Congestion Control for Small Buffer High Speed Networks

There is growing interest in designing high speed routers with small buffers that store only tens of packets. Recent studies suggest that TCP NewReno, with the addition of a pacing mechanism, can interact with such routers without sacrificing link utilization. Unfortunately, as we show in this paper, as workload requirements grow and connection bandwidths increase, the interaction between the congestion control protocol and small buffer routers produce link utilizations that tend to zero. This is a simple consequence of the inverse square root dependence of TCP throughput on loss probability. In this paper we present a new congestion controller that avoids this problem by allowing a TCP connection to achieve arbitrarily large bandwidths without demanding the loss probability go to zero. We show that this controller produces stable behavior and, through simulation, we show its performance to be superior to TCP NewReno in a variety of environments. Lastly, because of its advantages in high bandwidth environments, we compare our controller's performance to some of the recently proposed high performance versions of TCP including HSTCP, STCP, and FAST. Simulations illustrate the superior performance of the proposed controller in a small buffer environment.