Packet-Size Based Queuing Algorithm for QoS Support

Quality of Service (QoS) support for data flows typically requires the use of a scheduling algorithm. For better support of QoS, the scheduling algorithm should be able to provide an acceptable level of performance as well as the functionality required for different service models such as Integrated Services, Differentiated Services, and ATM. This functionality includes a perflow and an aggregated flow scheduling, shaping, priority, etc. In this paper, we described a new scheduling algorithm, Packet-size Based Queuing (PBQ) that supports the functionality in ways that are more efficient and flexible. The PBQ's scheduling discipline with a hierarchical structure provides a hierarchical class based flow management, hierarchical shaping, and priority scheme all at the same time. The hierarchical shaping functionality, unlike other traditional shaping algorithms, shapes a group of flows (or classes) in an aggregated way while providing a proper scheduling to each flow (or class) in the group locally. The priority scheme in PBQ helps to reduce the worst delay bound, which becomes larger when priority index calculation is simplified. With all this functionality, the resulting scheduling algorithm has as a primary goal implementation simplicity while still maintaining an acceptable level of performance.