A virtual time system for virtualization-based network emulations and simulations

Simulation and emulation are commonly used to study the behaviour of communication networks, owing to the cost and complexity of exploring new ideas on actual networks. Emulations executing real code have high functional fidelity, but may not have high temporal fidelity because virtual machines usually use their host's clock. To enhance temporal fidelity, we designed a virtual time system for virtualization-based network emulations and simulations, such that virtual machines perceive time as if they were running concurrently in physical world. Our time virtualization is not exact: there exist temporal errors primarily due to scheduler timeslice, which is tunable in our system. We then study the tradeoff between temporal fidelity and execution speed under different lengths of timeslices, both experimentally and analytically. We demonstrate that our virtual time system is flexible such that it can achieve different level of temporal accuracy at the cost of different execution speed.