Dynamic wavelength routing in multifiber WDM networks

The research, development, and deployment of wavelength division multiplexing (WDM) technology are now evolving at a rapid pace to fulfill the increasing bandwidth requirement and deploy new network services. Routing and wavelength assignment algorithms play a key role in improving the performance of wavelength-routed all-optical networks. We study networks with dynamic wavelength routing and develop accurate analytical models for evaluating the blocking performance under dynamic input traffic in different topologies. Two dynamic routing algorithms are first developed and the performances of the algorithms in single-fiber WDM networks are studied using both analytical models and simulation. We also develop efficient algorithms to optimally place a given number of wavelength converters on a path of a network. Finally we consider the effect of multiple fibers on WDM networks without wavelength conversion. We develop analytical models for evaluating the blocking performance of multifiber networks with fixed-path routing, alternate-path routing, and fixed-path least-congestion routing algorithms. The number of fibers required to provide high performance in multifiber networks with different routing algorithms are also studied

Study of Routing and Wavelength Assignment problem and Performance Analysis of Genetic Algorithm for All-Optical Networks

All-optical networks uses the concept of wavelength division multiplexing (WDM). The problem of routing and wavelength assignment (RWA) is critically important for increasing the efficiency of wavelength routed All-optical networks. For the given set of connections, the task of setting up lightpaths by routing and assigning a wavelength to each connection is called routing and wavelength allocation problem. In work to date, the problem has been formulated as integer linear programming problem. There are two variations of the problem: static and dynamic, in the static case, the traffic is known where as in dynamic case, connection request arrive in some random fashion. Here we adopt the static view of the problem. We have studied the Genetic Algorithm to solve the RWA problem and also we studied a modified Genetic Algorithm with reference to the basic model. We studied a novel opimization problem formulations that offer the promise of radical improvements over the existing methods. We adopt a static view of the problem and saw new integer- linear programming formulations, which can be addressed with highly efficient linear programming methods and yield optimal or near-optimal RWA policies. All-optical WDM networks are chracterized by multiple metrics (hop-count, cost, delay), but generally routing protocols only optimize one metric, using some variant shortest path algorithm (e.g., the Dijkstra, all-pairs and Bellman-ford algorithms). The multicriteria RWA problem has been solved combining the relevant metrics or objective functions. The performance of RWA algorithms have been studied across the different standard networks. The performance of both the algorithms are studied with respect to the time taken for making routing decision, number of wavelengths required and cost of the requested lightpaths. It has been observed that the modified genetic algorithm performed better than the existing algorithm with respect to the time and cost parameters

Routing and wavelength assignment in WDM optical networks

In this thesis, we focus on the routing and wavelength assignment problems in WDM all-optical networks. Since the general problem is difficult (NP-complete), we classify the problem into several models with different formulations. Our objectives are to analyze some subclasses of routing and wavelength assignment problems; to understand their special properties; to estimate algorithm bounds and performance; and, to design efficient heuristic algorithms. These goals are important because results that follow can help engineers design efficient network topologies and protocols, and eventually provide end-users with cost-effective high bandwidth.;We first study the off-line wavelength assignment problem in single fiber ring and tree networks: an optimal algorithm and an exact characterization of the optimal solution is given for binary and ternary tree topologies; an open problem based on path length restriction on trees, mentioned in the literature, is solved; and bounds are given for path-length and covering restrictions of the problem on ring networks. Then we consider multifiber optical networks, in which each link has several parallel fibers. We extend a stochastic model from the single-fiber case to the multifiber case and show that multifiber links can improve performance significantly. For some specific networks, such as ring and tree networks, we obtain some performance bounds. The bounds support our multifiber stochastic model conclusion. For practical importance, we also consider a WDM optical ring network architecture configuration problem as well as cost-effectiveness. We propose several WDM ring networks with limited fiber switching and limited wavelength conversion and these networks achieve almost optimal wavelength utilization. Attacking resource allocation within an WDM optical ring network to reduce overall equipment cost, we design a new algorithm and our simulation results indicate improvement of about 25%. This thesis also includes a new coloring problem partition-coloring and its applications.;In summary, the contributions in this thesis include several heuristic algorithms and theoretical tight upper bounds for both single fiber and multifiber all-optical networks. In particular, for ring networks we have proposed several network architectures to improve wavelength utilization and devised a new algorithm that combines routing and wavelength assignment to reduce hardware costs

Efficient embedding of virtual hypercubes in irregular WDM optical networks

This thesis addresses one of the important issues in designing future WDM optical networks. Such networks are expected to employ an all-optical control plane for dissemination of network state information. It has recently been suggested that an efficient control plane will require non-blocking communication infrastructure and routing techniques. However, the irregular nature of most WDM networks does not lend itself to efficient non-blocking communications. It has been recently shown that hypercubes offer some very efficient non-blocking solutions for, all-to-all broadcast operations, which would be very attractive for control plane implementation. Such results can be utilized by embedding virtual structures in the physical network and doing the routing using properties of a virtual architecture. We will emphasize the hypercube due to its proven usefulness. In this thesis we propose three efficient heuristic methods for embedding a virtual hypercube in an irregular host network such that each node in the host network is either a hypercube node or a neighbor of a hypercube node. The latter will be called a “satellite” or “secondary” node. These schemes follow a step-by-step procedure for the embedding and for finding the physical path implementation of the virtual links while attempting to optimize certain metrics such as the number of wavelengths on each link and the average length of virtual link mappings. We have designed software that takes the adjacency list of an irregular topology as input and provides the adjacency list of a hypercube embedded in the original network. We executed this software on a number of irregular networks with different connectivities and compared the behavior of each of the three algorithms. The algorithms are compared with respect to their performance in trying to optimize several metrics. We also compare our algorithms to an already existing algorithm in the literature

Boltzmann meets Nash: Energy-efficient routing in optical networks under uncertainty

Motivated by the massive deployment of power-hungry data centers for service provisioning, we examine the problem of routing in optical networks with the aim of minimizing traffic-driven power consumption. To tackle this issue, routing must take into account energy efficiency as well as capacity considerations; moreover, in rapidly-varying network environments, this must be accomplished in a real-time, distributed manner that remains robust in the presence of random disturbances and noise. In view of this, we derive a pricing scheme whose Nash equilibria coincide with the network's socially optimum states, and we propose a distributed learning method based on the Boltzmann distribution of statistical mechanics. Using tools from stochastic calculus, we show that the resulting Boltzmann routing scheme exhibits remarkable convergence properties under uncertainty: specifically, the long-term average of the network's power consumption converges within $\varepsilon$ of its minimum value in time which is at most $\tilde O(1/\varepsilon^2)$, irrespective of the fluctuations' magnitude; additionally, if the network admits a strict, non-mixing optimum state, the algorithm converges to it - again, no matter the noise level. Our analysis is supplemented by extensive numerical simulations which show that Boltzmann routing can lead to a significant decrease in power consumption over basic, shortest-path routing schemes in realistic network conditions.Comment: 24 pages, 4 figure

Resource efficient redundancy using quorum-based cycle routing in optical networks

In this paper we propose a cycle redundancy technique that provides optical networks almost fault-tolerant point-to-point and multipoint-to-multipoint communications. The technique more importantly is shown to approximately halve the necessary light-trail resources in the network while maintaining the fault-tolerance and dependability expected from cycle-based routing. For efficiency and distributed control, it is common in distributed systems and algorithms to group nodes into intersecting sets referred to as quorum sets. Optimal communication quorum sets forming optical cycles based on light-trails have been shown to flexibly and efficiently route both point-to-point and multipoint-to-multipoint traffic requests. Commonly cycle routing techniques will use pairs of cycles to achieve both routing and fault-tolerance, which uses substantial resources and creates the potential for underutilization. Instead, we intentionally utilize redundancy within the quorum cycles for fault-tolerance such that almost every point-to-point communication occurs in more than one cycle. The result is a set of cycles with 96.60% - 99.37% fault coverage, while using 42.9% - 47.18% fewer resources.Comment: 17th International Conference on Transparent Optical Networks (ICTON), 5-9 July 2015. arXiv admin note: substantial text overlap with arXiv:1608.05172, arXiv:1608.0516