Network emulator: A network virtualization testbed for overlay experimentations

Experimentation is typically the last step before launching a network application in the wild. However, it is often difficult to gather enough hardware resources for experimenting with a reasonably sized overlay application inside a controlled environment. Virtualization is thus a handy technique for creating such an experimentation testbed. We propose a tool called NEmu designed to create virtual dynamic networks for testing and evaluating prototypes of overlay applications with a complete control over the network topology and link bandwidths. NEmu builds host-based overlay networks by using emulators such as QEMU. We illustrate the use of NEmu in the context of a file distribution overlay application. We evaluate the impact of chained TCP connections on the application performances. We show that NEmu enables us to obtain performance results concerning data rates and delays for end hosts depending on the number of intermediate hosts and the networking parameters of the overlay.