Providing QoS guarantees in packet switches

The continuous growth in the demand for diversified quality-of-service (QoS) guarantees in broadband networks introduces new challenges in the design of next-generation packet switches. Packet scheduling is the most critical function involved in the provision of individual bandwidth and delay guarantees to the switched flows. Most of the scheduling techniques proposed so far assume the presence in the switch of a single contention point, residing in front of the outgoing links. Such an assumption is not consistent with many popular switch architectures, which typically have multiple contention points, located in both ingress and egress port cards, as well as in the fabric itself. We define a distributed scheduling architecture to provide differentiated QoS guarantees to individual traffic flows in a switch with multiple contention points. Our scheduling architecture is simple to implement, since it keeps per-flow scheduling confined to the port cards, and is suitable for applications in QoS frameworks for both IP and ATM networks