CSS: Cautious Slow Start algorithm to minimize packet drop rate

Abstract

Slow Start algorithm helps the TCP flows to quickly ramp up their congestion window (cwnd) by employing an exponential increase pattern. This pattern of increasing cwnd leads to consecutive loss of packets in bulk, and hence, results in large number of packets being re-transmitted. Recently, the limitations of this approach have become apparent as many Internet applications are becoming more sensitive to packet loss and latency. In this paper, we propose a Cautious Slow Start (CSS) algorithm which aims to mitigate the bulk packet losses that occur with the traditional Slow Start algorithm. This is achieved by increasing the cwnd cautiously, instead of doubling it. We validate the effectiveness of CSS algorithm by simulating a variety of Internet like scenarios in ns-2, and comparing its performance with that of the traditional Slow Start algorithm. CSS algorithm successfully mitigates the bulk packet losses, without affecting the overall link and buffer utilization.