Abstract
Evaluation of the availability and unavailability of optical connections is necessary for WDM optical networks to make efficient use of optical resources. Network providers will not be welling to upgrade their current protection plans unless these protection strategies are carefully investigated, providing them with optimal tradeoffs between the required protection degree and the corresponding cost. In this paper, a mathematical model based on the combinatorial and probability theories is developed to evaluate the availability and unavailability of protected optical connections in WDM networks employing M:N dedicated protection. This model works with any number of working and protected paths. Several numerical tests have been performed and their results are presented to investigate the availability and unavailability degrees for different number of working and protection paths. Moreover, we use Monte-Carlo simulation to verify the correctness of our mathematical model. Simulation results confirm not only the correctness of the proposed model but also its potential accuracy. The proposed analytical model provides an efficient tool for network providers to assess the anticipated improvement in the network availability by upgrading their survivability schemes to higher protection classes.