Research On Label Routing Design And Label Assignment Based On OpenFlow In Wide Area Network

Software-Defined Networking(SDN/OpenFlow)is a new network architecture,separating the control and data planes from closed system of traditional network,brings many advantages such as good controllability and flexibility.SDN has been introduced into many networks in different scenarios,including WANs.Applying SDN/OpenFlow to a wide area network has following technical challenge:limited by physical distances between nodes,there are large delays in the communications between the controller and switches,leading to a long time to build a new path for a new arriving flow.Current studies mainly uses source routing(such as SlickFlow)to solve this issue.There are problems in these solutions:harmful to hardware implementation since packets need to carry a header of large and various size,not conducive to promotion as they modify the OpenFlow protocol.This thesis researches the above issues in depth and proposes corresponding solutions,the main contributions of this thesis are as follows:(1)Propose a label routing approach in SDN-based WANs and a workable implement method of it without modifications to the OpenFlow protocol.Label information is stored in the VLAN header field of QinQ supported by OpenFlow.Compared with SlickFlow,the pushed header size is fixed and small.It is demonstrated that a label only increases transmission delay by 0.26-6.25%and operation delay by less than 0.52 us.The analysis and experimental results show that when a new flow arrives,label routing can reduce the communication volume between the controller and switches,thereby reduce the average delay.(2)Design a label assignment mechanism based on OpenFlow and discuss how to assign and manage labels for label routing.Based on Ryu controller,MongoDB and other technologies,we develop a system which can assign,manage,store label information with good scalability.Finally,we set up a prototype system of label assignment on the Centec V150 SDN switches and EX2000 topology connector.The experimental results show that the prototype system can effectively assign and delete labels and corresponding information in a network.(3)Based on traffic matrix,we discuss how to use our label assignment to achieve load balancing of links in a network.Firstly,we introduce the researches on the measurement of traffic matrix in SDN,and give a general method of measuring traffic matrix using OpenFlow.Then,based on the traffic matrix-based load balancing algorithm(TM-LB),we propose the ITM-LB algorithm.We simulate these algorithms using real and random traffic matrices,respectively.The experimental results show that both TM-LB and ITM-LB algorithm can achieve load balancing.However,,ITM-LB algorithm is better than TM-LB algorithm both in load balancing performance and algorithm efficiency.