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GenSim(Generic Simulator) is a simulator infrastructure which is on engineering development level and will be used at software validation and verification of satellite flight software. GenSim is able to run software simulator models which follow ESA SMP/SMI standard. But also GenSim has to handle HILS with real I/O card, e.g. MIL-STD-1553B card or RS-422 digital I/O board to communicate with real spacecraft equipments. So GenSim has various shapes according to the usage and may take some limitation of speed to run it as realtime. To overcome this limitation, GenSim is designed to cooperate with remote GenSim which is separated by physically but connected by ethernet connection. In this case, GenSim is split with two or more simulator parts and there are some communication and synchronization mechanisms which are needed to maintain connection between the separated simulator parts. Some parts may take a role of simulator controller and other parts may take a role of external I/O simulator for interfacing with real spacecraft components. Smooth running and timing margin would benefit most from spatial separation of GenSim. Of course complexity of simulation model development will be decreased since a huge model can be decomposed by dividing it with several distributed models. Distributed configuration of GenSim would make it easier when GenSim link with specialized simulator or system, e.g. camera simulator or 3D motion display system. A network is established to connect them with minimizing system complexity came from introducing system validation or mission validation requirement. SimNetwork is name of protocol which is invented to solve the interconnection methodology among distributed GenSims or between GenSim and the specialized simulators. SimNetwork is based on the ethernet TCP/IP stack and has simple protocol for control and data exchange between simulators which are connected via SimNetwork. A connection between simulators would be managed dynamically, so no s- - tatic pre-allocation is necessary. Dynamical connection and disconnection is crucial requirement to avoid unnecessary reconfiguration of simulators including GenSim during simulation process. At this paper, a preliminary design of distributed simulator concept and SimNetwork is presented.