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ABSTRACT: The emergence of new telematic applications and services is creating significant growth in the traffic carried over the optical transport network (OTN). One potential cost-effective approach for satisfying these demands consists in applying inverse-multiplexing techniques, such as virtual concatenation (VCAT). In this context, efficient load balancing can be achieved by exploiting multipath routing at the cost of introducing differential delay in the concatenated circuits. This effect can be compensated through appropriate delay compensation techniques (e.g., electrical buffering), which can act either in a centralized way with the buffering at the end nodes, or by distributing the differential delay throughout the intermediate nodes. In order to properly solve the routing and differential delay compensation distribution problem in the OTN, we propose two novel methods: a dual-step integer linear programming (ILP) model and a tabu search multi-stage heuristic. These strategies are compared with our two former proposals consisting of a single-step ILP model and an iterative search heuristic. The four solutions are further expanded to consider the possibility of using homogeneous or heterogeneous VCAT. The performance of these optimization methods is examined in two network topologies assuming that 100 Gb/s Ethernet streams are carried over 40 Gb/s channels (homogeneous case) or over a mixed combination of 40 Gb/s and 10 Gb/s channels (heterogeneous case) in the OTN. The results obtained show that, as expected, the smallest buffering requirements are obtained by both ILP models, with the dual-step version exhibiting also a significant reduction in the number of optical-to-electrical and electrical-to-optical operations used for intermediate compensation. In addition, the novel tabu search framework is able to surpass our former heuristic by simultaneously leveraging minimum link capacities and reducing the buffer sizes.
Journal of Optical Communications and Networking 10/2011; · 1.87 Impact Factor
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ABSTRACT: We propose an optimization method for cost-effective dimensioning of optical transport networks with multiple line rate capabilities and heterogeneous Ethernet service demands, while accounting for transceiver and regenerator expenditures, traffic grooming and inverse-multiplexing techniques, and fibre wavelength count limit.
Optical Communication (ECOC), 2010 36th European Conference and Exhibition on; 10/2010
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ABSTRACT: The use of inverse-multiplexing with diverse-path routing techniques in transport networks is expected to satisfy the traffic demands at the expense of lower capacity requirements. However, when the traffic between two nodes is routed over multiple paths, the different flows have different arrival times at the destination node. In order to compensate for this difference, known as differential delay, data has to be temporarily buffered in this node. Eventually, the size of the high-speed buffers involved may expand beyond acceptable figures, resulting in a cost increase that may even cancel the advantages attained with these techniques, in terms of network capacity. As an alternative to compensating for the delay only at the end-node, the use of distributed schemes can enable the reduction of the maximum buffer size per node, while preserving the capacity savings from diverse-path routing. Hence, this paper presents a novel model for optimizing the differential delay compensation across the network, when inverse-multiplexed diverse-path routing is employed. In order to quantify its gains, the framework is applied in the routing of 100 Gb/s Ethernet signals over high-speed optical transport networks (OTN) using virtually concatenated 40 Gb/s optical channel data units (ODUs). In the two reference network topologies evaluated, the buffer reduction obtained varied from 67% to more than 90%.
Systems and Networks Communications, 2009. ICSNC '09. Fourth International Conference on; 10/2009
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ABSTRACT: We propose an optimization framework for routing virtually-concatenated 100 Gb/s Ethernet signals over optical transport networks with optimal buffer dimensioning and minimum capacity requirements in distributed differential delay compensation architectures.
Optical Communication, 2009. ECOC '09. 35th European Conference on; 10/2009
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ABSTRACT: The cost-effectiveness of optical burst-switched (OBS) networks can be improved by reducing the number of contention resolution devices used without excessively penalizing performance. Proactively minimizing wavelength contention can assist in the task of reducing the number of these devices. This paper evaluates the performance of an OBS network using a small number of optical buffers and wavelength converters. The simulation results show that the optimal combination of converters and buffers depends not only on the traffic load, but also on the efficiency of the wavelength contention minimization strategy.
Photonics in Switching, 2009. PS '09. International Conference on; 10/2009
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ABSTRACT: This paper addresses the possibility of using traffic engineering in the wavelength domain as a way to improve the performance of optical burst-switched (OBS) networks. With that aim, we detail a heuristic traffic engineering strategy that determines the order by which the ingress nodes of the network should search for an available wavelength for burst transmission, in order to minimize the probability that data bursts going through overlapping paths reach a common fiber link using the same wavelength. By means of network simulation, it is shown that the proposed traffic engineering strategy outperforms the existing strategies in reducing burst loss in OBS networks. This trend holds for core nodes with different degrees of wavelength conversion, ranging from the absence of wavelength converters to the use of dedicated full-range wavelength converters. More specifically, it is shown that using only traffic engineering in the wavelength domain can dramatically reduce burst loss in networks without wavelength conversion or alternatively it can reduce the number of wavelength converters in networks based on shared wavelength conversion. The simulation results also show that by combining traffic engineering in the wavelength domain with the use of the inexpensive electronic buffers at the ingress nodes, the performance of OBS networks with dedicated full-range wavelength converters can be further improved at the expense of a slight increase in the burst transfer delay.
Journal of Lightwave Technology 09/2009; · 2.78 Impact Factor
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ABSTRACT: The prospects of optical burst switching (OBS) as a cost-effective optical networking paradigm depend both on the complexity of the network nodes deployed and on the network performance attained. Contention resolution devices, namely wavelength converters and fibre delay line (FDL) buffers, and the size of the optical space switch matrix determine, to a large extent, the complexity of the core nodes. Consequently, the cost-effectiveness of an OBS network can be improved by deploying only a small number of converters and buffers. Moreover, the use of strategies that minimize in advance the probability of contention can assist in the task of further reducing the number of these devices. This paper evaluates the loss performance of an OBS network based on shared wavelength converters and FDL buffers and using wavelength contention minimization at the ingress nodes in order to gain insight on the dimensioning of the core nodes that leads to an improved network performance.
Transparent Optical Networks, 2009. ICTON '09. 11th International Conference on; 08/2009
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ABSTRACT: A strategy for minimising the probability of contention in optical burst-switching (OBS) networks, by combining traffic engineering in the wavelength domain with delayed burst scheduling at the ingress nodes, has been proposed. The implementation of this strategy only requires an increase on the processing and electronic buffering capacities of the ingress nodes, while avoiding the use of complex and expensive optical buffers at the core nodes. The performance evaluation study has shown that the proposed strategy outperforms the burst-scheduling strategies described in the literature by several orders of magnitude, in terms of burst-blocking probability. Moreover, the performance improvements have been shown to depend on the average offered traffic load, number of wavelengths per link and maximum delay allowed at the ingress nodes.
IET Communications 04/2009; · 0.83 Impact Factor
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ABSTRACT: Optical burst switching (OBS) networks rely on complex and costly contention resolution strategies to reach reasonable bandwidth utilization efficiency. Recent research efforts have suggested that proactive contention minimization strategies based on selectively delaying bursts at the ingress edge nodes, exploiting their inexpensive electronic buffers, can assist in the task of relaxing the hardware requirements of the network core nodes. This paper considers the main strategies of selectively delaying bursts at the ingress nodes, establishing their similarities and differences. The performance of these strategies is evaluated and compared by means of network simulation. The results show that a contention minimization strategy using the selective ingress delays to increase the degree of isolation on different wavelengths of burst traffic going through overlapping paths achieves the largest reduction of burst losses. Moreover, this performance improvement can be attained while at the same time reducing the number of wavelength converters required at the core nodes and slightly relaxing the number of transmitters and receivers needed at the edge nodes, provided that tuneable devices are employed.
Optical Network Design and Modeling, 2009. ONDM 2009. International Conference on; 03/2009
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ABSTRACT: Optical burst switching (OBS) has been envisioned as a cost-effective paradigm for supporting IP packet traffic over optical transport networks. OBS network performance is hampered by resource contention at the network core nodes, requiring efficient strategies for avoiding and/or resolving contention. Strategies acting in the space domain can be exploited to achieve this goal without imposing additional hardware requirements on the core nodes. Previous works have focused either on reactive routing strategies, namely deflection routing, or on proactive routing strategies. This paper assesses the outcome of combining proactive routing for minimizing contention in advance with deflection routing for resolving contention. Using network simulation it is shown that the combined approach significantly improves the network performance over the use of only one routing strategy.
Transparent Optical Networks, 2007. ICTON '07. 9th International Conference on; 08/2007
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ABSTRACT: The future prospects of optical burst switching (OBS) networks would greatly benefit, in terms of cost and ease of implementation, from limiting or even avoiding the deployment of wavelength conversion capabilities at the network nodes. This paper proposes a new strategy for minimizing wavelength contention in OBS networks. Simulation results suggest that this strategy can significantly reduce the performance penalty of avoiding wavelength conversion at the network nodes. Moreover, the new strategy is shown to outperform a previously proposed strategy, in some cases by several orders of magnitude, in terms of average burst blocking probability.
Global Telecommunications Conference, 2006. GLOBECOM '06. IEEE; 01/2007
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Proceedings of the Symposium on Enabling Optical Networks and Sensors, SEON '05; 01/2005
