A weighted round robin engine used in scheduling the distribution of ATM cells

摘要

A weighted round robin (WRR) engine includes components to arbitrate emission of ATM cells assigned to different flows. In one embodiment termed an Inter-QoS WRR, the flows are linked to quality of service (QoS) parameters. A tag value is further assigned to each QOS parameter. Whenever the QoS is selected by the Inter-QoS WRR to have a flow emit an ATM cell, the tag value for the QoS is incremented by a weight assigned to the QoS. The QoS selected by the Inter-QoS WRR is the QoS with the lowest tag. If two or more QoSs are tied with the lowest tag, the highest numbered QoS is selected by the WRR. In another embodiment termed an Inter-Flow WRR, flows are linked based on a tag value assigned to the flow, independent of their QoS, enabling control of bandwidth of flows linked to the same QoS. Flows linked first are emitted first when the Inter-Flow WRR operates. A tag value assigned to a flow is incremented by the flow's rate limiting increment (I) each time the Inter-Flow WRR selects the flow for emitting an ATM cell. When multiple flows are linked together, they are linked according to their tag with the lowest tag linked first. IMAGE