Research On Routing And Wavelength Assignment For IP Over WDM Networks

With the development of networking technologies and new services of Internet, there is an explosive growth trend of Internet traffic, which are promoting the construction of broadband backbone network. Wavelength-division multiplexing (WDM) is a promising approach that can use the enormous bandwidth of the optical fiber. A single fiber can be employed for multiple data streams simultaneously. All-optical networks employing the concept of WDM and wavelength routing are considered as the transport networks for the future. Because the key elements of WDM networks are still expensive, it is important to undertake appropriate network framework and associated technologies to run IP traffic in such a network if we hope the network can perform robustly and have good resource usage, and, good scalability. In this paper we firstly illustrate the feasibility and advantages of eliminating intermediate layers, e.g. SDH/SONET and ATM, to map the IP packets directly into wavelength channels. Under this framework, we then focus our interest on the resource allocation of IP over WDM networks.Chapter 2 uses two ways to address the issues of QoS based resource allocation in IP over WDM networks. Firstly, for optical-layering approach, we propose a novel priority-based wavelength assignment algorithm. By calculating the relative capacity loss, we manage to assign wavelengths so as to guarantee the blocking probability of the high priority requests to a lower degree, and at the same time with the least influence on the lower priority. So the network's average blocking probability is minimized. Simulation results show that the algorithm performs well in dynamic traffic load situation. Secondly, for MPLS based approach, we study the problem of designing logical topology for virtual private networks (VPNs) over IP/WDM networks considering different QoS requirements. For a given network physical topology and long-term traffic pattern, design of delay-based logical topology can be formulated as a linear problem, a NP-hard problem, which is computationally intractable for large size of networks. So, we propose a heuristic algorithm to address the problems of routing and wavelength assignment. Simulation results show that the developed scheme performs well in terms of QoS performance metrics such as the lightpath hop length and the network maximal link load.For IP over WDM networks consist of OXCs and routers, which are inter-connected by optical fibers, Chapter 3 presents a novel routing and wavelength assignment algorithm based on K-shortest path. As the developed integrated dynamic resource allocation policy combines the characteristic of the IP layer and optical layer, it is natural that the algorithm has a better network usage than those traditional ways taking into account the two layers separately. Simulation resultsshow that the developed scheme performs very well in terms of performance metrics such as the hops of the lightpahs and the network blocking probability.In Chapter 4 we study the resource allocation considering link load balancing. Two methods, i.e., optical-layering method and MPLS based method, are used. For optical-layering approach, we propose an ant-based algorithm, which uses the ants' capability of finding shortest or near-shortest paths between a food source and their nests, to solve the logical topology reconfiguration problem. We give the ants routing formula based on dynamic load balancing and short path on the assumption that some conditions hold. The network nodes will be reconfigured when the algorithm converges to a new pattern. Simulation results show that our algorithm has a good effect. For IP over WDM networks using MPLS technology, it is important to take into account the combined routing at the IP and optical layers for the sake of a better network load balancing. Typically, routing in IP over WDM networks has been separated into IP and wavelength routing sub-problems and have been resolved separately, which result to a bad network load balancing. To solve this issue, in this Chapte...