On the impact of software failures on time division multiplexed Passive Optical Networks dependability

Passive Optical Networks (PONs) are widely regarded as the best suited technology for deploying broadband access networks. As new services emerge, the dependability of PONs has become critical as end users expect access networks to be highly reliable. Although PONs dependability regarding hardware failures has been extensively studied, very little attention has been drawn to software failures in PONs. Chiefly, this paper aims at performing an exhaustive analysis of the effect of software failures in PONs dependability and failure-related costs. Additionally, hardware failures are also included for the sake of completeness and comparison. By applying Duane's model for reliability growth to current literature results, the PON software dependability is estimated as a function of the testing phase duration. Then, a Markov cost model, accounting for both hardware and software failures is developed and solved by means of Monte Carlo simulations. Hence, the effect of software failures in PONs asymptotic availability, failure impact and dependability-related costs is detailed; revealing to be of utmost importance. Moreover, how the testing process duration affects these three parameters is also pinpointed.