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In this paper, we propose a new version of TCPW (TCP-Westwood) to (1) maintain friendliness to widely used protocols, such as TCP-Reno, as well as (2) improve efficiency in mixed wired-wireless networks with non-negligible random packet losses due to link errors. In addition to significant efficiency gains, TCPW has been shown to be unfriendly to existing protocols under certain RTT and/or router buffer capacities. Since friendliness to existing protocols is one of the most important issues in a real network environment where different protocols coexist, we propose TCPW-BBW (TCPW with Buffer and Bandwidth Estimation) to ensure the friendliness even under varying effective buffer capacities. Based on buffer capacity estimation mechanism, TCPW-BBE reacts more appropriately to a packet loss event, whether the loss is due to congestion or link errors. Simulation results show that TCPW-BBE maintains friendliness to TCP-Reno in networks for a broad range of buffer capacities, and RTTs, with/without RED routers, yet retaining the efficiency of the original TCPW.

SUMMARYThe paper presents a survey on OpenFlow related technologies that have been proposed as a means for researchers, network service creators, and others to easily design, test, and deploy their innovative ideas in experimental or production networks to accelerate research activities on network technologies. Rather than having programmability within each network node, separated OpenFlow controllers provide network control through pluggable software modules; thus, it is easy to develop new network control functions in executable form and test them in production networks. The emergence of OpenFlow has started various research activities. The paper surveys these activities and their results.