Survivability schemes for dynamic traffic in optical networks

Ph.DDOCTOR OF PHILOSOPH

Survivability aspects of future optical backbone networks

In huidige glasvezelnetwerken kan een enkele vezel een gigantische hoeveelheid data dragen, ruwweg het equivalent van 25 miljoen gelijktijdige telefoongesprekken. Hierdoor zullen netwerkstoringen, zoals breuken van een glasvezelkabel, de communicatie van een groot aantal eindgebruikers verstoren. Netwerkoperatoren kiezen er dan ook voor om hun netwerk zo te bouwen dat zulke grote storingen automatisch opgevangen worden. Dit proefschrift spitst zich toe op twee aspecten rond de overleefbaarheid in toekomstige optische netwerken. De eerste doelstelling die beoogd wordt is het tot stand brengen vanrobuuste dataverbindingen over meerdere netwerken. Door voldoende betrouwbare verbindingen tot stand te brengen over een infrastructuur die niet door een enkele entiteit wordt beheerd kan men bv. weredwijd Internettelevisie van hoge kwaliteit aanbieden. De bestudeerde oplossing heeft niet enkel tot doel om deze zeer betrouwbare verbinding te berekenen, maar ook om dit te bewerkstelligen met een minimum aan gebruikte netwerkcapaciteit. De tweede doelstelling was om een antwoord te formuleren om de vraag hoe het toepassen van optische schakelsystemen gebaseerd op herconfigureerbare optische multiplexers een impact heeft op de overleefbaarheid van een optisch netwerk. Bij lagere volumes hebben optisch geschakelde netwerken weinig voordeel van dergelijke gesofistikeerde methoden. Elektronisch geschakelde netwerken vertonen geen afhankelijkheid van het datavolume en hebben altijd baat bij optimalisatie

On Integrating Failure Localization with Survivable Design

In this thesis, I proposed a novel framework of all-optical failure restoration which jointly determines network monitoring plane and spare capacity allocation in the presence of either static or dynamic traffic. The proposed framework aims to enable a general shared protection scheme to achieve near optimal capacity efficiency as in Failure Dependent Protection(FDP) while subject to an ultra-fast, all-optical, and deterministic failure restoration process. Simply put, Local Unambiguous Failure Localization(L-UFL) and FDP are the two building blocks for the proposed restoration framework. Under L-UFL, by properly allocating a set of Monitoring Trails (m-trails), a set of nodes can unambiguously identify every possible Shared Risk Link Group (SRLG) failure merely based on its locally collected Loss of Light(LOL) signals. Two heuristics are proposed to solve L-UFL, one of which exclusively deploys Supervisory Lightpaths (S-LPs) while the other jointly considers S-LPs and Working Lightpaths (W-LPs) for suppressing monitoring resource consumption. Thanks to the ``Enhanced Min Wavelength Max Information principle'', an entropy based utility function, m-trail global-sharing and other techniques, the proposed heuristics exhibit satisfactory performance in minimizing the number of m-trails, Wavelength Channel(WL) consumption and the running time of the algorithm. Based on the heuristics for L-UFL, two algorithms, namely MPJD and DJH, are proposed for the novel signaling-free restoration framework to deal with static and dynamic traffic respectively. MPJD is developed to determine the Protection Lightpaths (P-LPs) and m-trails given the pre-computed W-LPs while DJH jointly implements a generic dynamic survivable routing scheme based on FDP with an m-trail deployment scheme. For both algorithms, m-trail deployment is guided by the Necessary Monitoring Requirement (NMR) defined at each node for achieving signaling-free restoration. Extensive simulation is conducted to verify the performance of the proposed heuristics in terms of WL consumption, number of m-trails, monitoring requirement, blocking probability and running time. In conclusion, the proposed restoration framework can achieve all-optical and signaling-free restoration with the help of L-UFL, while maintaining high capacity efficiency as in FDP based survivable routing. The proposed heuristics achieve satisfactory performance as verified by the simulation results

p-Cycle Based Protection in WDM Mesh Networks

Abstract p-Cycle Based Protection in WDM Mesh Networks Honghui Li, Ph.D. Concordia University, 2012 WDM techniques enable single fiber to carry huge amount of data. However, optical WDM networks are prone to failures, and therefore survivability is a very important requirement in the design of optical networks. In the context of network survivability, p-cycle based schemes attracted extensive research interests as they well balance the recovery speed and the capacity efficiency. Towards the design of p-cycle based survivableWDM mesh networks, some issues still need to be addressed. The conventional p-cycle design models and solution methods suffers from scalability issues. Besides, most studies on the design of p-cycle based schemes only cope with single link failures without any concern about single node failures. Moreover, loop backs may exist in the recovery paths along p-cycles, which lead to unnecessary stretching of the recovery path lengths. This thesis investigates the scalable and efficient design of segment p-cycles against single link failures. The optimization models and their solutions rely on large-scale optimization techniques, namely, Column Generation (CG) modeling and solution, where segment pcycle candidates are dynamically generated during the optimization process. To ensure full node protection in the context of link p-cycles, we propose an efficient protection scheme, called node p-cycles, and develop a scalable optimization design model. It is shown that, depending on the network topology, node p-cycles sometimes outperform path p-cycles in iii terms of capacity efficiency. Also, an enhanced segment p-cycle scheme is proposed, entitled segment Np-cycles, for full link and node protection. Again, the CG-based optimization models are developed for the design of segment Np-cycles. Two objectives are considered, minimizing the spare capacity usage and minimizing the CAPEX cost. It is shown that segment Np-cycles can ensure full node protection with marginal extra cost in comparison with segment p-cycles for link protection. Segment Np-cycles provide faster recovery speed than path p-cycles although they are slightly more costly than path p-cycles. Furthermore, we propose the shortcut p-cycle scheme, i.e., p-cycles free of loop backs for full node and link protection, in addition to shortcuts in the protection paths. A CG-based optimization model for the design of shortcut p-cycles is formulated as well. It is shown that, for full node protection, shortcut p-cycles have advantages over path p-cycles with respect to capacity efficiency and recovery speed. We have studied a whole sequence of protection schemes from link p-cycles to path p-cycles, and concluded that the best compromise is the segment Np-cycle scheme for full node protection with respect to capacity efficiency and recovery time. Therefore, this thesis offers to network operators several interesting alternatives to path p-cycles in the design of survivable WDM mesh networks against any single link/node failures

Crosslayer Survivability in Overlay-IP-WDM Networks

As the Internet moves towards a three-layer architecture consisting of overlay networks on top of the IP network layer on top of WDM-based physical networks, incorporating the interaction between and among network layers is crucial for efficient and effective implementation of survivability.This dissertation has four major foci as follows: First, a first-of-its-kind analysis of the impact of overlay network dependency on the lower layer network unveils that backhaul, a link loop that occurs at any two or more lower layers below the layer where traffic is present, could happen. This prompts our proposal of a crosslayer survivable mapping to highlight such challenges and to offer survivability in an efficient backhaul-free way. The results demonstrate that the impact of layer dependency is more severe than initially anticipated making it clear that independent single layer network design is inadequate to assure service guarantees and efficient capacity allocation. Second, a forbidden link matrix is proposed masking part of the network for use in situations where some physical links are reserved exclusively for a designated service, mainly for the context of providing multiple levels of differentiation on the network use and service guarantee. The masking effect is evaluated on metrics using practical approaches in a sample real-world network, showing that both efficiency and practicality can be achieved. Third, matrix-based optimization problem formulations of several crosslayer survivable mappings are presented; examples on the link availability mapping are particularly illustrated. Fourth, survivability strategies for two-layer backbone networks where traffic originates at each layer are investigated. Optimization-based formulations of performing recovery mechanisms at each layer for both layers of traffic are also presented. Numerical results indicate that, in such a wavelength-based optical network, implementing survivability of all traffic at the bottom layer can be a viable solution with significant advantages.This dissertation concludes by identifying a roadmap of potential future work for crosslayer survivability in layered network settings

Survivability schemes for metro ethernet networks

Ph.DDOCTOR OF PHILOSOPH

Groupage et protection du trafic dynamique dans les réseaux WDM

Avec les nouvelles technologies des réseaux optiques, une quantité de données de plus en plus grande peut être transportée par une seule longueur d'onde. Cette quantité peut atteindre jusqu’à 40 gigabits par seconde (Gbps). Les flots de données individuels quant à eux demandent beaucoup moins de bande passante. Le groupage de trafic est une technique qui permet l'utilisation efficace de la bande passante offerte par une longueur d'onde. Elle consiste à assembler plusieurs flots de données de bas débit en une seule entité de données qui peut être transporté sur une longueur d'onde. La technique demultiplexage en longueurs d'onde (Wavelength Division Multiplexing WDM) permet de transporter plusieurs longueurs d'onde sur une même fibre. L'utilisation des deux techniques : WDM et groupage de trafic, permet de transporter une quantité de données de l'ordre de terabits par seconde (Tbps) sur une même fibre optique. La protection du trafic dans les réseaux optiques devient alors une opération très vitale pour ces réseaux, puisqu'une seule panne peut perturber des milliers d'utilisateurs et engendre des pertes importantes jusqu'à plusieurs millions de dollars à l'opérateur et aux utilisateurs du réseau. La technique de protection consiste à réserver une capacité supplémentaire pour acheminer le trafic en cas de panne dans le réseau. Cette thèse porte sur l'étude des techniques de groupage et de protection du trafic en utilisant les p-cycles dans les réseaux optiques dans un contexte de trafic dynamique. La majorité des travaux existants considère un trafic statique où l'état du réseau ainsi que le trafic sont donnés au début et ne changent pas. En plus, la majorité de ces travaux utilise des heuristiques ou des méthodes ayant de la difficulté à résoudre des instances de grande taille. Dans le contexte de trafic dynamique, deux difficultés majeures s'ajoutent aux problèmes étudiés, à cause du changement continuel du trafic dans le réseau. La première est due au fait que la solution proposée à la période précédente, même si elle est optimisée, n'est plus nécessairement optimisée ou optimale pour la période courante, une nouvelle optimisation de la solution au problème est alors nécessaire. La deuxième difficulté est due au fait que la résolution du problème pour une période donnée est différente de sa résolution pour la période initiale à cause des connexions en cours dans le réseau qui ne doivent pas être trop dérangées à chaque période de temps. L'étude faite sur la technique de groupage de trafic dans un contexte de trafic dynamique consiste à proposer différents scénarios pour composer avec ce type de trafic, avec comme objectif la maximisation de la bande passante des connexions acceptées à chaque période de temps. Des formulations mathématiques des différents scénarios considérés pour le problème de groupage sont proposées. Les travaux que nous avons réalisés sur le problème de la protection considèrent deux types de p-cycles, ceux protégeant les liens (p-cycles de base) et les FIPP p-cycles (p-cycles protégeant les chemins). Ces travaux ont consisté d’abord en la proposition de différents scénarios pour gérer les p-cycles de protection dans un contexte de trafic dynamique. Ensuite, une étude sur la stabilité des p-cycles dans un contexte de trafic dynamique a été faite. Des formulations de différents scénarios ont été proposées et les méthodes de résolution utilisées permettent d’aborder des problèmes de plus grande taille que ceux présentés dans la littérature. Nous nous appuyons sur la méthode de génération de colonnes pour énumérer implicitement les cycles les plus prometteurs. Dans l'étude des p-cycles protégeant les chemins ou FIPP p-cycles, nous avons proposé des formulations pour le problème maître et le problème auxiliaire. Nous avons utilisé une méthode de décomposition hiérarchique du problème qui nous permet d'obtenir de meilleurs résultats dans un temps raisonnable. Comme pour les p-cycles de base, nous avons étudié la stabilité des FIPP p-cycles dans un contexte de trafic dynamique. Les travaux montrent que dépendamment du critère d'optimisation, les p-cycles de base (protégeant les liens) et les FIPP p-cycles (protégeant les chemins) peuvent être très stables.With new technologies in optical networking, an increasing quantity of data can be carried by a single wavelength. This amount of data can reach up to 40 gigabits per second (Gbps). Meanwhile, the individual data flows require much less bandwidth. The traffic grooming is a technique that allows the efficient use of the bandwidth offered by a wavelength. It consists of assembling several low-speed data streams into a single data entity that can be carried on a wavelength. The wavelength division multiplexing (WDM) technique allows carrying multiple wavelengths on a single fiber. The use of the two techniques,WDMand traffic grooming, allows carrying a quantity of data in the order of terabits per second (Tbps) over a single optical fiber. Thus, the traffic protection in optical networks becomes an operation very vital for these networks, since a single failure can disrupt thousands of users and may result in several millions of dollars of lost revenue to the operator and the network users. The survivability techniques involve reserving additional capacity to carry traffic in case of a failure in the network. This thesis concerns the study of the techniques of grooming and protection of traffic using p-cycles in optical networks in a context of dynamic traffic. Most existing work considers a static traffic where the network status and the traffic are given at the beginning and do not change. In addition, most of these works concerns heuristic algorithms or methods suffering from critical lack of scalability. In the context of dynamic traffic, two major difficulties are added to the studied problems, because of the continuous change in network traffic. The first is due to the fact that the solution proposed in the previous period, even if optimal, does not necessarily remain optimal in the current period. Thus, a re-optimization of the solution to the problem is required. The second difficulty is due to the fact that the solution of the problem for a given period is different from its solution for the initial period because of the ongoing connections in the network that should not be too disturbed at each time period. The study done on the traffic grooming technique in the context of dynamic traffic consists of proposing different scenarios for dealing with this type of traffic, with the objective of maximizing the bandwidth of the new granted connections at each time period. Mathematical formulations of the different considered scenarios for the grooming problem are proposed. The work we have done on the problem of protection considers two types of p-cycles, those protecting links and FIPP p-cycles (p-cycle protecting paths). This work consisted primarily on the proposition of different scenarios for managing protection p-cycles in a context of dynamic traffic. Then, a study on the stability of cycles in the context of dynamic traffic was done. Formulations of different scenarios have been proposed and the proposed solution methods allow the approach of larger problem instances than those reported in the literature. We rely on the method of column generation to implicitly enumerate promising cycles. In the study of path protecting p-cycles or FIPP p-cycles, we proposed mathematical formulations for the master and the pricing problems. We used a hierarchical decomposition of the problem which allows us to obtain better results in a reasonable time. As for the basic p-cycles, we studied the stability of FIPP p-cycles in the context of dynamic traffic. The work shows that depending on the optimization criterion, the basic p-cycles (protecting the links) and FIPP p-cycles (protecting paths) can be very stable

On Signaling-Free Failure Dependent Restoration in All-Optical Mesh Networks

Failure dependent protection (FDP) is known to achieve optimal capacity efficiency among all types of protection, at the expense of longer recovery time and more complicated signaling overhead. This particularly hinders the usage of FDP in all-optical mesh networks. As a remedy, the paper investigates a new restoration framework that enables all-optical fault management and device configuration via state-of-the-art failure localization techniques, such that the FDP restoration process. It can be implemented without relying on any control plane signaling. With the proposed restoration framework, a novel spare capacity allocation problem is defined, and is further analyzed on circulant topologies for any single link failure, aiming to gain a solid understanding of the problem. By allowing reuse of monitoring resources for restoration capacity, we are particularly interested in the monitoring resource hidden property where less or even no monitoring resources are consumed as more working traffic is in place. To deal with general topologies, we introduce a novel heuristic approach to the proposed spare capacity allocation problem, which comprises a generic FDP survivable routing scheme followed by a novel monitoring resource allocation method. Extensive simulation is conducted to examine the proposed scheme and verify the proposed restoration framework