Dual-Ring Network Reliability Analytical Solution with Application to Large Video Systems

Reliability of complex network systems is frequently assessed using Monte Carlo simulation because an analytical solution is not available or is overly complex. A variant of dual -ring redundancy has been implemented to support high reliability requirements of large video display systems such as advertising billboards, stadium displays and traffic management systems. This network scheme, with data feed segments being daisy-chained to network nodes in 2 directions (forward and reverse), can offer significant reliability benefits beyond simple parallel redundancy without increase in complexity. This paper describes an analytical solution for reliability calculation that is simple and can easily be applied to dual-ring networks with any number of nodes. This solution avoids problems common to expansion of terms when using the addition law of probability. This paper further explores the common failure independence assumption and notes that the dual-ring network reduces to an N+1 network in cases of dependent failures such as common-cause and common-mode. Analytical solution is also provided for system reliability with both independent and dependent failures present. Dual-ring networks for application in large video systems are found to be superior to other redundancy types with equivalent segment reliabilities. Such networks are no more complex than active parallel or N+1 networks. With these analytical solutions, reliability design trade-off studies can be undertaken using simple spreadsheet rather than the more complex Monte Carlo simulation.