TimeSync: Virtual time for scalable, high-fidelity hybrid network emulation

Hybrid network emulation (HNE) comprises a discrete event simulated network and virtual machines that send and receive traffic through the simulated network. It allows testing network applications rather than their models on simulated target networks, particularly mobile wireless networks. Scalability of this test approach is hindered by the time divergence problem: for complex, large-scale simulations, discrete event simulation time advances slower than real time, distorting packet propagation characteristics. To address this problem, we developed TimeSync, a system that uses discrete event simulation time to control and synchronize time advance on virtual machines for large-scale hybrid network emulation. In this paper, we describe how TimeSync controls and synchronizes time perception in hybrid network emulation between simulator and virtual machines, and present experimental results.