An experimental evaluation of CUBIC TCP in a small buffer regime

CUBIC TCP is an enhancement over BIC (Binary Increase Congestion Control) with a cubic window growth function. It has been optimized for high bandwidth-delay product environments and has been the default TCP implementation in Linux since kernel-2.6.18. In this paper, we conduct an experimental evaluation of CUBIC TCP in a small buffer regime; i.e. buffers of the order of a few tens of packets. The experiments are carried out using the NetFPGA platform. Our focus is on the interaction of long lived flows, with small buffers, over a range of bandwidth-delay product environments. In such a network environment, our work serves to exhibit the following effects. At smaller link capacities, there is a distinct impact on utilization as the number of users, and the round trip times vary. At larger link capacities, small buffers can readily induce synchronization effects. Our work highlights the need for a thorough investigation on the performance of CUBIC TCP, with small buffers, for next generation high speed networks.