Adaptive Pushout: A Buffer Management Scheme to Improve TCP Fairness in Wireless LANs

We propose to use a buffer management scheme, called adaptive pushout, in the transmission buffer of the access point (AP) in order to solve unfairness problems between competing TCP flows over wireless LANs. The adaptive pushout comes from the observation that multiple ACK segments in a TCP connection are redundant because of the cumulative acknowledgment mechanism of the TCP. Under the adaptive pushout, an arriving packet encountering the full buffer removes one of redundant ACKs from the transmission buffer of the AP to enter there. When the buffer is full and has no redundant ACK, the arriving packet adaptively chooses one of packets in the buffer for pushing it out from the buffer. The choice of the packet to be pushed out depends on the number of uplink and downlink TCP flows, which are continuously monitored in the proposal. We have conducted simulation experiments to show that the adaptive pushout greatly improves the fairness compared with existing proposals.