An efficient expression of timestamp and period in packet-based and cell-based schedulers

Scheduling algorithms are implemented in hardware in high-speed switches to provision quality-of-service guarantees in both cell-based and packet-based networks. Being able to guarantee end-to-end delay and fairness, timestamp-based fair queuing algorithms have received much attention in the past few years. In timestamp-based fair queuing algorithms, the size of timestamp and period determines the supportable rates in terms of the range and accuracy. Furthermore, it also determines the scheduler's memory in terms of off-chip bandwidth and storage space. An efficient expression can reduce the size of the timestamp and period without compromising the accuracy. We propose a new expression of the timestamp and period, which can be implemented in hardware for both high-speed packet-based and cell-based switches. As compared to fixed-point and floating-point number expression, when the size is fixed, the proposed expression has a better accuracy.