Research On Link Fault Recovery Mechanism Of SDN Based On Congestion Avoidance

With the wide application of the Internet,the inherent weakness of the traditional network architecture is becoming more and more prominent.Characterized by the separation of control plane and data plane,SDN(Software Defined Network)is a novel network architecture which realizes the flexibility and programmability of the network and greatly improves the efficiency of network management and openness.As to the common link failure phenomenon in the network,SDN has broken through the technical bottleneck of traditional network fault recovery for its special centralized control function.In this paper,we study the link fault recovery problem of SDN data layer in in-band control mode,and adopt different fault recovery mechanism for control traffic and data traffic to realize the reasonable allocation of link resources,the main work of this paper is as follows:Based on the research of the protection scheme of control traffic.this paper puts forward a kind of controller placement algorithm based on measurement of the importance of switch nodes.And the evaluation indexes of network resilience are redefined to realize the protection of control traffic.Then,a fast LBP algorithm is proposed to recover single link failure of the network effectively.Fault link formed is two disconnected subtrees divided from control network,and backup path is minimum weight link to reconnect the subtrees formed through algorithm.Finally,the simulation results show that the LBP algorithm proposed is better than to the FIR or BLR algorithms,and it has little difference to the shortest path resulted from the rerouting;Comparison of the backup path link length and resilience,obtained from Dijkstra algorithm and LBP algorithm,indicates that the lengths of the backup path link are various by different algorithm as to a given controller placement,otherwise,controller placement effects length of the backup path link as to a given algorithm.Aiming at the problem of congestion in link failure recovery.A CA-FC algorithm based on congestion avoidance is proposed for dynamicly adaptive link failure recovery scheme.In order to avoid congestion in fault link recovery and ensure the overall performance of the network,the transmission delay of the path,the current load of link and the resource consumption rate consumed by the recovery path are investigated.Then the overall structure of the link failure recovery system is designed through the algorithm used,and its modules are designed and implemented based on Ryu controller from the open source.Finally,in order to verify the performance of the algorithm,the SDN network is constructed in VMware environment by Ryu controller and Mininet simulation platform.Compared with the related simulation results,it has shown that the system can effectively repair the link failure and has a positive effect on the recovery time and the performance of network.