The Scalable Reservation Protocol (SRP) provides a light-weight reservation mechanism for adaptive multimedia applications. Our main focus is on good scalability to very large numbers of individual flows. End systems (i.e. senders and destinations) actively participate in maintaining reservations, but routers can still control their conformance. Routers aggregate flows and monitor the aggregate to estimate the local resources needed to support present and new reservations. There is neither explicit signaling of flow parameters, nor do routers maintain per-flow state.