5G PFCP N4会话建立与五类规则编排全流程拆解

sequenceDiagram
    participant SMF
    participant UPF

    Note over SMF,UPF: PFCP Association Setup (节点级)
    SMF->>UPF: PFCP Association Setup Request
    Note right of SMF: 携带: Node ID(SMF),<br/>Recovery Time Stamp
    UPF->>SMF: PFCP Association Setup Response
    Note left of UPF: 携带: Node ID(UPF),<br/>Recovery Time Stamp,<br/>UP Function Features
    Note over SMF,UPF: Association建立完成，可创建Session

graph TB
    subgraph PFCP_Association["PFCP Association (节点级)"]
        direction TB
        subgraph Session1["PFCP Session 1"]
            PDR1[PDR #1 - UL PDR]
            PDR2[PDR #2 - DL PDR]
            FAR1[FAR #1 - Forward to N6]
            FAR2[FAR #2 - Forward to N3]
            QER1[QER #1 - QoS Flow 1]
            QER2[QER #2 - QoS Flow 2]
            URR1[URR #1 - Usage Report]
            BAR1[BAR #1 - DL Buffer]
        end
        subgraph Session2["PFCP Session 2"]
            PDR3[PDR #3 - UL PDR]
            PDR4[PDR #4 - DL PDR]
            FAR3[FAR #3]
            QER3[QER #3]
        end
    end

    PDR1 -->|"关联"| FAR1
    PDR1 -->|"关联"| QER1
    PDR2 -->|"关联"| FAR2
    PDR2 -->|"关联"| QER2
    PDR2 -->|"关联"| URR1
    PDR2 -->|"关联"| BAR1

sequenceDiagram
    participant UE
    participant gNB
    participant AMF
    participant SMF
    participant UPF
    participant PCF

    UE->>gNB: UL NAS Transport<br/>(PDU Session Establishment Request)
    gNB->>AMF: N2 Message + NAS PDU
    AMF->>SMF: Nsmf_PDUSession_CreateSMContext Request
    Note right of SMF: DNN, S-NSSAI, SUPI<br/>PDU Session ID, Request Type

    SMF->>PCF: Npcf_SMPolicyControl Create
    PCF->>SMF: PCC Rules + QoS Parameters
    Note right of SMF: 获得QoS策略、<br/>计费规则、SDF模板

    Note over SMF: SMF选择UPF并构建<br/>PFCP规则集

    rect rgb(230, 240, 255)
        Note over SMF,UPF: N4/PFCP Session Establishment
        SMF->>UPF: PFCP Session Establishment Request
        Note right of SMF: Create PDR × N<br/>Create FAR × N<br/>Create QER × N<br/>Create URR × N<br/>Create BAR (可选)<br/>F-SEID, UE IP Address
        UPF->>SMF: PFCP Session Establishment Response
        Note left of UPF: Cause<br/>F-SEID (UPF侧)<br/>Created PDR (含F-TEID)<br/>UPF分配的N3隧道端点
    end

    SMF->>AMF: Namf_Communication_N1N2MessageTransfer
    Note right of SMF: N1: PDU Session Estab Accept<br/>N2: N2 SM Info<br/>(含UPF N3 F-TEID)
    AMF->>gNB: N2 PDU Session Resource Setup Request
    gNB->>UE: RRC Reconfiguration<br/>(含PDU Session配置)
    gNB->>AMF: N2 PDU Session Resource Setup Response<br/>(含gNB N3 F-TEID)
    AMF->>SMF: Nsmf_PDUSession_UpdateSMContext

    rect rgb(230, 240, 255)
        Note over SMF,UPF: N4/PFCP Session Modification (更新gNB隧道)
        SMF->>UPF: PFCP Session Modification Request
        Note right of SMF: Update FAR #DL<br/>更新N3 DL F-TEID为gNB隧道端点
        UPF->>SMF: PFCP Session Modification Response
    end

    Note over UE,UPF: 双向用户面数据通路就绪

graph TD
    subgraph PDI["PDI - 包检测信息"]
        direction TB
        A[Source Interface<br/>Access/Core/SGI/LAN]
        B[F-TEID<br/>GTP隧道端点标识]
        C[Network Instance<br/>DNN/APN]
        D[UE IP Address<br/>源/目的IP]
        E[SDF Filter<br/>五元组流量模板]
        F[QFI<br/>QoS Flow Identifier]
        G[Application ID<br/>应用检测标识]
    end

    subgraph PDR["PDR - 包检测规则"]
        PDI
        H[PDR ID<br/>规则唯一标识]
        I["Precedence<br/>优先级(0最高)"]
        J[Outer Header Removal<br/>去除GTP-U/IPv6头]
        K[Associated FAR ID]
        L["Associated QER ID(s)"]
        M["Associated URR ID(s)"]
    end

flowchart TD
    A["收到数据包"] --> B["匹配PDR<br/>(按Precedence优先级)"]
    B -->|"未匹配"| DROP1["丢弃"]
    B -->|"匹配PDR #n"| C["应用关联的QER<br/>(QoS门控/速率控制)"]
    C -->|"Gate=Closed"| DROP2["丢弃"]
    C -->|"Gate=Open"| D["应用关联的FAR<br/>(转发/丢弃/缓存)"]
    D -->|"DROP"| DROP3["丢弃"]
    D -->|"BUFFER"| BUF["缓存数据包<br/>触发DDN通知SMF"]
    D -->|"FORWARD"| E["封装/转发<br/>(Outer Header Creation)"]
    E --> F["应用关联的URR<br/>(用量统计)"]
    F --> G["发出数据包"]

    style A fill:#e1f5fe
    style G fill:#e8f5e9
    style DROP1 fill:#ffebee
    style DROP2 fill:#ffebee
    style DROP3 fill:#ffebee
    style BUF fill:#fff3e0

sequenceDiagram
    participant SMF
    participant UPF

    Note over SMF,UPF: 场景1: gNB隧道更新
    SMF->>UPF: PFCP Session Modification Request
    Note right of SMF: Update FAR #DL:<br/>Outer Header Creation =<br/>新gNB N3 F-TEID
    UPF->>SMF: PFCP Session Modification Response

    Note over SMF,UPF: 场景2: 专用QoS Flow建立
    SMF->>UPF: PFCP Session Modification Request
    Note right of SMF: Create PDR #3 (专用SDF Filter)<br/>Create FAR #3<br/>Create QER #2 (GBR QoS)
    UPF->>SMF: PFCP Session Modification Response

    Note over SMF,UPF: 场景3: UE进入CM-IDLE
    SMF->>UPF: PFCP Session Modification Request
    Note right of SMF: Update FAR #DL:<br/>Apply Action = BUFFER<br/>Associated BAR #1
    UPF->>SMF: PFCP Session Modification Response

stateDiagram-v2
    [*] --> AssociationSetup: SMF/UPF启动
    AssociationSetup --> Idle: Association建立成功
    Idle --> SessionEstablishment: PDU Session建立请求
    SessionEstablishment --> Active: Session创建成功
    Active --> SessionModification: QoS变更/切换/隧道更新
    SessionModification --> Active: 修改成功
    Active --> Suspended: UE进入CM-IDLE
    Note right of Suspended: DL FAR改为BUFFER模式
    Suspended --> SessionModification: UE重新寻呼<br/>恢复DL隧道
    SessionModification --> Active: 恢复成功
    Active --> SessionDeletion: PDU Session释放
    Suspended --> SessionDeletion: PDU Session释放
    SessionDeletion --> Idle: Session删除完成
    Idle --> AssociationRelease: 节点下线
    AssociationRelease --> [*]

# 过滤PFCP Session Establishment
pfcp.msg_type == 50

# 过滤PFCP Session Modification  
pfcp.msg_type == 52

# 过滤特定SEID的PFCP消息
pfcp.seid == 0x1234567890abcdef

# 过滤PFCP Association
pfcp.msg_type == 6 || pfcp.msg_type == 7