Network Update Technology In Software Defined Network

With the rapid development of the network,the disadvantages of the traditional network such as function coupling are increasingly prominent.In order to customize network functions more flexibly and push the network which was originally highly hardware-based to software-based,software defined network technology came into be-ing.In the software defined network,the control layer and the data layer are separated.The control layer centrally schedules and manages the data layer.This helps realize the flexible network update of the whole network.However,the unreasonable update plan will bring many problems,which will not only cause the degradation of network performance,but also bring the catastrophic network collapses.At the same time,up-date operation is very frequent in the software defined network,so it is very important to design an efficient update algorithm.This paper studies the update problem under different scenarios and designs two network update systems.The first proposed system is Hermes which actively predicts the flow rate and perceives the overall utility of the network.In order to analyze the maximum utility network update problem,this work presents a detailed optimization framework.This work also demonstrates the difficulty of the maximum utility network update problem and carefully analyzes the complexity of proposed algorithm.This work first proac-tively predicts the flow rate,and then use convex relaxation techniques to obtain an initial solution.To further increase the overall utility,this work continues to adjust the rate of each flow with a greedy method based on the initial solution,meanwhile guaranteeing congestion-free during update process.Extensive simulation and testbed experiments demonstrate that this work increases the total utility by 80%.At the same time,it reduces the total update time and control overhead by 40%and 55%,respec-tively.The second work is mainly concerned with how to utilize the synchronized net-work update feature proposed by OpenFlow 1.5 to design an update system.The pro-posed system is called Chronicle which can ensure the update process is congestion-free.Different from the first work,this work no longer cares about the network util-ity.It focuses on a more general problem of how to get an update plan guaranteeing congestion-free during the update process by scheduling the update time of each switch instead of reducing the rate of flows.To solve this problem,a series of concepts are in-troduced such as time-extended network,which can be well used to analyze and design update algorithm based on timed update.By constructing resource dependency graph,this work finds out the dependency between update blocks,then calculates the accurate update time and the corresponding forwarding rules for each switch.Extensive sim-ulation and testbed experiments show that this work can avoid congestion during the whole update process,reducing the makespan by 63%and the number of changed rules by 50%compared to state-of-the-art.The average gap between this work and optimal solution is less than 20%.