In this paper, we discuss the advanced simulation architecture for KSIMS (Korea Simulation System) models. Thus far, ROK models have participated in ROK-US combined exercises as members in a single combined ROK-US federation. Now facing the transformation era, ROK Armed Forces is preparing the Wartime Operational Control Authority Transfer between ROK-US in the year 2012. It is essential to design and implement the advanced simulation architecture to fulfill its specific needs and requirements---the new architecture should enable us to conduct various exercises independently with its own models while remaining able to conduct ROK-US bilateral (currently called combined) exercises interdependently in an interoperable and need-to-know basis. To achieve this purpose, we have designed the hierarchical federations to assure the fulfillment of functionality aligning with our requirements focused on the interoperability and security issues. We present our current results and on-going efforts to confirm the pros and cons of the design.