Finding an optimum maximum congestion window for TCP reno over 802.11 based ad hoc networks

Abstract

Bandwidth Delay Product (BDP) represents the maximum amount of allowed unacknowledged data in flight at any moment in the network. Due to the spatial reuse property of 802.11 MAC protocol in multi-hop ad hoc networks, the BDP of the path approximates 1/4 of the path length and is a value of several packets. With such a small BDP, TCP cannot work efficiently since its congestion window increases far beyond BDP most of the time, which can generate heavy congestion in the network. This paper presents a mathematical approach to derive an optimum maximum congestion window for TCP Reno over 802.11 based ad hoc networks. We adopt a Markov renewal approach to analyze the behavior of TCP Reno, which incorporates an accurate and realistic modelling of the fast-recovery process. Through analysis, we find that the optimum maximum congestion window is 6 packets for a multi-hop chain with any path length. © 2007 IEEE.