Processing packets in a system that includes a plurality of interconnected processing cores is described. The processing includes receiving packets into one or more queues, associating 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, mapping 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 at least one rate associated with a node not in the set, and processing the packets in the mapped processor cores according to the hierarchy.