Network emulation, in which real systems interact with a network simulation, is a common evaluation method in computer networking research. Until now, the simulation in charge of representing the network has been required to be real-time capable, as otherwise a time drift between the simulation and the real network devices may occur and corrupt the results. In this paper, we present our work on synchronized network emulation. By adding a central synchronization entity and by virtualizing real systems for means of control, we can build-up network emulations which contain both unmodified x86 systems and network simulations of any complexity.

This is a revised version of a paper originally presented at the ACM HotMetrics 2008 workshop.