5G SMS over NAS三路径与SMSF注册信令全链路拆解

graph TB
    subgraph "5G SMS三路径架构"
        UE[UE] -->|NAS Transport| AMF[AMF]
        AMF -->|N20: Nsmsf_SMSService| SMSF[SMSF]
        SMSF -->|N21: Nudm_SDM| UDM[UDM]
        SMSF -->|MAP/Diameter| SMSC[SMSC]

        UE -->|SIP MESSAGE| P_CSCF[P-CSCF]
        P_CSCF -->|IMS Core| IP_SM_GW[IP-SM-GW]
        IP_SM_GW --> SMSC

        AMF -->|N26| MME[MME]
        MME -->|SGs| MSC[MSC Server]
        MSC --> SMSC
    end

    style SMSF fill:#e1f5fe
    style AMF fill:#fff3e0
    style UDM fill:#e8f5e9

sequenceDiagram
    participant UE
    participant RAN as (R)AN
    participant AMF
    participant SMSF
    participant UDM

    Note over UE,AMF: 阶段一：Registration Request（含SMS指示）
    UE->>RAN: Registration Request<br/>5GS Registration Type=Initial<br/>SMS over NAS supported=1
    RAN->>AMF: N2 Registration Request<br/>+ NAS Registration Request

    Note over AMF: AMF检查UE SMS能力<br/>AMF选择SMSF

    AMF->>AMF: 本地策略/路由选择<br/>确定SMSF实例

    Note over AMF,UDM: 阶段二：SMSF激活与UDM注册
    AMF->>SMSF: Nsmsf_SMSService_Activate<br/>{SUPI, Access Type, GUAMI}
    SMSF->>UDM: Nudm_SDM_Get<br/>{SUPI, Subscription Data Type=SMS}
    UDM-->>SMSF: SMS Subscription Data<br/>{SMS-Subscribed, SMS-Teleservice-List}
    SMSF->>UDM: Nudm_UECM_Registration<br/>{SUPI, SMSF Identity, Access Type}
    UDM-->>SMSF: 201 Created<br/>UDM存储SMSF地址
    SMSF-->>AMF: 201 Created<br/>SMSF激活确认

    Note over AMF,UE: 阶段三：Registration Accept
    AMF->>RAN: N2 Registration Accept<br/>+ NAS Registration Accept<br/>SMS Services Supported=1
    RAN->>UE: Registration Accept<br/>SMS Services Supported=1

graph LR
    subgraph "SMSF选择决策树"
        A[AMF收到Registration<br/>SMS supported=1] --> B{本地配置<br/>SMSF列表?}
        B -->|有| C[从列表选择SMSF]
        B -->|无| D{NRF可用?}
        D -->|是| E[Nnrf_NFDiscovery<br/>查询SMSF实例]
        D -->|否| F[默认SMSF地址]
        E --> G{漫游场景?}
        G -->|VPLMN| H[选VPLMN SMSF]
        G -->|HPLMN| I[选HPLMN SMSF]
        C --> J[Nsmsf_Activate]
        F --> J
        H --> J
        I --> J
    end

    style A fill:#e3f2fd
    style J fill:#c8e6c9

┌─────────────────────────────────────┐
│        NAS Transport Message        │  ← TS 24.501 (UL NAS Transport)
│  ┌─────────────────────────────┐    │
│  │      CP-DATA / CP-ACK      │    │  ← TS 24.011 (CP层: 连接控制)
│  │  ┌─────────────────────┐    │    │
│  │  │    RP-DATA          │    │    │  ← TS 24.011 (RP层: 中继协议)
│  │  │  ┌─────────────┐    │    │    │
│  │  │  │  TPDU       │    │    │    │  ← TS 23.040 (SMS用户数据)
│  │  │  │  (SMS-SUBMIT)│    │    │    │
│  │  │  └─────────────┘    │    │    │
│  │  └─────────────────────┘    │    │
│  └─────────────────────────────┘    │
└─────────────────────────────────────┘

sequenceDiagram
    participant UE
    participant RAN as (R)AN
    participant AMF
    participant SMSF
    participant UDM
    participant SMSC

    Note over UE,SMSC: MO-SMS主叫发送流程

    UE->>RAN: UL NAS Transport<br/>Payload Container Type=SMS<br/>[CP-DATA[RP-DATA(SMS-SUBMIT)]]
    RAN->>AMF: N2 Uplink NAS Transport<br/>+ NAS消息

    Note over AMF: AMF解析NAS Transport<br/>识别SMS Payload<br/>根据SUPI查找已激活SMSF

    AMF->>SMSF: Nsmsf_SMSService_UplinkSMS<br/>{SUPI, SMS Payload, Access Type}

    Note over SMSF: SMSF解析CP/RP/TPDU<br/>校验用户短信签约

    SMSF->>UDM: Nudm_SDM_Get<br/>(可选，若未缓存签约数据)
    UDM-->>SMSF: SMS Subscription Data

    SMSF->>SMSC: MAP_FORWARD_SHORT_MSG<br/>或 Diameter S6c
    Note over SMSF,SMSC: RP-DATA转发至SMSC<br/>目标地址从RP-DATA中提取

    SMSC-->>SMSF: MAP_FORWARD_SHORT_MSG_ACK<br/>或 Diameter S6c ACK
    Note over SMSC: SMSC向目标地址<br/>投递短信(异步)

    SMSF-->>AMF: Nsmsf_SMSService_UplinkSMS Response<br/>[CP-DATA[RP-ACK(SMS-SUBMIT-REPORT)]]
    AMF->>RAN: N2 Downlink NAS Transport
    RAN->>UE: DL NAS Transport<br/>[CP-DATA[RP-ACK(SMS-SUBMIT-REPORT)]]

    UE->>RAN: UL NAS Transport<br/>[CP-ACK]
    RAN->>AMF: N2 Uplink NAS Transport
    AMF->>SMSF: Nsmsf_SMSService_UplinkSMS<br/>[CP-ACK]
    Note over UE,SMSF: CP层确认闭环

sequenceDiagram
    participant SMSC
    participant GMSC as SMS-GMSC
    participant UDM
    participant SMSF
    participant AMF
    participant RAN as (R)AN
    participant UE

    Note over SMSC,UE: MT-SMS被叫接收流程

    SMSC->>GMSC: 短信投递请求<br/>(含目标MSISDN)
    GMSC->>UDM: Nudm_UECM_Get<br/>{MSISDN,查询SMSF地址}
    UDM-->>GMSC: SMSF Identity + PLMN ID
    GMSC->>SMSF: 短信前转请求<br/>(MAP/Diameter)

    Note over SMSF: SMSF收到MT-SMS<br/>查找UE关联的AMF

    alt UE在CM-CONNECTED状态
        SMSF->>AMF: Namf_Communication<br/>_N1N2MessageTransfer<br/>{N1 SM Container=SMS}
        AMF->>RAN: N2 Downlink NAS Transport<br/>+ DL NAS Transport[CP-DATA[RP-DATA(SMS-DELIVER)]]
        RAN->>UE: DL NAS Transport<br/>[CP-DATA[RP-DATA(SMS-DELIVER)]]
    else UE在CM-IDLE状态
        SMSF->>AMF: Namf_Communication<br/>_N1N2MessageTransfer<br/>{N1 SM Container=SMS}
        Note over AMF: AMF缓存SMS<br/>触发寻呼
        AMF->>RAN: N1N2 Transfer Failure<br/>触发Paging
        RAN->>UE: Paging<br/>(SMS指示)
        UE->>RAN: Service Request
        RAN->>AMF: N2 Service Request
        AMF->>RAN: N2 Downlink NAS Transport<br/>+ DL NAS Transport[CP-DATA[RP-DATA(SMS-DELIVER)]]
        RAN->>UE: DL NAS Transport<br/>[CP-DATA[RP-DATA(SMS-DELIVER)]]
    end

    UE->>RAN: UL NAS Transport<br/>[CP-DATA[RP-ACK(SMS-DELIVER-REPORT)]]
    RAN->>AMF: N2 Uplink NAS Transport
    AMF->>SMSF: Nsmsf_SMSService_UplinkSMS<br/>[CP-DATA[RP-ACK]]
    SMSF->>GMSC: 短信投递确认
    GMSC->>SMSC: 投递成功通知

    UE->>RAN: UL NAS Transport<br/>[CP-ACK]
    RAN->>AMF: N2 Uplink NAS Transport
    AMF->>SMSF: Nsmsf_SMSService_UplinkSMS<br/>[CP-ACK]

MSISDN → SMS-GMSC查询UDM → 获取SMSF Identity → SMSF查询AMF → AMF寻呼/推送UE

sequenceDiagram
    participant AMF
    participant SMSF
    participant UDM

    Note over AMF,UDM: 场景：AMF触发去注册

    AMF->>SMSF: Nsmsf_SMSService_Deactivate<br/>{SUPI, Access Type}
    SMSF->>UDM: Nudm_UECM_Deregistration<br/>{SUPI, SMSF Identity}
    UDM-->>SMSF: 204 No Content<br/>UDM删除SMSF注册记录
    SMSF->>SMSF: 删除UE SMS上下文<br/>释放资源
    SMSF-->>AMF: 204 No Content<br/>去激活确认

stateDiagram-v2
    [*] --> CP_IDLE: SMS传输开始
    CP_IDLE --> CP_MM_PENDING: 发送CP-DATA
    CP_MM_PENDING --> CP_WAIT_FOR_ACK: 等待CP-ACK
    CP_WAIT_FOR_ACK --> CP_IDLE: 收到CP-ACK<br/>(正常完成)
    CP_WAIT_FOR_ACK --> CP_WAIT_RETRANS: CP-ACK超时
    CP_WAIT_RETRANS --> CP_WAIT_FOR_ACK: 重传CP-DATA
    CP_WAIT_RETRANS --> CP_IDLE: 重传次数耗尽<br/>(CP-ERROR)
    CP_MM_PENDING --> CP_IDLE: CP-ERROR<br/>(异常终止)

    state CP_IDLE {
        [*] --> RP_IDLE
        RP_IDLE --> RP_WAIT_FOR_ACK: 发送RP-DATA
        RP_WAIT_FOR_ACK --> RP_IDLE: 收到RP-ACK<br/>(成功)
        RP_WAIT_FOR_ACK --> RP_IDLE: 收到RP-ERROR<br/>(失败)
    }