Research On Elastic Optical Multicast Contention Resolution Methods Based On Spectrum Converter And FDL

With the continuous emergence of new broadband network applications,such as cloud computing,high-definition video,online games and so on,people has a higher requirement for network bandwidth.Traditional wavelength division multiplexing optical network allocates bandwidth by fixed wavelength grid,which leads to a great deal of waste for bandwidth resources.Compared with wavelength division multiplexing optical network,the elastic optical network based on orthogonal frequency division multiplexing divides spectrum resources into smaller granularity,dynamically allocates spectrum resources for the traffic request,and can effectively improves the spectrum utilization and bandwidth allocation flexibility,so it is widely regarded as one of the important evolution tends of next generation optical networks.At the same time,with the increasing proportion of new multicast traffic in the whole network,and the increasing demand for high-quality multicast applications,the network bandwidth is facing severe challenges.Furthermore,the replication and forwarding of multicast traffic requests at the switching nodes of the elastic optical network can lead to more intense spectrum contention among the traffic.Therefore,for the spectrum contention problem at the multicast switching node in elastic optical network,it is very important to design appropriate node architectures and scheduling algorithms to support the elastic optical multicast switching.In order to solve the spectrum contention in the elastic optical multicast switching node and reduce the node cost,the third chapter proposes an optical multicast switching node architecture which is applicable for the elastic optical network combined limited range spectrum converter with full range spectrum converter(CLFSC).Meanwhile,for the CLFSC architecture,the total scheduling algorithm is designed.When a traffic cannot be scheduled directly to the output,the contending traffic first uses a limited range spectrum converter(LRSC)to resolve the contention in optical spectrum domain.A double weights maximal clique scheduling algorithm is designed to establish the contention auxiliary graph according to the spectrum occupied by each traffic,and the number of frequency slots required by the traffic and the number of used LRSCs are considered as two weights of the auxiliary graph vertex.Then,graph coloring algorithm is introduced to select the scheduling scheme which uses the minimum number of LRSCs for achieving the maximum total number of frequency slots of output traffic to improve the utilization of spectrum converter and reduce the cost of node architecture.When LRSC is not available,if there is still contending traffic,a small number of full range spectrum converters(FRSC)are used to resolve the contention,further enhancing the contention-resolving ability of the switching node to and reduce the bandwidth blocking probability.Optical buffer technology combined with spectrum conversion technology can greatly improve the performance of optical switching nodes.In the fourth chapter of this thesis,we propose an elastic optical multicast switching node architecture which combines limited range spectrum converter and the feedback shared buffer.At the same time,the total scheduling strategy is proposed for the proposed architecture.When the traffic is contending at the output,the minimum difference scheduling algorithm is designed to solve the contention in the spectrum domain by using LRSC,which can minimize the unavailable spectrum,and improve the spectrum utilization rate.For the still contending traffic,a low latency scheduling algorithm is proposed to solve the contention in the time domain by using fiber delay line(FDL).The algorithm first selects the non-contending spectrum at the input of FDL,and then constructs the auxiliary graph of combining frequency domain and time domain to select the non-contending spectrum after delay,so as to avoid the spectrum contention at the FDL input and the destination output.Compared with the contrast algorithm,the simulation results show that the proposed architecture and scheduling algorithm greatly reduce the contention probability in the switching node,decrease the bandwidth blocking probability and average delay,and further improve the performance of the elastic optical multicast node.