Improving congestion avoidance algorithms for asymmetric networks

Congestion avoidance algorithms considering the network as a black-box model detect congestion through packet loss and variation in the throughput or in the round trip delay. In this paper we show, by means of analysis and simulation, an undesirable effect acting on delay and throughput based congestion avoidance algorithms. This effect is caused by congestion experienced by acknowledgements. We propose to change these algorithms by dividing the round trip time into a forward trip time and backward trip time. We show the performance improvement using this distinction. Finally, we describe a possible implementation in the TCP protocol.