This paper describes how systems will be interconnected in the future, the roles that they will play, and the trade-offs that affect these roles. Starting with a general model for structuring a network of systems, general trade-offs in cost and performance are discussed relative to where functions are placed in the network. Several general principles for data and function placement in a network of systems are derived from these trade-offs. The optimal roles for each of several layers of a network of systems are discussed. Finally, conclusions are drawn regarding the design of future networks of systems.