【5G核心网】5GC核心网之网元AMF

一. AMF 基础

    AMF: 接入及移动性管理功能 Access and Mobility Management Function TS 29518

     相当于 4GMME 的移动性管理功能，增加了 NAS 透传功能， 包括注册管理，连接管理，可达性管理，移动性管理，接入鉴权，接入授权

     合法监听

     转发 UE 和 SMF 之间的 SM 消息，转发 UE 和 SMSF 之间的 SMS 消息     

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

 

Service Name	Clause	Description	OpenAPI Specification File	apiName	Annex
Namf_Communication	6.1	AMF Communication Service	TS29518_Namf_Communication.yaml	namf-comm	A.2
Namf_EventExposure	6.2	AMF Event Exposure Service	TS29518_Namf_EventExposure.yaml	namf-evts	A.3
Namf_MT	6.3	AMF Mobile Terminated Service	TS29518_Namf_MT.yaml	namf-mt	A.4
Namf_Location	6.4	AMF Location Service	TS29518_Namf_Location.yaml	namf-loc	A.5

                                                                Table 5.1-2: API Descriptions

 

2. API Definitions

      {apiRoot}/<apiName>/<apiVersion>/<apiSpecificResourceUriPart>

      - The {apiRoot} shall be set as described in 3GPP TS 29.501 [5].

      - The <apiName> shall be "namf-comm".

      - The <apiVersion> shall be "v1".

      - The <apiSpecificResourceUriPart> shall be set as described in clause 6.1.3

    

                                     Figure 6.1.3.1-1: Resource URI structure of the Namf_Communication API

 

Resource name	Resource URI	HTTP method or custom operation	Description (Mapped Service Operations)
Individual ueContext	/ue-contexts/{ueContextId}
		PUT	CreateUEContext
	/ue-contexts/{ueContextId}/release	release (POST)	ReleaseUEContext
	/ue-contexts/{ueContextId}/assign-ebi	assign-ebi (POST)	EBIAssignment
	/ue-contexts/{ueContextId}/transfer	transfer (POST)	UEContextTransfer
	/ue-contexts/{ueContextId}/transfer-update	transfer-update (POST)	RegistrationStatusUpdate
n1N2Message collection	/ue-contexts/{ueContextId}/n1-n2-messages	POST	N1N2MessageTransfer
N1N2 Subscriptions Collection for Individual UE Contexts	/ue-contexts/{ueContextId}/n1-n2-messages/subscriptions	POST	N1N2MessageSubscribe
N1N2 Individual Subscription	/ue-contexts/{ueContextId}/n1-n2-messages/subscriptions/{subscriptionId}	DELETE	N1N2MessageUnSubscribe
n1N2Message transfer status notification callback	{n1N2MessageTransferFailureNotifyUrl} (NF Service Consumer provided callback reference)	POST	N1N2Transfer Failure Notification
subscriptions collection	/subscriptions	POST	AMFStatusChangeSubscribe
individual subscription	/{subscriptionId}	PUT	AMFStatusChangeSubscribe
		DELETE	AMFStatusChangeUnSubscribe
Non UE N2Messages collection	/non-ue-n2-messages/transfer	transfer (POST)	NonUEN2MessageTransfer
Non UE N2Messages Subscriptions collection	/non-ue-n2-messages/subscriptions	POST	NonUEN2InfoSubscribe
Non UE N2 Message Notification Individual Subscription	/non-ue-n2-messages/subscriptions/{n2NotifySubscriptionId}	DELETE	NonUEN2InfoUnsubscribe

                                                                    Table 6.1.3.1-1: Resources and methods overview

 

3. Namf_communication 服务

    Namf_communication 开启 NF 与 UE 通信，可以通过 N1 NAS 消息，或者通过 AN（支持 UE 和非 UE），该服务允许 NF 和 UE AN 通信定义如下：

• 提供为传输到 UE 的 N1 消息的服务操作
• 允许网元从 UE 为指定的 N1 消息的通知订阅以及取消订阅
• 允许网元从 AN 关于指定信息的通知订阅和取消订阅
• 提供用于向 AN 发起 N2 消息的服务操作
• 安全上下文管理
• UE 信息管理以及传输

    1.1 UEContextTransfer

         UE 发起注册或者移动注册触发 UEContextTransfer，NF（网元）服务消费者设置原因属性 “INIT_REG” / "MOBI_REG"，以及包括完成性保护注册请求消息，也会触发 UEContextTransfer 

         当目标 AMF接收注册请求，其 UE 的 5G-GUTI 和正在服务的 AMF 不一样，也就是与上次注册的 AMF 更改了，新 AMF 向旧 AMF 发起 UEContextTransfer 获取 UE 上下文，比如 UE 的 SUPI 和 MM 上下文

 

 

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，Globally Unique AMF Identifier 全球唯一的  AMF 标识符   <GUAMI> = <MCC><MNC><AMF Identifier>

    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，Subscription Permanent Identifier 用户的唯一永久身份标志

    LMF， Location Management Function

 

 

   接入和移动管理功能（AMF）包括以下功能

• -终止RAN CP接口（N2）  Termination of RAN CP interface (N2)
• -终止NAS（N1），NAS加密和完整性保护  Termination of NAS (N1), NAS ciphering and integrity protection
• -注册管理  Registration management
• -连接管理  Connection management
• -可达性管理  Reachability management
• -移动性管理  Mobility Management
• -合法拦截  Lawful intercept
• -为UE和SMF之间的SM消息提供传输  Provide transport for SM messages between UE and SMF
• -用于路由SM消息的透明代理  Transparent proxy for routing SM messages
• -接入身份验证  Access Authentication
• -接入授权  Access Authorization
• -提供UE和SMSF SMS消息的传输  Provide transport for SMS messages between UE and SMSF
• -安全锚功能（SEAF）  Security Anchor Functionality (SEAF) as specified in TS 33.501
• -监管服务的定位服务管理  Location Services management for regulatory services
• -为UE和LMF之间以及RAN和LMF之间的位置服务消息提供传输  Provide transport for Location Services messages between UE and LMF as well as between RAN and LMF
• -用于与EPS互通的EPS 承载 ID分配  EPS Bearer ID allocation for interworking with EPS
• -UE移动事件通知  UE mobility event notification
• -支持控制面CIoT 5GS优化  Support for Control Plane CIoT 5GS Optimisation
• -支持用户面CIoT 5GS优化  Support for User Plane CIoT 5GS Optimisation
• -提供外部参数  Provisioning of external parameters (Expected UE Behaviour parameters or Network Configuration parameters).
• -支持特定的网络切片认证和鉴权  Support for Network Slice-Specific Authentication and Authorization

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