5G UL CL上行分类器MEC本地分流信令流全链拆解

sequenceDiagram
    participant UE
    participant RAN as (R)AN/gNB
    participant AMF
    participant SMF
    participant PCF
    participant ULCL as UL CL UPF
    participant PSA1 as PSA-1<br/>(Central UPF)
    participant PSA2 as PSA-2<br/>(Local/Edge UPF)

    Note over UE,PSA1: 阶段1: 初始PDU Session已建立（仅PSA-1）

    Note over SMF,PCF: 阶段2: SMF决策插入UL CL
    SMF->>PCF: Npcf_SMPolicyControl_Update<br/>(获取路由策略/DNAI信息)
    PCF-->>SMF: 200 OK + Policy Update<br/>(含Traffic Steering Policy)

    Note over SMF,PSA2: 阶段3: 为本地DN建立PSA-2的N4会话
    SMF->>PSA2: PFCP Session Establishment Request<br/>(Create PDR + FAR + QER)
    PSA2-->>SMF: PFCP Session Establishment Response<br/>(F-TEID for DL)

    Note over SMF,ULCL: 阶段4: 配置UL CL UPF（插入分流规则）
    SMF->>ULCL: PFCP Session Modification Request<br/>(Create PDR: SDF→Local DN +<br/>Create FAR: Forward→PSA2 +<br/>Update FAR: Default→PSA1)
    ULCL-->>SMF: PFCP Session Modification Response

    Note over SMF,PSA1: 阶段5: 更新PSA-1下行隧道
    SMF->>PSA1: PFCP Session Modification Request<br/>(Update FAR: DL F-TEID指向UL CL)
    PSA1-->>SMF: PFCP Session Modification Response

    Note over UE,RAN: 阶段6: 数据面分流生效
    UE->>RAN: UL Data: 本地业务<br/>(目的IP=Edge App Server)
    RAN->>ULCL: GTP-U (N3隧道)
    ULCL->>PSA2: 匹配SDF Filter →<br/>转发到Local DN (N9隧道)
    PSA2->>MEC App: 本地数据网络

    UE->>RAN: UL Data: 互联网业务<br/>(目的IP=Internet)
    RAN->>ULCL: GTP-U (N3隧道)
    ULCL->>PSA1: 不匹配本地Filter →<br/>默认转发到Central DN (N9隧道)
    PSA1->>Internet: 互联网数据网络

    Note over PSA1,ULCL: 下行方向合并
    PSA2->>ULCL: DL Data (N9)
    PSA1->>ULCL: DL Data (N9)
    ULCL->>RAN: 合并后统一转发 (N3)
    RAN->>UE: DL Data

flowchart TD
    A[SMF决策点：<br/>是否插入UL CL？] --> B{触发条件判断}

    B -->|触发1| C[AF Influence on Traffic Routing<br/>TS 23.502 §4.3.6<br/>MEC应用通过NEF/PCF请求路由]
    B -->|触发2| D[UE移动性触发<br/>TA变更/Cell变更<br/>UE进入新的DNAI服务区]
    B -->|触发3| E[SMF本地策略/订阅数据<br/>基于DNN+S-NSSAI<br/>预配置的路由规则]

    C --> F[PCF下发SM Policy<br/>含Traffic Steering Decision<br/>DNAI + Routing Info]
    D --> G[SMF检测DNAI变更<br/>旧DNAI→新DNAI]
    E --> H[SMF查询UDM订阅数据<br/>获取本地路由策略]

    F --> I[SMF选择新的Local PSA-2<br/>基于DNAI和UPF拓扑]
    G --> I
    H --> I

    I --> J[建立PSA-2的PFCP会话]
    J --> K[配置UL CL分流规则]
    K --> L[更新PSA-1下行隧道]
    L --> M[可选：通知AF DNAI变更]

flowchart LR
    subgraph SMF发送的PFCP Session Est Req
        A1[Create PDR 1<br/>PDR ID=1<br/>Precedence=100<br/>PDI: SrcIface=ACCESS<br/>UE IP Addr<br/>F-TEID: UL CL→PSA2<br/>SDF Filter: permit out<br/>ip to 10.1.0.0/16] --> A2[Create FAR 1<br/>FAR ID=1<br/>Action=FORWARD<br/>DstIface=CORE<br/>Network Instance:<br/>local-dn.mec]
        A2 --> A3[Create QER 1<br/>QER ID=1<br/>QFI=7<br/>Gate Status=OPEN<br/>UL/DL MBR/GMBR]
        A3 --> A4[Create URR 1<br/>URR ID=1<br/>Method=VOLUME<br/>Volume Threshold]
    end

    subgraph PSA-2返回的Response
        B1[Cause=SUCCESS] --> B2[Created PDR 1<br/>F-TEID for DL<br/>TEID=0xA1B2C3D4<br/>IP=192.168.2.1]
    end

Create PDR:
  PDR ID = 2
  Precedence = 50              ← 高优先级，先于默认规则匹配
  PDI:
    Source Interface = ACCESS   ← 检测上行流量
    UE IP Address = 10.0.1.5   ← 匹配特定UE
    SDF Filter = "permit out ip from 10.0.1.5 to 10.1.0.0/16"
                                ← 目的地址为本地DN网段
  Outer Header Removal = GTP-U/IPv4

Create FAR:
  FAR ID = 2
  Apply Action = FORWARD
  Forwarding Parameters:
    Destination Interface = CORE
    Outer Header Creation:
      GTP-U IPv4
      TEID = 0xA1B2C3D4        ← PSA-2在步骤3中返回的DL F-TEID
      IP Address = 192.168.2.1  ← PSA-2的N9接口IP

Update FAR:
  FAR ID = 1                    ← 修改PDU Session建立时创建的默认FAR
  Apply Action = FORWARD
  Forwarding Parameters:
    Destination Interface = CORE
    Outer Header Creation:
      GTP-U IPv4
      TEID = 0x11111111         ← PSA-1的DL F-TEID
      IP Address = 10.10.1.1    ← PSA-1的N9接口IP

flowchart TD
    subgraph PFCP Session Modification Request
        A[Header<br/>S=1, MP=0<br/>SEID=0x12345678] --> B[Update FAR<br/>FAR ID=1]
        B --> C[Create PDR<br/>PDR ID=2]
        C --> D[Create FAR<br/>FAR ID=2]

        D --> E[Apply Action<br/>FORWARD]
        D --> F[Forwarding Parameters<br/>IE Group]
        F --> F1[Destination Interface<br/>CORE=0]
        F --> F2[Outer Header Creation<br/>GTP-U IPv4]
        F2 --> F2a[TEID=0xA1B2C3D4]
        F2 --> F2b[IP=192.168.2.1]

        C --> G[PDI IE Group]
        G --> G1[Source Interface<br/>ACCESS=1]
        G --> G2[UE IP Address<br/>10.0.1.5]
        G --> G3[SDF Filter<br/>permit out ip to 10.1.0.0/16]
        G --> G4[F-TEID<br/>N3上行隧道标识]
    end

UE发送上行数据包 → gNB封装GTP-U(N3) → UL CL UPF收到
    │
    ├── 匹配PDR-2（高优先级Precedence=50）
    │   ├── SDF Filter: 目的IP ∈ 10.1.0.0/16？
    │   ├── YES → 应用FAR-2 → 封装N9 GTP-U(Teid=A1B2C3D4) → PSA-2 → MEC App
    │   └── NO  → 不匹配，继续检查下一规则
    │
    └── 匹配PDR-1（低优先级Precedence=100，默认规则）
        ├── 匹配所有其他上行流量
        └── 应用FAR-1 → 封装N9 GTP-U(Teid=11111111) → PSA-1 → Internet

MEC App下行 → PSA-2 → 封装N9 GPT-U(Teid=ULCL_DL) → UL CL UPF
Internet下行 → PSA-1 → 封装N9 GPT-U(Teid=ULCL_DL) → UL CL UPF
                                                          │
                                              UL CL统一解封装N9
                                                          │
                                              封装N3 GTP-U(Teid=gNB_N3)
                                                          │
                                                     → gNB → UE

flowchart TB
    subgraph 场景A: SMF主动插入
        A1[SMF检测到：<br/>UE进入MEC服务区<br/>或策略匹配] --> A2[SMF选择PSA-2<br/>建立PFCP会话]
        A2 --> A3[SMF配置UL CL<br/>PFCP Modification]
        A3 --> A4[纯PFCP操作<br/>无需N2/NAS信令]
    end

    subgraph 场景B: I-SMF插入
        B1[UE移动到新的<br/>I-SMF服务区] --> B2[AMF选择新I-SMF<br/>触发PDU Session Mod]
        B2 --> B3[I-SMF插入UL CL<br/>+ 新PSA]
        B3 --> B4[涉及N2信令：<br/>N2 SM Info Update<br/>N9隧道切换]
    end

    subgraph 场景C: AF触发路由
        C1[MEC应用AF请求<br/>流量路由到边缘节点] --> C2[NEF/PCF下发策略<br/>DNAI+路由信息]
        C2 --> C3[SMF执行UL CL插入<br/>PFCP操作]
        C3 --> C4[可选：DNAI变更<br/>通知AF]
    end

SMF → PCF: Npcf_SMPolicyControl_UpdateNotify
  ├── Notification URI
  ├── DNAI = "edge-site-B"           ← 新DNAI
  └── AF notification correlation ID

PCF → AF: Npcf_PolicyAuthorization_Notify
  ├── DNAI change
  ├── New DNAI = "edge-site-B"
  └── Target App relocation info

# 过滤所有PFCP Session相关消息
pfcp && pfcp.seid == 0x12345678

# 过滤包含SDF Filter的PFCP消息
pfcp.sdf_filter

# 过滤特定TEID的GTP-U隧道
gtp.teid == 0xA1B2C3D4