Load balanced Birkhoff-von Neumann switches, part I: one-stage buffering

Motivated by the need for a simple and high performance switch architecture that scales up with the speed of fiber optics, we propose a switch architecture with two-stage switching fabrics and one-stage buffering. The first stage performs load balancing, while the second stage is a Birkhoff-von Neumann input-buffered switch that performs switching for load balanced traffic. Such a switch is called the load balanced Birkhoff-von Neumann switch in this paper. The on-line complexity of the switch is O(1). It is shown that under a mild technical condition on the input traffic, the load balanced Birkhoff-von Neumann switch achieves 100% throughput as an output-buffered switch for both unicast and multicast traffic with fan-out splitting. When input traffic is bursty, we show that load balancing is very effective in reducing delay, and the average delay of the load balanced Birkhoff-von Neumann switch is proven to converge to that of an output-buffered switch under heavy load. Also, by simulations, we demonstrate that load balancing is more effective than the conflict resolution algorithm, i-SLIP, in heavy load. When both the load balanced Birkhoff-von Neumann switch and the corresponding output-buffered switch are allocated with the same finite amount of buffer at each port, we also show that the packet loss probability in the load balanced Birkhoff-von Neumann switch is much smaller than that in an output-buffered switch, when the buffer is large.