Patent ID: 8165144

Claim:
A scheduling method at a network device, comprising: receiving traffic at a root node in a multi-level class hierarchy, said root node linked to at least two groups, wherein one of said groups is a high priority group which has priority over the other of said groups and comprises at least one high priority queue and at least one low priority queue, said multi-level class hierarchy comprising a first level comprising the root node, a second level comprising said groups, and a third level comprising said queues; directing the traffic received at said root node to one of said groups; directing traffic received at said high priority group to one of said high priority and low priority queues; determining an aggregate rate at said high and low priority queues; and processing packets at the network device, wherein processing comprises: accepting said packets at said high priority queue or said low priority queue if said aggregate rate does not exceed a specified rate; dropping at least some of said packets at said low priority queue and not dropping said packets at said high priority queue if said aggregate rate exceeds said specified rate and a rate at said high priority queue does not exceed said specified rate; and dropping at least some of said packets at said high priority queue if said rate at said high priority queue exceeds said specified rate; wherein said high priority queue comprises a priority propagation attribute and said priority propagation attribute allows a priority indication to be passed from a node to its parent on a per-packet basis so that low latency behavior is delivered through said hierarchy.