軟體定義網路之低延遲虛擬負載平衡器

Abstract

在雲端服務中，為了提供用戶QoS，負載平衡是很基本的議題。在過去，負載平衡都是以硬體裝置實現。雖然效能很好，但仍有許多缺點，例如價格昂貴、缺乏彈性等。考慮到上述缺點，服務商漸漸採用軟體負載平衡器。軟體負載平衡器能降低成本與複雜度，也提供彈性和高擴展性。然而，採用軟體負載平衡可能增加回覆時間及延遲。此篇論文中，針對伺服器群集，我們提出一個低延遲虛擬負載平衡器(LD-VLB)。它結合了網路功能虛擬化(NFV)和軟體定義網路(SDN)的概念，使網路功能：負載平衡和路由被虛擬化。LD-VLB解決了軟體與硬體負載平衡器所面臨的問題。透過結合NFV和SDN，它提供集中控制給虛擬化的網路環境。LD-VLB會蒐集運行中伺服器的CPU使用率。基於這些資料，LD-VLB會要求喚醒群集中的閒置伺服器來分享負載，或關閉伺服器以減少能源消耗。而且，它也會重作路由，並要求SDN控制器修改相關交換機之流量表，以平衡目前運行中伺服器的負載。實驗結果顯示，LD-VLB相較於靜態路由(SR)、輪替(RR)和最少連線(LC)，平均回覆時間分別降低了7.75%、30.29%和39.97%。此外，它的平均能源消耗也較低。

Load balancing is a fundamental issue in cloud environments for providing QoS services to users. In the past, load balancing was performed by hardware appliances which perform very well, yet it has several disadvantages, such as very expensive and lack of flexibility. Considering the disadvantages of hardware load balancers, providers adopted software load balancers which can reduce cost, complexity, and also support flexibility and scalability. However, adopting software load balancers may increase response time, thus increase delay. In this thesis, we propose a low delay virtual load balancer (LD-VLB), an approach that combines Network Function Virtualization (NFV) and Software-Defined Network (SDN) concepts, for a cluster of servers. Network functions, such as load balancing and routing, are virtualized. LD-VLB is a promising solution for resolving software and hardware load balancers problems. By integrating NFV with SDN, it provides centralized management and intelligence for virtual network environment. LD-VLB collects CPU utilization from active servers. Based on these data, LD-VLB will ask the cluster to activate idle servers to share loading, or to deactivate servers to reduce power consumption. It will redo routing to balance the loading of active servers and ask the SDN controller to change the flow rules of related switches. Experiment results show that average response time of LD-VLB is 7.75%, 30.29% and 39.97% lower than that of static routing (SR), round robin (RR) and least connection (LC), respectively. The average power consumption of LD-VLB is also slightly better than that of SR, RR and LC.