Research And Implementation Of Ethernet Link Failure Detection

With the development of computer technology and communication industry，Ethernettransmit speed grows from10M bps to100G, bps and it is applied in LAN and MAN. Atthe same time, the reliability and availability requirements of Ethernet networkrequirements are also getting higher and higher. The physical or logical link failure willcause the network crush, so it is very important to avoid the failure and to detect andrecover the failure rapidly.According to the research and statistics, over80%failures of Ethernet network aredue to link failure. This thesis mainly research on a type of Ethernet physical link fault,unidirectional link fault, as well as a type of logical link fault, bidirectional forwardingfault. Unidirectional link failure is usually the physical link fault. The fault will usuallycause a series of problem, for example, affect the MSTP detection network loop. Thebidirectional forwarding failure is usually the logic link fault, such as one of logic linkfailure of network layer3forwarding, the bidirectional forwarding detection is mainly usedin layer3forwarding before. Link failure detection generally cooperates with some otherprotocols to achieve fast failure recovery. This paper focuses on the research andimplementation of link failure detection itself.This thesis analyse the phenomenon and problems caused by unidirectional link, andpropose solutions to the failure. Unidirectional link detection eliminates unidirectional linkfailure, avoid network loops and broadcast storms. And introduce the principle andworking mode of bidirectional forwarding detection in detail, and also realizes abi-directional Forwarding Detection protocol in the network layer and datalink layer.The thesis implements the UDLD protocol based on data link layer on vxWorks operatingsystem. And the two protocols are applie to the layer2and layer3Ethernet switches ofFiberhome company, and achieves millisecond detection time.Chapter1of this thesis, first expounds the background of the Ethernet and discussionthe type of of Ethernet link failure. With analysis on the type of Ethernet link failure, propose the corresponding solutions to the different problem from physical link fault orlogic link fault. Chapter2proposes unidirectional link detection protocol for solutionunidirectional link failure and describes UDLD protocols in detail. Describes the principleand work processes of bidirectional forwarding detection protocol. By analysis of thecurrent bi-directional forwarding detection mechanism which applied on network layer,and propose a solution based on data link layer. Chapter3introduces the overall designscheme of UDLD protocol, implements the protocol related functions. And implementsBFD protocol based on network layer and data link layer. Chaper5shows the test resultsof the two protocols. Chaper6summarizes the paper.