Providing Fairness Through Detection and Preferential Dropping of High Bandwidth Unresponsive Flows

Stability of the Internet today depends largely on cooperation between end hosts that employ TCP (Transmission Control Protocol) protocol in the transport layer, and network routers along an end-to-end path. However, in the past several years, various types of traffic, including streaming media applications, are increasingly deployed over the Internet. Such types of traffic are mostly based on UDP (User Datagram Protocol) and usually do not employ neither end-to-end congestion norflow control mechanism, or else very limited. Such applications could unfairly consume greater amount of bandwidth than competing responsive flows such as TCP traffic. In this manner, unfairness problem and congestion collapse could occur. To avoid substantial memory requirement and complexity, fair Active Queue Management (AQM) utilizing no or partial flow state information were proposed in the past several years to solve these problems. These schemes however exhibit several problems under different circumstances.This dissertation presents two fair AQM mechanisms, BLACK and AFC, that overcome the problems and the limitations of the existing schemes. Both BLACK and AFC need to store only a small amount of state information to maintain and exercise its fairness mechanism. Extensive simulation studies show that both schemes outperform the other schemes in terms of throughput fairness under a large number of scenarios. Not only able to handle multiple unresponsive traffic, but the fairness among TCP connections with different round trip delays is also improved. AFC, with a little overhead than BLACK, provides additional advantages with an ability to achieve good fairness under a scenario with traffic of diff21erent sizes and bursty traffic, and provide smoother transfer rates for the unresponsive flows that are usually transmitting real-time traffic.This research also includes the comparative study of the existing techniques to estimate the number of active flows which is a crucial component for some fair AQM schemes including BLACK and AFC. Further contribution presented in this dissertation is the first comprehensive evaluation of fair AQM schemes under the presence of various type of TCP friendly traffic