On the use of pipesize estimators to improve TCP transient behavior

This paper presents a simulative analysis of a modification to the TCP congestion control mechanism called ESSE (early slow start exit), designed to improve the TCP startup phase by setting the slow start threshold according to a pipesize estimation based on the observation of few ACK arrival times. We evaluate the performance of ESSE by using various methods to estimate the pipesize as the ratio between the round trip time and the spacing between ACK. This algorithm is easy to implement and preserves the compatibility with the standard protocol since it requires changes to the sender side only. Simulative experiments show that ESSE allows us to speed-up TCP connections and drastically reduce the packet drop rate under several working conditions and load levels. Better performance of TCP can be observed for any of the considered estimators, which indicates that the algorithm is robust against estimation errors. Further, the characteristics of fairness and friendliness (towards Newreno) of the algorithm are investigated. According to our simulations, ESSE-modified protocols guarantee fair utilization of bandwidth among homogeneous and heterogeneous (Newreno) connections sharing a common link.