A system for scheduling utilization of a service resource by a plurality of flows of information packets, wherein the flows include rate-guaranteed synchronous flows and best-effort asynchronous flows, the asynchronous flows exploiting the service capacity of the resource left unexploited by the synchronous flows. A server visits the flows, in subsequent rounds, by visiting first the synchronous flows followed by the asynchronous flows. The server is configured for detecting any backlogged synchronous flow, and when the server visits any said backlogged synchronous flow, it allows the backlogged synchronous flow to utilize the resource for a given time, whereby the synchronous flows have a guaranteed transmission window on each round. When the server visits any asynchronous flow, the time elapsed since the last visit by the server to the same asynchronous flow is determined. If the visit to the asynchronous flow occurs later than expected based on a reference round time, the asynchronous flow being visited is restrained from utilizing the resource for the ongoing round, and if the visit occurs earlier than expected based on the reference round time the asynchronous flow being visited is allowed to utilize the resource for a respective given time.