Optical Multicast Routing Under Light Splitter Constraints

During the past few years, we have observed the emergence of new applications that use multicast transmission. For a multicast routing algorithm to be applicable in optical networks, it must route data only to group members, optimize and maintain loop-free routes, and concentrate the routes on a subset of network links. For an all-optical switch to play the role of a branching router, it must be equipped with a light splitter. Light splitters are expensive equipments and therefore it will be very expensive to implement splitters on all optical switches. Optical light splitters are only implemented on some optical switches. That limited availability of light splitters raises a new problem when we want to implement multicast protocols in optical network (because usual multicast protocols make the assumption that all nodes have branching capabilities). Another issue is the knowledge of the locations of light splitters in the optical network. Nodes in the network should be able to identify the locations of light splitters scattered in the optical network so it can construct multicast trees. These problems must be resolved by implementing a multicast routing protocol that must take into consideration that not all nodes can be branching node. As a result, a new signaling process must be implemented so that light paths can be created, spanning from source to the group members

Heuristic Solution to Protect Communications in WDM Networks using P-cycles

Optical WDM mesh networks are able to transport huge amount of information. The use of such technology however poses the problem of protection against failures such as fibre cuts. One of the principal methods for link protection used in optical WDM networks is pre-configured protection cycle (p-cycle). The major problem of this method of protection resides in finding the optimal set of p-cycles which protect the network for a given distribution of working capacity. Existing heuristics generate a large set of p-cycle candidates which are entirely independent of the network state, and from then the good sub-set of p-cycles which will protect the network is selected. In this paper, we propose a new algorithm of generation of p-cycles based on the incremental aggregation of the shortest cycles. Our generation of p-cycles depends on the state of the network. This enables us to choose an efficient set of p-cycles which will protect the network. The set of p-cycles that we generate is the final set which will protect the network, in other words our heuristic does not go through the additional step of p-cycle selectio

Performance Evaluation of the Labelled OBS Architecture

A comparison of three different Optical Burst Switching (OBS) architectures is made, in terms of performance criteria, control and hardware complexity, fairness, resource utilization, and burst loss probability. Regarding burst losses, we distinguish the losses due to burst contentions from those due to contentions of Burst Control Packets (BCP). The simulation results show that as a counterpart of an its additional hardware complexity, the labelled OBS (L-OBS) is an efficient OBS architecture compared to a Conventional OBS (C-OBS) as well as in comparison with Offset Time-Emulated OBS (E-OBS)

Un ex-voto peint exceptionnel : les quatre époques mémorables de Jean Joseph Aubergy

Cet article figure sur le site de la Maison Méditerranéenne des Sciences de l'Homme imageson.org à l'adresse : http://www.imageson.org/document136.htmlJean-Joseph Aubergy est un charpentier de marine né à Martigues (Bouches-du-Rhône) qui a participé aux campagnes napoléoniennes et qui, à la suite d'un accident du travail, réalise en 1836 un ex-voto peint, sorte de véritable récit de sa vie en images

Un ex-voto peint exceptionnel : les quatre époques mémorables de Jean Joseph Aubergy

Cet article figure sur le site de la Maison Méditerranéenne des Sciences de l'Homme imageson.org à l'adresse : http://www.imageson.org/document136.htmlJean-Joseph Aubergy est un charpentier de marine né à Martigues (Bouches-du-Rhône) qui a participé aux campagnes napoléoniennes et qui, à la suite d'un accident du travail, réalise en 1836 un ex-voto peint, sorte de véritable récit de sa vie en images

Life and death of a French shantytown

This chapter analyses the French and Roma social frameworks of domination that make the existence as well as the destruction of ta shantytown possible. The first two parts of the study explain the social and economic organisation of the Roma in the platz together with the Paris suburban context of implantation of the slum. The third part tries to explain the role of the platz\u2019s chief, his biography, the different forms which the expression of this power takes, and the reception and the internal institutions that limit it, namely: the preacher and the heads of household. The fourth part will study the conflict between destroying and keeping the platz: the struggle between the mayor, state representatives, civil society, and the judiciary. The real power of each was confirmed or inferred by a violent, decisive act: the destruction of eighty family houses

Application-Aware Protection in DWDM Optical Networks

International audienceFast recovery time and reduced resource utilization are the two main criteria for determining the quality of survivability mechanism. Now it is well-known that link-based protection and path-based protection provide respectively a short recovery time and reduced use of resources. To benefit from the both of these saliencies, we propose in this paper to use these mechanisms simultaneously. Indeed, demands mandating shorter recovery time will be protected using link-based protection. Meanwhile other demands will be protected using path-based protection. Simulation results show that the proposed solution achieves a good trade-off between resource utilization and recovery time

Hypo-Steiner heuristic for multicast routing in all-optical WDM mesh networks

International audienceIn sparse light splitting all-optical WDM networks, the more destinations a light-tree can accommodate, the fewer light-trees andwavelengths amulticast session will require. In this article, a Hypo-Steiner light-tree algorithm (HSLT) is proposed to construct a HSLT light-tree to include as many destinations as possible. The upper bound cost of the light-trees built by HSLT is given as N(N −1)/2, where N is the number of nodes in the network. The analytical model proves that, under the same condition, more destinations could be held in a HSLT than a Member-Only (Zhang et al., J. Lightware Technol, 18(12), 1917–1927 2000.) light-tree. Extensive simulations not only validate the proof but also show that the proposed heuristic outperforms the existing multicast routing algorithms by a large margin in terms of link stress, throughput, and efficiency ofwavelength usage

Required Density of Multicast Capable Optical Cross Connects to Assure Efficient Multicasting

International audienceMany algorithms are developed to deploy multicast in optical networks. Those algorithms are designed to resolve the main issue of multicasting in optical networks, which is not all optical cross-connect in the network are capable to split an incoming light signal to more than one output interface. Some of those algorithms are based on additional signaling exchanged to generate the appropriate multicast trees, some use rerouting to source, and some generate multiple multicast trees for the same multicast group. The performance of those algorithms depends basically on the number and location of multicast capable cross-connects. A multicast capable cross-connect (MCOXC) is an optical node equipped with light splitter that allows splitting an incoming light signal to any two or more output interfaces. This paper studies how many nodes in optical networks must be equipped with light splitters to assure good performance of multicast algorithms in sparse splitting networks. This depends basically on the topology in terms of number of nodes, the average node degree and the variation of the node degree distribution over the network nodes. The more the variation of the node degree is, the more splitters are required

Light-Hierarchy: The Optimal Structure for Multicast Routing in WDM Mesh Networks

Based on the false assumption that multicast incapable (MI) nodes could not be traversed twice on the same wavelength, the light-tree structure was always thought to be optimal for multicast routing in sparse splitting Wavelength Division Multiplexing (WDM) networks. In fact, for establishing a multicast session, an MI node could be crosswise visited more than once to switch a light signal towards several destinations with only one wavelength through different input and output pairs. This is called Cross Pair Switching (CPS). Thus, a new multicast routing structure light-hierarchy is proposed for all-optical multicast routing, which permits the cycles introduced by the CPS capability of MI nodes. We proved that the optimal structure for minimizing the cost of multicast routing is a set of light-hierarchies rather than the light-trees in sparse splitting WDM networks. Integer linear programming (ILP) formulations are developed to search the optimal light-hierarchies. Numerical results verified that the light-hierarchy structure could save more cost than the light-tree structure