Energy-Aware Traffic Engineering for Wired IP Networks

RÉSUMÉ Même si l'Internet est souvent considéré comme un moyen formidable pour réduire l'impact des activités humaines sur l'environnement, sa consommation d'énergie est en train de devenir un problème en raison de la croissance exponentielle du trafic et de l'expansion rapide des infrastructures de communication dans le monde entier. En 2007, il a été estimé que les équipements de réseau (sans tenir compte de serveurs dans les centres de données) étaient responsables d'une consommation d'énergie de 22 GW, alors qu'en 2010 la consommation annuelle des plus grands fournisseurs de services Internet (par exemple AT$T) a dépassé 10 TWh par an. En raison de cette tendance alarmante, la réduction de la consommation d'énergie dans les réseaux de télécommunication, et en particulier dans les réseaux IP, est récemment devenue une priorité. Une des stratégies les plus prometteuses pour rendre plus vert l'Internet est le sleep-based energy-aware network management (SEANM), selon lequel la configuration de réseau est adaptée aux niveaux de trafic afin d'endormir tous les éléments redondantes du réseau. Dans cette thèse nous développons plusieurs approches centralisées de SEANM, afin d'optimiser la configuration de réseaux IP qui utilisent différents protocoles (OSPF or MPLS) ou transportent différents types de trafic (élastique or inélastique). Le choix d'adresser le problème d'une manière centralisée, avec une plate-forme de gestion unique qui est responsable de la configuration et de la surveillance de l'ensemble du réseau, est motivée par la nécessité d'opérateurs de maintenir en tout temps le contrôle complet sur le réseau. Visant à mettre en œuvre les approches proposées dans un environnement réaliste du réseau, nous présentons aussi un nouveau cadre de gestion de réseau entièrement configurable que nous avons appelé JNetMan. JNetMan a été exploité pour tester une version dynamique de la procédure SEANM développée pour les réseaux utilisant OSPF.----------ABSTRACT Even if the Internet is commonly considered a formidable means to reduce the impact of human activities on the environment, its energy consumption is rapidly becoming an issue due to the exponential traffic growth and the rapid expansion of communication infrastructures worldwide. Estimated consumption of the network equipment, excluding servers in data centers, in 2007 was 22 GW, while in 2010 the yearly consumption of the largest Internet Service Providers, e.g., AT&T, exceeded 10 TWh per year. The growing energy trend has motivated the development of new strategies to reduce the consumption of telecommunication networks, with particular focus on IP networks. In addition to the development of a new generation of green network equipment, a second possible strategy to optimize the IP network consumption is represented by sleep-based energy-aware network management (SEANM), which aims at adapting the whole network power consumption to the traffic levels by optimizing the network configuration and putting to sleep the redundant network elements. Device sleeping represents the main potential source of saving because the consumption of current network devices is not proportional to the utilization level: so that, the overall network consumption is constantly close to maximum. In current IP networks, quality of service (QoS) and network resilience to failures are typically guaranteed by substantially over-dimensioning the whole network infrastructure: therefore, also during peak hours, it could be possible to put to sleep a non-negligible subset of redundant network devices. Due to the heterogeneity of current network technologies, in this thesis, we focus our efforts to develop centralized SEANM approaches for IP networks operated with different configurations and protocols. More precisely, we consider networks operated with different routing schemes, namely shortest path (OSPF), flow-based (MPLS) and take into account different types of traffic, i.e., elastic or inelastic. The centralized approach, with a single management platform responsible for configuring and monitoring the whole network, is motivated by the need of network operators to be constantly in control of the network dynamics. To fully guarantee network stability, we investigate the impact of SEANM on network reliability to failures and robustness to traffic variations. Ad hoc modeling techniques are integrated within the proposed SEANM frameworks to explicitly consider resilience and robustness as network constraints. Finally, to implement the proposed procedures in a realistic network environment, we propose a novel, fully configurable network management framework, called JNetMan. We use JNetMan to develop and test a dynamic version of the SEANM procedure for IP networks operated with shortest path routing protocols

Elastic Traffic Engineering Subject to a Fair Bandwidth Allocation via Bilevel Programming

The ability of TCP’s congestion control scheme to adapt the rate of traffic flows and fairly use all the avail- able resources is one of the Internet’s pillars. So far, how- ever, the elasticity of traffic has been disregarded in traffic engineering (TE) methodologies mainly because, only recently, the increase in access capacity has moved the bottlenecks from the access network to the operator network and hungry cloud-based applications have begun to use all the available bandwidth. We propose a new approach to TE with elastic demands which models the interaction between the network operator and the end-to-end congestion control scheme as a Stackelberg game. Given a set of elastic traffic demands only specified by their origin-destination pairs, the network operator chooses a set of routing paths (leader’s problem) which, when coupled with the fair bandwidth allocation that the congestion control scheme would determine for the chosen routing (follower’s problem), maximizes a network utility function. We present bilevel pro- gramming formulations for the above TE problem with two widely-adopted bandwidth allocation models, namely, max-min fairness and proportional fairness, and derive corresponding exact and approximate single-level mathematical programming reformulations. After discussing some key properties, we report on computational results obtained for different network topolo- gies and instance sizes. Interestingly, even feasible solutions to our bilevel TE problems with large optimality gaps yield substantially higher network utility values than those obtained by solving a standard single-level TE problem and then fairly reallocating the bandwidth a posteriori

On the energy cost of robustness and resiliency in IP networks

http://www.sciencedirect.com/science/article/pii/S1389128614003594International audienceDespite the growing concern for the energy consumption of the Internet, green strategies for network and traffic management cannot undermine Quality of Service (QoS) and network survivability. In particular, two very important issues that may be affected by green networking techniques are resilience to node and link failures, and robustness to traffic variations.In this paper, we study how achieving different levels of resiliency and robustness impacts the network energy-aware efficiency. We propose novel optimization models to minimize the energy consumption of IP networks that explicitly guarantee network survivability to failures and robustness to traffic variations. Energy consumption is reduced by putting in sleep mode idle line cards and nodes according to traffic variations in different periods of the day. To guarantee network survivability we consider two different schemes, dedicated and shared protection, which assign a backup path to each traffic demand and some spare capacity on the links along the path. Robustness to traffic variations is provided by tuning the capacity margin on active links in order to accommodate load variations of different magnitude. Furthermore, we impose some inter-period constraints to guarantee network stability and preserve device lifetime. Both exact and heuristic methods are proposed.Experimentations carried out on realistic networks operated with flow-based routing protocols (like MPLS) allow us to quantitatively analyze the trade-off between energy cost and level of protection and robustness. Results show that significant savings, up to 30%, may be achieved even when both survivability and robustness are fully guaranteed, both with exact and heuristic approaches

Energy Management Through Optimized Routing and Device Powering for Greener Communication Networks

Recent data confirm that the power consumption of the information and communications technologies (ICT) and of the Internet itself can no longer be ignored, considering the in- creasing pervasiveness and the importance of the sector on pro- ductivity and economic growth. Although the traffic load of com- munication networks varies greatly over time and rarely reaches capacity limits, its energy consumption is almost constant. Based on this observation, energy management strategies are being con- sidered with the goal of minimizing the energy consumption, so that consumption becomes proportional to the traffic load either at the individual-device level or for the whole network. The focus of this paper is to minimize the energy consumption of the net- work through a management strategy that selectively switches off devices according to the traffic level. We consider a set of traffic scenarios and jointly optimize their energy consumption assuming a per-flow routing. We propose a traffic engineering mathemat- ical programming formulation based on integer linear program- ming that includes constraints on the changes of the device states and routing paths to limit the impact on quality of service and the signaling overhead. We show a set of numerical results obtained using the energy consumption of real routers and study the impact of the different parameters and constraints on the optimal energy management strategy. We also present heuristic results to compare the optimal operational planning with online energy management operation

Energy Management Through Optimized Routing and Device Powering for Greener Communication Networks

Recent data confirm that the power consumption of the information and communications technologies (ICT) and of the Internet itself can no longer be ignored, considering the in- creasing pervasiveness and the importance of the sector on pro- ductivity and economic growth. Although the traffic load of com- munication networks varies greatly over time and rarely reaches capacity limits, its energy consumption is almost constant. Based on this observation, energy management strategies are being con- sidered with the goal of minimizing the energy consumption, so that consumption becomes proportional to the traffic load either at the individual-device level or for the whole network. The focus of this paper is to minimize the energy consumption of the net- work through a management strategy that selectively switches off devices according to the traffic level. We consider a set of traffic scenarios and jointly optimize their energy consumption assuming a per-flow routing. We propose a traffic engineering mathemat- ical programming formulation based on integer linear program- ming that includes constraints on the changes of the device states and routing paths to limit the impact on quality of service and the signaling overhead. We show a set of numerical results obtained using the energy consumption of real routers and study the impact of the different parameters and constraints on the optimal energy management strategy. We also present heuristic results to compare the optimal operational planning with online energy management operation

Multi-period traffic engineering of resilient networks for energy efficiency

In this paper we consider the problem of minimizing the energy consumption of IP networks, exploiting the traffic variations over a set of time intervals, while guaranteeing the network QoS and survivability. Energy savings are achieved by putting into sleep mode cards and chassis, when they are not necessary. Network survivability is based on a dedicated protection scheme, wherein a dedicated backup path is assigned to each demand. The multi-period optimization is constrained by inter-period limitations necessary for guaranteeing network stability. Both exact and heuristic methods are proposed. Results obtained with realistic networks operated with flow-based routing protocols (i.e. MPLS) show that up to 60% of the energy savings can be achieved without negatively affecting network resiliency