Research On Topology Discovery And Link Delay Measurement Of SDN Network

With the continuous expansion of the network scale,the types and number of network equipment and network applications are increasing,the computer network structure is becoming more and more complex,the emergence of SDN has effectively adapted to the needs of various network changes.Measurement and monitoring are the foundation of all network applications and the foundation for maintaining the safe and stable operation of the network,the typical function is to count the performance parameters of the network,the collection of performance parameters cannot be separated from the support of the underlying network topology.Based on the separation of the SDN control plane from the data plane and a highly centralized control method,the controller performance greatly affects the operation of the network.In order to reduce the burden of the controller that may be caused by the characteristics of the centralized control of the SDN controller,the thesis proposes a set of methods for determining the topology of the target network and measuring the delay in the context of SDN.This method has the following innovations:1.A new topology discovery protocol NewOFDP~+is proposed.Based on NewOFDP,by introducing a hash strategy in the topology discovery process,it effectively reduces the Packet-in messages that the controller needs to process,reduces the duplicate link discovery,and further reduces the burden on the controller.2.The NewOFDP~+with lock mechanism is proposed.Adding an unfair lock to the operation hash table process in NewOFDP~+,further reduces Packet-in messages that the controller needs to process,and the elimination rate of duplicate links is nearly 50%.However,due to factors such as discovery time and other factors,the applicable network range is narrower than NewOFDP~+.3.A multi-target delay measurement node selection algorithm based on GRAMI is proposed.By analyzing the relationship between the set of measurement node positions and the optimal overlay network,based on the constraints of network forwarding devices in the real world,using the linear programming method to convert the GRAMI offline calculation stage into a multi-objective optimization model,and using the multi-objective optimization algorithm NSGA-?to solve the mathematical model.This algorithm can obtain the optimal monitoring node position set and its overlay network that meet the problem's objective constraints in a short time.4.GRAMI online measurement phase delay measurement.Using the calculation results of the multi-target delay measurement node selection algorithm based on GRAMI,the measurement nodes are deployed and the detection paths are planned,and the probe packets are sent by the measurement nodes to measure the link delay.The simulation experiment results in Floodlight+Mininet show that this method can accurately measure the round-trip delay of the link.Through a large number of comparative experiments,the method of network topology discovery and link delay measurement in SDN proposed in the thesis can effectively reduce the burden of the controller at a small cost.