Sharing wavelength converters in multistage optical packet switches (original) (raw)
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Multi-stage optical packet switching fabric based on the broadcast-and-select principle is considered to implement the shared-per-node wavelength conversion scheme. This approach fairly allows to combine contention resolution in the wavelength and space domains. A scheduling algorithm is proposed to control optical packet forwarding in synchronous context. The results aim at showing how the sharing of wavelength converters impacts on node performance, the degree of sharing achieved with respect to the reference shared-per-node architecture, and at providing a meaningful support for cost-performance benchmarking studies. An important aspect dealt with in the paper is the complexity evaluation in terms of expensive optical components, tunable wavelength converters (TWCs) and semiconductor optical amplifiers (SOAs) used as optical gates. The multi-stage switching fabric is compared with the reference shared-per-node scheme in terms of complexity, thus showing the better scalability property of the proposed architecture, given the reduced number of optical gates employed.
Journal of Lightwave Technology, 2000
This paper describes an optical switch architecture based on the shared-per-wavelength strategy for contention resolution in the wavelength domain. This strategy impacts on wavelength converters requirements and switch organization, by allowing to obtain cost saving. The general sharing concept is first introduced and the related practical solution as a multistage switch architecture is presented and thoroughly analyzed in terms of performance, control and cost perspectives. Heuristic scheduling to manage packet forwarding in a synchronous context is developed and discussed in terms of computational complexity. A simple accurate analytical model is developed and validated against simulation to numerically evaluate packet loss performance of the shared-per-wavelength switch. The main achievement of the work is represented by the proposal of a feasible approach which leads to remarkable cost saving in terms of optical gates and wavelength converters under the conditions outlined.
This paper presents a combined scheme for the contention resolution in optical packet switches. The scheme leads to more efficient use of the buffer space compared to the output buffering scheme. The performance of the switch is further improved by utilizing the wavelength conversion. This can be accomplished at a limited cost as the wavelength converters are udlized in the shared buffer loop, and not in the input end. The superiority of the scheme has been established through extensive simulation and analytical study and the results are encouraging, paving the way for further research in this direction.
IEEE Globecom 2006, 2006
This paper describes the scheduling algorithms to control the optical packet forwarding in a multi-stage switch based on the broadcast-and-select principle. The aim of control algorithms is to fully exploit switch resources while avoiding contention in the wavelength and space domains. A multi-stage switch based on the shared per node wavelength conversion scheme is considered in a synchronous context. An analytical model is provided to calculate the packet loss probability in relation to different reference traffic scenarios. Results show how the sharing of wavelength converters impacts on node performance depending on the scheduling algorithm applied, and provide a meaningful support for optical packet switch design.
Shared-per-wavelength asynchronous optical packet switching: A comparative analysis
Computer Networks, 2010
This paper compares four different architectures for sharing wavelength converters in asynchronous optical packet switches with variable-length packets. The first two architectures are the well-known shared-per-node (SPN) and shared-per-link (SPL) architectures, while the other two are the shared-per-input-wavelength (SPIW) architecture, recently proposed as an optical switch architecture in synchronous context only, which is extended here to the asynchronous scenario, and an original scheme called shared-per-output-wavelength (SPOW) architecture that we propose in the current article. We introduce novel analytical models to evaluate packet loss probabilities for SPIW and SPOW architectures in asynchronous context based on Markov chains and fixed-point iterations for the particular scenario of Poisson input traffic and exponentially distributed packet lengths. The models also account for unbalanced traffic whose impact is thoroughly studied. These models are validated by comparison with simulations which demonstrate that they are remarkably accurate. In terms of performance, the SPOW scheme provides blocking performance very close to the SPN scheme while maintaining almost the same complexity of the space switch, and employing less expensive wavelength converters. On the other hand, the SPIW scheme allows less complexity in terms of number of optical gates required, while it substantially outperforms the widely accepted SPL scheme. The authors therefore believe that the SPIW and SPOW schemes are promising alternatives to the conventional SPN and SPL schemes for the implementation of next-generation optical packet switching systems.
Analysis of an optical packet switch with partially shared buffer and wavelength conversion
An analytical approach based on a reduced Markov chain (RMC) model of an optical packet switch with partially shared output buffer has been presented and a combined scheme for the contention resolution in optical packet switches has been proposed. The proposed scheme takes the advantage of output buffering, shared buffering and wavelength conversion to enhance the switch performance. The performance evaluation of the switch architecture based on RMC modelling has been validated through extensive simulation. Moreover, for a self-similar input traffic, the switch performance has been shown to achieve further improvement if a traffic shaping mechanism is incorporated at the input end of the switch architecture.
Performance evaluation of optical packet switches equipped with heterogeneous wavelength converters
Optics Express, 2009
An optical packet switch that shares both limited range and full range wavelength converters for contention resolution is proposed with the aim to guarantee a high conversion cost saving. To optimally dimension the number and the conversion range of the wavelength converters, an analytical model, validated by simulation, is introduced. Numerical results show that the proposed switch architecture allows for a conversion cost saving in the order of 90% with respect to a traditional architecture in which only shared full range wavelength converters are used.
Performance analysis of an optical packet switch with shared parametric wavelength converters
IEEE Communications Letters, 2000
The surge of facilitating the ever-growing number of service classes in the contemporary Internet backbone has persuaded researches worldwide to search for suitable underlying network topologies with desirable properties. Even in the presence of speedy optical technologies, the arrangement of nodes in a network can be highly influential in boosting network performance. Among all the topologies investigated so far, k-ary n-cubes have been reported to be widely adopted in the literature. However in a hybrid network, where the network comprises of a mixture of different types of topologies, the type and size of k-ary n-cubes can greatly influence the performance factor of the network. The objective of this paper is twofold. Firstly, we introduce a set of new metrics that can be used to analyze the performance behavior of simple regular meshes with their wrap-around variants (2-D and 3-D torus) for the Optical Packet Switching (OPS) paradigm. We then propose a simple and yet efficient switch-level analytical model for service differentiation in OPS in the presence of wavelength converters (WCs). The proposed model is further extended to include the impact of Fiber Delay Lines (FDLs) as well. Simulations are conducted for both cases to corroborate the accuracy of the models presented.
Journal of Lightwave Technology, 2008
An architecture is proposed for a Wavelength Division Multiplexed (WDM) optical packet switch equipped with both limited range wavelength converters (LRWCs) and shared full range wavelength converters (FRWCs). The FRWCs are used to overcome the performance degradation in terms of Packet Loss Probability due to the use of LRWCs only. A probabilistic model is proposed to dimension the number of shared FRWCs so that the same Packet Loss Probability of a switch equipped with only shared FRWCs is guaranteed. After introducing a cost model of the converters depending on the range conversion, we show that the architecture may allow a conversion cost saving in the order of 90%.
Architectures and performance of optical packet switching nodes
2006
ABSTRACT Packet switching over wavelength division multiplexing (WDM) channels is considered with the aim to investigate algorithms for wavelength assignment and to define feasible switch architectures, in the presence of connectionless or connection-oriented transfer modes. In particular, as regards the connection-oriented scenario, mapping of virtual connections onto wavelengths operated by network nodes is considered and procedures are proposed to achieve statistical multiplexing efficiency by dynamic wavelength re-assignment. Switch architectures to support dynamic wavelength encoding and the related performance evaluation are presented and discussed in the paper, evidencing the benefits of packet switching over WDM.