Fragmentation-aware algorithms for multipath routing and spectrum assignment in elastic optical networks

Abstract An innovative technology to expand transmission capacity of optical backbone networks is Elastic Optical Network (EON). EON adds flexibility to conventional WDM networks. In EON, the requested bandwidth could be allocated in a much efficient manner than in WDM networks. One of the important problems in EON is fragmentation created by dynamically establishing and tearing down lightpaths over the time, thus increasing connection blocking probability. In this article, six new algorithms are introduced to resolve the fragmentation problem and improve blocking probability; called Pure Multipath spectrum allocation in Two Stages (PM2S), multipath with considering PRE-assignment External Fragmentation Metric in two stages (PRE-EFM), multipath with considering POST assignment External Fragmentation Metric in two stages (POST-EFM), Fragmentation Measure Metric Aware with Routing and Spectrum Assignment (FMMA-RSA), Fragmentation Measure Metric Aware with Pre-Assignment (FMMA-PRE), and Fragmentation Measure Metric Aware with POST-assignment (FMMA-POST). Our main goal in these algorithms is reducing Blocking Probability (BP) by controlling fragmentation in each path since they try different ways in order to assign spectrum for a given connection request. Here, a connection demand is divided into multiple sizes to be setup in multiple routes. By providing this opportunity in spectrum allocation and assignment, connection blocking probability is improved as our performance evaluation results prove.