Research On Multicast Routing Algorithms In Elastic Optical Networks

With rapid growth of network traffics and popularity of broadband services, spectrum resources in networks become more valuable. Due to inflexible characteristic and spectrum resources being seriously wasted, traditional wavelength-routed all-optical networks faces severe challenges. In recent years, elastic optical networks is proposed. It characterized by flexible use of spectrum resources, using bandwidth variable technology based on OFDM modulation scheme, could dynamically allocate an appropriate amount of spectrum resources and configure the appropriate modulation format based on user needs and traffic volume, effectively overcoming the drawback of wavelength-routed all-optical networks. Besides, routing and spectrum allocation issues in elastic optical networks become more complex.In this thesis, multicast routing algorithms in elastic optical network are studied, and the main works are as follows:(1) Firstly, the thesis introduced the development of all-optical networks, background and technical features of elastic optical networks. Then, the thesis introduced research situations of multicasting technology in elastic optical networks, and analyzed factors and major problems of multicasting technology.(2) Based on the idea of giving optimum path priority to access, multicast routing algorithms are studied. Firstly, based on assessment of path spectrum availability, an algorithm is proposed, in which the path having maximum spectrum continuous degree has the superior to access. Then the concept of multicast tree spectrum continuous degree is proposed, and based on this concept, an algorithm is proposed, in which the path being used to maximize multicast tree spectrum continuous degree has priority to access. Finally, multicast tree spectrum availability is evaluated from the view of idle frequency slots, consistent idle frequency slots algorithm and effective idle frequency slots algorithm are respectively proposed. These algorithms are simulated and compared with MPH multicast routing algorithm, and results show that these algorithms have good blocking performance.(3) The thesis improved Dijkstra algorithm by changing the way to calculate link weight and path weight. The path calculated by improved Dijkstra algorithm has a more large extent spectrum availability, while ensuring that the path is not too long. The multicast routing algorithm based on improved Dijkstra simulated and analyzed in performance. In addition, effective path accessing algorithms are proposed, based on different routing strategies to calculate path once again. In the process of establishing multicast tree, while the multicast tree stop establishing due to no spectrum resources to use, calculate path once again by improved Dijkstra algorithm, as much as possible to ensure that the multicast tree continues to build and ultimately successfully established. These proposed algorithms are simulated and analyzed in performance.(4) By improving the existing multicast routing algorithm which is based on layered strategy, an algorithm based on selecting the minimum cost layer is proposed. By selecting the minimum cost multicast tree, it can effectively save spectrum resources. Simulation results show that blocking performance of the algorithm is significantly improved.