A parallel network simulation and virtual time-based network emulation testbed

To analyze large-scale systems with high fidelity, it is necessary for a network testbed to offer both realistic emulation (to represent software execution) and effective simulation (to model background computation and communication). We present a network testbed that integrates a light-weighted emulation system OpenVZ (modified earlier to operate in virtual time) with a parallel discrete-event network simulator S3F. Our algorithmic contributions lay in the design and management of virtual time as it transitions from emulation, to simulation, and back. We also address the unavoidable uncertainties involved in emulation behavior by finding analytical bounds for the error, and produced empirical data showing that the error is as small as the minimum system execution unit. In addition, we observe excellent system scalability with large-scale network experiments, and study the performance impact of the size of the synchronization window, which serves as a strong motivation for developing efficient emulation lookahead in our testbed. Keywords—parallel discrete event simulation; network emulation, virtual time