Using performability in the design of communication networks

Conventional network design techniques treat the concepts of performance an d reliability separately. This approach ensures that reliability requiremen ts are met and performance specifications are satisfied when all components are operational. However, it does not guarantee a graceful degradation of the performance of the network under conditions of failure. In order to der ive a fault-tolerant network, it is necessary to design the network with re spect to a combined measure of performance and reliability. Such a measure originated in the early 1980s and is referred to as performability. The aut hors propose a technique that uses performability in the design of communic ation networks, with the objective of deriving a design methodology for fau lt-tolerant networks. The benefits of using this approach, compared with co nventional design methods, are illustrated by means of a design example.