCsarejointlyoverloadingasingleMGthathasseveralvirtualMGs(virtualMG'i'interactingonlywithMGCi').ThecontroldoesnotneedtoknowhowmanyMGCsarecausingtheMGtobeoverloaded,norwhattheMGcapacityis.Informativereference[1]providesafullexplanationofonewaythiscanbeachieved,andinformativereference[2]providesfurthermaterialondesigningoverloadcontrols.Theoverloadcontrolislargelyspecifiedbysayinghowitshallbehave,butnothowitshouldbeimplementedtoachievethatbehaviour.Thishastwoimportantconsequences.Asafirstconsequence,partofthepackage(see8.5)definesasetofoverloadscenarios,andanyfully-compliantimplementationofthepackagemustautomatically(i.e.withouttheneedforoperatorinterventiontoadjustparametervaluesfromoneoverloadscenariotoanother)satisfyalltherequirementsforeachofthescenarios.Asasecondconsequence,notallconfigurableparameterscanbeknowntothispackagesincetheydependuponspecificimplementationsofthecontrol.Neverthelessthereisarequirementthattheimplementationshallprovideameansbywhichanoperatorcanchangeallparameterswhichaffecttheperformanceofthecontrol.Seeclause9fortheManagementRequirementsassociatedwiththispackage.Itisexpectedthattheywillberealisedbyaproprietarymanagementinterface,ortheuseofSNMP.SourceITU-TRecommendationH.248.11waspreparedbyITU-TStudyGroup16(2001-2004)andapprovedundertheWTSAResolution1procedureon29November2002.iiITU-TRec.H.248.11(11/2002)FOREWORDTheInternationalTelecommunicationUnion(ITU)istheUnitedNationsspecializedagencyinthefieldoftelecommunications.TheITUTelecommunicationStandardizationSector(ITU-T)isapermanentorganofITU.ITU-Tisresponsibleforstudyingtechnical,operatingandtariffquestionsandissuingRecommendationsonthemwithaviewtostandardizingtelecommunicationsonaworldwidebasis.TheWorldTelecommunicationStandardizationAssembly(WTSA),whichmeetseveryfouryears,establishesthetopicsforstudybytheITU-Tstudygroupswhich,inturn,produceRecommendationsonthesetopics.TheapprovalofITU-TRecommendationsiscoveredbytheprocedurelaiddowninWTSAResolution1.InsomeareasofinformationtechnologywhichfallwithinITU-T'spurview,thenecessarystandardsarepreparedonacollaborativebasiswithISOandIEC.NOTEInthisRecommendation,theexpressionAdministrationisusedforconcisenesstoindicatebothatelecommunicationadministrationandarecognizedoperatingagency.INTELLECTUALPROPERTYRIGHTSITUdrawsattentiontothepossibilitythatthepracticeorimplementationofthisRecommendationmayinvolvetheuseofaclaimedIntellectualPropertyRight.ITUtakesnopositionconcerningtheevid