Analytic models and comparative study of the latency and steady-state throughput of TCP Tahoe, Reno and SACK

In this paper we present analytic models to estimate the latency and steady-state throughput of TCP Tahoe, Reno and SACK and validate our models using both simulations and TCP traces collected from the Internet. We also conduct a study comparing the performance of these versions of TCP under different loss scenarios. In addition to being the first models for the latency of finite Tahoe and SACK flows, our model for the latency of TCP Reno gives a more accurate estimation of the transfer times than existing models. Our models show that under the losses introduced by the droptail queues which dominate most routers in the Internet, current implementations of SACK fail to provide adequate protection against timeouts and a loss of roughly more than half the packets in a round will lead to timeouts. We also show that with independent losses, SACK performs better than Tahoe and Reno and as losses become correlated, Tahoe can outperform both Reno and SACK