An SMP-based, low-latency, network interface unit and latency measurement system: the SNAPpy system

Latency is an explicit and possibly insidious issue associated with distributed interactive simulations (DISs), whether they are legacy simulations or simulations based on the DIS protocol or on the HLA (High Level Architecture) and RTI (Run-Time Infrastructure) standards. The implementation details of individual simulations, whether located entirely in one room or geographically distributed across a continent, will directly impact the latencies between various elements of the simulation. At SYSTRAN Corp., we have developed a Windows NT-based system, called SNAPpy (Simulation Network Analysis Project), that seeks to provide tools to both measure and reduce the latency associated with DISs. SNAPpy includes two major sections: an NIU (network interface unit) that is multi-threaded and built on an SMP (symmetric multiprocessor) and Windows NT platform, and the SNAP latency measurement section. This paper reviews the architecture of SNAPpy, going into specific details about its make-up and performance. Finally, SNAPpy's potential as a translator of legacy simulations into the HLA/RTI domain is described, and we introduce the SNAP-Lite Latency Measurement System, a new SYSTRAN product.