A framework for improving routing configurations using multi-objective optimization mechanisms

IP networks are nowadays well established technolo- gies being used to support a myriad of applications and services, thus assuming a crucial role in todays telecommunication sys- tems. Nevertheless, such infrastructures usually require network administrators to perform a wide set of complex planning and management tasks trying to attain adequate network configura- tions. Many of such management tasks can be mathematically for- mulated as NP-hard optimization problems, sometimes involving several objective functions. In this context, this work explores and demonstrates the potential of using computational intelligence methods as optimization engines to tackle complex network op- timization problems. In particular, Multi-objective Evolutionary Algorithms (MOEAs) are used to attain near-optimal link state routing configurations robust to distinct operational conditions. As result, network administrators will be provided with a set of alternative routing configurations representing distinct tradeoffs between the considered optimization goals. The robustness of the proposed methods is illustrated by presenting several multi-objective optimization examples able to improve the performance and resilience levels of a network infrastructure. Moreover, the devised methods are integrated in a freely available Traffic Engineering optimization framework able to be used by network administrators interested in this particular research field.This work has been supported by COMPETE: POCI-010145-FEDER-007043 and FCT Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013

Energy management in communication networks: a journey through modelling and optimization glasses

The widespread proliferation of Internet and wireless applications has produced a significant increase of ICT energy footprint. As a response, in the last five years, significant efforts have been undertaken to include energy-awareness into network management. Several green networking frameworks have been proposed by carefully managing the network routing and the power state of network devices. Even though approaches proposed differ based on network technologies and sleep modes of nodes and interfaces, they all aim at tailoring the active network resources to the varying traffic needs in order to minimize energy consumption. From a modeling point of view, this has several commonalities with classical network design and routing problems, even if with different objectives and in a dynamic context. With most researchers focused on addressing the complex and crucial technological aspects of green networking schemes, there has been so far little attention on understanding the modeling similarities and differences of proposed solutions. This paper fills the gap surveying the literature with optimization modeling glasses, following a tutorial approach that guides through the different components of the models with a unified symbolism. A detailed classification of the previous work based on the modeling issues included is also proposed

Intra-domain traffic engineering with shortest path routing protocols

Throughout the last decade, extensive deployment of popular intra-domain routing protocols such as open shortest path first and intermediate system–intermediate system, has drawn an ever increasing attention to Internet traffic engineering. This paper reviews optimization techniques that have been deployed for managing intra-domain routing in networks operated with shortest path routing protocols, and the state-of-the-art research that has been carried out in this direction.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Intra-domain traffic engineering with shortest path routing protocols

Throughout the last decade, extensive deployment of popular intra-domain routing protocols such as open shortest path first (OSPF) and intermediate system–intermediate system (IS-IS), has drawn an ever increasing attention to internet traffic engineering. This paper reviews optimization techniques that have been deployed for managing intra-domain routing in networks operated with shortest path routing protocols, and the state-of-the-art research that has been carried out in this direction.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

An Optimization Problem of Internet Routing

As the Internet usage grows, existing network infrastructure must deal with increasing demand. One way to deal with this is to increase network capacity, and another, is to set network parameters appropriately. In this dissertation we contribute to the latter approach by determining the unique network paths data must flow over from its origin to its destination, while accounting for an Active Queue Management method, Random Early Detection (RED). We formulate a mixed integer non-linear program to determine the data paths, referred to as a routing policy. We prove that determining an optimal routing policy that accounts for RED is NP-Hard. Furthermore, in order for the generated routing policies to be real-world implementable, also known as realizable, we must determine weights for all arcs in the network such that solving the all pairs shortest path problem using these weights reproduces the routing policies. We show that determining if our generated routing policies are realizable is NP-Hard. Fortunately, using traffic data from three real-world networks, we are able to find realizable routing policies for these networks that account for RED, using an off-the-shelf solver, and policies found perform better than those used in those networks at the time the data was collected

Conception et optimisation robuste des réseaux de télécommunications

Les réseaux de communication devenant de plus en plus présents dans nos activités quotidiennes, l'interruption ou une une dégradation significative des services fournis par le réseau deviennent de moins en moins tolérables. Une conception robuste des réseaux de communication, anticipant les pannes éventuelles d'équipements ou les variations du trafic, devient donc de plus en plus nécessaire. Cette thèse traite de plusieurs problèmes de conception et de planification robustes. Nous étudions tout d'abord le problème de la conception et du dimensionnement d'une topologie de communication résiliente et proposons un modèle de conception intégrant les coûts et contraintes des équipements ainsi que de nombreuses contraintes opérationnelles (nœuds potentiels, capacités modulaires, délais de communication). Un algorithme exact et deux approximations sont proposés pour résoudre ce problème. Les résultats numériques montrent que des économies substantielles peuvent être effectuées en intégrant les coûts d'équipements dans la phase amont de la conception. Les variations sur les volumes de trafic sont devenus un des problèmes majeurs auxquels sont confrontés les opérateurs. Il devient ainsi nécessaire d'intégrer explicitement l'incertitude sur la demande en trafic dans les problèmes de planification. Nous étudions deux problèmes d'optimisation robuste du routage : (1) le problème de conception des VPN dans le cadre du modèle hose et (2) le problème d'optimisation des métriques de routage IGP avec incertitude sur la demande. Nous formulons des modèles mathématiques de chacun de ces problèmes et proposons des heuristiques basées sur des techniques de recherche locale pour les résoudre.With communication networks getting more and more present in our daily activities, network outages or even significant degradations of the quality of service become less and less tolerable. This calls for a robust design of communication networks anticipating possible failures or shifts in the expected traffic demands. This thesis addresses several robust design and planning problems arising in the telecommunication area. We first address the problem of designing and dimensioning a survivable network topology. We propose a novel network design model integrating all equipment costs and constraints and including several operational constraints (potential nodes, modular capacities, delay constraints). One exact and two heuristic algorithms are proposed to solve this problem. Numerical results show that significant cost-savings can be achieved when equipment costs are taken into account in the early stages of the design process. The variation in traffic volumes has become one of the most important problems faced by network operators. Designing a network using a single ``busy hour'' traffic matrix more and more strains credibility due to the high volatility of traffic patterns. Thus, there is a need to incorporate demand uncertainty into the network routing problems explicitly. We study two robust route optimization problems: (1) the problem of VPN design under the hose model of demand uncertainty and (2) the problem of link weight optimization under demand uncertainty. We establish mathematical models for both problems and propose efficient approximation algorithms based on local-search techniques to solve them

Operational research:methods and applications

Throughout its history, Operational Research has evolved to include a variety of methods, models and algorithms that have been applied to a diverse and wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first aims to summarise the up-to-date knowledge and provide an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion. It should be used as a point of reference or first-port-of-call for a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order