"Synchronization as the key to parallel and distributed computing requires a robust mechanism to handle communication among concurrent processes. In this paper we propose a flattened parallel simulator for DEVS and Cell-DEVS based on the classical null-message and lookahead based synchronization mechanism. We first present how flattening the architecture reduces communication overheads among participating nodes. Then we propose our blocking mechanism used to suspend the logical processes. After that we present our lookahead computation and null-message mechanism used to avoid causality errors as well as deadlock. Our conservative mechanism is implemented in WARPED kernel and can be used by any DEVS and Cell-DEVS parallel simulators who wish to adapt a conservative synchronization approach."--From the paper.