Research On Service-oriented Resource Assignment In Elastic Optical Networks

The explosive growth of data traffic has brought severe challenges for telecommunication backbone network with limited bandwidth resources.Compared with wavelength division multiplexing optical networks using coarse wavelength granularity,elastic optical networks based on optical orthogonal frequency division multiplexing use much finer granularity and bandwidth-variable optical devices,which significantly improves flexibility and efficiency of spectrum resources.Hence it is generally regarded as a stronger supporting technology of substrate network.However,due to the constraints of spectrum continuity and contiguity,there are a large amount of spectrum fragmentations,resulting in ineffective spectrum utilization.Meanwhile,network virtualization technology is introduced into elastic optical networks for overcoming the ossification of the current Internet,making resource assignment harder.Thus this thesis mainly studies the resource assignment of unicast and virtual optical network request in elastic optical networks.And the main innovative contributions are listed as follows:Firstly,aiming at spectrum fragmentation induced by mixed line rate requests provisioning,a fragmentation-avoiding spectrum assignment strategy based on spectrum partition is proposed.For alleviating spectrum fragmentation,the whole optical spectrum is split into several dedicated partitions according to the size and arrival rate of all request types.Based on this,each partition is first used to transmit requests with the same rate in the first-fit spectrum assignment;and other partitions are used to search available spectrum resources in the last-fit spectrum assignment when there are no available spectrum resources in the dedicated partition.Meanwhile,a partition selection formula is designed to minimize the interference of spectrum resources during the last-fit spectrum assignment.Moreover,these requests that are not transmitting in their dedicated partitions are moving to their dedicated partitions,ensuring the contiguity of spectrum resources of dedicated partitions.The simulation results indicate that the proposed algorithm can reduce the bandwidth blocking probability and improve spectrum efficiency.Secondly,aiming at the over-long embedding lightpath and spectrum fragmentation over transparent elastic optical networks,a coordinated embedding algorithm based on node-importance awareness is proposed.In the stage of node embedding,in order to alleviate spectrum fragmentation and to improve the compactness of node embedding,the spectrum compactness of embedding lightpath and the adjacency between embedding node and embedded nodes are evaluated.And then two node-ranking formulas are designed.Meanwhile,for reducing the probability of the success of node embedding but the failure of link embedding,a coordinated node-link embedding algorithm is proposed.When a pair of adjacent virtual nodes is successfully embedded,the virtual optical link between them is embedded instantly,while spectrum resources are allocated,which minimizes the hops of lightpath embedded by virtual optical link.The simulation results indicate that the proposed algorithm can use the least spectrum resources to accommodate more virtual optical network demands,and reduce the embedding hops of virtual optical link.