Link-layer fragmentation and retransmission impact on TCP performance in 802.11-based networks

Our objective in this paper is to examine the behavior of TCP in 802.11-based networks. The focus of this work is mainly on the effect of the fragmentation and frames retransmission handled at the MAC layer on the TCP end-to-end performance. The packet loss rate and the end-to-end delay of TCP connections are analyzed and evaluated. Some preliminaries relationships between the estimated TCP retransmission time-out and the maximum number of retransmissions at the MAC level are derived. The obtained results show how the number of fragments and the maximum number of retransmissions should be tuned in order to reach a desired values of both TCP delay and loss rate. The main contribution of this work is the development of an analytical framework that could be used as a basis for the development of a cross-layer cooperative scheme between the retransmission mechanisms TCP and MAC protocols.