1. A method for processing packets in a system that comprises a plurality of interconnected processing cores, the method comprising: 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.