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Showing papers by "Bernard Cousin published in 2011"


Proceedings ArticleDOI
27 Apr 2011
TL;DR: It is shown that under certain traffic condition MB-OFDM may offer useful flexibility in the context of increasing wavelength bit rates.
Abstract: In this paper, we present a novel networking technique based on optical Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM). We highlight the interesting features of the solution with respect to existing ones (fully opaque optical networks and transparent networks) for optical metro and core networks. We show that under certain traffic condition MB-OFDM may offer useful flexibility in the context of increasing wavelength bit rates.

16 citations


Journal ArticleDOI
TL;DR: The cost bounds of the light-trees built for a multicast session in unweighted WDM networks are studied and the approximation ratios of some classical multicast light-tree computation algorithms, i.e., the reroute-to-source (R2S) and member-only (MO) algorithms, are derived in both un Weighted and non-equally-weightedWDM networks.
Abstract: The construction of light-trees is one of the principal subproblems for all-optical multicast routing in sparse splitting wavelength division multiplexing (WDM) networks. Due to the light splitting constraint and the absence of wavelength converters, several light-trees may be required to establish a multicast session. However, the computation of the cost-optimal multicast light-trees is NP-hard. In this paper, first we study the cost bounds of the light-trees built for a multicast session in unweighted WDM networks. Then, partially based on this result, the approximation ratios of some classical multicast light-tree computation algorithms, i.e., the reroute-to-source (R2S) and member-only (MO) algorithms, are derived in both unweighted and non-equally-weighted WDM networks. Moreover, integer linear programming formulations are introduced and carried out to search the optimal light-trees for multicast routing. The cost bounds and approximation ratios of the R2S and MO algorithms in some candidate WDM backbone networks are examined through simulations.

14 citations


Proceedings ArticleDOI
09 May 2011
TL;DR: An extension of the well known routing protocol AODV (Ad hoc On-demand Distance Vector) is presented to improve the multipath routing strategy with a path classification enabling the choice of the paths having the best energy level.
Abstract: Routing in ad hoc mobile networks is a problem which is not satisfactorily solved yet. Traditional techniques of routing are not well adapted to new networks. Indeed, their lack of reactivity with respect to the traffic and network changes make them not easily usable but at the price of an oversizing of the network resources (network bandwidth, node memory utilization, node CPU load, etc). The research community was interested these last years in the improvement of the ad hoc routing, and among the solutions suggested the multipath routing has been considered. Multiple paths are exploited in order to ensure reliability, quick time reaction to changes with a low overhead generated by the control messages. We present in this article, an extension of the well known routing protocol AODV (Ad hoc On-demand Distance Vector). We propose to improve the multipath routing strategy with a path classification enabling the choice of the paths having the best energy level.

13 citations


Proceedings ArticleDOI
05 Jun 2011
TL;DR: Two ILP formulations for a novel monitoring cost model that apply for both passive and active monitoring are come up with to jointly minimize the monitor location cost and the anomaly detection cost, thereby obtaining a monitoring solution that minimizes the total monitoring cost.
Abstract: To reduce monitoring cost, the number of monitors to be deployed have to be minimized and the overhead of monitoring flows on the underlying network have to be reduced. In a recent work, we demonstrated, using ILP formulations, that there is a trade-off between theses two minimization objectives. However, we have shown that the trade-off could be efficiently balanced by jointly optimizing monitor location and anomaly detection costs. The problem is NP-complete, hence ILPs could not deliver solutions for large networks. In this paper, we address the scalability issues. We propose two greedy algorithms that jointly optimize monitor location cost and anomaly detection cost. The first algorithm is based on an exhaustive heuristic that explores all paths that are candidate to be monitored, in order to select a subset of paths that reduces the total monitoring cost. On the opposite, the second algorithm is based on a selective heuristic that avoids exploring all the candidate paths to further improve the scalability. The main challenge of this heuristic is to not degrade the solution quality. The two algorithms have been evaluated through extensive simulations on networks of hundred of billions of paths. The comparison of the solutions delivered by the two algorithms to each other and to the solutions delivered by the ILP demonstrates that the selective algorithm provides near-optimal solutions, while achieving a desirable scalability with respect to the network size and significant reduction of the computation time.

10 citations


Proceedings ArticleDOI
26 Oct 2011
TL;DR: An efficient distributed inter-domain algorithm that computes constrained paths among a set of domains, exploring multiple inter- domain routes is proposed and it is demonstrated that the algorithm not only increases success rate in delivering feasible paths, but also admits more connections and keeps a reasonable runtime.
Abstract: Internet usages have changed with the emergence of value added services relying on a higher interactivity and needs for a better quality of experience (QoE). Telecommunication operators have to face a continuing growth of new types of Internet traffic (video, games, telepresence, etc.) imposing not only a more efficient utilization of their network infrastructure resources, but also the generation of new revenues to pursue investments and sustain the increasing demand. Such services generally cross multiple domains, but inter-domain routing protocols still have some limitations in terms of service assurance. For example, BGP's single route announce for a destination limits potential traffic engineering features (e.g. no quality of service price/efficiency optimisation, inter-domain shared route protection, inter-domain load balancing, etc.). In order to provision end-to-end inter-domain connections that obey to constraints such as bandwidth, delay, jitter, and packet loss for these services, an interesting approach is to compute end-to-end (e2e) paths over multiple inter-domain routes. This will allow establishing more efficiently the inter-domain connections with respect to requested QoS constraints and sharing these constraints (and associated revenues) among multiple operators to globally accept more demands in the system, while keep satisfying the customer QoE. To address these challenges, we propose an efficient distributed inter-domain algorithm that computes such constrained paths among a set of domains, exploring multiple inter-domain routes. We demonstrate that our algorithm not only increases success rate in delivering feasible paths, but also admits more connections and keeps a reasonable runtime.

10 citations


Proceedings ArticleDOI
04 Oct 2011
TL;DR: A novel algorithm is proposed that integrates the node protection concept of the p-cycle approach to achieve more efficient resource utilization in dynamic multicast traffic in WDM networks and achieves the lowest blocking probability, but has the highest computational time among the NPCC and ESHN algorithms.
Abstract: In this paper, we consider link-and-node failure recovery in dynamic multicast traffic in WDM networks. We extend the node protection concept of the p-cycle approach to achieve more efficient resource utilization. Then, we propose a novel algorithm that integrates our concept for the node protection, named node-and-link protecting p-cycle based algorithm (NPC). We also propose a second algorithm, named node-and-link protecting candidate p-cycle based algorithm (NPCC). This algorithm deploys our concept for node protection and relies on a candidate p-cycle set to speed up the computational time. We compare our proposed algorithms to the ESHN algorithm, which is reported to be the most efficient algorithm for protecting dynamic multicast sessions. Extensive simulations show that the NPC algorithm achieves the lowest blocking probability, but has the highest computational time among the NPCC and ESHN algorithms. The NPCC algorithm outperforms the ESHN algorithm in terms of resource utilization efficiency and computational time.

9 citations


Journal ArticleDOI
TL;DR: This work tries to formulate the multicast light-trees problem as a Mixed-Integer Linear Programming (MILP) by developing a set of equivalent linear equations to replace the non-linear ones.
Abstract: Given a multicast session in Wavelength Division Multiplexing (WDM) networks, we try to find the multicast light-trees with the minimum power budget while taking into account the optical power loss as light splitting loss, node tapping loss and light attenuation loss. Although light splitting causes non-linear power relationship, we succeed to formulate this problem as a Mixed-Integer Linear Programming (MILP) by developing a set of equivalent linear equations to replace the non-linear ones. The distribution of power loss is analyzed by simulations, which suggests to bound the combined power loss ratio of the node tapping loss and the light attenuation in each source-destination path, and make power-symmetric light-trees by properly using light-splitters in order to minimize the overall power loss.

6 citations


Proceedings ArticleDOI
04 Oct 2011
TL;DR: It is shown that confidentiality is far from being the only constraint to global multi-domain monitoring, and therefore, the confidentiality constraint has been relaxed, in order to investigate other performance metrics; namely, the monitoring cost, the quality of monitored paths, the anomaly detection delays, and the fairness of monitoring load distribution among domains.
Abstract: Mutli-domain monitoring aims at guaranteeing QoS for services crossing several domains. It is often desirable to perform global monitoring to guarantee end-to-end QoS for services across domains and to reduce the monitoring cost. However, global monitoring might be infeasible due to confidentiality constraints. The alternative solution is to perform per-domain monitoring. In this work, we propose to evaluate global and per-domain monitoring techniques. For this end, we study the properties of multi-domain networks and the requirements of multi-domain monitoring. We formulate the problem as an Integer Linear Program (ILP). We show that it is a Nondeterministic Polynomial Time Hard (NP-Hard) problem, and therefore, we devise a heuristic that meets multi-domain properties. We show that confidentiality is far from being the only constraint to global multi-domain monitoring. In our evaluation, the confidentiality constraint has been relaxed, in order to investigate other performance metrics; namely, the monitoring cost, the quality of monitored paths, the anomaly detection delays, and the fairness of monitoring load distribution among domains. Simulation results on random topologies show that per-domain monitoring outperforms global monitoring for all these metrics, except the monitoring cost that is slightly lower for global monitoring.

4 citations


Book ChapterDOI
22 Aug 2011
TL;DR: HID-MCP is a hybrid algorithm that combines the advantages of pre-computation and on-demand computation to obtain end-to-end QoS paths to improve the path computation results in a single domain or in multiple domains.
Abstract: In this paper we tackle the challenging problem of Quality of Service (QoS) routing in multiple domains. We propose a novel inter-domain QoS routing algorithm named HID-MCP. HID-MCP benefits from two major concepts that ensure high performance in terms of success rate and computational complexity. First, HID-MCP is a hybrid algorithm that combines the advantages of pre-computation and on-demand computation to obtain end-to-end QoS paths. Second, HIDMCP integrates crankback mechanisms for improving the path computation results in a single domain or in multiple domains. Extensive simulations confirm the efficiency of our algorithm on randomly generated topologies.

3 citations


Journal ArticleDOI
TL;DR: It is proved that the problem of minimizing the total cost while establishing a multipoint-to-point session can be solved in polynomial time of O, which can approximate to the optimal total cost with a ratio of k.
Abstract: In this article, the routing and wavelength assignment (RWA) problem for supporting multipoint-to-point communications in all-optical WDM mesh networks is investigated. Two efficient algorithms, namely reverse shortest path tree routing (RSPT) and k-bounded edge disjoint path routing (EDPR), are proposed. We proved that the problem of minimizing the total cost while establishing a multipoint-to-point session can be solved in polynomial time of O(|V|log|V| + |V| + |E|) by the RSPT algorithm, where |V| and |E| denote the number of nodes and the number of edges in the network, respectively. Nevertheless, the solution provided by the EDPR algorithm produces a significant reduction in the maximum number of wavelengths required per link (i.e., the link stress) for a multipoint-to-point session compared to RSPT algorithm. EDPR algorithm can also approximate to the optimal total cost with a ratio of k. Simulations are done to assess these two algorithms. Numerical results demonstrate their efficiencies in supporting multipoint-to-point communications in all-optical WDM networks.

1 citations