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Showing papers by "Bernard Cousin published in 2007"


Journal ArticleDOI
Wojtek Bigos1, Bernard Cousin, Stephane Gosselin1, M. Le Foll1, Hisao Nakajima1 
TL;DR: It is demonstrated that by mapping efficiently the spare capacity of the MPLS layer onto the resources of the optical layer one can achieve up to 22% savings in the total configuration cost and up to 37% in the Optical layer cost.
Abstract: In this paper we study different options for the survivability implementation in MPLS over optical transport networks (OTN) in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single layer and multilayer survivability and present various methods for spare capacity allocation (SCA) to reroute disrupted traffic. The comparative analysis shows the influence of the offered traffic granularity and the physical network structure on the survivability cost: for high bandwidth LSPs, close to the optical channel capacity, the multilayer survivability outperforms the single layer one, whereas for low bandwidth LSPs the single layer survivability is more cost-efficient. On the other hand, sparse networks of low connectivity parameter use more wavelengths for optical path routing and increase the configuration cost, as compared with dense networks. We demonstrate that by mapping efficiently the spare capacity of the MPLS layer onto the resources of the optical layer one can achieve up to 22% savings in the total configuration cost and up to 37% in the optical layer cost. Further savings (up to 9 %) in the wavelength use can be obtained with the integrated approach to network configuration over the sequential one, however, at the increase in the optimization problem complexity. These results are based on a cost model with different cost variations, and were obtained for networks targeted to a nationwide coverage

40 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigate two approaches to the survivability deployment: single layer and multilayer survivability and present various methods for spare capacity allocation (SCA) to reroute disrupted traffic.
Abstract: In this paper we study different options for the survivability implementation in MPLS over Optical Transport Networks (OTN) in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single layer and multilayer survivability and present various methods for spare capacity allocation (SCA) to reroute disrupted traffic. The comparative analysis shows the influence of the offered traffic granularity and the physical network structure on the survivability cost: for high bandwidth LSPs, close to the optical channel capacity, the multilayer survivability outperforms the single layer one, whereas for low bandwidth LSPs the single layer survivability is more cost-efficient. On the other hand, sparse networks of low connectivity parameter use more wavelengths for optical path routing and increase the configuration cost, as compared with dense networks. We demonstrate that by mapping efficiently the spare capacity of the MPLS layer onto the resources of the optical layer one can achieve up to 22% savings in the total configuration cost and up to 37% in the optical layer cost. Further savings (up to 9 %) in the wavelength use can be obtained with the integrated approach to network configuration over the sequential one, however, at the increase in the optimization problem complexity. These results are based on a cost model with different cost variations, and were obtained for networks targeted to a nationwide coverage.

25 citations


Proceedings ArticleDOI
TL;DR: In this paper, centralized and distributed algorithms are proposed to solve the k-coverage sensing problem and maximize network lifetime by scheduling sleep intervals for some sensors and still providing continuous service with help of the remaining active sensors.
Abstract: Redundant sensing capabilities are often required in sensor network applications due to various reasons, e.g. robustness, fault tolerance, or increased accuracy. At the same time high sensor redundancy offers the possibility of increasing network lifetime by scheduling sleep intervals for some sensors and still providing continuous service with help of the remaining active sensors. In this paper centralized and distributed algorithms are proposed to solve the k-coverage sensing problem and maximize network lifetime. When physically possible, the proposed robust Controlled Greedy Sleep Algorithm provides guaranteed service independently of node and communication errors in the network. The performance of the algorithm is illustrated and compared to results of a random solution by simulation examples.

24 citations


Proceedings ArticleDOI
01 May 2007
TL;DR: In this paper, centralized and distributed algorithms are proposed to solve the k-coverage sensing problem and maximize network lifetime by scheduling sleep intervals for some sensors and still providing continuous service with help of the remaining active sensors.
Abstract: Redundant sensing capabilities are often required in sensor network applications due to various reasons, e.g. robustness, fault tolerance, or increased accuracy. At the same time high sensor redundancy offers the possibility of increasing network lifetime by scheduling sleep intervals for some sensors and still providing continuous service with help of the remaining active sensors. In this paper centralized and distributed algorithms are proposed to solve the k-coverage sensing problem and maximize network lifetime. When physically possible, the proposed robust controlled greedy sleep algorithm provides guaranteed service independently of node and communication errors in the network. The performance of the algorithm is illustrated and compared to results of a random solution by simulation examples.

23 citations


Proceedings ArticleDOI
02 Jul 2007
TL;DR: This paper evaluates the impact of the arrival order, then proposes two preemption strategies so as to reorder arrivals and evaluates these strategies applied to the shortest constrained path computation algorithm.
Abstract: In multi-protocol label switching-traffic engineering (MPLS-TE) networks with distributed tunnel path computation on head-end routers, tunnel requests are handled one by one, in an uncoordinated manner without any knowledge of future and other requests. The order in which requests are handled has a significant impact on the network optimization and blocking probability. If it is not possible to control the arrival order, in return it is possible, in some cases, to reorder requests using the preemption function. This paper evaluates the impact of the arrival order, so as to determine efficient orders. It then proposes two preemption strategies so as to reorder arrivals and evaluate these strategies applied to the shortest constrained path computation algorithm.

4 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigate two approaches to the survivability deployment: single layer and multilayer survivability and present various methods for spare capacity allocation (SCA) to reroute disrupted traffic.
Abstract: In this paper we study different options for the survivability implementation in MPLS over Optical Transport Networks in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single layer and multilayer survivability and present various methods for spare capacity allocation (SCA) to reroute disrupted traffic. The comparative analysis shows the influence of the traffic granularity on the survivability cost: for high bandwidth LSPs, close to the optical channel capacity, the multilayer survivability outperforms the single layer one, whereas for low bandwidth LSPs the single layer survivability is more cost-efficient. For the multilayer survivability we demonstrate that by mapping efficiently the spare capacity of the MPLS layer onto the resources of the optical layer one can achieve up to 22% savings in the total configuration cost and up to 37% in the optical layer cost. Further savings (up to 9 %) in the wavelength use can be obtained with the integrated approach to network configuration over the sequential one, however, at the increase in the optimization problem complexity. These results are based on a cost model with actual technology pricing and were obtained for networks targeted to a nationwide coverage.

3 citations


01 Jan 2007
TL;DR: This paper proposes a method which reconfigures unicast connections efficiently and without connection break, and shows that the reconfiguration time requires by the algorithm is lower than usual reconfigurations methods, and scales well with the number of nodes in the network.
Abstract: To prevent from topology changes, failures, or overloads, network management requires frequently computation and reconfiguration of established connections. When the number of established connections in the network is very large, the optimization of the reconfiguration task is essential to have short latency. When the communications using these connections are real-time, traffic interruption is not acceptable, and thus the scheduling of the reconfiguration tasks can be difficult. In this paper, we propose a method which reconfigures unicast connections efficiently and without connection break. Our simulations show that the reconfiguration time requires by our algorithm is lower than usual reconfiguration methods, and scales well with the number of nodes in the network.

3 citations


Proceedings ArticleDOI
26 Dec 2007
TL;DR: A solution based on the preemption mechanism so as to improve performances of distributed multi-protocol label switching-traffic engineering (MPLS-TE) path computation, where requests are handled one by one, in an uncoordinated manner without any knowledge of future and other requests.
Abstract: In this paper, we evaluate a solution based on the preemption mechanism so as to improve performances of distributed multi-protocol label switching-traffic engineering (MPLS-TE) path computation, where requests are handled one by one, in an uncoordinated manner without any knowledge of future and other requests. Our solution is motivated by the considerable impact of the tunnel setup order on the network load and blocking probability. If it is not possible to control this order, in return it is possible, in some cases, to reorder requests using the pre-emption function. After evaluating the impact of the tunnel setup order, we study the use of preemption to reorder LSP setup, with various algorithms, including shortest path first (SPF), widest shortest path (WSP) and shortest widest path (SWP). We show that the preemption is well suited to shortest path based algorithms and the performances in terms of blocking rate are significantly improved.

1 citations