***********23.503附录B：Duringthenetworkmigration,DRAandBSFmaycoexistinoperatorsnetwork.TheDRAcanbeaconsumerofNbsfservicesandtheBSFcanprovidebindingfunctionalityfordifferentsubscribers.WhentheAFusingRx,suchasP-CSCF,sendsRxrequesttotheDRA,iftheDRAhasnobindinginformationforthesubscriber,basedonconfigurationorviaNRF,itselectstheBSF.ThentheDRAcanquerytheBSFbyinvokingNbsf_Managementdiscoveryserviceoperation,togettherelevantPCFaddress,basedonwhichtheDRAroutestheRxrequesttotheselectedPCF.NOTE: TheDRAdecidestoselectaBSFbasedonuserIPaddressrange.***数据业务可能一起回落到LTE；（双注册场景数据业务可不回落？）************4G没有oNAS方案，推荐5G使用oIP方案给出几个维度的对比分析：现网实现、改造影响、终端要求、业务应用场景、推导出oNAS不推荐***************1.TheSMFdeterminesthattheservingUPFneedstobechangedduetoeventsthatmaybenefitfromsuchchange.2.ThePDUSessionReleaseprocedureisinitiatedasdescribedinclause?4.3.4.TheSMFsendsanN1SMInformationtotheUEviatheAMFbyinvokingNamf_Communication_N1N2MessageTransferasdescribedinStep3bofclause?4.3.4.2.ThePDUSessionReleaseCommandmessageinN1SMInformationcontainsthePDUSessionIDandCauseindicatingthataPDUSessionre-establishmenttothesameDNisrequired.3. UponreceptionofPDUSessionReleaseCommandwithCauseindicatingthataPDUSessionre-establishmenttothesameDNisrequiredassentinstep?2,theUEgeneratesanewPDUSessionIDandinitiatesPDUSessionEstablishmentprocedureasdescribedinclause?4.3.2.2.Then,theAMFselectsanSMFasdescribedinTS?23.501?[2],clause?6.4.2andtheSMFcanselectanewUPF(i.e.UPF2)forthere-establishedPDUSessionofSSCmode2.***ThePDUSessionAddressLifetimevalueisdeliveredtotheUEupperlayersinePCOandindicateshowlongthenetworkiswillingtomaintainthePDUSession.*****1. UEhasanestablishedPDUSessionwithaU