Analytic models for the latency and steady-state throughput of tcp tahoe, reno, and sack

Abstract

Continuing the process of improvements made to TCP through the addition of new algorithms in Tahoe and Reno, TCP SACK aims to provide robustness to TCP in the presence of multiple losses from the same window. 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. 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. The improved accuracy is partly due to a more accurate modeling of the timeouts, evolution of cwnd during slow start and the delayed ACK timer. Our models also show that, under the losses introduced by the droptail queues which dominate most routers in the Internet, current implementations of SACK can 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.

Stochastic Hybrid Systems: Application to Communication Networks

“…This equation is valid at least for simple network topologies, small values of p drop , and one acknowledgments per ACK packet (n ack = 1). Generalizations can be found, e.g., in [41,46].…”

“…A great deal of effort has been placed in characterizing the steady-state behavior of these flows [35,36,40,41,46]. In particular, in studying the relationship between the average transmission rate µ, the average round-trip time RT T , and the per-packet drop rate p drop for a single TCP flow.…”

Comparison of TCP congestion control mechanisms Tahoe, Newreno and Vegas

“…TCP Tahoe is briefly described in [8]. With fast retransmit, when a packet is lost, instead of waiting for the retransmission timer to expire, if tcprexmtthresh (usually three) duplicate ACKs are received, the sender infers a packet loss and retransmits the lost packet.…”

Impact of cross traffic burstiness on the packet-scale paradigm

“…Most congestion control protocols are analyzed for their steady-state throughput by conducting stochastic analysis of their window growth functions [3], [4], [5]. Most of these analyses incorporate the impact of packet losses and round trip-times (RTTs), considering these to be the major influences on the throughput of a transfer.…”