Research And Design Of An OpenFlow-based Link Fault Tolerance Algorithm

With the development of computer technology, the Internet has gradually entered into people’s daily life and work, Software Defined Network has become a hotspot of research on future Internet. In SDN networks, link failures is very usual, and network robustness and fault tolerance are also very important aspects. As one of the available options to ensure the quality of network service, fault tolerance has many related studies in the traditional networks, but how to use OpenFlow protocol to achieve efficient link fault tolerance in this new architecture of SDN network still has great room for research works.This article presents the study of link fault tolerance mechanisms based on OpenFlow.By analyzing the existing link recovery and path protection mechanism, we propose an OpenFlow-based segment protection mechanism. We use breadth-first search algorithm to find a shortest path as the working path, and then calculate the backup path for each link of the working path. The method of calculating the backup path is to treat the current link starting point as the starting point, and the end point of the working path as the end point of the backup path, to calculate the shortest path by the breadth-first search algorithm. In this way, we can ensure that the backup path is optimal. Based on the fast-failover type of OpenFlow version 1.3, controller distributes group table for OpenFlow switch, and we select LoS as fault detection mechanism to monitor the state of the switch.The experiment is deployed on Mininet 2.0, and we implement the algorithm as a module in RYU according OpenFlow protocol under the version 1.3. We do the experiments for the link recovery mechanism, path protection mechanism and OpenFlow-based segment protection mechanism separately, and choose the recovery time as the main evaluation index. The experimental results show that the OpenFlow- based segment protection mechanism we proposed has the shortest recovery time.