【原】5G(SA)网络中的PDU会话建立

在5G(SA)网络中PDU会话(PDU Session)建立相当于4G(LTE)中的PDN建立。PDU会话建立主要目的是分配终端(UE)IP并通知UE涉及的各核心网络单元(应用层组件)的IP地址。PDU会话建立另一个重要作用是建立QoS流，此外还有QFI和QRI。

        ***在IP分配方面，PDU会话建立对应于LTE中的PDN连接过程。

一、PDU会话资源设置

• 为一个或多个PDU会话和相应QoS流，在Uu接口和NG-U接口上为终端（UE)进行资源分配；

• 为给定终端(UE)配置相应的数据承载(DRB)。

二、PDU会话资源建立流程

5G(SA)PDU会话信令流程在TS 38.413 - 8.2.1中进行了定义，如下图所示：

                         图1.PDU会话资源建立流程图

***在5G(SA)网络中终端(UE)的PDU会话资源建立都是由核心网元AMF发起，无线网络NG-RAN完成资源分配后，回复“建立响应”。

三、PDU会话资源请求内容

• PDU会话资源设置请求列表；

•     PDU Session NAS-PDU；

•     PDU会话ID；

• RAN寻呼优先级；

• PDU会话资源建立请求传输IE；

•     UL NG-U UP TNL信息；

•     其他UL NG-U UP TNL信息；

•     通用网络实例；

•     网络实例；

•     UP传输层信息列表；

•     冗余UL NG-U UP TNL信息；

•     每个TNL信息冗余 QoS流；

•     每个TNL信息附加冗余DL QoS流；

•     TSC流量特征；

•     PDU会话类型；

•     安全指示；

• 完整性保护指示；

• 密保指示；

• 最大完整性保护数据速率下行链路；

• 最大完整性保护数据速率上行链路；

•     PDU会话聚合最大比特率；

•     QoS流级别QoS参数；

•     附加QoS流信息；

•     QoS监控请求；

• 流级QoS参数；

•     GBR QoS流信息；

• 备选QoS参数集列表；

•     冗余QoS流指示器；

•     冗余PDU会话信息；

•     PDU会话预期的UE活动行为。

四、PDU会话资源设置响应

• PDU会话资源设置响应传输(内容）。

•     完整性保护结果；

•     保密保护结果IE；

•     当前QoS参数集索引；

•     次要NG-RAN节点的全局RAN节点ID；

•     每个TNL信息的QoS流；

•     QoS流未能建立列表；

•     PDU会话资源设置不成功传输。

五、PDU会话示例

5.1 NG Setup Request

Internet Protocol Version 4, Src: 10.0.0.185, Dst: 10.0.0.162

   ......（IP协议版本，源点IP地址，目标IP地址)

Stream Control Transmission Protocol, Src Port: 48041 (48041), Dst Port: 38412 (38412)(SCTP 源端口48041，目的端口38412)

    Source port: 48041

    Destination port: 38412

    Verification tag: 0x790ad620

    [Association index: 65535]

    Checksum: 0x3dba6023 [unverified]

    [Checksum Status: Unverified]

    DATA chunk(ordered, complete segment, TSN: 3757580128, SID: 0, SSN: 0, PPID: 60, payload length: 58 bytes)

        Chunk type: DATA (0)

            0... .... = Bit: Stop processing of the packet

            .0.. .... = Bit: Do not report

        Chunk flags: 0x03

            .... 0... = I-Bit: Possibly delay SACK

            .... .0.. = U-Bit: Ordered delivery

            .... ..1. = B-Bit: First segment

            .... ...1 = E-Bit: Last segment

        Chunk length: 74

        Transmission sequence number: 3757580128

            [This chunk is acked in frame: 138]

                [The RTT to SACK was: 0.000032008 seconds]

        Stream identifier: 0x0000

        Stream sequence number: 0

        Payload protocol identifier: NGAP (60)

        Chunk padding: 0000

NG Application Protocol(NG AP协议）

    NGAP-PDU: initiatingMessage (0)--初始信息

        initiatingMessage

            procedureCode: id-NGSetup (21)

            criticality: reject (0)

            value

                NGSetupRequest

                    protocolIEs: 4 items

                        Item 0: id-GlobalRANNodeID（无线网ID）

                            ProtocolIE-Field

                                id: id-GlobalRANNodeID (27)

                                criticality: reject (0)

                                value

                                    GlobalRANNodeID: globalGNB-ID (0)

                                        globalGNB-ID

                                            pLMNIdentity: 00f110

                                    Mobile Country Code (MCC): Unknown (1)

                                    Mobile Network Code (MNC): Unknown (01)

                                    gNB-ID: gNB-ID (0)

           gNB-ID: 00123450 [bit length 28, 4 LSB pad bits,......]

                        Item 1: id-RANNodeName（无线网名称）

                            ProtocolIE-Field

                                id: id-RANNodeName (82)

                                criticality: ignore (1)

                                value

                                    RANNodeName: gnb0012345

                        Item 2: id-SupportedTAList（支持TA列表）

                            ProtocolIE-Field

                                id: id-SupportedTAList (102)

                                criticality: reject (0)

                                value

                                    SupportedTAList: 1 item

                                        Item 0

                                            SupportedTAItem

                                                tAC: 100 (0x000064)

                                                broadcastPLMNList: 1 item

                                                    Item 0

                                                        BroadcastPLMNItem

                                         pLMNIdentity: 00f110

                                  Mobile Country Code (MCC):Unknown (1)

                                  Mobile Network Code (MNC):Unknown (01)

                                 tAISliceSupportList: 1 item

                                  Item 0

                                  SliceSupportItem

                                  s-NSSAI  sST: 01

                     Item 3: id-DefaultPagingDRX（Paging默认支持DRX)

                            ProtocolIE-Field

                                id: id-DefaultPagingDRX (21)

                                criticality: ignore (1)

                                value

                                    PagingDRX: v128 (2)

5.2 NG Setup Response

Internet Protocol Version 4, Src: 10.0.0.162, Dst: 10.0.0.185

   .......

Stream Control Transmission Protocol, Src Port: 38412 (38412), Dst Port: 48041 (48041)

   ......

NG Application Protocol

    NGAP-PDU: successfulOutcome (1)(NGAP-PDU成功输出)

        successfulOutcome

            procedureCode: id-NGSetup (21)

            criticality: reject (0)

            value

                NGSetupResponse

                    protocolIEs: 4 items

                        Item 0: id-AMFName

                            ProtocolIE-Field

                                id: id-AMFName (1)

                                criticality: reject (0)

                                value

AMFName:amarisoft.amf.5gc.mnc001.mcc001.3gppnetwork.org(AMF名称）

Item 1:id-ServedGUAMIList(服务GUAMI列表）

                            ProtocolIE-Field

                                id: id-ServedGUAMIList (96)

                                criticality: reject (0)

                                value

                                    ServedGUAMIList: 1 item

                                        Item 0

                       ServedGUAMIItem  gUAMI

                        pLMNIdentity: 00f110

                        Mobile Country Code (MCC): Unknown (1)

                        Mobile Network Code (MNC): Unknown (01)

        aMFRegionID: 80 [bit length 8,1000 0000 decimal value 128]

        aMFSetID: 0100 [bit length 10,6 LSB pad bits, 0000 0001  00.. ....

decimal value 4]

        aMFPointer: 04 [bit length 6, 2 LSB pad bits,0000 01.. decimal value 1]

     Item 2: id-RelativeAMFCapacity（相关AMF能力）

                            ProtocolIE-Field

                                id: id-RelativeAMFCapacity (86)

                                criticality: ignore (1)

                                value

                                    RelativeAMFCapacity: 50

      Item 3: id-PLMNSupportList（支持PLMN列表）

                            ProtocolIE-Field

                                id: id-PLMNSupportList (80)

                                criticality: reject (0)

                                value

                                    PLMNSupportList: 1 item

                                        Item 0

                                            PLMNSupportItem

                                                pLMNIdentity: 00f110

                                Mobile Country Code (MCC): Unknown (1)

                                Mobile Network Code (MNC): Unknown (01)

                                sliceSupportList: 1 item(支持切片列表）

                                                    Item 0

                                                        SliceSupportItem

                                                            s-NSSAI

                                                                sST: 01