Most current schemes for multicast routing assume that multicast routers participate both in forwarding multicast packets and in control algorithms for routing, resource reservation, and group management. By separating data and control flow, and by centralizing control in distinct control elements, we have designed a simple and scalable approach to IP multicast that we call Centralized Multicast. We present the details of our approach, a proof of its correctness, analysis of its performance, and a discussion of its advantages over current schemes.