The Joint Experimental Federation (JEF) is a large collection of simulations federated together by the US Joint Forces Command (JFCOM) and the Military Services to support Millennium Challenge 2002. The federation stimulates Service C4I devices to create a Common Operating Picture for a Joint Force Headquarters. The MC02 construct also included concurrent Service experiments, such as the Navy's Fleet Battle Experiment and the Air Force's Joint Expeditionary Force Experiment.

JFCOM asked the Services to nominate simulations that would drive their C4I systems and realistically portray military capabilities. The JEF was constructed by linking the nominees together via the Defense Modeling and Simulation Office's Run Time Infrastructure (RTI). The resulting federation linked RTI and Distributed Interactive Simulation (DIS) federates and live exercise feeds into a single geographically distributed simulation. Federation integration took a year and was primarily a process of resolving conflicting simulation approaches. Significant extensions allowed RTI-1.3NG to achieve the scalability and fault tolerance required for MC02. The federation simulated over 34,000 battlefield platforms over a Wide Area Network and allowed individual simulation federates or communications links to fail and restart without restarting the entire federation. A common Federation Object Model (FOM) and Federation Agreements were developed based on the Real-time Platform Reference FOM.

While federations allow for simulation reuse, they also have drawbacks. Interactions gravitate to the least common denominator models and the effort required to implement new capabilities is significantly multiplied. The real power behind the federation concept is that it allows disparate groups to use their own simulations in common experiments.