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1、INTERNATIONALTELECOMMUNICATIONUNIONCCITTE.721THEINTERNATIONAL(11/1988)TELEGRAPHANDTELEPHONECONSULTATIVECOMMITTEESERIESE:OVERALLNETWORKOPERATION,TELEPHONESERVICE,SERVICEOPERATIONANDHUMANFACTORSTrafficengineering–ISDNtrafficengineeringNETWORKGRADEOFSERVICEPARAMETERSINIS
2、DNReeditionofCCITTRecommendationE.721publishedintheBlueBook,FascicleII.3(1988)NOTES1CCITTRecommendationE.721waspublishedinFascicleII.3oftheBlueBook.ThisfileisanextractfromtheBlueBook.WhilethepresentationandlayoutofthetextmightbeslightlydifferentfromtheBlueBookversion,
3、thecontentsofthefileareidenticaltotheBlueBookversionandcopyrightconditionsremainunchanged(seebelow).2InthisRecommendation,theexpression“Administration”isusedforconcisenesstoindicatebothatelecommunicationadministrationandarecognizedoperatingagency.©ITU1988,2007Allright
4、sreserved.Nopartofthispublicationmaybereproduced,byanymeanswhatsoever,withoutthepriorwrittenpermissionofITU.RecommendationE.721NETWORKGRADEOFSERVICEPARAMETERSINISDN1IntroductionThisRecommendationproposesnetworkGradeofService(GOS)parametersforcircuit-switchedandpacket-
5、switchedservicesinISDN,basedontheISDNGradeofServiceconceptandguidelinesforselectingGOSparametersprovidedinRecommendationE.720.Theseparametersaredefinedassumingthatthenetworkandthenetworkcomponentsarefullyoperational.2Circuit-switchedservicesInthecurrentISDNspecificati
6、ons,callestablishmentandreleaseforallcircuit-switchedservicesprovidedviaB-channels(voice,data,image)willusetheout-of-bandcallcontrolproceduresdefinedbyRecommenda-tionQ.931andS.S.No.7(ISUP)signallingprotocols.Thus,forthetrafficGOSparametersthatrelatetocallestablishment
7、andreleasephases,asinglesetofparameterscanbeusedforallcircuit-switchedservicesprovidedbytheISDN.ThefollowingfourtrafficGOSparametersarerecommendedforcircuit-switchedcallsinISDN:1)pre-selectiondelay(overlapsending),2)post-selectiondelay,3)callreleasedelay,and4)probabil
8、ityofend-to-endblocking.ThedefinitionsofthesetrafficGOSparametersaregivenbelow.ThedelayGOSparametersarebasedonthemessageflow
