Blocking performance of tree establishment in time-space switched optical networks

Multicasting in the optical layer has gained significant importance in the recent years due to several factors. Most of the research work in this area concentrate either on minimizing the number of wavelengths required to meet a given static demand or on multicast route selection algorithms to achieve efficient utilization of fiber bandwidth. Very few significant research has been found, to the best of authors\u27 knowledge, in developing an analytical model for evaluating the blocking performance of tree establishment in optical networks, which motivates this research. In this paper, an analytical model for evaluating the blocking performance of multicast tree establishment in time-space switched optical networks is developed. The performance of different switch architectures are then studied using the analytical model. it is observed that if the multicast tree has very low degree of branching, the blocking probability of establishing the tree is the same as that of establishing a path with same number of links

Multicast Routing In Optical Access Networks

Widely available broadband services in the Internet require high capacity access networks. Only optical networking is able to efficiently provide the huge bandwidth required by multimedia applications. Distributed applications such as Video-Conferencing, HDTV, VOD and Distance Learning are increasingly common and produce a large amount of data traffic, typically between several terminals. Multicast is a bandwidth-efficient technique for one-to-many or many-to-many communications, and will be indispensable for serving multimedia applications in future optical access networks. These applications require robust and reliable connections as well as the satisfaction of QoS criteria. In this chapter, several access network architectures and related multicast routing methods are analyzed. Overall network performance and dependability are the focus of our analysis

All optical multicasting in wavelength routing mesh networks with power considerations: design and operation

Wavelength routing Wavelength Division Multiplexing (WDM) are optical networks that support all-optical services. They have become the most appealing candidate for wide area backbone networks. Their huge available bandwidth provides the solution for the exponential growth in trayc demands that is due to the increase in the number of users and the surge of more bandwidth intensive network applications and services. A sizable fraction of these applications and services are of multi-point nature. Therefore, supporting multicast service in this network environment is very critical and unique. The all-optical support of various services has advantages, which includes achieving the signal transparency to its content. Nevertheless, the all-optical operational support comes with an associated cost and new issues that make this problem very challenging. In this thesis, we investigate the power-related issues for supporting multicast service in the optical domain, referred to as All-Optical Multicasting (AOM). Our study treats these issues from two networking contexts, namely, Network Provisioning and Connection Provisioning. We propose a number of optimal and heuristic solutions with a unique objective function for each context. In this regard, the objective function for the network provisioning problem is to reduce the network cost, while the solutions for the connection provisioning problem aim to reduce the connection blocking ratio. The optimal formulations are inherently non-linear. However, we introduce novel methods for linearizing them and formulate the problems as Mixed Integer Linear Programs. Also, the design of the heuristic solutions takes into account various optimization factors which results in efficient heuristics that can produce fast solutions that are relatively close to their optimal counterparts, as shown in the numerical results we present

IP multicast over WDM networks

Ph.DDOCTOR OF PHILOSOPH

Virtual Source Based Multicast Routing in WDM Optical Networks

10.1023/A:1011443013088Photonic Network Communications33213-22

MATHEMATICAL PROGRAMMING ALGORITHMS FOR NETWORK OPTIMIZATION PROBLEMS

In the thesis we consider combinatorial optimization problems that are defined by means of networks. These problems arise when we need to take effective decisions to build or manage network structures, both satisfying the design constraints and minimizing the costs. In the thesis we focus our attention on the four following problems: - The Multicast Routing and Wavelength Assignment with Delay Constraint in WDM networks with heterogeneous capabilities (MRWADC) problem: this problem arises in the telecommunications industry and it requires to define an efficient way to make multicast transmissions on a WDM optical network. In more formal terms, to solve the MRWADC problem we need to identify, in a given directed graph that models the WDM optical network, a set of arborescences that connect the source of the transmission to all its destinations. These arborescences need to satisfy several quality-of-service constraints and need to take into account the heterogeneity of the electronic devices belonging to the WDM network. - The Homogeneous Area Problem (HAP): this problem arises from a particular requirement of an intermediate level of the Italian government called province. Each province needs to coordinate the common activities of the towns that belong to its territory. To practically perform its coordination role, the province of Milan created a customer care layer composed by a certain number of employees that have the task to support the towns of the province in their administrative works. For the sake of efficiency, the employees of this customer care layer have been partitioned in small groups and each group is assigned to a particular subset of towns that have in common a large number of activities. The HAP requires to identify the set of towns assigned to each group in order to minimize the redundancies generated by the towns that, despite having some activities in common, have been assigned to different groups. Since, for both historical and practical reasons, the towns in a particular subset need to be adjacent, the HAP can be effectively modeled as a particular graph partitioning problem that requires the connectivity of the obtained subgraphs and the satisfaction of nonlinear knapsack constraints. - Knapsack Prize Collecting Steiner Tree Problem (KPCSTP): to implement a Column Generation algorithm for the MRWADC problem and for the HAP, we need also to solve the two corresponding pricing problems. These two problems are very similar, both of them require to find an arborescence, contained in a given directed weighted graph, that minimizes the difference between its cost and the prizes associated with the spanned nodes. The two problems differ in the side constraints that their feasible solutions need to satisfy and in the way in which the cost of an arborescence is defined. The ILP formulations and the resolution methods that we developed to tackle these two problems have many characteristics in common with the ones used to solve other similar problems. To exemplify these similarities and to summarize and extend the techniques that we developed for the MRWADC problem and for the HAP, we also considered the KPCSTP. This problem requires to find a tree that minimizes the difference between the cost of the used arcs and the profits of the spanned nodes. However, not all trees are feasible: the sum of the weights of the nodes spanned by a feasible tree cannot exceed a given weight threshold. In the thesis we propose a computational comparison among several optimization methods for the KPCSTP that have been either already proposed in the literature or obtained modifying our ILP formulations for the two previous pricing problems. - The Train Design Optimization (TDO) problem: this problem was the topic of the second problem solving competition, sponsored in 2011 by the Railway Application Section (RAS) of the Institute for Operations Research and the Management Sciences (INFORMS). We participated to the contest and we won the second prize. After the competition, we continued to work on the TDO problem and in the thesis we describe the improved method that we have obtained at the end of this work. The TDO problem arises in the freight railroad industry. Typically, a freight railroad company receives requests from customers to transport a set of railcars from an origin rail yard to a destination rail yard. To satisfy these requests, the company first aggregates the railcars having the same origin and the same destination in larger blocks, and then it defines a trip plan to transport the obtained blocks to their correct destinations. The TDO problem requires to identify a trip plan that efficiently uses the limited resources of the considered rail company. More formally, given a railway network, a set of blocks and the segments of the network in which a crew can legally drive a train, the TDO problem requires to define a set of trains and the way in which the given blocks can be transported to their destinations by these trains, both satisfying operational constraints and minimizing the transportation costs