Showing papers by "Bernard Cousin published in 2008"

Distance priority based multicast routing in WDM networks considering sparse light splitting

Abstract: As we know, the member-only algorithm in provides the best links stress and wavelength usage for the construction of multicast light-trees in WDM networks with sparse splitting. However, the diameter of tree is too big and the average delay is also too large, which are intolerant for QoS required multimedia applications. In this paper, a distance priority based algorithm is proposed to build light-trees for multicast routing, where the Candidate Destinations and the Candidate Connectors are introduced. Simulations show the proposed algorithm is able to greatly reduce the diameter and average delay of the multicast tree (up to 51% and 50% respectively), while keep the same or get a slightly better link stress as well as the wavelength usage than the famous Member-Only algorithm.

Robust $k$ -Coverage Algorithms for Sensor Networks

Abstract: Robustness, fault tolerance, and a long lifetime are key requirements of sensor networks used in real-world applications. Dense sensor networks with high sensor redundancy offer the possibility of redundant sensing and low duty-cycle operation at the same time; thus, the required robust sensing services can be provided along with an elongated lifetime. In this paper, the controlled greedy sleep algorithm is analyzed. With low local communication overhead, the proposed algorithm is able to solve the k -coverage sensing problem while it effectively preserves energy in the network. In addition, it can adapt to dynamic changes in the network, such as node failures. The quality of service (networkwide k-coverage) is guaranteed independently of communication errors in the network (as long as it is physically possible); message losses affect only the network lifetime. Node failures may cause a temporary decrease in the coverage service. The robustness of the algorithm is proven, and its behavior is illustrated by simulation examples.

Multi-criteria p-cycle network design

Abstract: The major challenge of p-cycle network design resides in finding an optimal set of p-cycles protecting the network for a given working capacity. Existing solutions (exact and heuristic approaches), for solving the problem, find the set of p-cycles protecting the network through two steps: one step for generating candidate p-cycles and a second step for selecting the efficient ones. In this paper, we present a novel heuristic approach, which computes an efficient set of p-cycles protecting the network in one step. Our heuristic approach takes into consideration two different criteria: the redundancy and the number of p-cycles involved in the solution. Simulation study shows that our approach necessitates a lower redundancy and fewer p-cycles to protect the network compared to state-of-the-art approaches.

Avoidance of multicast incapable branching nodes for multicast routing in WDM networks

Abstract: Although many multicast routing algorithms have been proposed in order to reduce the total cost in WDM optical networks, the link stress and delay are two parameters which are not always taken into consideration. This paper proposes a novel wavelength routing algorithm, which tries to avoid the multicast incapable branching nodes (MIB, branching nodes without splitting capability) to diminish the link stress for the shortest path based multicast tree and maintains good parts of the shortest path tree to reduce the end-to-end delay. Firstly a DijkstraPro algorithm with priority assignment and node adoption is introduced to produce a shortest path tree with up to 38% fewer MIB nodes, and then critical articulation and deepest branch heuristics are used to process the MIB nodes. Finally distance based reconnection algorithm is proposed to create the multicast tree or forest.

Distributed PLR-based backup path computation in MPLS networks

Abstract: In this article, we provide mechanisms enabling the backup path computation to be performed on-line and locally by the Points of Local Repair (PLRs), in the context of the MPLS-TE fast reroute. To achieve a high degree of bandwidth sharing, the Backup Path Computation Entities (BPCEs), running on PLRs, require the knowledge and maintenance of a great quantity of bandwidth information (non aggregated link information or per path information) which is undesirable in distributed environments. To get around this problem, we propose a distributed PLR (Point of Local Repair)-based heuristic (DPLRH) which aggregates and noticeably decreases the size of the bandwidth information advertised in the network while maintaining the bandwidth sharing high. DPLRH is scalable, easy to be deployed and balances equitably computations on the network routers. Simulations show that with the transmission of a small quantity of aggregated information per link, the ratio of rejected backup paths is low and close to the ideal.

Etude numérique de la résolution spectro-temporelle de contention de burst et réalisation d'un noeud OBS

Abstract: L'objectif de cet article est de degager a l'aide d'un simulateur les metriques et les comportements de la resolution spectro-temporelle de contention de bursts. Des resultats sur l'impact du nombre de longueurs d'onde et du nombre de lignes a retards optique sont presentes ainsi que sur l'influence des delais de ces lignes a retard. Nous y decrivons aussi l'architecture de noeud OBS que nous developpons en laboratoire pour l'etude de ces mecanismes.

Targeted Distribution of Resource Allocation for Backup LSP Computation

Abstract: Under the hypothesis of single failures in the network, some backup paths cannot be active at the same time because they protect against the failure of different components. Hence, share the bandwidth between such backup paths is central to optimize the bandwidth allocated in the network and to decrease the bandwidth wasting. In this paper, we propose a novel algorithm, based on targeted distribution of resource allocation (TDRA), to compute the backup label switched paths (LSPs) in a distributed multiprotocol label switching (MPLS) environment. Our algorithm is scalable, efficient and capable to protect against the three types of failure risk: node, link and shared risk link group (SRLG). Indeed, the TDRA algorithm decreases the quantity of information (resource or bandwidth allocation) transmitted in the network with the selection of nodes to be advertised (with the selection of recipient nodes). Furthermore, bandwidth availability is increased by sharing bandwidth between backup LSPs as long as possible. Simulations show that the ratio of rejected backup LSPs obtained with the transmission of a small quantity of information in the network is low.

Comparaison de l'obs conventionnel et de l'obs a label

Abstract: Dans cet article, nous montrons, a l'aide de simulations, les differents comportements de l'OBS ("Optical Burst Switching") conventionnel et de l'OBS a label vis-a-vis de la resolution de contentions spectro-temporelles. Nous montrons que le temps d' "offset" et les contentions de BCP ("Burst Control Packet") sont les principaux inconvenients de l'OBS conventionnel entrainant des performances generales moindres que l'OBS a label.