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

Abstract

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.