Research On Consistent Flow Update Problem In Software Defined Networks

The rapid development of network technology has provided people in contemporary society with a more convenient and high-quality life.However,with the increasing scale of the network,network management and maintenance tasks have also become increasingly complex.Traditional network architecture is facing unprecedented challenges under the current network development situation,such as relatively closed architecture,inflexible management ways and overcomplicated network protocols.As a new paradigm of network architecture,Software defined networks(SDN)conforms to the needs of network development and focuses on solving the key problems of the traditional network architecture.SDN seperates the control plane from the data plane,and introduces a controller to centrally manage all forwarding devices in the entire network.This software-based programmable control plane brings great flexibility to network management and releases powerful potential for optimizing the network.However,the asynchrony of the data plane causes various abnormal behaviours during the management of the SDN network.This dissertation mainly studies the problems of the consistent flow update in software defined networks,aiming to avoid various abnormal phenomena during flow update,so that the network can provide better reliablity and better performance.The main research contents of this dissertation are as follows:(1)Research on the consistent flow update problem in software defined network.A Fast and Consistent flow update(FCFU)strategy in the software defined network is proposed,which can avoid abnormal network beheaviors during the flow update by arranging the update sequence of the flows reasonably.This strategy first weakens the original strong dependency through flow segmentation technology,and enables the ability of parallel update.Then,by analyzing the dependency between the sub-flow segments and multiple resources,the update schedule with less numbers of rounds is obtained.Finally,in order to avoid out-of-order packets,consistent flow update is achieved based on the delay queue.Experimental results show that,compared with the existing flow update algorithm,this strategy can shorten the total completion time of flow update by20.6%,while ensuring that no congestion and packet reordering occur during the update period.(2)Research on the problem of the consistent network update in hybrid software defined network.A safe and fast network update strategy(HSFUS)in the hybrid software defined network is proposed.This statregy first constructs a shortest path tree,which rooted at the destination node to be updated,and then in each iteration determines whether each leaf node of the shortest path tree meets the update consistency.By continuously adjusting the shortest path tree,an operation sequence that meets the upate requirements is finally obtained.For operations that cannot continue to update due to network inconsistencies,the final update is completed through a two-stage update method.The experimental results show that the algorithm proposed in this dissertation can safely and consistenly complete the network update in the hybrid software defined network.Compared with similar algorithms,the update sequence can be obtained in a shorter calculation time,which additionally occupies less TCAM(Ternary Content Addressable Memory)resources and avoids link congestion during network update.