5G UL CL上行分类器插入与MEC本地分流信令流拆解

sequenceDiagram
    participant UE
    participant RAN as (R)AN/gNB
    participant AMF
    participant SMF
    participant ULCL as UPF(UL CL)
    participant PSA1 as UPF(PSA1) 中央锚点
    participant PSA2 as UPF(PSA2) 本地锚点
    participant PCF

    Note over UE,PCF: 阶段一：触发决策
    UE->>RAN: 移动到MEC区域/触发AF请求
    SMF->>SMF: 检测到DNAI变化或收到AF Influence请求<br/>决定插入UL CL + PSA2

    Note over UE,PCF: 阶段二：N4会话准备
    SMF->>PSA2: N4 Session Establishment Request<br/>(Create PDR + FAR for Local DN)
    PSA2-->>SMF: N4 Session Establishment Response<br/>(F-TEID for N3/N9)

    SMF->>ULCL: N4 Session Establishment Request<br/>(Create PDR#1: UL→PSA2 + FAR#1)<br/>(Create PDR#2: UL→PSA1 + FAR#2)<br/>(Create PDR#3: DL from PSA1 → UE + FAR#3)<br/>(Create PDR#4: DL from PSA2 → UE + FAR#4)
    ULCL-->>SMF: N4 Session Establishment Response<br/>(F-TEID for N3)

    SMF->>PSA1: N4 Session Modification Request<br/>(Update FAR: DL forwarding to UL CL N9)
    PSA1-->>SMF: N4 Session Modification Response

    Note over UE,PCF: 阶段三：N2会话修改
    SMF->>AMF: Namf_Communication_N1N2MessageTransfer<br/>(N2 SM Info: UL CL F-TEID + QoS)
    AMF->>RAN: N2 PDU Session Resource Modify<br/>(N2 SM Info + NAS PDU Session Modify)
    RAN->>RAN: 建立到UL CL的新N3隧道
    RAN-->>AMF: N2 PDU Session Resource Modify Response<br/>(AN Tunnel Info)
    AMF->>SMF: Nsmf_PDUSession_UpdateSMContext<br/>(AN Tunnel Info)

    Note over UE,PCF: 阶段四：隧道激活
    SMF->>ULCL: N4 Session Modification Request<br/>(Update FAR#3/#4: AN Tunnel Info)
    ULCL-->>SMF: N4 Session Modification Response

    Note over UE,PCF: 数据面激活
    rect rgb(230, 245, 255)
        Note over UE,PSA2: 激活后的数据面路径
        UE->>RAN: 上行数据包
        RAN->>ULCL: N3隧道（UL CL F-TEID）
        ULCL->>PSA2: [匹配本地过滤器] N9→N6→Local DN
        ULCL->>PSA1: [匹配默认过滤器] N9→N6→Central DN
        PSA2->>ULCL: 下行数据（来自Local DN）
        PSA1->>ULCL: 下行数据（来自Central DN）
        ULCL->>RAN: 合并下行数据
        RAN->>UE: 下行数据
    end

    Note over UE,PCF: 阶段五：策略通知（可选）
    SMF->>PCF: Npcf_SMPolicyControl_Update<br/>(DNAI change notification)
    PCF-->>SMF: Policy Update Ack

flowchart TD
    A[SMF检测到UE位置变化/AF请求] --> B{当前DNAI == 目标DNAI?}
    B -->|是| C[无需插入UL CL<br/>保持当前路径]
    B -->|否| D{SSC模式?}
    D -->|SSC Mode 1| E[不能改变PSA<br/>通过UL CL插入实现本地分流]
    D -->|SSC Mode 2| F[先释放旧PSA<br/>再建立新PSA+UL CL]
    D -->|SSC Mode 3| G[先建立新PSA+UL CL<br/>再释放旧PSA]
    E --> H[选择UL CL UPF<br/>选择PSA2 UPF]
    F --> H
    G --> H
    H --> I[建立N4会话<br/>编排PDR/FAR规则]
    I --> J[N2会话修改<br/>激活数据面隧道]

flowchart LR
    subgraph UL_CL_UPF["UL CL UPF规则编排"]
        direction TB
        subgraph PDR_Table["PDR检测表"]
            PDR1["PDR#1<br/>Precedence: 100<br/>Src: ACCESS<br/>SDF: dst=10.0.0.0/8<br/>→FAR#1"]
            PDR2["PDR#2<br/>Precedence: 200<br/>Src: ACCESS<br/>SDF: default<br/>→FAR#2"]
            PDR3["PDR#3<br/>Precedence: 100<br/>Src: CORE(PSA1)<br/>UE IP match<br/>→FAR#3"]
            PDR4["PDR#4<br/>Precedence: 100<br/>Src: CORE(PSA2)<br/>UE IP match<br/>→FAR#4"]
        end
        subgraph FAR_Table["FAR动作表"]
            FAR1["FAR#1<br/>Action: FORWARD<br/>Dst: CORE<br/>N9→PSA2"]
            FAR2["FAR#2<br/>Action: FORWARD<br/>Dst: CORE<br/>N9→PSA1"]
            FAR3["FAR#3<br/>Action: FORWARD<br/>Dst: ACCESS<br/>N3→RAN"]
            FAR4["FAR#4<br/>Action: FORWARD<br/>Dst: ACCESS<br/>N3→RAN"]
        end
        PDR1 --> FAR1
        PDR2 --> FAR2
        PDR3 --> FAR3
        PDR4 --> FAR4
    end

PFCP Session Establishment Request
├── Node ID (SMF ID)
├── F-SEID (SMF侧PFCP会话端点)
├── Create PDR #1
│   ├── PDR ID = 1
│   ├── Precedence = 100
│   ├── PDI (Packet Detection Information)
│   │   ├── Source Interface = ACCESS (0)
│   │   ├── F-TEID = AN Tunnel Endpoint (待后续Update)
│   │   ├── UE IP Address = x.x.x.x
│   │   └── SDF Filter = "permit out ip from any to 10.0.0.0/8"
│   ├── Outer Header Removal = GTP-U/UDP/IPv4
│   ├── FAR ID = 1
│   └── QER ID = 1
├── Create FAR #1
│   ├── FAR ID = 1
│   ├── Apply Action = FORW (Forward)
│   └── Forwarding Parameters
│       ├── Destination Interface = CORE (1)
│       ├── Network Instance = "local.instance.mec"
│       └── Outer Header Creation = N9 GTP-U to PSA2 F-TEID
├── Create QER #1
│   ├── QER ID = 1
│   ├── Gate Status = OPEN
│   ├── QFI = 7 (URLLC QoS Flow)
│   ├── UL Maximum Bitrate = 100 Mbps
│   └── DL Maximum Bitrate = 100 Mbps
└── Create URR #1
    ├── URR ID = 1
    ├── Measurement Method = VOLUME
    ├── Reporting Triggers = VOLUME_THRESHOLD
    └── Volume Threshold = 1 GB

                    ┌─────────────────┐
                    │   Central DN    │ (Internet/核心网业务)
                    └────────┬────────┘
                             │ N6
                    ┌────────▼────────┐
                    │   UPF (PSA1)    │ ← 中央PDU会话锚点
                    └────────┬────────┘
                             │ N9 (GTP-U)
                    ┌────────▼────────┐
           ┌────────│  UPF (UL CL)    │────────┐
           │        └────────┬────────┘        │
           │                 │ N3 (GTP-U)       │ N9 (GTP-U)
           │        ┌────────▼────────┐        │
           │        │   (R)AN / gNB   │        │
           │        └────────┬────────┘        │
           │                 │ Uu               │
           │        ┌────────▼────────┐        │
           │        │       UE        │        │
           │        └─────────────────┘        │
           │                                   │
           │  ┌─────────────────┐    ┌─────────▼─────────┐
           │  │ UPF (PSA2)      │    │ (UL CL内部路由)    │
           │  │ 本地锚点        │◄───┤ PDR#1匹配→FAR#1   │
           │  └────────┬────────┘    │ PDR#2匹配→FAR#2──►│──PSA1
           │           │ N6          └───────────────────┘
           │  ┌────────▼────────┐
           └─►│   Local DN      │ (MEC应用服务器)
              │ (Edge Server)   │
              └─────────────────┘

sequenceDiagram
    participant SMF
    participant ULCL as UPF(UL CL)
    participant PSA1 as UPF(PSA1)
    participant PSA2 as UPF(PSA2)
    participant AMF
    participant RAN as (R)AN

    Note over SMF,PSA2: 触发：UE移出MEC区域 / AF撤销请求
    SMF->>PSA2: N4 Session Release Request
    PSA2-->>SMF: N4 Session Release Response

    SMF->>ULCL: N4 Session Release Request
    ULCL-->>SMF: N4 Session Release Response

    SMF->>PSA1: N4 Session Modification Request<br/>(Update FAR: DL→新N3直连gNB)
    PSA1-->>SMF: N4 Session Modification Response<br/>(PSA1 N3 F-TEID)

    SMF->>AMF: Namf_Communication_N1N2MessageTransfer<br/>(N2 SM: PSA1 N3 F-TEID)
    AMF->>RAN: N2 PDU Session Resource Modify<br/>(更新隧道端点为PSA1)
    RAN-->>AMF: N2 PDU Session Resource Modify Response
    AMF->>SMF: Nsmf_PDUSession_UpdateSMContext

    Note over SMF,RAN: 数据面恢复为 UE→RAN→PSA1→Central DN

stateDiagram-v2
    [*] --> Normal: PDU会话建立<br/>(单PSA，无UL CL)
    Normal --> UL_CL_Insertion: DNAI变化/AF请求<br/>触发UL CL插入
    UL_CL_Insertion --> Dual_PSA_Active: N4建立+N2修改完成<br/>双锚点激活
    Dual_PSA_Active --> Dual_PSA_Active: 持续分流<br/>本地+中央流量并行
    Dual_PSA_Active --> UL_CL_Removal: UE移出MEC区域<br/>或AF撤销
    UL_CL_Removal --> Normal: UL CL移除完成<br/>恢复单锚点
    Dual_PSA_Active --> PSA_Relocation: SSC Mode 3<br/>PSA切换
    PSA_Relocation --> Dual_PSA_Active: 新PSA建立<br/>旧PSA保持
    PSA_Relocation --> Normal: 旧PSA释放<br/>UL CL移除