Routing And Spectrum Asssignment In Elastic Optical Netwroks

Due to the expanding deployment of network applications such as distributed video services, telemedicine systems, and data backup among large-scale storage systems, optical networks are required to further enhance their bandwidth provisioning capabilities with diverse QoS differentiations. However, the conventional fixed-grid optical networks with large and static granularities will lead to inefficiency of resources utilization. SLICE (Spectrum-Sliced Elastic Optical Path Network) was proposed to deal with this issue by breaking up the spectrnm grids and accommodating data traffic dynamically according to user’s requests. Like the routing and spectrnm allocation (RWA) problem in traditional fixed grid networks, SLICE networks should solve routing and spectrum allocation (RSA) problem which is even more complex due to the fragmentation of spectrums. In this paper we mainly focus on this issue and provide solutions with necessary evaluations.Firstly, for the unicast scenarios, we analyzed transmission quality of signals with different bitrates and modulation formats, and by setting "maximum spectrnm utilization" as the optimization objective we proposed a multi-path and multi-modulation format (MP-MM) algorithm to allocate spectrnm resource. Simulation results verified that the MP-MM algorithm allocates resources in a more rational way, which can significantly reduce the network blocking rate.Secondly, for the multicast scenarios,we attempted to break up the spectrnm consistency constraints by introducing all-optical modulation format converter. By analyzing the effect of splitter and modulation format converter on signal degradation and introducing the indicator of "longest equivalent transmission distance" to ensure the quality of optical transmission, we further proposed a MFC-MC-RSA algorithm considering the modulation multicasting format conversion. Simulation results verified that the MFC-MC-RSA algorithm has a better spectral efficiency in comparison with traditional algorithms where only a single modulation format is used.Finally, in order to verify the effectiveness of the proposed RSA mechanisms, we implemented an OpenFlow-based network control platform with multicast capability. By introducing a WSON node with multicast modulation format conversion as well as an extended OpenFlow control interface, the OpenFlow-controlled dynamic multicast with was successfully demonstrated.