Comparaison des stratégies de redondance dans les réseaux ad hoc

Session Ad HocInternational audienceDans ce papier, nous analysons une approche originale en combinant les processus de recouvrement de route et de chemin dans un réseau ad hoc hétérogène utilisant deux technologies sans fil Zigbee et WiFi pour améliorer la robustesse du réseau. Nous proposons une architecture de redondance multi-niveau qui s'appuie sur des protocoles normalisés IEEE et IETF. Elle prend en charge toutes les étapes du processus de recouvrement de chemin depuis la détection de la rupture d'un lien sur le chemin primaire jusqu'à la reprise du trafic sur le chemin secondaire. Une formulation analytique de la fiabilité de chacun des trois schémas de recouvrement de base (recouvrement lien par lien, de bout en bout et par segment) est proposée. L'étude de performance montre l'avantage en terme de fiabilité du recouvrement par segment par rapport aux deux autres politiques. Il apparaît aussi qu'en terme de fiabilité, la gestion des pannes de la route primaire doit s'effectuer au niveau du routage par des protocoles multipath plutôt que par la couche transport

On Routing for Extending Satellite Service Life in LEO Satellite Networks

International audienceWe address the problem of routing for extending the service life of satellites in Iridium-like LEO constellations. Satellites in LEO constellations can spend over 30% of their time under the earth’s umbra, time during which they are powered by batteries. While the batteries are recharged by solar energy, the depth of discharge they reach during eclipse significantly affects their lifetime – and by extension, the service life of the satellites themselves. For batteries of the type that power Iridium satellites, a 15% increase to the depth of discharge can practically cut their service lives in half. We present two new routing metrics – LASER and SLIM – that try to strike a balance between performance and battery depth of discharge in LEO satellite constellations. Our basic approach is to leverage the deterministic movement of satellites for favoring routing traffic over satellites exposed to the sun as opposed to the eclipsed satellites, thereby decreasing the average battery depth of discharge – all without adversely affecting network performance Simulations show that LASER and SLIM can reduce the depth of discharge by about 11% and 16%, respectively, which can lead to as much as 100% increase in the satellite batteries lifetime. This is accomplished by trading off very little in terms of end-to-end delay

Augmenting the Energy-Saving Impact of IEEE 802.3az via the Control Plane

International audienceIEEE 802.3az, the recent standard for Energy Efficient Ethernet, is one of the main contributions of the ICT industry to the global quest for energy efficiency. Energy consumption reduction is accomplished by essentially replacing the continuous IDLE of legacy IEEE 802.3 cards with a Low Power Idle. While this is an important step in the right direction, studies have shown that the energy saving with IEEE 802.3az highly depends on the traffic load and stops for link utilizations as low as 25%. In addition to the standardization effort for creating energy efficient networking hardware, several solutions have been proposed for energy efficient routing, OSPF in particular. However, most solutions are transparent to and usually leave open the question of how exactly are the energy savings realized in hardware. Simply routing less or no traffic through certain links will not automatically lead to those links consuming less energy. We present EAGER and CARE, two OSPF metrics customized for augmenting the energy saving of IEEE 802.3az line cards - the only available off-the-shelf, standard-complying hardware for saving energy in OSPF networks. The principle underlying the design of EAGER and CARE is that of creating a synergy between the control plane of OSPF routers and IEEE 802.3az compliant line cards, without requiring changes to the respective standards and/or the hardware. Simulation results show that EAGER and CARE can increase the amount of energy saved when using IEEE 802.3az line cards by 2× on a network of routers. Furthermore, the results show that CARE strikes a good balance between energy efficiency and traditional network performance metrics

Adaptation Process for Ad hoc Routing Protocol

International audienceBecause of several constraints in ad hoc networks, an adaptive ad hoc routing protocol is increasingly required. In this paper, we propose a synopsis of an adaptation process for an adaptive ad hoc routing protocol. Next, we put into practice the analysis of the process of adaptation to mobility by realizing an adaptive routing protocol: CSR (Cluster Source Routing) which is an extension of a widely used ad hoc routing protocol: DSR (Dynamic source Routing). Mobility and density metrics are considered to CSRDSR mode switching, it moves from a flat architecture working in DSR to a virtual hierarchical architecture. With this mode switching, CSR can enhance the scalability of the DSR routing protoco

Frugal Topologies for Saving Energy in IP Networks

International audienceRecent years have seen the advent of energy conservation as a key engineering and scientific challenge of our time. At the same time, most IP networks are typically provisioned to 30%-40% average utilization, leading to a significant waste of energy. Current approaches for creating more frugal networks rely on instantaneous and global knowledge of the traffic matrix and network congestion levels - a requirement that can be impractical for many network operators. We introduce a new traffic-agnostic metric for quantifying the quality of a frugal topology, the Adequacy Index (ADI).We show that the problem of minimizing the power consumption of a network subject to a given ADI threshold is NP-hard and present two polynomial time heuristics - ABStAIn and CuTBAck. We perform extensive simulations using topologies and traffic matrices from 3 real networks. Our results show that ABStAIn and CuTBAck are as effective as an exponential time traffic based solution at creating frugal topologies and outperform a state of the art polynomial time traffic based solution by about 80%. Furthermore, the median link utilization observed with ABStAIn and CuTBAck is similar to that with traffic based solutions, with the maximum link utilization never exceeding 80%

Towards generic satellite payloads: software radio

Satellite payloads are becoming much more complex with the evolution towards multimedia applications. Moreover satellite lifetime increases while standard and services evolve faster, necessitating a hardware platform that can evolves for not developing new systems on each change. The same problem occurs in terrestrial systems like mobile networks and a foreseen solution is the software defined radio technology. In this paper we describe a way of introducing this concept at satellite level to offer to operators the required flexibility in the system. The digital functions enabling this technology, the hardware components implementing the functions and the reconfiguration processes are detailed. We show that elements of the software radio for satellites exist and that this concept is feasible

Etude analytique de la fiabilité dans les réseaux ad hoc multi-domiciliés

National audienceLa redondance est le principal moyen pour améliorer la robustesse et la disponibilité des chemins dans les réseaux mobiles ad hoc. Dans ce document, nous analysons deux niveaux de redondance proposés dans la littérature afin de faciliter le recouvrement de la communication entre deux nœuds (1) la redondance de routes à travers les protocoles de routage multipath (2) le concept de multihoming procurant une redondance de niveau transport. Nous montrons l'avantage de l'intégration multihoming-multipath dans les réseaux ad hoc en termes de fiabilité et de disponibilité et proposons une méthode de calcul de la fiabilité des chemins dans un réseau mobile ad hoc multi-domicilié utilisant cette approche

Performance Evaluation of Energy Efficient Policies for Ethernet Switches

International audienceEnergy efficiency has emerged as a defining scientific and engineering challenge of our time. Ethernet, as the dominant wireline technology, has been a focus of intense research and development efforts with the goal of significantly decreasing its energy consumption. In 2010 the IEEE Std 802.3az, which uses a Low Power Idle (LPI) mode to reduce the energy consumption of a link when there is no data traffic, was approved. Recently, the major manufacturers have brought to market the first switches the implement the new energy efficient standard. In this paper, we make use of the first generation of hardware that support the IEEE 802.3az to get a better understanding of the behavior of energy efficient mechanisms for ethernet. Based on measurement on DLINK switches that are IEEE 802.3az compliant, we build a power model that reflects more accurately the power used by real hardware in practice. We use the measurement-driven power model to analyze the behavior of Lazy Start, the state of the art algorithm for energy efficient ethernet, in the ns-3 simulator. Based on our analysis, we provide recommendations for improvements and potential directions for future work

Politiques de robustesse en réseaux ad hoc

Les réseaux sans fil sont sujets à des perturbations voire des pannes de liens et de noeuds en raison des caractéristiques intrinsèques de leur support de communication ; ces pannes sont aggravées par les particularités de relayage et de mobilité des noeuds dans les réseaux ad hoc. Ces réseaux requièrent donc la conception et la mise oeuvre des protocoles robustes au niveau de toutes les couches protocolaires. Dans cette thèse, nous choisissons une approche de robustesse pour améliorer les performances des communications dans un réseau mobile ad hoc. Nous proposons et étudions deux architectures de protection (protection par une analyse prédictive et protection par redondance de routes) qui sont couplées avec une restauration de niveau routage. Concernant la phase de détection, le protocole de routage utilise les notifications de niveau liaison pour détecter les pannes de liens. La première solution repose sur un protocole de routage réactif unipath dont le critère de sélection de routes est modifié. L idée est d utiliser des métriques capables de prédire l état futur des routes dans le but d améliorer leur durée de vie. Pour cela, deux métriques prédictives reposant sur la mobilité des noeuds sont proposées : la fiabilité des routes et une combinaison fiabilité-minimum de sauts. Pour calculer ces métriques prédictives, nous proposons une méthode analytique de calcul de la fiabilité de liens entre noeuds. Cette méthode prend compte le modèle de mobilité des noeuds et les caractéristiques de la communication sans fil notamment les collisions inter-paquets et les atténuations du signal. Les modèles de mobilité étudiés sont les modèles Random Walk et Random Way Point. Nous montrons l impact de ces métriques sur les performances en termes de taux de livraison de paquets, de surcoût normalisé et de ruptures de routes. La seconde solution est une protection par redondance de routes qui s appuie sur un protocole de routage multipath. Dans cette architecture, l opération de recouvrement consiste soit à un basculement sur une route secondaire soit à une nouvelle découverte. Nous montrons que la redondance de routes améliore la robustesse de la communication en réduisant le temps de restauration. Ensuite, nous proposons une comparaison analytique entre les différentes politiques de recouvrement d un protocole multipath. Nous en deduisons qu un recouvrement segmenté donne les meilleurs résultats en termes de temps de restauration et de fiabilitéDue to the unreliability characteristics of wireless communications, and nodes mobility, Mobile Ad hoc Networks (MANETs) suffer from frequent failures and reactivation of links. Consequently, the routes frequently change, causing significant number of routing packets to discover new routes, leading to increased network congestion and transmission latency. Therefore, MANETs demand robust protocol design at all layers of the communication protocol stack, particularly at the MAC, the routing and transport layers. In this thesis, we adopt robustness approach to improve communication performance in MANET. We propose and study two protection architectures (protection by predictive analysis and protection by routes redundancy) which are coupled with a routing level restoration. The routing protocol is responsible of the failure detection phase, and uses the mechanism of link-level notifications to detect link failures. Our first proposition is based on unipath reactive routing protocol with a modified route selection criterion. The idea is to use metrics that can predict the future state of the route in order to improve their lifetime. Two predictive metrics based on the mobility of nodes are proposed : the routes reliability and, combining hop-count and reliability metrics. In order to determine the two predictive metrics, we propose an analytical formulation that computes link reliability between adjacent nodes. This formulation takes into account nodes mobility model and the the wireless communication characteristics including the collisions between packets and signal attenuations. Nodes mobility models studied are Random Walk and Random Way Point. We show the impact of these predictive metrics on the networks performance in terms of packet delivery ratio, normalized routing overhead and number of route failures. The second proposition is based on multipath routing protocol. It is a protection mechanism based on route redundancy. In this architecture, the recovery operation is either to switch the traffic to alternate route or to compute a new route. We show that the routes redundancy technique improves the communication robustness by reducing the failure recovery time. We propose an analytical comparison between different recovery policies of multipath routing protocol. We deduce that segment recovery is the best recovery policy in terms of recovery time and reliabilityTOULOUSE-INP (315552154) / SudocSudocFranceF

Convergence architecture for home service communities

Nowadays, home networks have integrated day to day life through the classical internet access and deliver numerous services to end users. This home entrance is a real opportunity for operators to deploy services directly between homes. However, one major issue is the interconnection between Home Networks (HN) which requires suitable architectures and efficient authentication mechanisms. In this paper, two network architectures were proposed to interconnect HNs in order to support home service delivery and then compared with the IMS as reference architecture. The first architecture was based on a centralized SIP solution and used HTTP digest for authentication purpose; while the second proposition consisted in a distributed architecture based on pure P2P and Identity based cryptography. The study of these two solutions has been undergone through the simulation of a simple photo sharing scenario. As a result, the centralized SIP solution can be relevant for an average number of users and the easiest way to deploy new services. The decentralized solution (pure P2P) can be deployed for small service communities and may be compliant to larger system with improved algorithms