OpenFlow-Assisted Spectrum Allocation And Defragmentaion In Software-Defined Elastic Optical Networks

With small bandwidth allocation granularity and agile spectrum management, the elastic optical networks (EONs) can improve the spectral efficiency of lightpaths and also bring intelligence into the optical layer. By decoupling the data and control planes, software-defined networking (SDN) makes the network programmable, dynamic and application-aware. The combination of EONs and SDN leads to SD-EONs, which sup-port centralized network controll and management (NC&M), bring new opportunities for enhancing the flexibility and programmability of optical networks, and giving net-work operators more freedom to customize their infrastructure dynamically.Spectrum fragmentation, which refers to the isolated, non-aligned, and smallsized unused FS blocks in the optical spectrum, can lead to low spectrum utilization and in-creases the blocking probability of future requests. The situation becomes more severe when EONs have to support highly dynamic traffic along with frequent lightpath as-sembling/disassembling (e.g., in an inter-datacenter network). In order to fully exploit the aforementioned advantages of EONs and address the problem of spectrum fragmen-tation. EONs need a more sophisticated and efficient control plane.In this work, we investigate spectrum allocation and online defragmentation (DF) in both single-and multi-domain SD-EONs based on OpenFlow (OF).We first discuss the overall system design of SD-EONs and OF extentions to sup-port basic routing and spectrum assignment (RSA) and efficient online DF with RSA re-configurations. We consider sequential DF and parallel DF in sigle-domain SD-EONs. In sequentrial DF, we modify our previous DF algorithm to make sure that the recon-figurations can be performed in batches and the " make-before-break " scheme can be applied to all of them. The modified algorithm is implemented in an OF controller, and we design OF extensions to facilitate synchronous batch reconfiguration (SBR), which will reduce the latency to configure the data plane equipments. Then, we further sim-plify the DF operations by designing and implementing parallel DF that can accomplish all the DF-related lightpath reconfigurations simultaneously. All these DF implementa-tions are experimentally demonstrated in an SD-EON control plane testbed that consists of 14 stand-alone OF agents and one OF controller, which are all implemented based on high-performance Linux servers.Then we investigate how to apply multi-domain scenarios to SD-EONs. We de-sign the functionalities in the control plane to facilitate multi-domain tasks, and pro-pose an inter-domain protocol (IDP) to enable OF controllers in different SD-EON do-mains to operate cooperatively for multidomain routing and spectrum assignment. In order to eliminate spectrum fragmentation in multi-domain EONs, we propose to realize fragmentation-aware RSA (FA-RSA) in multi-domain SD-EONs with the cooperation of multiple OF controllers. The proposed system is implemented and experimentally demonstrated in a multinational SD-EON control plane testbed that consists of two ge-ographically distributed domains located in China and USA, respectively.