近年來逐漸受到重視的軟體定義網路(Software Defined Networking ,SDN)的虛擬化與可程式化能力紓解了上述大型網路管理的困境。伺服器負載平衡(Load balancing)是典型的網路管理應用，業界一般使用專屬設備負責導引流量，其缺點是設備昂貴且未考慮不同業者服務業態的特殊性。 本研究建議以SDN為網路管理架構，以程式化方式進行伺服器負載平衡。在負載平衡演算法中，我們使用伺服器健康指標的概念，作為網路流量引導的依據。 伺服器健康指標是伺服器的各種狀態的綜合衡量，包括 CPU負載、軟體缺陷以及可能的硬體故障等，不同服務業態可依其服務的特殊性而調整指標的構成內容及其權重。本研究建議以SNMP 協定讀取OID Table的方式取得伺服器狀態。 本研究方法採用Mininet以模擬方式進行實驗，並以Python與JAVA程式語言實作負載平衡演算法。實驗結果顯示本研究方法可以使用軟體取代昂貴的硬體負載平衡設備，並在SDN架構上成功運作。 In the recent years, the virtuality and programmability of Software Defined Networking (SDN) have been placed more and more attention. These mitigate the predicament of large-scale network management. Load balancing of server is the typical application of network management. In industry, exclusive equipment is usually used to take charge of the flow direction. The shortcoming would be expensiveness in terms of cost. Meanwhile, it doesn’t take the particularity between different service providers into account. This research proposes to use SDN as network management framework and to proceed the load balancing of server by programming. In load balancing algorithm, we use the concept of server health index as the basis of network flow direction. Server health index is the synthetic measurement of every status of the server, including CPU loading, software defects, and probable hardware breakdown. Different service providers can adjust the index’s composing section and the proportion of each section according to the particularity of its service. This research proposes to acquire the server status in a way of SNMP protocol to read OID table. The method of this research adopts Mininet to carry out the experiments by simulations. Meanwhile, it uses Python and JAVA language to practice load balancing algorithm. The experimental result reveals that this research method can replace costly load balancing hardware with software and achieve satisfactory result in SDN framework simultaneously.
