Dumych S. Methods and algorithms for increasing the data flows switching efficiency in optical transport networks.

The thesis is devoted to solving an actual scientific task of developing models and algorithms for data flows switching in optical transport networks with complex topological structure in conditions of dynamic traffic behavior and heterogeneous requirements of data transmission quality. Current state-of-the art technologies for packet switching in optical transport networks have been studied. The main restrictions for network performance were assessed such as complicated traffic aggregation in the edge node of optical burst switching network due to heterogeneous traffic requirements and complex data flows distribution among network nodes. Additional challenge is to improve the structure of the switching node to make it well suited for packets switching according to dynamic traffic intensity and various traffic classes. The method of traffic aggregation in the edge node of optical burst switching network has been proposed. It was contributed approach allows to increase the efficiency of optical channels utilization while supporting the target quality of data flows transmission. Simulation results show that buffer threshold method results in smallest burst size distributed around 100 kB. However, during two hours of simulation buffer load for buffer threshold algorithm did not increased higher than 60%. For the time threshold method, bursts aggregated to much larger size approximately distributed around 250 kB. But, buffer overloaded very frequently that resulting in approx. 30% packet losses. Proposed adaptive threshold method for busts aggregation was proved as effective solution for optical burst switching networks. According to our simulation, buffer always loaded up to 90%, but almost never touches 100% limit resulting in approx. 3% of lost packets. Despite of this, bursts size is distributed around 200 kB, which seems to be large enough for effective throughput utilization, but still less than for the time threshold method. The model of differentiated burst segmentation based on packets sorting within the burst according to its priority. Proposed model allows to improve the quality of data flows transmission by decreasing the probability of traffic loss for the packets of higher priority. The method of switching in the core node of optical burst switching network has been developed. Proposed method is well suited for hybrid hardware and software implementation of the header packet processing subsystem. This solution allows to speed up the processing of burst header packets that simultaneously decreases the switching delay and the latency of data flows transmission. The new modified model of hybrid hardware and software control unit for the core node of optical burst switching network was contributed. The main novelty of this model is that it is based on field programmable gate arrays. Proposed approach enables independent dynamic reconfiguration of separate units of the node based on software defined networking.