(3W-)Availability-Aware Routing in optical WDM networks: when, where and at what time

Network operators, when provisioning a connection, should consider its availability requirements. Availability-Aware Routing (AAR) is considered a good strategy in order to satisfy a connection´s availability requirements. The core idea of AAR is that the statistical availability provided to a connection can be a-priori estimated in the provisioning phase based on the network links´ statistical availability. We argue that, in practice, the actual value of link availability depends on (1) when the connection is routed (since failure rates throughout the year are different), (2) where the connection is routed (since the failure rates can be different, e.g., in rural and urban areas), and (3) at what time the connection is routed (since the failure rates vary in time, e.g., from day to night). Moreover, the failure rate is not homogeneous along a link and a detailed time- and location-aware availability calculation is required. In this study, we first build a case-study, based on practical values, to show how availability changes based on time and location. Then we propose a new AAR algorithm for dynamic traffic, called 3W-availability aware routing (3WAR), which captures the actual provide based on “when, where and at what time” the connection is routed. We finally show numerical examples in a dynamic scenario with connection holding times varying from hours to years. Results demonstrate that our approach uses fewer resources than the traditional approach and minimizes the gap between actual availability and targeted availability, while still satisfying connection availability requirements.