Prevision-Based Load Balancing with OpenFlow for Campus Networks

This study focuses on the development of a prevision-based load balanced system for campus networks by applying OpenFlow. We establish a dedicated path together with the use of a dynamic policy routing decision mechanism to reduce the number of hop counts for rule-matched packets. Through the multi-controller deployment, we can trigger the load balancing operations before the packets reach its designated switch, hence to avoid asynchronous messages. In addition, we also develop a sCacheTable mechanism for the load balancer to enhance the ratio of flow matches and to reduce the forwarding requests to the controller. We implement these mechanisms on top of the RYU OpenFlow controller to emulate the system and evaluate its effectiveness. From the experimental results, due to trigger the load balancing operations upon packets visiting the campus network the first time, the addition of sCacheTable can not only achieve the balancing effect, but also increase the match ratio in OpenFlow switch. Therefore, our prevision-based load balanced system is feasible and may improve the overall system performance.本研究著眼於以OpenFlow網路協定開發一套適用於校園網路的快速預知式負載平衡系統。藉由新增動態政策路由判斷機制，針對符合特徵的外來流量建立一條專屬路徑，減少來源封包至目的地所需經過的站點，並透過多控制器機制，在特定封包一進入校園時，便提前觸發負載平衡系統進行判斷。此外，我們藉由新增sCacheTable機制，增加flow比對吻合的機率，以降低非同步訊息的產生，減少封包拜訪控制器的次數，進而提升整體效能。在本研究中，我們採用RYU控制器實作加入sCacheTable後的最小網路負載演算法，並進行情境模擬，進而評估其有效性。 由實驗結果得知，由於封包在進入校園網路的第一時間即觸發負載平衡判斷，在加入sCacheTable機制後的負載平衡系統除了可以達到負載平衡的效果，並確實可以有效提升非第一次流入的封包在交換器中比對成功的機率，進而提升整體系統運作效率。摘要....................................................i Abstract...............................................ii 目錄..................................................iii 圖目錄..................................................v 第一章 導論..............................................1 1.1 前言................................................1 1.2 問題描述與動機.......................................2 1.3 論文貢獻.............................................3 1.4 論文架構.............................................3 第二章 相關研究..........................................4 2.1 OpenFlow............................................4 2.2 OpenFlow Table......................................5 2.3 交換器flow entry比對機制.............................6 2.4多控制器機制..........................................7 2.5 RYU.................................................8 2.6 Open vSwitch........................................8 第三章 系統設計與架構....................................10 3.1 系統架構............................................10 3.2 多控制器設計........................................11 3.3 sCacheTable 機制...................................13 3.4 負載平衡交換器......................................15 3.5 負載平衡機制........................................16 第四章 系統模擬與分析....................................19 4.1 flow match entry反應時間分析........................19 4.2 模擬環境建置........................................21 4.2.1 以Open vSwitch建置虛擬OpenFlow交換器..............22 4.2.2 安裝環境模擬軟體Mininet...........................24 4.2.3 安裝RYU SDN Framework控制器.......................25 4.3多控制器架構.........................................26 4.4 sCacheTable建置....................................29 4.5 負載平衡機制........................................33 4.6 系統效能分析........................................34 4.7 造訪負載平衡控制器事件數分析.........................36 4.8負載平衡度分析.......................................38 第五章 結論與未來展望....................................43 參考文獻................................................4