【5G核心网】5GC核心网之网元AMF

AMF: 接入及移动性管理功能 Access and Mobility Management Function

5G 核心网架构

     N1 UE <--> AMF  NAS

     N2 AN  <--> AMF  NGAP  TS 38.413 [34]  AN 节点和 AMF 之间的应用层协议

 

Service Name	Service Operations	Operation Semantic	Known Consumer(s)
Namf_Communication	UEContextTransfer	Request/ Response	Peer AMF
	CreateUEContext	Request/ Response	Peer AMF
	ReleaseUEContext	Request/ Response	Peer AMF
	RegistrationStatusUpdate	Request/ Response	Peer AMF
	N1MessageNotify	Subscribe / Notify	SMF, SMSF, PCF, LMF, Peer AMF
	N1MessageSubscribe		SMF, SMSF, PCF
	N1MessageUnSubscribe		SMF, SMSF, PCF
	N1N2MessageTransfer	Request/ Response	SMF, SMSF, PCF, LMF
	N1N2TransferFailureNotification	Subscribe / Notify	SMF, SMSF, PCF, LMF
	N2InfoSubscribe	Subscribe / Notify	NOTE 1
	N2InfoUnSubscribe		NOTE 1
	N2InfoNotify		AMF, LMF
	EBIAssignment	Request/Response	SMF
	AMFStatusChangeSubscribe	Subscribe / Notify	SMF, PCF, NEF, SMSF, UDM
	AMFStatusChangeUnSubscribe	Subscribe / Notify	SMF, PCF, NEF, SMSF, UDM
	AMFStatusChangeNotify	Subscribe / Notify	SMF, PCF, NEF, SMSF, UDM
	NonUeN2MessageTransfer	Request/Response	Peer AMF, CBCF, PWS-IWF, LMF
	NonUeN2InfoSubscribe	Subscribe / Notify	CBCF, PWS-IWF
	NonUeN2InfoUnSubscribe		CBCF, PWS-IWF
	NonUeN2InfoNotify		CBCF, PWS-IWF, LMF
Namf_EventExposure	Subscribe	Subscribe / Notify	NEF, SMF, UDM, NWDAF
	Unsubscribe	Subscribe / Notify	NEF, SMF, UDM, NWDAF
	Notify	Subscribe / Notify	NEF, SMF, UDM, NWDAF
Namf_MT	EnableUEReachability	Request/Response	SMSF
	ProvideDomainSelectionInfo	Request/Response	UDM
Namf_Location	ProvidePositioningInfo	Request/Response	GMLC
	EventNotify	Subscribe / Notify	GMLC
	ProvideLocationInfo	Request/Response	UDM
	CancelLocation	Request/Response	GMLC
NOTE 1: In this Release of the specification no known consumer is identified to use this service operation.

                                                         Table 5.2.2.1-1: List of AMF Services TS 23502

 

1. AMF 程序初始化以及启动

   1.1 启动 httpcallback 服务

     httpcallback.AddService(router)，实现在 afm/httpcallback 中，URL 以及 handler 如下所示：

Name	Pattern	HandlerFunc
Index	/	Index
SmContextStatusNotify	/smContextStatus/:guti/:pduSessionId	SmContextStatusNotify
AmPolicyControlUpdateNotifyUpdate	/am-policy/:polAssoId/update	AmPolicyControlUpdateNotifyUpdate
AmPolicyControlUpdateNotifyTerminate	/am-policy/:polAssoId/terminate	AmPolicyControlUpdateNotifyTerminate
N1MessageNotify	/n1-message-notify	N1MessageNotify

    1.2 根据配置文件中的服务列表启动服务

       serviceNameList: - namf-comm - namf-evts - namf-mt - namf-loc - namf-oam

for _, serviceName := range factory.AmfConfig.Configuration.ServiceNameList {
	switch models.ServiceName(serviceName) {
	case models.ServiceName_NAMF_COMM:
		communication.AddService(router)
	case models.ServiceName_NAMF_EVTS:
		eventexposure.AddService(router)
	case models.ServiceName_NAMF_MT:
		mt.AddService(router)
	case models.ServiceName_NAMF_LOC:
		location.AddService(router)
	}
}

    1.3 初始化 amf 上下文

     通过配置文件，较简单，amf 监听端口为 29518

	self := context.AMF_Self()
	util.InitAmfContext(self)

	addr := fmt.Sprintf("%s:%d", self.HttpIPv4Address, self.HttpIpv4Port)

    1.4 根据 ngap IP 列表建立 SCTP 服务

      TCP是以字节为单位传输的，SCTP是以数据块为单位传输的

      TCP通常是单路径传输，SCTP可以多路径传输

	for _, ngapAddr := range self.NgapIpList {
		sctpListener = sctp.Server(ngapAddr)
	}

     1.5 核心处理流程

      实现在 amf/handler/hander.go

go handler.Handle()

    1.6 注册到 NRF

      amf id 组成 regionId: 16bits, setId: 10bits, ptrId: 6bits     =

      调用 NRF Nnrf_NFManagement，注册

// Register to NRF
profile, err := consumer.BuildNFInstance(self)
if err != nil {
	initLog.Error("Build AMF Profile Error")
}

_, self.NfId, _ = consumer.SendRegisterNFInstance(self.NrfUri, self.NfId, profile)

 

名词解释：

    SCTP，Stream Control Transmission Protocol

    PLMN，Public Land Mobile Network  公共陆地移动网 ，一般特指某个运营商的网络覆盖区域

    MCC，Mobile Country Code

    MNC，Mobile Network Code

    GUAMI，全球唯一的  AMF 标识符    =

    TAI，Tracking Area Identity    跟踪区域标识

    GUTI，Globally Unique Temporary UE Identity  全局唯一的临时UE标识，目的减少在通信中显示使用UE的永久性标识，提升安全性

    SUPI，用户的唯一永久身份标志

 

   配置文件：

info:
  version: 1.0.0
  description: AMF initial local configuration

configuration:
  amfName: AMF
  ngapIpList:
    - 127.0.0.10
  sbi:
    scheme: http
    ipv4Addr: 127.0.0.1
    port: 29518
  serviceNameList:
    - namf-comm
    - namf-evts
    - namf-mt
    - namf-loc
    - namf-oam
  servedGuamiList:
    - plmnId:
        mcc: 208
        mnc: 93
      amfId: cafe00
  supportTaiList:
    - plmnId:
        mcc: 208
        mnc: 93
      tac: 1
  plmnSupportList:
    - plmnId:
        mcc: 208
        mnc: 93
      snssaiList:
        - sst: 1
          sd: 010203
        - sst: 1
          sd: 112233
  supportDnnList:
    - internet
  nrfUri: http://localhost:29510
  security:
    integrityOrder:
      - NIA2
      - NIA0
    cipheringOrder:
      - NEA2
      - NEA0
  networkName:
    full: free5GC
    short: free
  t3502: 720
  t3512: 3600
  non3gppDeregistrationTimer: 3240