A Load Balancing Scheme for Birkhoff-von Neumann Input-Queued Switches

In this paper, we propose a novel load-balancing scheme for the Birkhoff-von Neumann input-queued (BvN-IQ) switch, which we call the cyclic exchange. According to the cyclic exchange scheme, in each time slot each linecard transfers a cell from its non-empty VOQ to the empty VOQ of another linecard which is destined for the same output. In order to guarantee the cell sequence in this procedure, we propose a simple rule of selecting the cells to be transferred for load balancing, and prove the sequence guarantee by the proposed rule. Since the cyclic exchange is performed locally between two linecards, its communication and computation overhead is not too heavy to implement. To be specific, the communication overhead of the proposed scheme is the transmission of N bits and its computation overhead corresponds to a priority encoder with a fixed highest priority. The simulation results show that the proposed scheme achieves 100% throughput asymptotically and shorter delay than the two-stage switch.