CBF: A high-performance scheduling algorithm for buffered crossbar switches

Buffered crossbar switches have been considered as a viable alternative to buffer-less crossbar switches to improve the switching performance. An architecture that combines the strength of the VOQ architecture with an internally buffered crossbar fabric presents key advantages over the IQ switches. The adoption of VOQs at the input side eradicates the HoL blocking problem. Whereas, the use of the internal buffers reduces the output contention and enables totally distributed arbitration. Hence, overcoming the bottleneck of IQ switches. In this paper, we show the important role that the internal buffers play in the arbitration process. We propose a scheduling scheme named Critical internal Buffer First (CBF), which is based on the internal buffer information only. The input scheduling is based on the Youngest internal Buffer First (YBF) and followed by an output scheme based on the Oldest internal Buffer First (OBF). Our scheme was shown, through simulation, to achieve very high throughput. It outperforms all existing schemes in many traffic patterns. More interestingly, our scheme shows very good stability performances without maintaining any kind of information about the input VOQs.