4G和5G网络传输通道-SCTP.docx
4G和5G网络传输通道-SCTP#5g#4g#SCTP在4G和5G网络中无线节点（eNodeB/gNB涧，与核心网元都是由SCTP连接的；通过协议X2AP/S1AP/XnAP/NGAP进行控制信息传递。SCTP（流控制传输协议）是Internet协议族中可靠传输协议,通过IP网络传输电信消息。它结合了TCP（面向连接）和UDP（无连接）协议的几个特性，也负责数据传输并具有拥塞控制机制和提高发送数据包时的容错机制。由于其高度的灵活性，SCTP还用于其他应用程序（如服务器的管理和管理）。做为流控制传输协议，SCTP也是一个类似TCP的传输协议。它具有可靠、按顺序传输数据的特点；提供对多宿主支持，其连接的一个或两个端点可以包含多个IP地址，这使得冗余网络路径之间的透明故障转移成为可能。一、移动通信网络SCTP应用在蜂窝通信系统中SCTP是eNB和MME（4G）和gNB和AMF（5G）之间的使用如下图所示：Transport1ayerprotoco1fortheseinterfaces<36,300-Figure4.1>4G1TE38.300-FigUr%虐盟起宇5GNR图1.4G和5G网络中SCTP的应用二、SCTP协议栈在4G和5G网络接口协议栈中除顶层支持的无线网络层应用协议外，其传输层结构相同。<36.412-Figure4,1>38.41”gM葡厂寿云图2.4G和5G网络中SCTP协议栈三、SCTP数据包结构4G(1TE)和5G(NR)系统中SCTP承载的数据包基本相同，结构如下图所示：IPSCTPNGAPPay1oad(Data)5G/NR图3.4G和5G网络中SCTP数据包结构四、SCTP建立流程与TCP一样SCTP需通过初始握手来建立两个端点之间的连接；与TCP经过3次握手相比，SCTP须经过4步握手；初始建立过程如下：No.TimeSourceDestinationProto1engthInfb(1)1317.61282788710.e.18510.e.162SCTP82INIT(2)13117.612877198e.e.e.i62e.e.e.i85SCTP36INIT-ACK13217.61763864610.0.0.185e.e.e.i62SCTP278CKIE-ECHO(4)13317.617653624e.e.e.i6210.e.0.185SCTP图4.SCTP初次建立流程五、SCTP建立消息5.1 INrr(初始建立)InternetProtoco1Version4,Src:10.0.0.185,Dst:10.0.0.1620100.=Version:4.0101=Header1ength:20bytes(5)DifferentiatedServicesFie1d:0x02(DSCP：CSO,ECN:ECT(0)000000.=DifferentiatedServicesCodepoint:Defau1t(0)10=Exp1icitCongestionNotification:ECN-Capab1eTransportcodepoint,10,(2)Tota11ength:68Identification:0x0000(0)F1ags:0×40,Don,tfragment0=Reservedbit:Notset.1=Don,tfragment:Set.0=Morefragments:NotsetFragmentOffset:0Timeto1ive:64Protoco1:SCTP(132)HeaderChecksum:0x24dava1idationdisab1edHeaderchecksumstatus:UnverifiedSourceAddress:10.0.0.185DestinationAddress:10.0.0.162StrecunContro1TransmissionProtoco1,SrcPort:48041(48041),DstPort:38412(38412)Sourceport:48041Destinationport:38412Verificationtag:0×00000000Associationindex:65535Checksum:0×0ffaab98unveritiedChecksumStatus:UnverifiedINITchunk(Outboundstreams:8,inboundstreams:65535)Chunktype:INIT(1)0=Bit:Stopprocess!ngofthepacket.0=Bit:DonotreportChunkf1ags:0x00Chunk1ength:36Initiatetag:0×8d10a6cfAdvertisedreceiverwindowcredit(a_rwnd):106496Numberofoutboundstreams:8Numberofinboundstreams:65535initia1TSN:3757580128Supportedaddresstypesparameter(Supportedtypes:IPv4)Parametertype:Supportedaddresstypes(0×000c)0=Bit:Stopprocess!ngofchunk.0=Bit:donotreportParameter1ength:6Supportedaddresstype:IPv4address(5)Parameterpadding:0000ECNparameterParametertype:ECN(0×8000)1=Bit:Skipparameterandcontinueprocess!ngofthechunk.0=Bit:DonotreportParameter1ength:4ForwardTSNsupportedparameterParametertype:ForwardTSNsupported(0xc000)1=Bit:Skipparameterandcontinueprocess!ngofthechunk.1=Bit:DoreportParameter1ength:45.2 INrr_ACK(初始建立响应)internetProtoco1Version4,Src:10.0.0.162,Dst:10.0.0.1850100.=Version:4.0101=Header1ength:20bytes(5)DifferentiatedServicesFie1d:0x02(DSCP:CSO,ECN:ECT(O)000000.=DifferentiatedServicesCodepoint:Defau1t(0)10=Exp1icitCongest!onNotification:ECN-Capab1eTransportcodepoint,10'(2)Tota11ength:292Identification:0x0000(0)F1ags:0×40,Don,tfragment0=Reservedbit:Notset.1=Don,tfragment:Set.0=Morefragments:NotsetFragmentOffset:0Timeto1ive:64Protoco1:SCTP(132)HeaderChecksum:0x23fava1idationdisab1edHeaderchecksumstatus:UnverifiedSourceAddress:10.0.0.162DestinationAddress:10.0.0.185Streamcontro1TransmissionProtoco1,SrcPort:38412(38412),DstPort:48041¢48041)Sourceport:38412Destinationport:48041verificationtag:0×8d10a6cfAssociationindex:65535Checksum:0×30678470unverifiedChecksumStatus:Unverifiedinit_ackchunk(Outboundstreams:8,inboundstreams:8)Chunktype:INIT_ACK(2)0=Bit:Stopprocessingofthepacket.0=Bit:DonotreportChunkf1ags:0x00Chunk1ength:260Initiatetag:0x790ad620Advertisedreceiverwindowcredit(a_rwnd):106496Numberofoutboundstreams:8Numberofinboundstreams:8initia1TSN:4169966867Statecookieparameter(Cookie1ength:228bytes)Parametertype:Statecookie(0x0007)0=Bit:Stopprocessingofchunk.0=Bit:donotreportParameter1ength:232Statecookie:4124569d7e0548bdbfbc4c54e0af0c95e938d9f500000000000000000000000000000000.ECNparameterParametertype:ECN(0×8000)1=Bit:Skipparameterandcontinueprocess!ngofthechunk.0=Bit:donotreportParameter1ength:4ForwardTSNsupportedparameterParametertype:ForwardTSNsupported(OxcOOO)1=Bit:Skipparameterandcontinueprocess!ngofthechunk.1=Bit:DoreportParameter1ength:45.3 COOK1E_ECHO(COOK1E响应)InternetProtoco1Version4,Src:10.0.0.185,Dst:10.0.0.162O1OO.=Version:4.O1O1=Header1ength:20bytes(5)DifferentiatedServicesFie1d:0x02(DSCP：CSO,ECN:ECT(O)000000.=DifferentiatedServicesCodepoint:Defau1t(0)10=Exp1icitCongestionNotification:ECN-Capab1eransportcodepoint,10,(2)Tota11ength:264Identification:0x0000(0)F1ags:0x40,Don,tfragment0=Reservedbit:Notset.1=Don,tfrag
