High capacity data transfers over the Internet routinely fail to meet end-to-end performance expectations. The default transport control protocol for best effort data traffic is currently TCP, which does not scale well to 100 Mbps and higher networks over long distances. In congestion avoidance, TCP is not swift enough to fully utilize resources over paths with a high delay bandwidth product. First attempts to alleviate this problem by equipping TCP with increased aggressiveness have shown the disadvantage of poor fairness with the ubiquitous standard TCP-Reno, or in some cases, even among two connections running over the same path. We propose a new delay sensitive-congestion avoidance mode (TCP-Africa) that allows for scalable, aggressive behavior in large underutilized links, yet falls back to the more conservative TCP-Reno algorithm once links become well utilized and congestion is imminent. Through ns2 simulations we argue for the safety, efficiency, and fairness of TCP-Africa.

Timix is a distributed real-time kernel that is being developed to support multisensor robot systems. The overall structure of the kernel is described, including a hierarchy of interprocess communication primitives and a generic way to interact with external devices. A simple multisensor robot that is being implemented using Timix is also presented. Three salient aspects of Timix are as follows. First, it is possible to estimate the amount of time that a real-time process takes to execute since the execution times of system calls are bounded. Second, an hierarchy of communication methods, which differ in synchronization, time and space overheads, and bandwidth requirements, are provided to allow the programmer to choose the one most applicable to a particular application, depending on the real-time requirements. Finally, new devices, which ar directly controlled by application processes, can be integrated into the system without changing the kernel.>