Research On Virtual Topology Design In Optical Networks

Since the21st century, with the constant development of global information technology, traffic in the networks evolves in the direction of IP. This evolution trend promotes profound changes in the traditional optical networks, and optical networks are developing rapidly in the direction of intelligence and wide bandwidth. Virtual topology design is the core of the optical network design, and it has attracted much attention of international researchers. Recently, the ossification issue of the Internet has become more and more serious, but network virtualization provides a revolutionary approach to address this issue by sharing platform for various types of network architectures. Introducing the virtualization concept into the optical networks increases the agility and flexibility of networks.An important issue that needs to be addressed is the virtual optical network embedding problem when deploying virtual optical networks over substrate networks. Several existing embedding approaches focus primarily on the performance of one aspect and result in poor performance of other aspects. Therefore, how to establish a reasonable mechanism for efficient mapping and design a high-performance virtual optical network topology become particularly significant, and they are also the main contents of this dissertation. With the support of related research projects in the laboratory, the main contributions and achievements in my paper are listed as follows:Firstly, the virtual topology design problem is studied in deeply. This issuer is described by putting a general overview and it can be approximately decomposed into four sub-problems which are resolved in sequence. The sub-problems are topology sub-problem, lightpath routing sub-problem, wavelength assignment sub-problem and traffic routing sub-problem. Then introduce the key factors considered in the virtual topology design process and recommend the related heuristic algorithms according to these factors.Secondly, research focuses on the virtual network embedding (VNE) problem. An architecture of virtual optical networks over substrate networks utilizing virtualization is given. Based on this architecture, the mathematical model of VNE is established. Then a novel algorithm VNE_LB is proposed to solve the VNE problem and intends to balance spectrum load as well as minimizing the total number of used frequency slots for the virtual optical networks. And two conventional virtual optical network embedding schemes (VNE_BLSL scheme and VNE_RCFS scheme) are introduced for comparison. We consider the square deviation of spectrum resource load (SDSRL), the average substrate path hop count per virtual optical link (ASPHC) and the spectrum usage (SU), as the major performance metrics. We evaluate the performance of the algorithms through extensive experiments in the NSFNET network. Simulations show that the VNE LB scheme achieves a better tradeoff between balancing spectrum resource load and reducing the usage of spectrum resources compared to the conventional VNE_RCFS scheme and the VNE BLSL scheme.Thirdly, we develop the optical network planning and optimization software platform with the support of laboratory project. And make an introduction of overall system architecture and implementation of main functional modules which I am responsible for.