RELIABILITY OPTIMIZATION IN THE DESIGN OF DISTRIBUTED SYSTEMS.

A useful measure of reliability in distributed systems is the terminal reliability between a pair of nodes. This is the probability that at least one communication path exists between these nodes. An interesting optimization problem is to maximize the terminal reliability between a pair of computing elements under a given budget constraint. Three iterative algorithms for terminal reliability maximization are presented. The first two algorithms require the computation of terminal reliability expressions and are therefore efficient for only small networks. The third algorithm, which is developed for large distributed systems, does not require this computation; it maximizes approximate objective functions and gives accurate results. Several examples illustrate the approximate optimization algorithm, and the error involved is estimated.