In this article, a new technique for grooming low-speed traffic demands into high-speed optical routes is proposed. This enhancement allows a transparent wavelength-routing switch (WRS) to aggregate traffic en route over existing optical routes without incurring expensive optical-electrical-optical (OEO) conversions. This implies that: a) an optical route may be considered as having more than one ingress node (all inline) and, b) traffic demands can partially use optical routes to reach their destination. The proposed optical routes are named "lighttours" since the traffic originating from different sources can be forwarded together in a single optical route, i.e., as taking a "tour" over different sources towards the same destination. The possibility of creating lighttours is the consequence of a novel WRS architecture proposed in this article, named "enhanced grooming" (G+). The ability to groom more traffic in the middle of a lighttour is achieved with the support of a simple optical device named lambda-monitor (previously introduced in the RingO project). In this article, we present the new WRS architecture and its advantages. To compare the advantages of lighttours with respect to classical lightpaths, an integer linear programming (ILP) model is proposed for the well-known multilayer problem: traffic grooming, routing and wavelength assignment The ILP model may be used for several objectives. However, this article focuses on two objectives: maximizing the network throughput, and minimizing the number of optical-electro-optical conversions used. Experiments show that G+ can route all the traffic using only half of the total OEO conversions needed by classical grooming. An heuristic is also proposed, aiming at achieving near optimal results in polynomial tim

Abstract-Optical Transport Networks (OTN) must be prepared in terms of better resource utilization, for accommodating unicast and multicast traffic together. Light-trees have been proposed for supporting multicast connections in OTN. Nevertheless when Traffic Grooming is applied in light-trees, resources can be underutilized as traffic can be routed to undesirable destinations in order to avoid Optical-Electrical-Optical (OEO) conversions. In this paper, a novel architecture named S/G Lighttree for supporting unicast/multicast connections is proposed. The architecture allows traffic dropping and aggregation in different wavelengths without performing OEO conversions. A heuristic that routes traffic demands using less wavelengths by taking advantage of the proposed architecture is designed as well. Simulation results show that the architecture can minimize the number of used wavelengths and OEO conversions when compared to light-trees.

Internet traffic demands are constantly increasing and a considerable amount of this increase is expected to be of multicast type. Optical Transport Networks (OTN) must be prepared in terms of better resource utilization for accommodating multicast traffic. For this purpose multicast traffic grooming has been considered. Light-trees have been proposed for supporting multicast connections in OTN. Nevertheless when light-trees are used with traffic grooming, resources can be overutilized as traffic can be routed to undesirable destinations in order to avoid Optical-Electrical-Optical (OEO) conversions. In this paper a novel architecture named S/G Light-tree for supporting multicast connections is proposed. The architecture allows to eliminate and aggregate traffic in different wavelengths without performing OEO conversions. The architecture uses labels supported by Generalized Multiprotocol Label Switching (GMPLS). A heuristic that routes traffic demands using less wavelengths by taking advantage of the proposed architecture is designed as well. Simulation results show that the architecture can minimize the number of used wavelengths and OEO conversions when compared to light-trees.

Wavelength Division Multiplexing (WDM) networks have been adopted as a near-future solution for the broadband Internet. In previous work we proposed a new architecture, named Enhanced Grooming (G+), that extends the capabilities of traditional optical routes (lightpaths). In [3,4,5,6] problem. The model studies the network throughput and the number of OEO conversions made. An heuristic is also proposed.In this paper the operating cost of performing G+ and classical grooming is studied by analyzing the prices of the components that each node uses to route a given set of demands. This is done by using a new path-based ILP model that takes into account the components market prices and minimizes the total cost. Due to the complexity of the model, the network is assumed to have full wavelength conversion. NETWORK ARCHITECTURESIn this section both architectures considered in this paper are described. The WRS functionality can be classified as:* Send Traffic performing electro-optical conversion (EO): the node has Traffic queued electronically (from itself or from a dropped optical route) and needs to transmit it. * Receive Traffic performing optical-electro conversion (OE): the node has Traffic that needs to be converted from optical to electrical because it is the destination or it has to be forwarded using another optical route. * Forward Traffic all optically (00): an optical path that does not carry traffic needs to be buffered electronically, so the node just has to switch the optical route from one port to another. A. The Classical Lightpaths Lightpaths are end-to-end optical connections established between any pair of WRSs in an optical network. In order to allow a large set of different lightpath configurations in a network, a typical WRS architecture must both forward optically lightpath traffics to other WRS without making OEO conversions and, transmit (or receive) optical traffic over (or from)a lightpath. For more details about a classical WRS the reader is referred to [7].

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