Resource Management in Survivable Multi-Granular Optical Networks

The last decade witnessed a wild growth of the Internet traffic, promoted by bandwidth-hungry applications such as Youtube, P2P, and VoIP. This explosive increase is expected to proceed with an annual rate of 34% in the near future, which leads to a huge challenge to the Internet infrastructure. One foremost solution to this problem is advancing the optical networking and switching, by which abundant bandwidth can be provided in an energy-efficient manner. For instance, with Wavelength Division Multiplexing (WDM) technology, each fiber can carry a mass of wavelengths with bandwidth up to 100 Gbits/s or higher. To keep up with the traffic explosion, however, simply scaling the number of fibers and/or wavelengths per fiber results in the scalability issue in WDM networks. One major motivation of this dissertation is to address this issue in WDM networks with the idea of waveband switching (WBS). This work includes the author\u27s study on multiple aspects of waveband switching: how to address dynamic user demand, how to accommodate static user demand, and how to achieve a survivable WBS network. When combined together, the proposed approaches form a framework that enables an efficient WBS-based Internet in the near future or the middle term. As a long-term solution for the Internet backbone, the Spectrum Sliced Elastic Optical Path (SLICE) Networks recently attract significant interests. SLICE aims to provide abundant bandwidth by managing the spectrum resources as orthogonal sub-carriers, a finer granular than wavelengths of WDM networks. Another important component of this dissertation is the author\u27s timely study on this new frontier: particulary, how to efficiency accommodate the user demand in SLICE networks. We refer to the overall study as the resource management in multi-granular optical networks. In WBS networks, the multi-granularity includes the fiber, waveband, and wavelength. While in SLICE networks, the traffic granularity refers to the fiber, and the variety of the demand size (in terms of number of sub-carriers)

Framework for waveband switching in multigranular optical networks: part I-multigranular cross-connect architectures

Optical networks using wavelength-division multiplexing (WDM) are the foremost solution to the ever-increasing traffic in the Internet backbone. Rapid advances in WDM technology will enable each fiber to carry hundreds or even a thousand wavelengths (using dense-WDM, or DWDM, and ultra-DWDM) of traffic. This, coupled with worldwide fiber deployment, will bring about a tremendous increase in the size of the optical cross-connects, i.e., the number of ports of the wavelength switching elements. Waveband switching (WBS), wherein wavelengths are grouped into bands and switched as a single entity, can reduce the cost and control complexity of switching nodes by minimizing the port count. This paper presents a detailed study on recent advances and open research issues in WBS networks. In this study, we investigate in detail the architecture for various WBS cross-connects and compare them in terms of the number of ports and complexity and also in terms of how flexible they are in adjusting to dynamic traffic. We outline various techniques for grouping wavelengths into bands for the purpose of WBS and show how traditional wavelength routing is different from waveband routing and why techniques developed for wavelength-routed networks (WRNs) cannot be simply applied to WBS networks. We also outline how traffic grooming of subwavelength traffic can be done in WBS networks. In part II of this study [Cao , submitted to J. Opt. Netw.], we study the effect of wavelength conversion on the performance of WBS networks with reconfigurable MG-OXCs. We present an algorithm for waveband grouping in wavelength-convertible networks and evaluate its performance. We also investigate issues related to survivability in WBS networks and show how waveband and wavelength conversion can be used to recover from failures in WBS networks

Wavelengths switching and allocation algorithms in multicast technology using m-arity tree networks topology

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University London.In this thesis, the m-arity tree networks have been investigated to derive equations for their nodes, links and required wavelengths. The relationship among all parameters such as leaves nodes, destinations, paths and wavelengths has been found. Three situations have been explored, firstly when just one server and the leaves nodes are destinations, secondly when just one server and all other nodes are destinations, thirdly when all nodes are sources and destinations in the same time. The investigation has included binary, ternary, quaternary and finalized by general equations for all m-arity tree networks. Moreover, a multicast technology is analysed in this thesis to transmit data carried by specific wavelengths to several clients. Wavelengths multicast switching is well examined to propose split-convert-split-convert (S-C-S-C) multicast switch which consists of light splitters and wavelengths converters. It has reduced group delay by 13% and 29% compared with split-convert (S-C) and split-convert-split (S-C-S) multicast switches respectively. The proposed switch has also increased the received signal power by a significant value which reaches 28% and 26.92% compared with S-C-S and S-C respectively. In addition, wavelengths allocation algorithms in multicast technology are proposed in this thesis using tree networks topology. Distributed scheme is adopted by placing wavelength assignment controller in all parents’ nodes. Two distributed algorithms proposed shortest wavelength assignment (SWA) and highest number of destinations with shortest wavelength assignment (HND-SWA) algorithms to increase the received signal power, decrease group delay and reduce dispersion. The performance of the SWA algorithm was almost better or same as HND-SWA related to the power, dispersion and group delay but they are always better than other two algorithms. The required numbers of wavelengths and their utilised converters have been examined and calculated for the researched algorithms. The HND-SWA has recorded the superior performance compared with other algorithms. It has reduced number of utilised wavelengths up to about 19% and minimized number of the used wavelengths converters up to about 29%. Finally, the centralised scheme is discussed and researched and proposed a centralised highest number of destinations (CHND) algorithm with static and dynamic scenarios to reduce network capacity decreasing (Cd) after each wavelengths allocation. The CDHND has reduced (Cd) by about 16.7% compared with the other algorithms

Estudo de caso de técnicas de utilização de transponders em redes ópticas elásticas

The growth in data traffic is mainly caused due to both the increasing number of subscriber and new applications that require high transmission rates. Optical networks have been the most suitable way to support this demand. One of the biggest challenges faced by these networks is optimizing the use of the available spectrum. The technologies that may lead to better use of the available optical spectrum is the one that allows to the divide the spectrum narrow slices. This approach is known as Elastic Optical Networks (EON), EONS are an evolution of WDM (Wavelength Division Multiplexing) networks. Moreover translucent elastic optical network may be designed from a transparent network by the addition of certain amount of regenerators 3R distributed in a strategically way in the network. In a translucent network, some nodes are transparent and other ones are opaque or translucent. Therefore, in such networks the question of deciding which nodes are translucent or transparent arises. This problem is known as Regenerator Placement (RP). The RP consists of to decide at which of EONs will be deployed 3R regenerators and as well as the number of 3R should be placed at each node. After the RP problem is solved, the regenerator allocation algorithm (RA) is responsible to determine whether to use, or not, the 3R regenerators deployed in each intermediate node of a given route. In EONs, the use of regenerators can be done by lack of quality in the transmission, by spectrum conversion or to improve modulation format. In this thesis, three algorithms to perform regenerator assignment for EONs are proposed. EONs with sparse regeneration and dynamic traffic are considered. The proposed algorithms are: The FLR-RA (First Longest Reach Regenerator Assignment), which tries to use as less as possible regenerators along a route, the FNS-RA (First Narrowest Spectrum Regenerator Assignment), which tries to use as less as possible spectrum along a route, and the exhaustive, that returns either the solution that uses the fewest possible number of regenerators or occupy fewest possible number of slots along a given route. The algorithms a simulated in two network topologies. The results show, in the simulated scenarios, that the FLR-RA reaches smaller blocking probabilities when the number of regenerators deployed in network is small, while the FNS-RA reaches smaller blocking probabilities in the cases in which many regenerators are placed in network. The FLR-RA and FNS-RA heuristics show similar results to the exhaustive, meaning that the heuristics present a good performance.O crescimento da demanda por tráfego de dados é ocasionado pelo aumento de assinantes e pelo aparecimento de novos aplicativos que exigem maiores taxas de transmissão. As redes ópticas têm sido o meio mais adequado para suportar essa demanda. Um dos grandes desafios enfrentados por essas redes é otimizar o uso do espectro disponível. Uma das tecnologias que permitem uma melhor utilização desse espectro é a que possibilita divisão do espectro em pequenas faixas espectrais. Essa abordagem conhecida como redes ópticas elásticas (EON, Elastic Optic Network). A rede óptica elástica translúcida é projetada em uma rede transparente acrescida de uma certa quantidade de regeneradores 3R distribuídos de forma estratégica na rede. Em uma rede translúcida, alguns nós são transparentes e outros são opacos ou translúcidos. Surge então a questão de decidir quais “nós” são translúcidos ou transparentes. Esse problema é conhecido como colocação de regeneradores (RP, Regenerator Placement). O RP consiste em decidir a quais “nós” das EONs serão adicionados regeneradores 3R e quantos deverão ser colocados em cada nó. Após ser resolvido o problema de RP, cabe ao algoritmo de atribuição de regeneradores (RA, Regenerator Allocation) determinar como usar esse recurso de regeneração 3R e determinar em que nó do caminho o regenerador será ou não usado. Nas EONs, o uso de regeneradores pode ser feito por falta de qualidade na transmissão, por conversão de espectro ou para melhorar o formato de modulação. Nesta dissertação, são analisados três algoritmos de atribuição de regeneradores para as EONs aplicadas à rede esparsa de tráfego dinâmico, visando à redução da probabilidade de bloqueio. O FLR-RA (First Longest Reach Regenerator Assignment), que economiza regeneradores na rede, o FNS-RA (First Narrowest Spectrum Regenerator Assignment), que economiza espectro na rede, e o exaustivo, que escolhe uma das possíveis soluções ótimas, ou uma solução que apresenta o menor número total de slots para implementá-la (FNS-RA) ou uma solução que apresenta o menor número total de regeneradores para implementá-la (FLR-RA). Os algoritmos foram simulados em duas topologias de rede. Os resultados mostram que nos cenários simulados o FLR-RA atinge uma menor probabilidade de bloqueio quando o número de regeneradores adicionado na rede é pequeno, enquanto o FNS-RA atinge menores probabilidades de bloqueio nos casos nos quais muitos regeneradores são colocados na rede. As heurísticas FLR-RA e FNS-RA apresentam resultados similares ao exaustivo, isto mostra que as heurísticas apresentam um bom desempenho

Scheduling algorithms for throughput maximization in data networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 215-226).This thesis considers the performance implications of throughput optimal scheduling in physically and computationally constrained data networks. We study optical networks, packet switches, and wireless networks, each of which has an assortment of features and constraints that challenge the design decisions of network architects. In this work, each of these network settings are subsumed under a canonical model and scheduling framework. Tools of queueing analysis are used to evaluate network throughput properties, and demonstrate throughput optimality of scheduling and routing algorithms under stochastic traffic. Techniques of graph theory are used to study network topologies having desirable throughput properties. Combinatorial algorithms are proposed for efficient resource allocation. In the optical network setting, the key enabling technology is wavelength division multiplexing (WDM), which allows each optical fiber link to simultaneously carry a large number of independent data streams at high rate. To take advantage of this high data processing potential, engineers and physicists have developed numerous technologies, including wavelength converters, optical switches, and tunable transceivers.(cont.) While the functionality provided by these devices is of great importance in capitalizing upon the WDM resources, a major challenge exists in determining how to configure these devices to operate efficiently under time-varying data traffic. In the WDM setting, we make two main contributions. First, we develop throughput optimal joint WDM reconfiguration and electronic-layer routing algorithms, based on maxweight scheduling. To mitigate the service disruption associated with WDM reconfiguration, our algorithms make decisions at frame intervals. Second, we develop analytic tools to quantify the maximum throughput achievable in general network settings. Our approach is to characterize several geometric features of the maximum region of arrival rates that can be supported in the network. In the packet switch setting, we observe through numerical simulation the attractive throughput properties of a simple maximal weight scheduler. Subsequently, we consider small switches, and analytically demonstrate the attractive throughput properties achievable using maximal weight scheduling. We demonstrate that such throughput properties may not be sustained in larger switches.(cont.) In the wireless network setting, mesh networking is a promising technology for achieving connectivity in local and metropolitan area networks. Wireless access points and base stations adhering to the IEEE 802.11 wireless networking standard can be bought off the shelf at little cost, and can be configured to access the Internet in minutes. With ubiquitous low-cost Internet access perceived to be of tremendous societal value, such technology is naturally garnering strong interest. Enabling such wireless technology is thus of great importance. An important challenge in enabling mesh networks, and many other wireless network applications, results from the fact that wireless transmission is achieved by broadcasting signals through the air, which has the potential for interfering with other parts of the network. Furthermore, the scarcity of wireless transmission resources implies that link activation and packet routing should be effected using simple distributed algorithms. We make three main contributions in the wireless setting. First, we determine graph classes under which simple, distributed, maximal weight schedulers achieve throughput optimality.(cont.) Second, we use this acquired knowledge of graph classes to develop combinatorial algorithms, based on matroids, for allocating channels to wireless links, such that each channel can achieve maximum throughput using simple distributed schedulers. Third, we determine new conditions under which distributed algorithms for joint link activation and routing achieve throughput optimality.by Andrew Brzezinski.Ph.D