IDF: Intelligent Defragmentation Method in Elastic Optical Networks based on decision making algorithms

•Propose link defragmentation in Elastic Optical Networks based on Multiple Criteria Decision Making.•Consider some extra space to transfer “dying” or “interfering” connections.•Use some criteria to choose the best connection and best action to perform on it.•The defragmentation method includes moving, transferring to the extra space or re-routing the chosen connections.•The method can efficiently reduceblocking probability and increase the performance of network. Spectrum fragmentation is one of the most important issues in Elastic Optical Networks. This issue happens when terminating connections release their occupied frequency slots and make free spaces between other connections on the network links. These free spaces may be unusable to serve future coming connection requests. In this paper, we introduce a new method based on Multi Criteria Decision Making systems to defrag the frequency spectrum of the links. In each step of the defragmentation operation, this method chooses the most suitable connection based on some choosing criteria and performs proper action on it that could be moving to better place, or transferring it to the extra space (extra frequency slots at the end of the frequency spectrum), or re-routing it to a better route. Our simulation results show that the proposed method reduces connection-blocking probability at a good rate.