Leveraging symbiotic relationship between simulation and emulation for scalable network experimentation

A testbed capable of representing detailed operations of complex applications under diverse large-scale network conditions can be extremely helpful for investigating potential system design and implementation problems, and studying application performance issues, such as scalability and robustness, even before the applications are deployed in a real environment. We introduce a novel method that combines high-performance large-scale network simulation and high-fidelity network emulation, and thereby enables real instances of network applications and protocols to run in real operating environments, and be tested under large-scale simulated network settings. In our approach, network simulation and emulation form a symbiotic relationship, through which they are synchronized for an accurate representation of the large-scale traffic behavior. We introduce a model downscaling method, along with an efficient queuing model and a traffic reproduction technique, which can significantly reduce the synchronization overhead and improve computational efficiency, while maintaining the accuracy of the system. We validate our approach with extensive experiments via simulation and with a real-system prototype.