| The objective of this research is to develop a methodology for the development of complex disaster tolerant system requirements, specifically, establishing minimum disaster free operating periods and providing the ability to measure risk through an evaluation of potential loss based on a proposed system design. The developed methodology will allow a system designer to determine the expected losses from multiple system failures in a proposed system network design structure so that proper quantitative disaster tolerant requirements may be established. The methodology and mathematical model developed in this dissertation contribute to the greater good of the trade study discipline within the system engineering process. Specifically, complex systems are developed with less risk to catastrophic failure by establishing disaster tolerant requirements in the preliminary design stage. This methodology is developed from a systems perspective through the use of systems engineering principals and processes. It advances the modern system requirements development processes towards achieving effective disaster tolerant requirements during system design.;The proliferation of geographically distributed, interconnected, and complex networks throughout both the Government and the private sector has increased the vulnerability for cascading failures with widespread consequences. Secure and reliable operation of these systems is fundamental to the economy, national security, and the quality of life of a nation. However, avoiding failures in complex IT application systems is a challenge due to their large-scale, nonlinear, and time dependent behavior where mathematical models describing such systems are typically vague or non-existent. Critical sectors of our society are becoming increasingly dependent upon highly distributed information systems that operate in unbounded networks, such as the Internet. As these sectors continue to grow and expand in a distributed nature, the importance that they be able to resist and circumvent disasters similarly increases. These factors, combined with recent global events, including natural disasters and terrorist activities, emphasize the need that a disaster event must be considered from a systems perspective and approached using systems engineering principals and processes for requirements planning in the early system design phase of system development.;Computer and communication networks have become critical elements of modern society. These network infrastructure systems not only have global reach, they also have impact on virtually every aspect of human endeavor. They have become principal enabling agents in business, industry, government and defense. Major economic sectors, including defense, energy, transportation, telecommunications, manufacturing, financial services, health care, and education, all depend on a vast array of networks operating on local, national, and global scales. This pervasive societal dependency on network infrastructures magnifies the consequences of intrusions, accidents, and failures, and amplifies the critical importance of ensuring disaster tolerant infrastructure systems.;Disaster tolerance is a superset of fault tolerance. The model for disaster tolerance is different since it is assumed that failures occur due to massive numbers of individual faults. Disasters may be either natural, such as a flood, or man-made, such as a terrorist event. In either case, the system model is one of multiple individual system faults that occur nearly simultaneously or close together in time as a series of related events [1]. Fault tolerant system research and development has been evolving for many years and has built on the methods and analysis of reliability theory. The typical high-level approach to fault tolerant system design is as follows: (1) Determine a model for a system; (2) Characterize a failure as a fault model; (3) Analyze the behavior of the system with the fault model present; (4) Redesign the system to function correctly even when the fault is present. (Abstract shortened by UMI.)... |
