Emmanuel Dotaro

Routing and wavelength assignment of scheduled lightpath demands

We present algorithms that compute the routing and wavelength assignment (RWA) for scheduled lightpath demands in a wavelength-switching mesh network without wavelength conversion functionality. Scheduled lightpath demands are connection demands for which the setup and teardown times are known in advance. We formulate separately the routing problem and the wavelength assignment problem as spatio-temporal combinatorial optimization problems. For the former, we propose a branch and bound algorithm for exact resolution and an alternative tabu search algorithm for approximate resolution. A generalized graph coloring approach is used to solve the wavelength assignment problem. We compared the proposed algorithms to an RWA algorithm that sequentially computes the route and wavelength assignment for the scheduled lightpath demands.

Impact of intermediate traffic grouping on the dimensioning of multi-granularity optical networks

We demonstrate the interest of multi-granularity optical networks to decrease the number of ports for the optical switching matrices by grouping some wavelengths into bands and some bands into fibers at some intermediate nodes.

Multiservice optical network: main concepts and first achievements of the ROM program

With the tremendous introduction of internet protocol (IP) applications, the quality-of-service (QoS) becomes more and more an emergent issue. Concrete solutions can be adopted (IP/ATM/SONET/WDM) opening the way to new types of applications (interactive applications through the exploitation of voice and video) in a short-term approach. However, all the telecommunication community tries to provide new solutions offering capacity and flexibility in a simpler manner. In this paper, we present the concepts of a multiservice optical network studied in the framework of a French Research Program. The QoS could be offered through the combined exploitation of electronic memories in the edges and optical resources in the core of the optical network and through the coexistence of different types of connections. In particular, the traffic shaping in the edges is highlighted through simulation and demonstrates the real impact of this function to maintain the logical performance at its highest level. To propose concrete solutions for its implementation, two network scenarios are proposed. The first one, for the backbone, exhibits a novel optical packet switching architecture taking benefit of the massive presence of wavelengths to solve the contention. The second one, for the metro, shows a second optical packet switching architecture really adapted to the cost constraints (upgradability, compactness, granularity).

Resolving the fairness issue in bus-based optical access networks

Packet-based optical access ring is becoming a promising solution in metropolitan networks. Its performance depends mainly on how optical resource sharing takes place among the different competing access nodes. This network architecture has mostly been explored with regard to synchronous transmission (i.e., slotted WDM ring). However, in this article we focus on the performance of asynchronous transmission-based networks with variable packet sizes. We investigate the fairness issue that is likely to arise between upstream and downstream nodes sharing a common data channel. Furthermore, we show that sharing the channels available bandwidth fairly but arbitrarily between access nodes, as in slotted WDM rings, does not resolve the fairness problem in asynchronous systems. In this regard, we exhibit the inherent limitations of the token bucket access rate-based algorithm once applied to asynchronous transmission bus-based networks. To alleviate the aforementioned problem, we devise a new strategy called traffic control architecture using remote descriptors (TCARD). The proposed solution is based on a preventive mechanism to grant access to the shared resource. As illustrated in the article, the proposed solution alleviates performance degradation and resource underutilization while achieving fairness among bus nodes.

ROUTING AND WAVELENGTH ASSIGNMENT OF SCHEDULED LIGHTPATH DEMANDS IN A WDM OPTICAL TRANSPORT NETWORK

We present RWA algorithms for a new class of traffic model where, besides the source, destination and size (number of lightpaths) of the traffic demands, their set-up and tear-down dates are known. They are called Scheduled Lightpath Demands (SLDs). We model the RWA problem as a spatio-temporal combinatorial optimization problem and provide two solution algorithms. The time disjointness that could exist among SLDs is taken into account in order to maximize the utilization of resources and hence, minimize the amount of globally required resources. We compare our algorithms to an online RWA algorithm and show that taking into account the time disjointness of demands can lead to a gain of resources of 20 % in average.

Distributed aggregation in all-optical wavelength routed networks

In this paper, we propose and evaluate a new concept of traffic aggregation in mesh networks that aims to eliminate the bandwidth underutilization problem existing in all-optical wavelength routed networks. The proposed solution is based on the distribution of the aggregation process. So, instead of limiting the utilization of lightpaths capacity to the ingress node, each node along the path is allowed to fill on the fly this optical resource according to its availability. Therefore, the lightpath will be shared by several connections traveling from multiple ingress nodes to a single egress node. This technique combines the benefits of optical bypass and the statistical multiplexing gain. In order to gauge the value of the proposed solution, we formulate the problem using integer linear programming and study its performance through different scenarios using a prototype network. Our results show that distributed aggregation technique can improve significantly the network throughput and reduce the network cost.

Multi-region networks: generalized multi-protocol label switching (GMPLS) as enabler for vertical integration

Multi-region networks (MRN) is the generalized multi-protocol label switching (GMPLS)-based solution for vertical integration. Considering limitations of current interworking models and requirements for integration, MRN gives the possibility to operate domains hosting several technologies as a single network. While using a single instance of the control plane, multi-layer operations are profiled and optimized thanks to a limited number of protocol extensions. Routing and signaling are extended in order to support internal node adaptation capability and deterministic switching capability indication along the explicit route, respectively.

Matching fairness and performance by preventive traffic control in optical multiple access networks

We present and evaluate a novel protocol of traffic control that aims at solving the fairness issue typical of shared medium networks such as metropolitan rings. The proposed solution called TCARD (Traffic Control Architecture using Remote Descriptors) is based on a preventive mechanism to grant access to the resource -- i.e. free bandwidth is preserved by a node according to the traffic requirements from the other network nodes. A review of the existing methods used to manage fairness in ring networks is done and points out their inherent problems (performance issues, resource wastage or inadequacy). In contrast, we show how the new protocol addresses the above limitations, notably through a performance evaluation study. The major conclusion is the ability to avoid the degradation in performances and the resource sub-utilization while achieving fairness within the network.

A scalable transparent waveband-based optical metropolitan network

We propose a novel transparent, waveband-based, dual hubbed and protected DWDM optical metropolitan network with hierarchical rings, offering attractive cost and scalability properties. We analyze its physical feasibility and economic relevance in the sub-terabit/s capacity range.

Multi-Granularity Optical Networks

Considering the telecommunication traffic boom, one can wonder if routing nodes will provide the corresponding switching capacity. Introducing Multi-Granularity Optical Networks concept, this paper gives a cost-effective solution. First, a MG-OXC architecture is proposed, then the “natural” distribution of the traffic among the granularities is presented. Finally, a Multi-Granularity planning process is described. Based on the most advantageous feature of optical technologies, the proposed approach solves the switching matrix size limitation.