A Novel Mechanism to Improve Performance of TCP Protocol over Asymmetric Networks
An asymmetric network is one in which there is a mismatch between the characteristics of the forward and reverse channel. Typically, the forward channel is capable of high transmission rates and the reverse channel has lesser bandwidth. Cable modem networks and satellite networks are some technologies that exhibit network asymmetry. TCP, due to its widespread acceptance, is also used in asymmetric networks. However, the reverse channel being a bottleneck causes many problems in the behavior of traditional TCP protocols. The TCP protocol is heavily dependent on ACKs. The variation in the ACK arrival rate, caused due to network asymmetry, results in slower initial window growth and burstiness on the forward channel. Existing approaches to improve the performance of TCP in asymmetric networks use techniques such as reduction in number of ACKs. However, these approaches do not take into consideration the high bandwidth availability in the forward direction for early ramp up of TCP window. In this paper, we present a new approach, Mild Aggression which exploits the high forward channel bandwidth, by modifying the RTT estimate and incrementing the cwnd by Mild Aggression factors, to improve the performance of TCP in an asymmetric environment.