| With the rapid development of computer network technology over the past decade, the Internet has currently covered throughout the world. Internet is also responsible for billions of equipments’accessing, communication and data exchanges. With the rapid development of the Internet technology, the number of business requirements on the Internet is also rising. Not only the exponential growth of network traffic, but also the complexity of business is growing. In the certain situation, traditional computer network based on the TCP/IP architecture revealed defects of fixed structure. Traditional network structure has shortcomings in the resource scheduling, security and other aspects.A research group of Stanford University proposed new network architecture in order to solve this problem:SDN (Software-defined networking). The main idea of SDN is separation and virtualization. By separating the control plane and the data plane, SDN simplifies the existing network architecture and realizes the automated responses of network state changes. Programmable network achieves software modification and network controlling. It has greatly enhanced the flexibility and convenience of network resource scheduling.The communication protocol between control layer and infrastructure layer is the key to achieving the separation of controllers and data in SDN. Openflow protocol with flexible configuration and standard specification has become a standard communication protocol in SDN.The status and role of Openflow protocol in SDN architecture were researched in this thesis. By reading and analyzing the Openflow source code, we research Openflow principle, features, and implementation mechanisms. Openflow protocol has been implemented and verified by building a network platform for SDN in this thesis. A network architecture called "One-control" based on Openflow is proposed in this work in order to apply Openflow to the real network."One-control" structure takes the advantage of Openflow protocol to optimize the security performance of the network of cloud services.The research and main work are listed as following:1. The development history of SDN and current research on SDN were studied in-depth in this thesis. We stated the important role of Openflow protocol in SDN. Three kinds of messages supported by Openflow protocol were researched:controller-to-switch, asynchronous and symmetry. Devices that supported Openflow protocol were discussed, especially a kind of Openflow switch: Open vSwitch.2. The Openflow source code is analyzed in the thesis using Source Insight. The functions related to the generation and transmissions of packets were researched. Diagrams of the called function procedure were summarized. Openflow protocol connection establishment, message transmission and message handling were analyzed from the perspective of source code. And other communication processes between control layer and infrastructure layer.3. Openflow protocol communication mechanisms and processes were verified in this thesis. Simulation platform of SDN based on Floodlight and Mininet was built. The Openflow packets captured by Wireshark were analyzed specifically in different network topologies. In this way, Openflow protocol was verified.4. A virtual private cloud infrastructure called "One-control" based on Openflow protocol was proposed. To take advantage of Openflow protocol, we focus on the lack of security and not easy to operate in cloud services. As a result,"One-control" was designed."One-control" network architecture takes advantage of the convenience and flexibility of Openflow and makes use of Openflow secure channel. This architecture realized the logical separation of different customers’ networks, enhanced network security and reduced the complexity of cloud service. |
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