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1、DOCSIS DOCSIS 协议分析协议分析1议议 程程 介绍 DOCSIS；DOCSIS PHY；DOCSIS MAC DOCSIS CM与CMTS的交互过程；介绍 DOCSIS 1.1；DOCSIS 1.1 关键概念；DOCSIS QoS 特性集；新 MAC 管理消息；分段数据包（Fragmentation）；DOCSIS 1.1 安全；DOCSIS 1.1 上行调度算法；Concatenation；数据有效负载帧头压缩；DOCSIS 2.0 Protocol Analysis。2DOCSIS Protocol DOCSIS Protocol 演变演变 19971997DOCSIS 1.0
2、DOCSIS 1.019991999DOCSIS 1.1DOCSIS 1.1DOCSIS 2.0DOCSIS 2.02001200119951995MCNSMCNSNew MAC FeaturesBackward compatibility“Quality of Service”Increased Security New Phy LayerIncreased BandwidthIncreased RobustnessGlobal Standard for MAC-Data over HFC3DOCSIS DOCSIS 标准标准x 4 Splitters 2 or 3 WayDual Wind
3、ow SM Fiber 1310/1550 nmDual Window FO Transceivers Multitaps 8 PortAmplifiers 1GHz 2-WayCable ModemCustomer Premises EquipmentCMTSDOCSIS Network Servers Provisioning DHCP TFTP ToDTODTFTPDHCPPROV交换机/路由器1 GHz Coaxial CableUpstreamDownstreamOSSIOSSI(Operations Support System Interface)CMTS-NSICMTS-NSI
4、(CMTS Network Side Interface Specifications)RFIRFI(Radio Frequency Interface Specifications)BPI-/BPI+BPI-/BPI+(Security Interface)CMCI(Cable Modem Customer Side Interface Specifications)4DOCSIS 1.0 DOCSIS 1.0 功能功能l开放协议性 n非私有的。l支持CM即插即用l被设计为尽力可达n早期版本标准不指定CM最小速率；n由用户在1.0 CMs和CMTSs间设定最小速率；n支持尽力可达和CIR（保
5、证最低的传输速率）的网络服务；u CIR(Committed Information rate):除了突发，正常时提供CM的最小速率。n不支持 CBR（承诺速率）服务。l灵活性:nDOCSIS 1.0增加 MAC和 PHY参数，灵活控制CM，以确保网络的稳健。l安全与管理nBPI(Baseline Privacy)和BPI管理CM。n兼容SNMP。n远程软件更新。5CMTSCMTS架构架构HFCHFC的参考模型的参考模型TxTxRxRxCATVCATV分配网分配网Video 1Video 2Data下行混频器下行混频器上行分支器上行分支器Data调制解调逻辑桥接、路由CMTSCMTS前前 端端
6、IPIP骨干网骨干网交换机路由器光传输CMCM(透明桥)CPECPE6DOCSISDOCSIS与与CATVCATV频谱频谱下行频率 88-860 MHz上行 5-42/65 MHz5 MHz 42 MHz 54 MHz 550 MHz Local VideoSatellite VideoAddressable ConvertersIPPVIPPVLocal Video750/860 MHz Digital VideoDOCSIS TelephonyDOCSIS Telephony88 MHz 7802.3 Ethernet,ATM MAC LAYERDOCSIS DOCSIS 协议簇协议簇80
7、2.3 Ethernet,ATM MAC LAYERFiber Optic,Coax,UTP Copper PHYSICAL LAYERCable MAC SUBLAYER LLC Security SUBLAYERDownstream Transmission Convergence SUBLAYERCable PMD SUBLAYERUpstream Cable PMDInternet Protocol IP NETWORK LAYERFTP DHCP TFTP SMTP SNMP Telnet ports APPLICATIONS LAYERInternet Protocol IP NE
8、TWORK LAYERFTP DHCP TFTP SMTP SNMP Telnet ports APPLICATIONS LAYERIP RoutingRIP,OSPFMAC Transparent Bridging Cable MAC SUBLAYER LLC Security SUBLAYERDownstream Transmission Convergence SUBLAYERCable PMD SUBLAYERUpstream Cable PMDInternet Protocol IP NETWORK LAYERFTP DHCP TFTP SMTP SNMP Telnet ports
9、APPLICATIONS LAYERFiber Optic,Coax,UTP Copper PHYSICAL LAYERInternet Protocol IP NETWORK LAYERFTP DHCP TFTP SMTP SNMP Telnet ports APPLICATIONS LAYERx 4 MAC Transparent Bridging CMTSCMTSCMCMHFC NetworkHFC NetworkHybrid Fiber Optic Coaxial HFC Network PHYSICAL LAYERCMTSCMTS8CMTS广域网CMTS-NSIHFCCMTVPCTe
10、lRFI上/下行RFI上/下行CMCICMTRI透明的IP传输系统SNMPTFTPDHCPUDPIP、IGMPLLC/DIXARP链路安全MAC传输汇聚（只对下行）PMD网络层以上数据链路层物理层DOCSISDOCSIS与与OSIOSI9北美北美DOCSIS 1.x DOCSIS 1.x 下行下行 Physical Media Dependent Physical Media Dependent SublayerSublayer l下行：91-857 MHz，+/-30khzl6 MHz channel widthsn连续调制n两种调制类型：64QAM、256QAMn两种符号速率u 5.0 M
11、Symbols per secu 5.3 MSymbols per secl一端发送多端接收lCM侦听下行信号6 bits per symbol8 bits per symbolData Rate Bandwidth Channel Width(MHz)64QAM Speed(bits/sec)256 QAM Speed(bits/sec)6 MHz North AmericanDOCSIS30MbpsLess10%FEC27Mbps43MbpsLess 10%FEC39 Mbps10Data Rate Bandwidth 6 bits per symbol8 bits per symbol5
12、8MbpsLess10%FEC52Mbps40MbpsLess10%FEC36Mbps8 MHz EuropeanDOCSIS256 QAM Speed(bits/sec)64QAM Speed(bits/sec)Channel Width(MHz)l 欧标DOCSIS 是基于 DOCSIS 1.0/1.1 规范制定的欧标物理子层和MAC；l DVB(Digital Video Broadcasting)在下行8MHz通道QAM调制；l 64或256 QAM 可达到 6.952Msps 符号速率；l 5-65 MHz 上行频率范围欧洲欧洲DOCSIS 1.x DOCSIS 1.x 下行下行Ph
13、ysical Media Dependent Physical Media Dependent SublayerSublayer 11北美北美DOCSIS 1.x DOCSIS 1.x 上行上行Physical Media Dependent Physical Media Dependent SublayerSublayer l上行 5-30/42MHzl在 UCD中定义符号速率l时分多址（TDMA）：把时间分割成周期性的帧(Frame)每一个帧再分割成若干个时隙向CMTS发送信号 2 bits per symbolSymbol Rate(ksym/sec)16032064012802560C
14、hannel Width (KHz)20040080016003200QPSK Speed(bits/sec)320,000 bps640,000 bps1,280,000 bps2,560,000 bps5,120,000 bps16QAM (bits/sec)640,000 bps1,280,000 bps2,560,000 bps5,120,000 bps10,240,000 bps4 bits per symbolKsym/sec=kbpsl一点对多点的接收方式lCM数据在上行调制发送12MPEG HeaderMPEG Headerpointer_field DOCSIS Payloa
15、dpointer_field DOCSIS Payload (4 bytes)(1 byte)(183 or 184 bytes)北美北美DOCSIS 1.x PHYDOCSIS 1.x PHYl 下行传输汇聚子层（下行传输汇聚子层（PHY)PHY)nMPEG II 帧长为：183/184 bytes nMPEG 数据帧头 PID为：0 x1FFEMPEG HeaderMPEG Header Continuation of MAC Frame#1 Continuation of MAC Frame#1 (4 bytes)(184 bytes)MPEG HeaderMPEG Headerpoin
16、ter_field Tail of MAC#1pointer_field Tail of MAC#1 (4 bytes)(1 byte)M bytes M bytesStart of MAC#2Start of MAC#2l 一个MPEG帧头帧头可装载多个可装载多个DOCSIS MAC DOCSIS MAC 帧帧MPEG HeaderMPEG Headerpointer field Start of MAC frame#1pointer field Start of MAC frame#1 (4 bytes)(1 byte)(up to 183 bytes)13DOCSISDOCSISMACMAC层层lCMTS对CM作带宽分配控制；l在上行，时隙和时隔又由微时隙(minislot)组成；l带宽分配的最小单位：微时隙l支持CoS（Class of Service）；l安全：BPI；l服务标识 SIDs 14 bitsn0 x0000 未初始化的 CM SID；n0 x3FFF 信令，对所有 CMs；n组播 SIDs用于请求或数据包；n组播 MAC 01:E0:2F:00:00:01。14
