PDU会话修改三触发源与QoS Flow动态调整信令全链路拆解

flowchart TD
    A[PDU Session Modification] --> B[UE-Initiated<br/>TS 23.502 §4.3.3.2]
    A --> C[Network-Initiated<br/>TS 23.502 §4.3.3.2]
    A --> D[AN-Initiated<br/>TS 23.502 §4.3.3.3]

    B --> B1[请求新Packet Filter]
    B --> B2[修改现有QoS参数]
    B --> B3[删除Packet Filter]

    C --> C1[PCF策略变更]
    C --> C2[SMF本地决策]
    C --> C3[AF请求触发]

    D --> D1[AN资源释放]
    D --> D2[AN QoS调整]

sequenceDiagram
    participant UE
    participant RAN as (R)AN
    participant AMF
    participant SMF
    participant PCF
    participant UPF
    participant UDM

    Note over UE,UDM: Step 1-4: UE发起修改请求
    UE->>AMF: NAS Transport<br/>PDU Session Modification Request
    Note right of UE: 携带: PDU Session ID,<br/>Procedure Transaction ID,<br/>QoS rules (建议的),<br/>Packet Filters

    AMF->>SMF: Nsmf_PDUSession_UpdateSMContext<br/>N1 SM container + PDU Session ID
    Note right of AMF: 携带: N1 SM Container,<br/>PDU Session ID,<br/>SUPI

    Note over SMF,UDM: Step 5-6: SMF策略授权（条件步骤）
    SMF->>UDM: Nudm_SDM_Get<br/>获取签约数据（如需要）

    alt SMF已与PCF建立N7会话
        SMF->>PCF: Npcf_SMPolicyControl_Update<br/>报告UE请求
        Note right of SMF: 携带: Policy Control<br/>Request Triggers,<br/>UE Request的QoS参数
        PCF-->>SMF: 200 OK<br/>PCC Rules + QoS决策
        Note left of PCF: 携带: 新/修改/删除的<br/>PCC Rules,<br/>Session Rules,<br/>Policy Control<br/>Request Triggers
    end

    Note over SMF,UPF: Step 7: N4 Session Modification
    SMF->>UPF: N4 Session Modification Request
    Note right of SMF: 携带: FAR, QER, URR,<br/>PDR (新/修改/删除)
    UPF-->>SMF: N4 Session Modification Response

    Note over SMF,UE: Step 8-11: 下发修改命令
    SMF->>AMF: N1N2MessageTransfer<br/>N1: PDU Session Modification Command<br/>N2: SM Information
    Note right of SMF: N1: QoS Rules, QoS Flow<br/>参数, Packet Filters<br/>N2: QFI, QoS Profile,<br/>Tunnel Info

    AMF->>RAN: N2 PDU Session Resource<br/>Setup/Modify Request

    RAN->>UE: RRC Reconfiguration<br/>DRB映射更新
    Note right of RAN: QoS Flow→DRB映射

    Note over UE,UPF: Step 12-16: 完成确认
    UE->>RAN: RRC Reconfiguration Complete
    RAN-->>AMF: N2 PDU Session Resource<br/>Setup/Modify Response
    Note left of RAN: 携带: AN Tunnel Info,<br/>接受的QoS Flow列表

    AMF->>SMF: Nsmf_PDUSession_UpdateSMContext<br/>N2 SM Info + N1 SM Container

    UE->>AMF: NAS Transport<br/>PDU Session Modification Complete ACK

    AMF->>SMF: Nsmf_PDUSession_UpdateSMContext<br/>N1 SM Container (ACK)

QoS Rule :=
  QoS Rule Identifier (1 octet)
  Rule Operation Code (2 bits):
    00 = Create new QoS rule
    01 = Delete existing QoS rule  
    10 = Modify existing QoS rule
    11 = Create new QoS rule and replace
  DQR bit (1 bit): 1 = Default QoS Rule
  Number of Packet Filters (6 bits)
  Packet Filter List:
    Packet Filter Identifier
    Packet Filter Direction (2 bits):
      00 = DL, 01 = UL, 10 = Bidirectional
    Packet Filter Components:
      IPv4/IPv6 remote address + mask
      Protocol Number (TCP/UDP/ICMP...)
      Local/Remote port range
      Security Parameter Index (IPsec)
      Type of Service/Traffic Class
      Flow Label (IPv6)
  QoS Rule Precedence (1 octet)
  QFI (6 bits) — 关联到具体QoS Flow

{
  "policyControlRequestTriggers": ["UE_REQUEST"],
  "uePendingPolicyUpdate": true,
  "qosInformation": {
    "5qi": 8,
    "maxbrUl": "100 Mbps",
    "maxbrDl": "200 Mbps"
  },
  "qosMonData": {
    "reqQosMonParams": ["DOWNLINK"],
    "repFreqs": ["EVENT_TRIGGERED"]
  }
}

{
  "pccRules": [{
    "pccRuleId": "pcc-rule-1",
    "refQosData": ["qos1"],
    "flowInfos": [{
      "flowDescription": "permit out ip from any to assigned 10.1.1.2",
      "packFiltId": "pf-1"
    }],
    "precedence": 100
  }],
  "qosDecs": [{
    "qosId": "qos1",
    "5qi": 8,
    "maxbrUl": "50 Mbps",
    "maxbrDl": "100 Mbps",
    "arp": {"priorityLevel": 5, "preemptCap": "NOT_PREEMPT", "preemptVuln": "NOT_PREEMPTABLE"}
  }],
  "policyCtrlReqTriggers": ["PLMN_CHANGE", "RES_MO_RE", "UE_IP_CH"]
}

flowchart LR
    subgraph PCC Rule到N4规则的映射
        A[PCC Rule] --> B[PDR<br/>Packet Detection Rule]
        A --> C[FAR<br/>Forwarding Action Rule]
        A --> D[QER<br/>QoS Enforcement Rule]
        A --> E[URR<br/>Usage Reporting Rule]
    end

    B --> B1[Source Interface: CORE<br/>F-TEID: N3隧道<br/>PDI: SDF Filter]
    C --> C1[Action: FORWARD<br/>Destination Interface:<br/>ACCESS or CORE]
    D --> D1[QFI: 8<br/>Gate Status: OPEN<br/>MBR: 50Mbps UL<br/>GBR: 10Mbps UL]
    E --> E1[Measurement Method:<br/>VOLUME<br/>Reporting Triggers]

sequenceDiagram
    participant AF
    participant PCF
    participant SMF
    participant AMF
    participant RAN as (R)AN
    participant UE
    participant UPF

    Note over AF,UPF: PCF/SMF-Initiated PDU Session Modification

    alt AF触发
        AF->>PCF: Npcf_PolicyAuthorization_Update<br/>请求新的QoS资源
        Note right of AF: 携带: Media Component,<br/>Flow Description, QoS Reference
    end

    PCF->>SMF: Npcf_SMPolicyControl_UpdateNotify<br/>策略更新通知
    Note left of PCF: 携带: 新/修改/删除的<br/>PCC Rules,<br/>QoS Decisions

    SMF-->>PCF: 200 OK (N7响应)<br/>确认接受策略

    Note over SMF: SMF根据PCC Rules<br/>生成N4规则和QoS Flow描述

    SMF->>UPF: N4 Session Modification Request
    UPF-->>SMF: N4 Session Modification Response

    SMF->>AMF: Namf_Communication_N1N2MessageTransfer<br/>N1: Modification Command<br/>N2: SM Information

    AMF->>RAN: N2 PDU Session Resource Modify Request
    Note right of AMF: 如果UE在CM-IDLE状态:<br/>先触发Service Request/Paging

    RAN->>UE: RRC Reconfiguration
    UE->>RAN: RRC Reconfiguration Complete

    RAN-->>AMF: N2 PDU Session Resource Modify Response

    UE->>AMF: NAS: PDU Session Modification Complete ACK
    AMF->>SMF: Nsmf_PDUSession_UpdateSMContext

    Note over SMF: Step: 如果需要更新UPF<br/>下行隧道信息
    SMF->>UPF: N4 Session Modification<br/>(更新DL FAR的隧道信息)

sequenceDiagram
    participant RAN as (R)AN
    participant AMF
    participant SMF
    participant PCF
    participant UPF

    Note over RAN,UPF: AN-Initiated PDU Session Modification<br/>(TS 23.502 §4.3.3.3)

    Note over RAN: 触发条件:<br/>1. QoS Flow失败通知<br/>2. AN资源释放<br/>3. GBR QoS Flow通知

    RAN->>AMF: N2 PDU Session Resource<br/>Modify Indication<br/>或 N2 Resource Release

    Note right of RAN: 携带: PDU Session ID,<br/>QoS Flow List,<br/>Cause Value

    AMF->>SMF: Nsmf_PDUSession_UpdateSMContext<br/>N2 SM Information

    Note over SMF: SMF处理但不向PCF<br/>发送策略更新

    SMF->>UPF: N4 Session Modification<br/>(可选，取决于场景)
    UPF-->>SMF: N4 Response

    SMF->>AMF: Nsmf_PDUSession_UpdateSMContext Response<br/>N2 SM Information (ACK)

    AMF->>RAN: N2 PDU Session Resource<br/>Modify Acknowledge

stateDiagram-v2
    [*] --> NotExist: PDU Session建立时<br/>创建Default QoS Flow

    NotExist --> Active: PDU Session Modification<br/>(Add QoS Flow)
    Active --> Modified: PDU Session Modification<br/>(Modify QoS参数)
    Modified --> Active: 修改完成

    Active --> Inactive: AN资源释放<br/>(AN-Initiated)
    Inactive --> Active: 网络侧重新激活<br/>(PCF/SMF-Initiated)

    Active --> NotExist: PDU Session Modification<br/>(Remove QoS Flow)
    Modified --> NotExist: 删除
    Inactive --> NotExist: SMF决定永久释放

    state Active {
        [*] --> GBR_Flow: 5QI=1-79
        [*] --> NonGBR_Flow: 5QI=80-255
        GBR_Flow: 维持GFBR/MFBR
        NonGBR_Flow: Best Effort
    }

# 捕获NAS PDU Session Modification
nas-5gs.message_type == 0xC1 || nas-5gs.message_type == 0xC2 || nas-5gs.message_type == 0xC3

# PDU Session Modification Request = 0xC1 (193)
# PDU Session Modification Command = 0xC2 (194)  
# PDU Session Modification Complete = 0xC3 (195)

# 捕获N4 PFCP Session Modification
pfcp.message_type == 52  # PFCP Session Modification Request
pfcp.message_type == 53  # PFCP Session Modification Response

# 捕获N7 Policy Update
http2.header.value contains "npcf-smpolicycontrol" && http2.header.value contains "update"