SIMNET used the concept of “dead reckoning” to correlate the positions of the objects and actors within the simulated environment. Duncan (Duke) Miller, the BBN SIMNET program manager, first used this term, which harks back to the earliest days of ship navigation, to explain how simulators were able to communicate state change information to each other while minimizing network traffic. Essentially, the approach involves calculating the current position of an object from its previous position and velocity (which is composed of vector and speed elements) (Pimental and Blau 1994). The SIMNET protocols provided that whenever the true state of a simulator deviated by more than a certain threshold from its state as computed by dead reckoning, the simulator was obligated to send out a new state update message.