Experimental Study of Router Buffer Sizing

During the past four years, several papers have proposed rules for sizing buffers in Internet core routers. Appenzeller et al. suggest that a link needs buffer of size O(C/ N), where C is the capacity of the link, and N is the number of flows sharing the link. If correct, buffers could be reduced by 99 % in a typical backbone router today without loss in throughput. Enachecsu et al., and Raina et al. suggest that buffers can be reduced even further to 20-50 packets if we are willing to sacrifice a fraction of link capacities, and if there is a large ratio between the speed of core and access links. If correct, this is five orders of magnitude reduction in buffer sizes. Each proposal is based on theoretical analy-sis, and validated using simulation. Given the potential ben-efits (and the risk of getting it wrong!) it is worth asking if these results hold in real, operational networks. In this paper, we report buffer-sizing experiments performed on real net-works- either laboratory networks with commercial routers as well as customized switching and monitoring equipmen