Network protection with guaranteed recovery times using recovery domains

We consider the problem of providing network protection that guarantees the maximum amount of time that flow can be interrupted after a failure. This is in contrast to schemes that offer no recovery time guarantees, such as IP rerouting, or the prevalent local recovery scheme of Fast ReRoute, which often over-provisions resources to meet recovery time constraints. To meet these recovery time guarantees, we provide a novel and flexible solution by partitioning the network into failure-independent “recovery domains”, where within each domain, the maximum amount of time to recover from a failure is guaranteed. We show the recovery domain problem to be NP-Hard, and develop an optimal solution in the form of an MILP for both the case when backup capacity can and cannot be shared. This provides protection with guaranteed recovery times using up to 45% less protection resources than local recovery. We demonstrate that the network-wide optimal recovery domain solution can be decomposed into a set of easier to solve subproblems. This allows for the development of flexible and efficient solutions, including an optimal algorithm using Lagrangian relaxation, which simulations show to converge rapidly to an optimal solution. Additionally, an algorithm is developed for when backup sharing is allowed. For dynamic arrivals, this algorithm performs better than the solution that tries to greedily optimize for each incoming demand.National Science Foundation (U.S.) (NSF grant CNS-1017800)National Science Foundation (U.S.) (grant CNS-0830961)United States. Defense Threat Reduction Agency (grant HDTRA-09-1-005)United States. Defense Threat Reduction Agency (grant HDTRA1-07-1-0004)United States. Air Force (Air Force contract # FA8721-05-C-0002

Resource Allocation Schemes And Performance Evaluation Models For Wavelength Division Multiplexed Optical Networks

Wavelength division multiplexed (WDM) optical networks are rapidly becoming the technology of choice in network infrastructure and next-generation Internet architectures. WDM networks have the potential to provide unprecedented bandwidth, reduce processing cost, achieve protocol transparency, and enable efficient failure handling. This dissertation addresses the important issues of improving the performance and enhancing the reliability of WDM networks as well as modeling and evaluating the performance of these networks. Optical wavelength conversion is one of the emerging WDM enabling technologies that can significantly improve bandwidth utilization in optical networks. A new approach for the sparse placement of full wavelength converters based on the concept of the k-Dominating Set (k-DS) of a graph is presented. The k-DS approach is also extended to the case of limited conversion capability using three scalable and cost-effective switch designs: flexible node-sharing, strict node-sharing and static mapping. Compared to full search algorithms previously proposed in the literature, the K-DS approach has better blocking performance, has better time complexity and avoids the local minimum problem. The performance benefit of the K-DS approach is demonstrated by extensive simulation. Fiber delay line (FDL) is another emerging WDM technology that can be used to obtain limited optical buffering capability. A placement algorithm, k-WDS, for the sparse placement of FDLs at a set of selected nodes in Optical Burst Switching (OBS) networks is proposed. The algorithm can handle both uniform and non-uniform traffic patterns. Extensive performance tests have shown that k-WDS provides more efficient placement of optical fiber delay lines than the well-known approach of placing the resources at nodes with the highest experienced burst loss. Performance results that compare the benefit of using FDLs versus using optical wavelength converters (OWCs) are presented. A new algorithm, A-WDS, for the placement of an arbitrary numbers of FDLs and OWCs is introduced and is evaluated under different non-uniform traffic loads. This dissertation also introduces a new cost-effective optical switch design using FDL and a QoS-enhanced JET (just enough time) protocol suitable for optical burst switched WDM networks. The enhanced JET protocol allows classes of traffic to benefit from FDLs and OWCs while minimizing the end-to-end delay for high priority bursts. Performance evaluation models of WDM networks represent an important research area that has received increased attention. A new analytical model that captures link dependencies in all-optical WDM networks under uniform traffic is presented. The model enables the estimation of connection blocking probabilities more accurately than previously possible. The basic formula of the dependency between two links in this model reflects their degree of adjacency, the degree of connectivity of the nodes composing them and their carried traffic. The usefulness of the model is illustrated by applying it to the sparse wavelength converters placement problem in WDM networks. A lightpath containing converters is divided into smaller sub-paths such that each sub-path is a wavelength continuous path and the nodes shared between these sub-paths are full wavelength conversion capable. The blocking probability of the entire path is obtained by computing the blocking probabilities of the individual sub-paths. The analytical-based sparse placement algorithm is validated by comparing it with its simulation-based counterpart using a number of network topologies. Rapid recovery from failure and high levels of reliability are extremely important in WDM networks. A new Fault Tolerant Path Protection scheme, FTPP, for WDM mesh networks based on the alarming state of network nodes and links is introduced. The results of extensive simulation tests show that FTPP outperforms known path protection schemes in terms of loss of service ratio and network throughput. The simulation tests used a wide range of values for the load intensity, the failure arrival rate and the failure holding time. The FTPP scheme is next extended to the differentiated services model and its connection blocking performance is evaluated. Finally, a QoS-enhanced FTPP (QEFTPP) routing and path protection scheme in WDM networks is presented. QEFTPP uses preemption to minimize the connection blocking percentage for high priority traffic. Extensive simulation results have shown that QEFTPP achieves a clear QoS differentiation among the traffic classes and provides a good overall network performance

Nodal distribution strategies for designing an overlay network for long-term growth

Scope and Method of Study:This research looked at nodal distribution design issues associated with building an overlay network on top of an existing legacy network with overlay network switches and links not necessarily matching the switch and link locations of the underlying network. A mathematical model with two basic components, switch costs and link costs, was developed for defining the total cost of a network overlay. The nature of the underlying legacy topology determines the dominant factor, link or switch costs to the total cost function as well as the unit cost for switches and links.Findings and Conclusions:The three design heuristics presented first, locate overlay switches at nodes in the center of the legacy network as opposed to the periphery; second, locate overlay switches at legacy nodes with high connectivity; and third, locate overlay switches at legacy nodes with high traffic flow demands, can be used to help point to the direction of keeping costs under control when design changes are required. Applying the concept of efficient frontiers to the world of network design and building a suite of best designs gives the network designer greater insight into how to design the best network in the face of changing real-world constraints. For the cost model and the case studies evaluated using the design strategies in this study, distributed approaches generally tend to be a good choice when the link costs dominate the total cost function because total path distances and therefore link costs need to be minimized in preference over switch costs. A distributed overlay tends to have lower link costs because there is usually a greater probability that total path distances can be minimized because of greater connectivity. More connections set up the potential for more traffic flow path choices allowing each traffic flow to be sent along shorter paths. In legacy network topology designs that have many nodes with high connectivity, the overlay link costs can be relatively similar between designs and the switch costs can have a large impact upon total cost

Network protection with service guarantees

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013.This electronic version was submitted and approved by the author's academic department as part of an electronic thesis pilot project. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from department-submitted PDF version of thesis.Includes bibliographical references (p. 167-174).With the increasing importance of communication networks comes an increasing need to protect against network failures. Traditional network protection has been an "all-or-nothing" approach: after any failure, all network traffic is restored. Due to the cost of providing this full protection, many network operators opt to not provide protection whatsoever. This is especially true in wireless networks, where reserving scarce resources for protection is often too costly. Furthermore, network protection often does not come with guarantees on recovery time, which becomes increasingly important with the widespread use of real-time applications that cannot tolerate long disruptions. This thesis investigates providing protection for mesh networks under a variety of service guarantees, offering significant resource savings over traditional protection schemes. First, we develop a network protection scheme that guarantees a quantifiable minimum grade of service upon a failure within the network. Our scheme guarantees that a fraction q of each demand remains after any single-link failure, at a fraction of the resources required for full protection. We develop both a linear program and algorithms to find the minimum-cost capacity allocation to meet both demand and protection requirements. Subsequently, we develop a novel network protection scheme that provides guarantees on both the fraction of time a flow has full connectivity, as well as a quantifiable minimum grade of service during downtimes. In particular, a flow can be below the full demand for at most a maximum fraction of time; then, it must still support at least a fraction q of the full demand. This is in contrast to current protection schemes that offer either availability-guarantees with no bandwidth guarantees during the down-time, or full protection schemes that offer 100% availability after a single link failure. We show that the multiple availability guaranteed problem is NP-Hard, and develop solutions using both a mixed integer linear program and heuristic algorithms. Next, we consider the problem of providing resource-efficient network protection that guarantees the maximum amount of time that flow can be interrupted after a failure. This is in contrast to schemes that offer no recovery time guarantees, such as IP rerouting, or the prevalent local recovery scheme of Fast ReRoute, which often over-provisions resources to meet recovery time constraints. To meet these recovery time guarantees, we provide a novel and flexible solution by partitioning the network into failure-independent "recovery domains", where within each domain, the maximum amount of time to recover from a failure is guaranteed. Finally, we study the problem of providing protection against failures in wireless networks subject to interference constraints. Typically, protection in wired networks is provided through the provisioning of backup paths. This approach has not been previously considered in the wireless setting due to the prohibitive cost of backup capacity. However, we show that in the presence of interference, protection can often be provided with no loss in throughput. This is due to the fact that after a failure, links that previously interfered with the failed link can be activated, thus leading to a "recapturing" of some of the lost capacity. We provide both an ILP formulation for the optimal solution, as well as algorithms that perform close to optimal.by Gregory Kuperman.Ph.D

Differentiated quality-of-recovery and quality-of-protection in survivable WDM mesh networks

In the modern telecommunication business, there is a need to provide different Quality-of-Recovery (QoR) and Quality-of-Protection (QoP) classes in order to accommodate as many customers as possible, and to optimize the protection capacity cost. Prevalent protection methods to provide specific QoS related to protection are based on pre-defined shape protection structures (topologies), e.g., p -cycles and p -trees. Although some of these protection patterns are known to provide a good trade-off among the different protection parameters, their shapes can limit their deployment in some specific network conditions, e.g., a constrained link spare capacity budget and traffic distribution. In this thesis, we propose to re-think the design process of protection schemes in survivable WDM networks by adopting a hew design approach where the shapes of the protection structures are decided based on the targeted QoR and QoP guarantees, and not the reverse. We focus on the degree of pre-configuration of the protection topologies, and use fully and partially pre-cross connected p -structures, and dynamically cross connected p -structures. In QoR differentiation, we develop different approaches for pre-configuring the protection capacity in order to strike different balances between the protection cost and the availability requirements in the network; while in the QoP differentiation, we focus on the shaping of the protection structures to provide different grades of protection including single and dual-link failure protection. The new research directions proposed and developed in this thesis are intended to help network operators to effectively support different Quality-of-Recovery and Quality-of-Protection classes. All new ideas have been translated into mathematical models for which we propose practical and efficient design methods in order to optimize the inherent cost to the different designs of protection schemes. Furthermore, we establish a quantitative relation between the degree of pre-configuration of the protection structures and their costs in terms of protection capacity. Our most significant contributions are the design and development of Pre-Configured Protection Structure (p-structure) and Pre-Configured Protection Extended-Tree (p -etree) based schemes. Thanks to the column generation modeling and solution approaches, we propose a new design approach of protection schemes where we deploy just enough protection to provide different quality of recovery and protection classe

Pour un mécanisme de protection différenciée unique contre la gestion ainsi que les pannes : DiffServ*

L'avènement de l'Internet multiservice met fin à l'ère du réseautage de nature meilleur effort. Cette nouvelle caractéristique est très souhaitable et prometteuse sur plusieurs plans mais elle reste sujette à la capacité du réseau de protéger chaque catégorie de trafic selon sa priorité et ses exigences en qualité de service. Quand le réseau est déployé sur une infrastructure optique, une des préoccupations des plus importantes est sa capacité de survie et le maintien d'un service adéquat à toutes les applications suite à une panne physique. Nous savons qu'une simple coupure de fibre provoque des pertes énormes en capacité de transmission et si laissée sans surveillance, elle peut causer des dégradations majeures dans la qualité de service perçue par les usagers du réseau. Bien qu'il existe déjà des mécanismes de protection physique qui sont conçus spécifiquement pour remédier à de telles situations, ces options sont généralement très coûteuses et difficilement adaptable aux besoins variés de chaque classe de trafic d'un réseau multiserviceNous proposons alors un modèle innovateur de protection différenciée du trafic, DiffServ*, qui permet de répondre aux exigences particulières en qualité de service et de protection de chacune des classes de trafic et qui introduit une robustesse accrue et des économies importantes en matière d'utilisation de ressources d'un réseau IP/WDM. DiffServ* se distingue par l'utilisation combinée de l'architecture des services différenciées à la couche logique d'un réseau et de la technique d'agrégation de liens ou canaux disjoints à sa couche physiqueNotre modèle de protection différenciée du trafic en cas de pannes a été soumis à l'épreuve, nous avons utilisé la simulation pour étudier sa performance et nous l'avons comparé à un modèle de protection physique homologue, DiffProtect. Les résultats montrent que DiffServ* permet en moyenne de garantir une meilleure protection que DiffProtect en cas de pannes simples et multiples. DiffProtect n'est plus performant que dans certaines situations de pannes et de trafic très particulières. Une évaluation subséquente de la fiabilité d'un réseau qui utilise DiffServ*, une étude de coût de son déploiement et une étude de cas qui cible les réseaux MPLS-DiffServ TE confirment davantage la supériorité de DiffServ* par rapport à tout autre option de protection différenciée envisageableNous rappelons que DiffServ* se base sur les techniques de différenciation de service de la couche logique pour protéger le trafic en cas de pannes de composantes optiques. Ceci est inédit puisque ces mêmes techniques sont originalement conçues que pour protéger le trafic en cas de congestion dans la couche logique. Alors pour démontrer définitivement que DiffServ* est réalisable et fonctionnel nous réalisons une expérience de déploiement pratique de DiffServ* en laboratoire à l'aide d'équipements de communication réel. Malgré les divergences techniques entre la modélisation théorique de DiffServ* et de son implémentation, DiffServ* est démontré performant, fiable, économique et réalisable en pratiqueNous clôturons ce projet par une planification de déploiement ; cette dernière permet de généraliser le déploiement de DiffServ* à toute topologie IP/WDM et d'en dimensionner la couche logique. Notre procédure approche les situations qui requièrent la fiabilité spécifique de DiffProtect en offrant un modèle d'optimisation complet sur le déploiement de la protection MixProtect multicouche qui utilise DiffServ* et DiffProtect dans le même résea