Method Of Path Allocation And Evaluation For SDNs

As a new network structure,SDN has become one of the most popular technologies in the industry(recognized as one of the ten new technologies by Infoword in 2011).With the rapid development of network and increasing richness of application type,as a vital part of social infrastructure,the structure and function of Internet become more complicated while the management ability gets weaker.Especially as the core of network,carrier function of the routers,such as packet filtering,DiffServ,multicast,quality of service(QoS)and traffic engineering,continues to expand.The original defined "dumb,simple" data-forwarding unit has become unbearably bloated.The tightly coupled hardware inside the router makes the function upgrade more and more complicated,which seriously hampers the deployment of traditional routers in the new network system.This feature of routers severely limits the development of network technology.In order to solve the stated problems existed in TCP/IP architecture,many countries in the world have conducted extensive research on the future Internet,such as the US GENI,the EU FIRE,Japan JGN2plus,China's SOFIA and so on.To study the architecture of the future Internet,first thing to consider is the redesign and deployment of network core router,which should allow users to define the function module of the router by themselves.Then it should redesign the routing protocol under the new architecture,to achieve new protocols,which can adapt to the developing new Internet.The emerging SDN is expected to solve the problem.However,as a new network architecture,SDN overturns the operating mode of traditional network,resulting in a lot of difficulties inevitably.Being the heart and soul of computer networks,the importance of routing protocol is self-evident.The core issue of routing protocols is the path allocation problem,which has certainly become one of the most important problems in SDN.Different from traditional BGP network,SDN is a kind of entralized control system.In the process of the path allocation,control panel needs to consider the selection of the end-to-end path and the update of the flow table.However,from the user's perspective,whether the performance of the designed path allocation scheme meets the-application requirements,needs to be considered.To improve the efficiency of data exchange in SDN,this dissertation starts from several aspects,including path selection,flow table distribution and the universal assessment methods of path allocation.The main contributions include the following three parts:1.The path selection method for multiple path requests in SDN Due to lack of the flow table entry,the controller might receive multiple end to end path requests in a very short time.With limited network resources,the actual number of paths distributed may not satisfy all the requests.To solve the problem,this dissertation proposed a load balancing path selection scheme.Based on the analysis of the model,the scheme puts forward the objective function of maximizing the path allocation and optimizing the network load balancing,and transforms the problem into multi-objective optimization problem.The NP-Complete and NP-Hard properties of the selection problem are determined by three-dimensional matching and multidimensional matching reduction method respectively,and it is proved that it has strong non-similarity.On the basis of theoretical analysis,an effective approximation algorithm in a certain approximate range over polynomial time is proposed,which makes it possible to achieve better selection of more paths and achieve optimal network load under multi-end-path request.2.Flow table update based on load balancing in SDNThe fine-grained processing requirements of the flow causes the controller to respond to more flow requests.Although the controller can deploy the control logic to the data forwarding unit in advance through the active decision mechanism to reduce the processing overhead between the data plane and the controller,the change of the control logic is usually dynamic,especially when the network topology changes or there is a mobile node.However,the pre-installation the flow table will also waste resources as lots of the flow table space cannot be released.In fact,most of the duration of the flow is very short.In addition,the delay between the controller and the switch may affect the order in which the controller receives the events and the order in which the controller rules are installed on the switch,which affects the consistency of the control logic.According to the stated problems,this dissertation proposed a flow table update method based on load balancing for SDNs.By comparing the load of the control plane and data plane in each domain,this dissertation dynamically installs flow entry based on a combination of source routing and direct installation,thus it can reduce the controller's load and dynamically adjust the load balance of control plane and data plane,and also reduce the flow entry installation delay and end-to-end transmission delay as well as the probability of the inconsistency of control logic.3.The comprehensive assessment models and methods for path allocation scheme under the different scenariosThe needs of SDN network perfonnance change under different scenarios.Therefore,the assessment of the path allocation scheme in SDN cannot be generalized.It requires to a combination with specific applications or scenarios.To obtain a comprehensive,accurate assessment of the existing path allocation schemes,as well as to facilitate the selection of the optimal solution under different network environments and self-performance evaluation of designed schemes for the researchers,this dissertation proposes a comprehensive performance evaluation method for the path allocation schemes under different scenarios.By modeling,analyzing and quantifying network performance indicators,including the type of network,data,resource and domain,the proposed method conducts a comprehensive performance analysis and finally presents a comprehensive assessment of performance of the path allocation scheme combined with the performance preference parameters.