The threshold hop-limit effect in -cycles: Comparing hop- and circumference-limited design.

Abstract: -cycles offer an approach to protection of optical transport networks which is fully pre-connected and as fast as a ring-based protection but with mesh-like capacity efficiency. As a result, -cycles are receiving much study and attention. One open question is, however, whether -cycle network design exhibits a “threshold hop-limit” effect corresponding to that aspect of span-restorable mesh networks. To study this question we extend the existing -cycle network design theory to include the capability of direct restriction of protection path lengths, rather than indirect restriction through cycle circumference limits. A second practical question is how well simple limitation of cycle circumferences serves as a surrogate for a more involved design method of directly asserting a hop (or distance) limit on the maximum length of protection paths. The answers to these questions, and the methods developed to address them, both enhance our ability to design -cycle networks in which limitations to optically transparent reach (or other hop or distance limitations) can be directly taken into account. The main findings are that -cycles do exhibit threshold hop-limiting effects at about three or four hops above those in corresponding mesh networks and that cycle limiting is a simple and effective surrogate for direct limitation on path lengths in -cycle design problems. [Copyright &y& Elsevier]