Routing And Spectrum Allocation For Multicast In Elastic Optical Networks

With the fast development of the Internet, the network traffic increases yearly, and the enormous Internet traffic has brought new challenges to the underlying network. The coarse and fixed spectrum granularity of traditional wavelength division multiplexing (WDM) networks results in spectrum wastage, and the network management of WDM networks is inflexible. While the elastic optical network (EON) can provide massive and variable bandwidth to adapt dynamic demands by flexible network management and control, which avoids some drawbacks of the WDM network. Hence it is considered to be a promising solution for the next generation optical networks, and attracts lots of research interests. Meanwhile, multicast is one of the important traffic pattern and contributes a lot to the total network traffic. And supporting multicast is critical for some multicast based applications with enormous and increasing bandwidth requirements, such as the cloud computing, teleconferencing, distance learning and etc. Compared to IP multicast, optical multicast can know better about the underlying network, avoids some inefficient optical to electorial to optical (O/E/O) conversions and can support transparent transmission, therefore it can provide better support for multicast.However, multicast in EON brings great challenges to the network management and control, and routing, modulation and spectrum assignments (RMSA) is one of the fundamentally problem in EON provisioning. Three sub-problems, routing, modula-tion selection and spectrum assignment and the influence between each other need to be addressed. The routing and spectrum assignment (RSA) problem has been proven to be NP-hard, and the RMSA problem with consideration of multicast and flexible mod-ulation selection can be more sophisticated. In this paper, we will focus on this problem and aim to propose efficient solutions for it under different scenarios.First of all, we address the RMSA in multicast incapable (MI) network, which fits the situation that most switches do not support multicast. We leverage an overlay multicast (OL-M) approach and propose a spectrum-efficient OL-M member only relay scheme, and the simulation results indicate the proposed OL-M-SFMOR can be the most spectrum efficient algorithm method in multicast-capable network.Then, we investigate the all-optical multicast, which is much more transponder/energy efficient with smaller delay and can achieve transparent transmission. And it could be the next step of the development of optical multicast. Here, we proceed to handle the all-optical multicast in an ideal network environment, which is to study the all-optical rout-ing and spectrum assignment (RSA) problem. An integrated RSA collaborated with a layered graph approach is proposed to solve the two sub-problems routing and spectrum assignment jointly, and it can achieve higher spectrum utilization and lower blocking probabilities.After that, we further investigate the more practical impairment and splitting-aware RMSA (ISa-RMSA) for multicast. Firstly, we point out that the RMSA for multicast in EON differs a lot compared to the routing and wavelength assignments (RWA) prob-lem in wavelength division multiplexing (WDM) networks due to various modulation selection and different spectrum assignment scheme. And we discuss the light-tree and light-forest structure in both of them, and illustrate that the light-forest structure fits EON better than WDM networks. What’s more, we abstract the minimum light-forest problem and prove its APX-completeness. Finally, several time- and spectrum-efficient ISa-RMSA algorithms are designed based on the analysis above, and one of them can solve the minimum light-forest problem with a fixed approximation ratio.