網際網路的蓬勃發展帶動了資訊科技的革命，隨著傳輸頻寬與可靠度的提升，由個人電腦獨立處理日常工作的模式已經逐漸轉移至雲端，藉由資料中心內部連接至高速網路的龐大的伺服器群集進行運算後，再回傳給使用者。近年來由於伺服器數量的提升與虛擬機器的廣泛部署，資料中心網路架構趨於扁平化，亦即對Layer 2網路的擴張與Layer 3環境的收縮，以適應諸如虛擬機遷移等無法橫跨Layer 3的新技術。然而，這也對網路帶來了極大挑戰。傳統上於Layer 2乙太網路中所採用的生成樹協定，因其收斂時間與收斂後形成單一傳輸路徑的限制，在日益擴增的網路環境下逐漸顯得力不從心，無法利用冗餘鏈路，犧牲了寶貴的頻寬資源。因此近年來，許多企業與研究單位皆致力於重新思索並打造新的網路架構，打破舊有協定的限制，以更有效的利用資料中心的網路資源。
本論文主要在軟體定義網路的環境中提出了一個具備多重路徑之封包轉送機制，並實作了數個模組於OpenFlow Controller中，讓不同來源的封包能夠分配到不同的傳輸路徑上，以避免壅塞、丟失與延遲等情形發生在關鍵鏈路而癱瘓系統，並能提升整理網路頻寬的利用率。同時，此機制在模擬環境與NetFPGA開發板運行之OpenFlow交換器所搭建的真實實驗環境中，均顯示其在OpenFlow enabled網路中能提供一個優於傳統協定的方案。

The rapid growth of the Internet has led to a revolution in information technology. With the increase of transmission bandwidth and reliability, using PC to deal with daily works is moving to the cloud, by computing through massive servers with high-speed network connections in a data center to get results. Due to the rising number of servers and widely-deployed virtual machines, the data center network architecture becomes flat recently. The flat structure, Layer 2 network expanding and Layer 3 network shrinking, is formed to adapt to new technologies like VM migration that cannot cross Layer 3. However, this brings great challenges to current network. Traditionally, Spanning Tree Protocol is used in Layer 2 Ethernet, but the convergent time and the limit to single path convergence make it impotent in large network. The protocol also uses the redundant links rarely, and sacrifices the precious bandwidth in data center. Therefore, many corporations and research units have been working on this to rethink and build a new network architecture to break old limits and make better use of resources.
In this thesis, a multiple-path enabled packet forwarding mechanism in software defined network is proposed. Several modules are implemented in the OpenFlow Controller to distribute packets with different sources to distinct paths. This avoids situations like congestion, packet loss and delay in key links that may paralyze the system, and ascend the bandwidth use rate of the whole network on the other hand. Meanwhile, the mechanism shows a better result in OpenFlow enabled network than the traditional way in both emulation and real environment with NetFPGA based OpenFlow switches.

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