Reliability models for fault-tolerant private network applications

A private or corporate network connects the offices of a single large organization, such as an airline or a bank, using leased private lines. To improve the reliability of network applications, fault-tolerance can be incorporated directly into the private network. In this paper, we use a state-space model to capture the effect of dynamic rerouting and repair and investigate the effect on reliability of different repair-and-rerouting strategies at the application or call level. To reduce the potentially large state space that results, we construct an approximate Markov model with a smaller state space by lumping together similar states. The lumped model includes coverage parameters that can be estimated without considering the original model in its entirety. This allows the state-space model to be solved accurately and efficiently. We compare results of the approximation technique with results obtained by a complete simulation of the original network. We expect similar approximation techniques to be effective on models with large state spaces which obtain processes with many time-scales