This paper presents the DDSOS framework developed at Arizona State University, which supports the simulation, development, and evaluation of large scale distributed systems such as network-centric and system-of-systems applications. The distinct features of the framework include automated simulation code generation from the specification, code deployment, simulation of different architectures with a templatebased platform builder, service-oriented multi-agent simulation for easy reconfiguration, and dynamic analyses of results from evaluation and monitoring. The framework and the associated tools have been implemented and applied in several governmental and industrial projects.