軟體定義網路(Software-Defined Networking, SDN) 是一種將路由器的控制平面從資料平面分離出來並且程式化的技術，讓網路管理員可以使用軟體以中央控制的方式來動態規劃整個網路，而不用更動現有的設備。SDN 技術在近幾年來成為熱門的話題，尤其是在雲端服務應用上，SDN 可以利用本身可程式化的優點，根據實際網路的使用狀況來提供當下所需的服務策略來滿足用戶的需求。
然而在網路規模不斷增長的情況下，現有的控制器架構常常會出現無法負荷突如其來的網路流量之狀況，造成整體網路的表現下降，因此在這篇論文中，我們設計了一個應用於軟體定義網路的控制器負載調整方法，並提出了一個交換器遷移的協定，讓控制器在偵測到本身負載過高時自動通過交換器遷移進行負載調整。最後，我們針對所提出的方法進行實驗評估，結果證明本系統能有效且快速的在控制器超過負荷能力前進行負載調整，並且不會對網路造成明顯的負擔。

Software-Defined Network (SDN) is an approach to decoupling the routing decision unit (control plane) from the transfer unit (data plane) which enables the control plane to become directly programmable. The network administrator dynamically controls the whole network without changing their equipment. SDN has become a hot issue in recent years, especially in cloud application services because it has the advantage of being a programmable optimized network regardless of the network conditions.
However, while the Internet constantly continues to expand, the existing controller architecture can not afford the instantaneous traffic which results in a network performance degradation. Therefore, in this paper, we designed a loading adaption approach for the controller of a Software-Defined Network. Additionally, we propose a migration protocol, so that when the controller detects excessive traffic it will automatically process loading adaption through the switch migration. In the end, we conducted experiments to evaluate our proposing approach. The results show that our system can perform the load adaption efficiently and rapidly before the controller is overwhelmed, and it will not cause significant overhead to the network.

Table of Contents i
List of Figures iii
List of Tables v
1 Introduction 1
2 Background 3
2.1 Cloud computing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Software-Defined Network . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 OpenFlow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3.1 Role Request Message in OpenFlow . . . . . . . . . . . . . . . 7
2.3.2 OpenFlow message . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4 Wireshark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.5 PackETH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 Related work 11
4 Design Framework 14
4.1 Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.1.1 Load Measurements . . . . . . . . . . . . . . . . . . . . . . . 16
4.1.2 Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1.3 Adaptation Decision . . . . . . . . . . . . . . . . . . . . . . . 18
4.1.4 Switch Migration . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.2 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.2.1 Building Environment . . . . . . . . . . . . . . . . . . . . . . 23
4.2.1.1 Ryu . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.2.1.2 OpenvSwitch . . . . . . . . . . . . . . . . . . . . . . 24
i
4.2.1.3 Mininet . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.2.2 Ryu Controller with Load Adaptation . . . . . . . . . . . . . 28
4.2.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5 Analysis 32
5.1 Experimental Environment . . . . . . . . . . . . . . . . . . . . . . . . 32
5.2 The Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.3 The Effect of Migration . . . . . . . . . . . . . . . . . . . . . . . . . 36
6 Conclusion 38
6.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
6.2 Future work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

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