在混合軟體定義網路的企業網路下結合流量和線路資訊去放置軟體定義網路交換器

Abstract

軟體定義網路是一個新興的網路架構，可以集中式的管理交換器。與傳統的架構不同，軟體定義網路可直接程式化的性質帶來了大量的好處，像是更簡單的管理和功能更多的網路應用。然而把現有的網路轉換到軟體定義網路，可不是只要按一個按鍵就可以辦到的，最主要的侷限是預算的限制，尤其是在企業網路下採用軟體定義網路時更是如此。因此我們可以改使用混合軟體定義網路─一個結合了傳統和軟體定義網路交換器的架構，而我們發現在混合軟體定義網路下有兩個重要的挑戰點：該如何去監測流量和該在哪裡放置軟體定義網路交換器。 在這篇研究中，我們嘗試去修改一個現有的在純軟體定義網路下運作的網路監測方法，使其能在混合軟體定義網路下運作，這是為了展示混合軟體定義網路下的確能實現軟體定義網路所帶來的好處，同時也為了紀錄流量蹤跡以供未來放置交換器時的參考。然後我們提出了一個基於貪婪法的放置策略，結合了流量大小和鄰邊數目的資訊，來選擇該放置那些交換器。我們用仿真模擬的方法，展示了修改過後的網路監測方法的可行性，結果顯示我們可以做到低錯誤率的實時監測。另一方面，我們用模擬的方式，在現實的企業拓樸下評測我們的放置策略，結果表明我們只要把25%聚合層的交換器升級成軟體定義網路交換器，我們就可以讓整個網路如同在純軟體定義網路下一樣的運作，如果我們更進一步限制路由路徑的選擇，我們甚至可以只升級不到15%的交換器即可達到相同的效果。

Software-Defined Networking (SDN) is an emerging architecture that switches are centralizedly controlled. Unlike legacy architecture, SDN's direct programmability brings a lot of benefits, such as easier management and more complicated network applications. However, changing existing network into SDN is not an 'one-click' feature. The budget constraint is the primary limitation, especially for introducing SDN into enterprise networks. Therefore, we may instead use hybrid SDN, an architecture combining legacy and SDN switches. We find that there are two important challenges in hybrid SDN: how to measure traffics and where to deploy SDN switches. In this paper, we try to modify an existing network measurement for pure SDN network to be applied in hybrid SDN enterprise network, which just shows the SDN benefits in hybrid SDN network and records traffic traces for reference of future deployment. Then, we presents a greedy-based deployment strategy, which combines the information of traffic volume and node degree for switch selection. We demonstrate the feasibility of our modified network measurement by emulation. Our results suggest that we can get real-time measurement with low error rate. On the other hand, we evaluate our deployment strategy by simulation on real-world enterprise topology, and it shows that with about 25% aggregation/distribution switches upgraded to SDN, we can make whole network operate like it is a pure SDN. If we further limit the selection of routing path, we can achieve this goal by upgrading even less than 15% switches.