In this paper we describe a distributed-memory parallel implementation of the Open Network Emulator (ONE), a network simulator that combines the controllability of simulation with the direct code execution advantages of emulation and experimental testbeds. ONE uses a scaled real-time model called Relativistic Time (RT). We describe a RT-based reactive global warp detection algorithm to exploit lookahead. The Distributed ONE system provides a platform for network simulation that combines model

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... delity (existing network applications can be compiled and instantiated within ONE without modification), temporal fidelity, and good scalability. We present strong and weak scaling performance results for the Distributed ONE system on up to sixteen nodes of a distributed-memory parallel cluster, on simulations involving up to 16,000 virtual hosts.