Multi-State Reliability Evaluation of Local Area Networks

Given the contemporary importance of communications systems and infrastructures in general, networks need to be designed and operated in such a way that failures can be reduced, alleviated, or mitigated. Network components might for instance fail due to equipment failing, malicious attacks, planned or, unplanned activities, and so on. This paper presents a three-state system model (Good, Poor, and Fail). This model is demonstrated via two examples covering the proposed multistate model in detail. The first example studies a firewall system with two components in two operational modes, namely active-active and active-standby. The second example covers a simple private cloud setup with three layers, namely firewall, server, and service layer. The first example is solved by two methods (a) Tabular form of exhaustive enumeration; (b) Multi-state Decision Diagrams (MDD). The second Example is solved by (a) The exhaustive enumeration method, and (b) Dividing the system into 3 subsystems and integrating their results. The results of this study indicate that the firewall block modes of operation have a major impact on the studied systems. Firewalls in active-active mode significantly improve the probability of system's Up state. The findings of this study should be of great help to designers to better design services to increase service availability.