<p><a href="http://www.osa-jon.org/virtual_issue.cfm?vid=16">Feature Issue on High Availability in Optical Networks</a></p>The core idea of availability-based routing consists of exploiting the availability as a link-state metric: this kind of approach has received attention by virtue of the ability to avoid excessively unavailable paths. A recent availability-based heuristic design technique for reliable optical transport networks [IEEE Sel. Areas Commun. 23, 1520 (2005)] showed that the availability metric returns results in line with the traditional length or hop metric, due to the close relationship between availability and length of the link. We break the direct relationship between length and availability by considering a highly available backbone next to a less reliable peripheral section of the network. Under this availability-unbalanced scenario, we analyze the trade-offs between capacity and availability: pros and cons of the availability metric emerge much more clearly. Performance of an availability-based metric is shown and discussed applying dedicated path protection. In addition we provide, for the first time to our knowledge, analytical proof of the optimality (under certain hypothesis) of the proposed maximal availability routing approach for dedicated path protection.
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