5G UL CL上行分类器与BP分支点本地分流全链路信令拆解

UE ──► (R)AN ──┬─ I-UPF(UL CL) ──┬─► PSA1 ──► 中心DN/Internet
               │                  │
               │                  └─► PSA2 ──► 本地DN/MEC
               │
               └─ I-UPF(BP)  ────┬─► PSA1 (IPv6 Prefix-1) ──► 中心DN
                                  │
                                  └─► PSA2 (IPv6 Prefix-2) ──► 本地MEC

sequenceDiagram
    participant UE
    participant RAN
    participant AMF
    participant SMF
    participant PCF
    participant ULCL_UPF as I-UPF(UL CL)
    participant PSA1 as PSA1(中心)
    participant PSA2 as PSA2(本地/MEC)

    Note over UE,PSA2: Step 0: PDU Session已建立，UE→PSA1直连

    UE->>RAN: Mobility Registration Update
    RAN->>AMF: N2 Mobility Registration(含UserLocationInfo)
    AMF->>SMF: Nsmf_PDUSession_UpdateSMContext<br/>(UserLocationInfo, AccessType)

    Note over SMF: SMF检测到UE移入DNAI-2区域<br/>决定插入UL CL和PSA2

    SMF->>PCF: Npcf_SMPolicyControl_Update<br/>(UserLocation, DNAI change)
    PCF-->>SMF: Policy Decision(含Traffic Steering Info)

    Note over SMF: SMF选择I-UPF(支持UL CL)和PSA2

    SMF->>PSA2: N4 Session Establishment Request<br/>(PDR: UE IP→PSA2, FAR→N6 Local DN)
    PSA2-->>SMF: N4 Session Establishment Response<br/>(F-TEID for N9 DL)

    SMF->>ULCL_UPF: N4 Session Establishment Request<br/>(PDR1: SDF→Local, FAR→PSA2<br/>PDR2: Default, FAR→PSA1)
    ULCL_UPF-->>SMF: N4 Session Establishment Response<br/>(F-TEID for N3/N9)

    SMF->>PSA1: N4 Session Modification Request<br/>(更新FAR: DL→ULCL N9 tunnel)
    PSA1-->>SMF: N4 Session Modification Response

    SMF->>AMF: Nsmf_PDUSession_UpdateSMContext Response<br/>(N2 SM Info: UL CL N3 F-TEID)
    AMF->>RAN: N2 PDU Session Resource Setup Request<br/>(UL CL N3 F-TEID)
    RAN-->>AMF: N2 PDU Session Resource Setup Response<br/>(RAN N3 F-TEID)
    AMF->>SMF: Nsmf_PDUSession_UpdateSMContext<br/>(RAN N3 F-TEID)

    SMF->>ULCL_UPF: N4 Session Modification Request<br/>(更新Access侧F-TEID为RAN)
    ULCL_UPF-->>SMF: N4 Session Modification Response

    Note over UE,PSA2: 数据路径建立：<br/>UE→RAN→UL CL→PSA1(中心)<br/>UE→RAN→UL CL→PSA2(本地MEC)

stateDiagram-v2
    [*] --> 收到上行报文
    收到上行报文 --> 检查PDR1: 目的IP匹配本地DN?

    检查PDR1: 目的IP匹配本地DN? --> 匹配: FAR-LOCAL转发至PSA2
    检查PDR1: 目的IP匹配本地DN? --> 不匹配: 检查PDR2
    检查PDR2 --> FAR-CENTRAL转发至PSA1

    匹配: FAR-LOCAL转发至PSA2 --> [*]
    FAR-CENTRAL转发至PSA1 --> [*]

sequenceDiagram
    participant UE
    participant RAN
    participant AMF
    participant SMF
    participant BP_UPF as I-UPF(BP)
    participant PSA1 as PSA1(Prefix-1)
    participant PSA2 as PSA2(Prefix-2)

    Note over UE,PSA2: PDU Session建立请求(IPv6 Multi-homing)

    UE->>AMF: NAS PDU Session Establishment Request<br/>(DNN, S-NSSAI, PDU Type=IPv6)
    AMF->>SMF: Nsmf_PDUSession_CreateSMContext

    SMF->>PSA1: N4 Session Est.(PDR: Prefix-1, FAR: N6 DN1)
    PSA1-->>SMF: N4 Response(F-TEID, IPv6 Prefix-1)

    Note over SMF: SMF决策需要本地分流<br/>选择BP UPF和PSA2

    SMF->>PSA2: N4 Session Est.(PDR: Prefix-2, FAR: N6 DN2/MEC)
    PSA2-->>SMF: N4 Response(F-TEID, IPv6 Prefix-2)

    SMF->>BP_UPF: N4 Session Est.<br/>(PDR1: Src Prefix-1→PSA1<br/>PDR2: Src Prefix-2→PSA2)
    BP_UPF-->>SMF: N4 Response(F-TEID)

    SMF->>AMF: CreateSMContext Response<br/>(N2 SM Info)
    AMF->>RAN: N2 PDU Session Resource Setup
    RAN-->>AMF: N2 Response
    AMF->>SMF: UpdateSMContext(RAN F-TEID)

    SMF-->>UE: NAS PDU Session Establishment Accept<br/>(Interface ID→Prefix-1)

    Note over UE: UE通过Router Solicitation<br/>获得Prefix-2

    UE->>PSA1: Router Solicitation(Prefix-1链路)
    PSA1-->>UE: Router Advertisement(Prefix-1)

    Note over SMF: SMF触发PSA2侧前缀分配

    SMF->>BP_UPF: N4 Modification(下发Prefix-2 RA触发)
    BP_UPF->>UE: Router Advertisement(Prefix-2)

    Note over UE,PSA2: 数据路径：<br/>源Prefix-1→BP→PSA1→DN1<br/>源Prefix-2→BP→PSA2→MEC

flowchart TB
    A[UE移入新TA区域] --> B{AMF检测超出<br/>H-SMF服务范围?}
    B -->|是| C[选择I-SMF]
    B -->|否| D[H-SMF直接管理<br/>UL CL/BP插入]
    C --> E[I-SMF建立<br/>N4会话至I-UPF/UL CL]
    E --> F[I-SMF通过<br/>N16a接口通知H-SMF]
    F --> G[H-SMF更新PSA<br/>N4会话FAR]
    G --> H[数据路径：<br/>UE→I-UPF/UL CL→PSA1/PSA2]

PFCP Session Establishment Request
├── Node ID (SMF标识)
├── F-SEID (SMF侧PFCP会话端点)
├── Create PDR (规则组1: 本地流量)
│   ├── PDR ID = 1
│   ├── Precedence = 100
│   ├── PDI (Packet Detection Information)
│   │   ├── Source Interface = ACCESS (0)
│   │   ├── F-TEID (UL CL N3/N9接收TEID)
│   │   ├── UE IP Address = 10.1.1.2
│   │   ├── SDF Filter
│   │   │   ├── Flow Description: "permit out ip from any to 192.168.100.0/24"
│   │   │   └── ToS Traffic Class: (可选)
│   │   └── Application ID: (可选，用于App检测)
│   ├── Outer Header Removal = GTP-U/UDP/IPv4
│   ├── FAR ID = 1
│   ├── QER ID(s) = (关联QoS规则)
│   └── URR ID(s) = (关联计费规则)
├── Create FAR (FAR-1: 本地转发)
│   ├── FAR ID = 1
│   ├── Apply Action = FORW (Forward)
│   └── Forwarding Parameters
│       ├── Destination Interface = CORE (1)
│       ├── Network Instance = "local.mec.dnn"
│       ├── Outer Header Creation
│       │   ├── Outer Header Type = GTP-U/UDP/IPv4
│       │   ├── TEID = 0xAAA (PSA2 N9 DL TEID)
│       │   └── IPv4 Address = PSA2_IP
│       └── Transportation Level Marking = DSCP value
├── Create PDR (规则组2: 中心流量)
│   ├── PDR ID = 2
│   ├── Precedence = 200 (低于规则组1)
│   ├── PDI
│   │   ├── Source Interface = ACCESS
│   │   ├── F-TEID (同上)
│   │   └── UE IP Address = 10.1.1.2
│   └── FAR ID = 2
├── Create FAR (FAR-2: 中心转发)
│   ├── FAR ID = 2
│   ├── Apply Action = FORW
│   └── Forwarding Parameters
│       ├── Destination Interface = CORE
│       ├── Outer Header Creation
│       │   ├── TEID = 0xBBB (PSA1 N9 DL TEID)
│       │   └── IPv4 Address = PSA1_IP
│       └── ...
└── Create QER / URR (可选)