The quantitative impact of survivable network architectures on service availability

This article presents results from research that included the modeling of various self-healing structures in order to compute the service availability between any two nodes within a given survivable network. In particular, terminal-pair availabilities are computed for a service-bearing transport signal that traverses a unidirectional path-switched ring (UPSR) system, a bidirectional line-switched ring (BLSR) system, a series of interconnected ring (UPSR and/or BLSR) systems, called a ring chain, within a general ring-based mesh network, and a series of interconnected point-to-point systems within a general point-to-point mesh network. In addition, these network structures are evaluated with varying degrees of fiber link and system interconnection node survivabilities; specifically, two-fiber and four-fiber link configurations are evaluated, and an intersystem nodal survivability factor a is used to characterize a transport signal of a given service level. Based on the results of these computations, several key observations are highlighted that should be considered when planning and designing short- and long-haul self-healing networks.