雲端運算中其中一個重要的技術是虛擬化。虛擬化可以使多台虛擬機器分享實體機器的資源，達到資源共享並提升硬體資源的使用效率同時降低基礎設備的開銷。隨著虛擬環境中虛擬機器的增加，虛擬交換機的重要性也隨之提升。虛擬網路的概念為利用虛擬交換機將虛擬機器連結起來並負責處理虛擬機器間及對外的網路交換。虛擬交換機可以利用硬體或是軟體實現。在此篇論文中，我們在KVM的虛擬環境中利用軟體實現的虛擬交換機Open vSwitch將虛擬機器連結起來。Open vSwitch是一個開放原始碼的虛擬交換機，主要功能是提供內部及外部虛擬機器的連結及網路第二層的相關功能。我們主要目的為評估當系統存在相關負載時，這些負載對執行在虛擬機器上相關服務效能的影響，同時我們量測與分析不同虛擬交換機建置的效能與負載。

One of the main technologies of cloud computing is virtualization. Virtualization can let the Virtual Machines (VMs) share the physical resource simultaneously so that the utilization of hardware resource will increase and meanwhile cost down the infrastructure. With the proliferation of VMs, the important of virtual switches also arise. The concept of network virtualization is connecting VMs using virtual switches and the virtual switches are responsible for the packet switching between VMs. Virtual switch can be designed and implemented by software or hardware. In this paper, the virtual environment we implement is Kernel-based Virtual Machine (KVM) and we connect the VMs with Open vSwitch. Open vSwitch is an open source virtual switch, the main function is to provide inter- and intra- connections among VMs and works on layer 2. The main idea is that we want to figure out the impact of system’s workload to the performance of application running on the VMs. We also measure and analyze the performance and overhead of different deployments of virtual switch.

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