Real-time systems and applications are becoming increasingly complex and often comprise multiple communicating tasks. The management of the individual tasks is well-understood, but the interaction of communicating tasks with different timing characteristics is less well-understood. We discuss several representative inter-task communication flows via reserved memory buffers (possibly interconnected via a real-time network) and present RAD-Flows, a model for managing these interactions. We provide proofs and simulation results demonstrating the correctness and effectiveness of RAD-Flows, allowing system designers to determine the amount of memory required based upon the characteristics of the interacting tasks and to guarantee real-time operation of the system as a whole.