Reducing Redundant Control Overhead For Fast Response In Distributed Control Of SDN

With the expansion of data traffic and network scale,traditional structure of network faces enormous challenges in handling huge numbers of network events.In contrast,SDN,Software-Defined Network,decouples the network control plane and data plane,enhancing the capability of network management and response to network events.Network control is usually triggered by an internal or external network event.The former includes network dynamics caused by the controller via policy enforcement,while the latter usually means data plane changes,e.g.,link and node failures,which call for rapid response from the network controllers to ensure the steady running of network.In the distributed control of SDN,most existing literature employs consensus-based mechanisms to ensure multiple controllers manage the network like a single controller logically.Consensus mechanisms require that before controllers execute network management,the network information among controllers must be consistent,ensuring the optimal management for network events during the network control,which incurs large latency.Recently,eventual consistency mechanism is proposed for rapid response to network events.Eventual consistency means network information among all controllers will converge after event response,not in the every stage of network management.However,eventual consistency mechanism simplifies the coordination between controllers,resulting redundant control for one single network event.In this paper,based on the analysis of consensus mechanisms and eventual consistency mechanisms,an eventual-consistent-based SDN distributed control method that rapidly respond to network events and reduce the redundant control overhead is proposed.To solve the control overhead in eventual consistency mechanisms,the idea of backbone nodes in wireless sensor networks is used in this paper to select a subset of responding control nodes for network event handling in the control plane of SDN.The conditions of this subset to be used in SDN control plane is analyzed,the optimal problem of the subset in Graph Theory is proposed and the solution to the subset is derived as minimum dominating set from the similar problem in Graph Theory.Based on the responding subset of controllers,the process of network events forwarding is discussed,an algorithm for network events forwarding and handling in control plane is proposed and the experimental results indicate the effect in rapid response and control overhead reducing,as well as the feasibility of the algorithm.