and simulation in virtual time requires that emulated execution bursts be ascribed a duration in virtual time and that emulated execution and simulation executions be coordinated within this common virtual time basis. This article shows how the open-source tool TimeKeeper for coordinating emulations in virtual time can be integrated with three different existing software emulations/simulations (CORE, Mininet, and EMANE) and with two existing network simulators (ns-3 and S3F). The integration does not require modification to those tools. However, the information that TimeKeeper needs to administer these emulations has to be extracted from each. We discuss the issues and challenges we encounter there, and the solutions. The S3F integration is specialized and shows how we can treat bursts of emulated execution just like an event handler in a discrete-event simulation. Through these case studies, we show the impact that the time dilation factor has on available resources, execution time, and fidelity of causality and that deleterious behaviors suffered under best-effort management of emulation processes can be corrected by integration with TimeKeeper. The key contribution is that we have shown how, using TimeKeeper, it is possible to bring virtual time to many existing emulators without needing to change them.

Conjoinment of emulation and simulation in virtual time requires that emulated execution bursts be ascribed a duration in virtual time, and that emulated execution and simulation executions be coordinated within this common virtual time basis. This paper shows how an open source tool TimeKeeper for coordinating emulations in virtual time can be integrated with three different existing software emulations/simulations: CORE, ns-3, and S3F. We describe for each of these the modifications made to the tools to support this integration, and examine experiments designed to assess the accuracy of the combined models. Timekeeper permits much tighter sychronization of emulation and simulation than has ever been achieved before.

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