Simulator network design has changed from proof-of-principle demonstrations to a production training medium as new contracts call for the implementation of simulator networks designed to a standard protocol. The prototype standards for Distributed Interactive Simulations (DIS) address the information content required for the interconnection of dissimilar simulations and the rules for DIS usage. These rules currently center on the control and execution of network exercises and have not yet addressed the issues of system validation and system performance measurement. This paper briefly discusses current trends in simulator interoperability. It then discusses the concept of fidelity differential and its impact on team training. It discusses various methods of measuring fidelity differential and their relative merits. Finally, it suggests a set of performance metrics that should be applied to simulation networking standards.