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

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}
	/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
individual subscription	/{subscriptionId}	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