Impact of Link Availability Uncertainty on Network Reliability: Analyses with Variances

Since modern society largely depends on several network infrastructures such as telecommunications and various types of power, the reliability of networked systems needs to be accurately evaluated. Traditionally, network reliability has been evaluated on the assumption that the availability of each link is precisely given. However, in reality, it may be given with a degree of uncertainty, e.g., with variance, which must be propagated into the network reliability. To the best of our knowledge, no literature has investigated this issue because, since even computing the reliability itself belongs to a computationally tough class, computing the variance seems much harder.This paper proposes an efficient algorithm to compute the variance of the network reliability given the variance in link availability. We experimentally verify the performance of our algorithm and show that it can compute the variance of network reliability within 0.1 seconds for real topologies with nearly 200 links. We also perform extensive analyses on the variance of network reliability and reveal that network reliability tends to be accurate and that the variance in reliability does not significantly exceed the variance in link availability. Even when some links have a substantial variance in availability, the impact on network reliability is marginal.