Impact of Buffer Size on TCP Start-Up

The Slow Start (SS) phase at the beginning of a TCP connection affects the performance of short transfers especially on long delay links such as Satellite Links. Many works have tried to improve the performance of this phase either by accelerating the congestion window increase or by setting the SS threshold at the beginning of the connection to a more accurate value in order to avoid losses and a long Timeout. However, these works don’t account for the size of buffers in network nodes. In this paper, we present a general analysis of this first phase as a function of the network and TCP parameters. Among our results, we show that as claimed, the previous works improve the performance on paths with large buffers. However, on paths with small buffers, completely different results can be obtained.