Research On Routing Technology In Software Defined Network Based On Openflow

SDN/OpenFlow has emerged as a revolution for current network architecture, which aims to decouple control and data plane. This new architecture has attracted much attention because of its centralized management. SDN is composed by application layer, control layer and device layer. The whole network is managed by control layer, while device layer takes charge of packet forwarding. Network operators can develop specific applications to determine the network behavior. OpenFlow network, which is a famous instance of SDN, consists of controller, OpenFlow switches and OpenFlow protocol. OpenFlow switches communicate with controller via OpenFlow protocol.OpenFlow is facing the following challenges.(1)Congestion Routing Management Problem:The traditional method of congestion routing management is rerouting the flow nearby the congested nodes. However, this method cannot make full use of the global network topology resources. When focusing on the flow rerouting at congested nodes, it may not compute the optimal paths in some cases and even worse it may not converge to a feasible path. In OpenFlow Networking, we can take advantage of the centralized management of controller towards the network, and propose an efficient network congestion management strategy.(2) Hybrid Network Routing Problems. OpenFlow is in the early stages of development. It is unrealistic to deploy large-scale OpenFlow network. Therefore, combining traditional IP network and OpenFlow network is a solution to alleviate this problem. However, current OpenFlow topology discovery and routing schemes are data link layer technologies. As a result, using these methods, hosts in OpenFlow network can not communicate directly with the hosts in traditional IP core network. It is necessary to propose a new routing scheme for hybrid network.This thesis has studied deeply on these issues above, the main contributions of this thesis are as follows:1) OpenFlow network is managed by centralized controller. In order to manage congestion effectively, we propose a new routing congestion management scheme (CMTA-OF) which is related to service feature. In CMTA-OF, controller obtains the global distribution of network traffic, and then it chooses one or a few data flows from congestion link with minimal transfer overhead to reroute. The new routing paths can be computed based on service feature of flows, distribution of network traffic and network topology. Both theoretical analysis and experimental result show that CMTA-OF is able to ease network congestion effectively, ensure service quality, enhance network throughput and resource utilization as well when comparing with current OpenFlow LABERIO scheme.2) This thesis also presents a new IP_LLDP protocol to solve the routing problem of hybrid network. This protocol contains the following three part:IP address allocation, constructing virtual topology and address rewriting scheme. IP_LLDP protocol is designed to enable two OpenFlow switches to communicate with each other through traditional IP network, and it shows good scalability and independence. Finally we creat a simple OpenFlow network testbed in our lab. We demonstrate the feasibility of IP_LLDP from the aspect of constructing topology, computing routing paths and creating flow tables.