In order to improve fairness and stability of TCP best-effort service we propose a new congestion control algorithm using packet loss information obtained from Selective Acknowledgments (SACK), and evaluate its effectiveness by simulation. The proposed scheme is for an environment consisting of Random Early Detection (RED) routers which drop each arriving packet with a certain probability after a threshold. The proposed mechanism adjusts the decrease in congestion window for Fast Recovery and the increase in congestion window per ACK during the congestion avoidance phase according to the number of lost packets. Simulation results show that not only the bandwidth allocation fairness is improved but also throughput deviation is markedly reduced resulting in more stable transport capability.

Progress made in the field of high speed networking technology has led to the planning and prototyping of true high-bandwidth applications with very high throughput and low delay requirements. In this study we approach the problem of high throughput demand from the aspect of protocols and introduce the handling of error control in the application layer level as opposed to the transport layer since the eventual destination of data is the application itself. This scheme, called ACER (Application Conscious Error Recovery), is proposed and defined for bulk data transfers. A simple analytic throughput comparison of the sliding window scheme with go-back-N, and ACER is given later, Also, a prototype implementation of ACER for bulk data transfer and experimental measurement results are presented. Besides, we investigate the performance of the scheme by simulation for various network models. Finally, we present a discussion of extending the scheme to different traffic patterns and applications.

Intelligent Transport System (ITS), aiming to provide innovative services related to traffic management, road safety and convenience, has drawn much attention in academic and industrial worlds in recent years. Japan has been considered as an advanced country in ITS development. This paper first gives an overview of the current ITS operated in Japan including Vehicle Information and Communication System (VICS), Electronic Toll Collection System (ETC), and ITS-spot system. Then this paper introduces the trends and the directions of future ITS including the development of driver-assistant type of road safety system in Japan and USA, and the potential use of white space to meet the additional ITS needs in the future.

Packet scheduling is one of the key mechanisms that will be employed in the network nodes (routers and switches) for supporting multiple quality of services. In this paper we propose a new packet scheduling algorithm called Urgency-based Round Robin (URR) which computes an index for flows in order to keep track of instantaneous bursts. Basically the index is employed as a measure of the time-dependent service necessity for each flow thus making it possible to detect those flows which might be in need of momentary service. Also, we propose a novel weight allocation scheme to be used together with the scheduler with the aim of preventing network underutilization. Our algorithm can be considered as a version of Weighted Round Robin (WRR) with improved delay characteristics. We show analytically that URR has the desired capability of upper-bounding unfairness. We also show, by simulation, that URR can improve delay performance even under extremely bursty traffic conditions without bandwidth overprovisioning. We also give simulation results for network traffic which exhibits long range dependency (self-similarity) and show that URR is again more effective than a plain round robin multiplexer.