Roger M. Kieckhafer

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This paper describes the Multicomputer Architecture for Fault-Tolerance (MAFT), a distributed system designed to provide extremely reliable computation in real-time control systems. MAFT is based on the physical and functional partitioning of executive functions from application functions. The implementation of the executive functions in a special-purpose(More)
ÐIn a fault-tolerant distributed system, it is often necessary for nonfaulty processes to agree on the value of a shared data item. The criterion of Approximate Agreement does not require processes to achieve exact agreement on a value; rather, they need only agree to within a predefined numerical tolerance. Approximate Agreement can be achieved through(More)
Firewalls form the first line of defense in securing internal networks from the Internet. A Firewall only provides security if all traffic into and out of an internal network passes through the firewall. However, a single firewall through which all network traffic must flow represents a single point of failure. If the firewall is down, all access is lost. A(More)
Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 x 10(19) electron volts and the positions of active galactic nuclei (AGN) lying within approximately 75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these(More)
The failure and repair of modules in an N-Modular Redundant (NMR) system are governed by a failure time distribution and repair time distribution, respectively. It is generally reasonable to assume that a module's failure time distribution is a simple exponential distribution. However, it is not reasonable to assume that the repair time distribution is also(More)