Improve TCP performance over ATM-UBR with FED+

We had previously proposed a fuzzy logic-based buffer management scheme (BMS) called fuzzy early detection (FED), designed to improve transmission control protocol (TCP) performance over the unspecified bit rate service of asynchronous transfer mode networks. Since a weakness in FED was discovered later, we present a refined version of it named FED+ here. Maintaining the design architecture and algorithm of FED, FED+ further adopts per virtual connection accounting to achieve its design goals. The effects of TCP implementation, TCP maximum segment size, switch buffer size and network propagation delay on FED+ performance are studied through simulation. Its performance is then compared with those of pure early packet discard, P-random early detection and FED. Our evaluations show that FED+ is superior to the others if the issues of efficiency, fairness, robustness, buffer requirement and the ease of tuning control parameters of a BMS are considered collectively.