Abstract
We consider the two-terminal reliability and link importance analysis of fault tolerant network systems in this paper. Two practical issues, imperfect coverage (IPC) and common-cause failures (CCF), which have generally been ignored by existing network models, are incorporated. The methodology is to separate the consideration of both IPC and CCF from the combinatorics of the solution and then solve the reduced problems using binary decision diagrams (BDD). The application and advantages of the proposed separable approach are illustrated using a concrete analysis of an example network system. Due to the consideration of IPC and CCF, our approach can evaluate a wider class of practical network systems as compared with existing network approaches. Due to the nature of the BDD and the separation of IPC and CCF from the solution combinatorics, our approach has low computational complexity and is easy to implement. The systems without IPC or CCF appear to be special cases of our approach.