目前主要的MPLS技术.pptx

Defining FlowsHost Bp1Host Ap3 1 1 2 2Each packet of a traditional flow must be processed by the routerThe first packet of an MLS flow is processed by the router;all subsequent packets are switchedHost BConventional EnvironmentFirst PacketSubsequent PacketsHost AMultilayer Switched Environmentp2ABDefining MPLS 多协议标记交换多协议标记交换（Multiprotocol Label Switching，MPLS）是一种介于第二层和是一种介于第二层和第三层之间的标记交换技术，第三层之间的标记交换技术，是专门为是专门为IP设计的，设计的，可以将第二层的高速交换能力可以将第二层的高速交换能力和第三层的灵活特性结合起来，和第三层的灵活特性结合起来，使使IP网具备高速交换、流量控制、网具备高速交换、流量控制、QoS等性能。等性能。MPLS发展简史发展简史多年以前，人们期盼多年以前，人们期盼ATM能做任何事情，随着能做任何事情，随着Internet的发的发展，人们试图通过展，人们试图通过ATM传语音、传图像，但由于传语音、传图像，但由于ATM自身的自身的一些限制，使得它无法适应一些限制，使得它无法适应Internet高速发展的今天。同时，高速发展的今天。同时，由于点到点的连接，人们难以承受其高昂价格以及对带宽资由于点到点的连接，人们难以承受其高昂价格以及对带宽资源的严重浪费。然而，由于源的严重浪费。然而，由于IP网的开放性，人们又很难实现网的开放性，人们又很难实现端到端的连接，同时，语音数据包的传输也带来了很多问题。端到端的连接，同时，语音数据包的传输也带来了很多问题。因而，将因而，将ATM网和网和IP网合二为一是人们早期的一个初衷网合二为一是人们早期的一个初衷 当时最早采用的方式是当时最早采用的方式是IP over ATM，但遇到了非常多的但遇到了非常多的问题和困难，如问题和困难，如IP地址与地址与ATM地址之间的映射问题。地址之间的映射问题。ATM的优点在于其固定长度的包，主要特点用硬件实现转发，因的优点在于其固定长度的包，主要特点用硬件实现转发，因为固定长度的包，只看到包头的这些转发信息就可直接转发。为固定长度的包，只看到包头的这些转发信息就可直接转发。因此，硬把两个协议捆绑在一起不能成功，也不能真正推广。因此，硬把两个协议捆绑在一起不能成功，也不能真正推广。后来，另外一些人试图尝试把两种协议的优势结合起来后来，另外一些人试图尝试把两种协议的优势结合起来,即即将传统的将传统的ATM网的转发机制和网的转发机制和IP网的寻址和路由的机制结网的寻址和路由的机制结合起来，这就产生了合起来，这就产生了IP交换技术进而通过交换技术进而通过IETF组织推出了组织推出了MPLS协议。协议。CISCO标签交换（标签交换（Tag Switching）目前主要的目前主要的MPLS技术技术IBMARIS(集中式基于路由的IP交换技术)*采用控制流量而不是采用控制流量而不是采用数据流量来设置前向表采用数据流量来设置前向表 MLS ComponentsMLS-SEMultilayerSwitching Switch EngineMLSPMultilayer Switching ProtocolMulticast Hello Messages sent to MLS-SE by MLS-RP to Inform:MAC addresses used on different VLANs Routing/accesslists changes occurring on MLS-RPCisco85xx75XX72XX4XXXORRSMMLS-RPMultilayer Switching Route Processor多层交换路由处理器多层交换路由处理器多层交换交换机引擎多层交换交换机引擎多层交换协议多层交换协议MLS-RP AdvertisementMLS-RP sends out multicast hello messages Messages contain MAC,VLAN,and route informationMessages use the CGMP multicast well-known addressCGMP(Cisco组管理协议组管理协议),确保确保SWITCH的互操作性的互操作性Hello MessageHello MessageAll switches receive the hello messageLayer 3 switches process the hello messageIP multicast passes transparently through non-Cisco switchesReceiving MLSP Hello MessagesReceiving MLSP Hello MessagesHello MessageI am not a Layer 3 Switch but I will still pass on the message.Assigning XTAGsMLS-RP AMLS-RP BThe MLS-SE assigns a unique identifier to each MSL-RPXTAG value is a one-byte value that the MLS-SE attaches to the MAC addressUsed to delete a specific Layer 3 entries when then MLS-RP fails or exits the networkMLS-RP CMLS-RP A=XTAG34MLS-RP B=XTAG11MLS-RP C=XTAG28Candidate PacketCandidate PacketSource MAC=0010.f663.d000Destination MAC=0010.0679.5800L3 InformationL3 InformationL2 InformationL2 InformationSource IP=172.16.10.123Destination IP=172.16.22.57Establishing an MLS Cache EntryThe MLS-SE receives initial frameThe MLS-SE reads and recognizes the destination MAC AddressThe MLS-SE checks the MLS cache for like entries The MLS-SE forwards the frame to the MLS-RP 1 1 2 2 3 3 4 4B0010.0679.5800172.16.68.130090.b133.7000172.16.22.57 1 1 2 2 3 3Cache Entry?A0010.f663.d000172.16.10.123 4 4B0010.0679.5800172.16.68.130090.b133.7000172.16.22.57A0010.f663.d000172.16.10.123Source MAC=0010.0679.5800Destination MAC=0090.b133.7000Enable PacketEnable PacketSource IP=172.16.10.123Destination IP=172.16.22.57L3 InformationL3 InformationL2 InformationL2 InformationEstablishing an MLS Cache Entry(cont.)The MLS-RP receives the frame and consults the routing tableThe MLS-RP rewrites the header with the new destination MAC addressThe MLS-RP enters its own MAC address for the source address The MLS-RP forwards the frame to the MLS-SE 5 5 6 6 7 7 8 8 5 5 6 6 8 8 7 7MLS-RP IP MLS-RP ID XTAG MLS-RP MAC-Vlans172.16.68.13 001006795800 28 00-10-67-95-80-00 1,41,42Establishing an MLS Cache Entry(cont.)AB0010.f663.d000172.16.10.1230010.0679.5800172.16.68.130090.b133.7000172.16.22.57MLS CacheCandidate Packet XTAG=28The MLS-SE receives the frame The MLS-SE compares the XTAGs of the candidate and enable packetsThe MLS-SE records the enable packet information in the MLS cache The MLS-SE forwards the frame to the destination 9 9101011111212 9 9Enable Packet XTAG=2810101212Destination IP Source IP Port DstPrt SrcPrt Destination Mac Vlan Port172.16.22.57 172.16.10.123 UDP 1238 60224 00-90-b1-33-70-00 45 2/9MLS Cache Entry1111Switching Subsequent Frames in a FlowThe MLS-SE receives subsequent frames in the flowThe MLS-SE compares the incoming frame with the MLS cache entryThe MLS-SE rewrites the frame header The MLS-SE forwards the frame to the destination1313141415151616Incoming FrameIncoming FrameSource MAC=0010.f663.d000Destination MAC=0010.0679.5800L3 InformationL3 InformationL2 InformationL2 InformationSource IP=172.16.10.123Destination IP=172.16.22.57Destination IP Source IP Port DstPrt SrcPrt Destination Mac Vlan Port172.16.22.57 172.16.10.123 UDP 1238 60224 00-90-b1-33-70-00 45 2/9MLS Cache EntrySource IP=172.16.10.123Destination IP=172.16.22.57L3 InformationL3 InformationL2 InformationL2 InformationRewritten FrameRewritten FrameSource MAC=0010.0679.5800Destination MAC=0090.b133.70000010.f663.d000172.16.10.1230090.b133.7000172.16.22.57AB1313141415151616MLS Topology Example 1 R2MLS-RPBR2R2R1MLS-SEAHost A sends a packet to the default gatewayR1 rewrites the frame header to reflect the destination as the next-hop router(R2)MLS-SE forwards the frame to R2R2 rewrites the frame header to reflect the destination as Host BMLS-SE forwards the frame to Host BAll subsequent frames are switched 1 1 2 2 3 3 4 4 5 5 1 1 2 2 3 3 4 4 6 6 5 5 6 6MLS Topology Example 2 MLS-RPMLS-SE3MLS-SE2MLS-SE1ABHost A sends a packet to the default gatewayMLS-SE1 forwards the frame to MLS-SE2MLS-SE2 forwards the frame to MLS-SE3MLS-SE3 forwards the frame to MLS-RP1MLS-RP1 rewrites the frame header and forwards the frame to MLS-SE3MLS-SE3 forwards the frame to MLS-SE2MLS-SE2 forwards the frame to MLS-SE1MLS-SE1 forwards the frame to Host BAll subsequent frames are switched through MLS-SE1Entries in MLS-SE2 and 3 time out 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 91010 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 910101010Summarize 1 1 2 2Host BFirst PacketSubsequent PacketsHost AMultilayer Switched EnvironmentMPLS Route Once Switch ManyMPLS应用领域应用领域 在在IP网络的网络的QoS方面；方面；在在IP网络的流量工程方面；网络的流量工程方面；在在IP网络的服务功能方面，如网络的服务功能方面，如VPN。MPLSMPLS发展前景和意义发展前景和意义发展前景和意义发展前景和意义Everything over IP 骨干走向边缘骨干走向边缘替代替代ATM 结合底层光设备结合底层光设备简化简化IPv6实施实施为新厂商带来商机为新厂商带来商机提高网络使用率提高网络使用率