Real-time communications in homogeneous and heterogeneous computer networks
Biao Chen, Wei Zhao · 1996
This dissertation studies the problems of providing communication service for real-time applications in high-speed networks. Many real-time systems including embedded command and control system such as flight control system, industrial process control system, and multimedia system such as video conferencing, are inherently distributed and sensitive to delay performance. The stringent performance requirements imposed by such systems are not only on computation but also on communication in networks. Furthermore, many real-time systems also have fault-tolerant requirements in the sense that tasks (messages) have to be executed (delivered) on time even if there are faults in the system. In this study we concentrate on designing and managing computer networks in order to support fault-tolerant real-time communication. The issues to be addressed include network architecture design, fault management, traffic characterization, routing, and resource management. Networks can be classified as either homogeneous or heterogeneous networks. In a homogeneous network all communications are performed using the same protocols. A heterogeneous network consists of multiple homogeneous network segments. In this dissertation, we develop methodologies of fault-tolerant real-time communication for both homogeneous and heterogeneous networks. For homogeneous networks we study wormhole routing network and FDDI high-speed LAN. They have been widely deployed in real-time systems. Among heterogeneous networks we study the ATM-based heterogeneous network, which is believed to be the computer network for the future. Because real-time communication is our focus, we first concentrate on providing real-time message delivery guarantees in a network in the absence of faults. We then demonstrate how to extend our results to support integrated fault-tolerant real-time communication. Real-time communication is a relatively new area. Much of the work reported in this dissertation is the very first in this field. Compared with the previous work, this dissertation makes the following significant contributions. First, we develop distributed regulated transmission control schemes for wormhole routing networks to solve the problem of unfair link access which may severely degrade network's real-time performance. Second, for FDDI networks, we generalize the existing timing properties, design optimal synchronous bandwidth allocation scheme, and use worst case archivable utilization to evaluate performance of resource management schemes. Third, we develop a methodology to obtain end-to-end delay guarantee in heterogeneous network. Finally, we come up with integrated architecture and management solution to support fault-tolerant real-time communication.