Packets are processed in a system that comprises a plurality of interconnected processor cores. The system receives packets into one or more queues. The system associates at least some nodes in a hierarchy of nodes with at least one of the queues, and at least some of the nodes with a rate. The system maps a set of one or more nodes to a processor core based on a level in the hierarchy of the nodes in the set and based on at least one rate associated with a node not in the set. The packets are processed in one or more processor cores including the mapped processor core according to the hierarchy.