1,721,130 research outputs found
Simulation and Analytical Approximation of ATM Multistage Shared Buffer Switch
No full textA multistage ATM switch based on Clos interconnection of shared buffer switching elements is analyzed with the aim to develop design tools suitable for switch dimensioning in the range of ATM cell loss target. Starting from a simulation activity, which obtains the main switch performance and shows the effects of architectural and operational options, an approximated model is proposed. It is based on the discovery that statistical correlations in later stages of Clos network reduces so that it is feasible to treat different queue lengths as independent random variables to evaluate the cell loss performance of a shared buffer switching element. Approximate dimensioning of the whole switch is also performed. Results are given and verified in the range tractable by simulation for uniform and multiplexed bursty traffi
TCP Performance over Optical Burst-Switched Networks with Different Access Technologies
No full textDifferent access networks are here considered when interconnected with an optical wide area network based on the optical burst switching transfer mode. End-to-end performance is evaluated when the TCP protocol is employed. The effects on TCP of access network protocols and of the burst assembly procedure performed at the ingress edge nodes are evaluated both in wired and wireless scenarios, with optical and electrical technologies. The influence of the assembly time out in the different access contexts is presented and numerical investigations are performed by means of ns-2 simulations.Results show that end-to-end throughput is mostly influenced by the delay introduced by access protocols, which arises in the different scenarios, and by the assembly time out. These results provide meaningful insights for the overall system design and, in particular, for the setting of the inter-working unit parameters
Comparative analysis of power consumption in asynchronous wavelength modular optical switching fabrics
No full textNext-generation optical routers will be designed to support the flexibility required by Future Internet services and, at the same time, to overcome the power consumption bottleneck which appears to limit throughput scalability in today routers. A model to evaluate average power consumption in asynchronous optical switching fabrics is here presented to compare these architectures with other synchronous and asynchronous solutions. The combination of wavelength modular switching fabrics with low spatial complexity and asynchronous operation is demonstrated to be the most power-efficient solution among those considered which employ wavelength converters, through presentation and discussion of a thorough set of numerical results. (C) 2011 Elsevier B.V. All rights reserved
TCP Performance in Hybrid Multigranular OBS Networks
No full textThis paper studies TCP performance with different offset times which arise when hybrid multi-granular technology is employed in OBS core nodes. Multi-granular switches are promising devices to match dynamic application needs while optimizing switch costs and feasibility. They foster optical burst switching in multi-service contexts where switching matrices are designed and optimized in application awareness. OBS base offset time is strictly dependent on switching matrix set up time which, in presence of hybrid technology, is different from path to path. These differences impact on end-to-end performance and in particular on TCP throughput. This work studies end-to-end performance for two basic classes of connections, namely slow and fast connections. Simulations results based on a careful set up of ns-2 simulations according to test bed configurations described in literature are provided to show the effects of the employment of different optical technologies on the TCP throughput
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
3-Level Integrated Hybrid Optical Network (3LIHON) to Meet Future QoS Requirements
No full textThis paper presents a new hybrid network architecture including different transport technologies to support a wide range of services. In particular the proposed hybrid network provides three service levels, and a possible set of foreseeable services with different QoS needs is mapped into these levels to show the effectiveness of the hybrid networking in managing multi-service requests. In the switching nodes of the network, each service level is associated to a different switching technology, thus optimizing the switch implementation. In the nodes of the network, the service levels are distinguished based on optical encoding techniques, while an output collision stage manages the access to the output wavelengths. Performance studies show the effectiveness of the output collision mechanism
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Sharing Wavelength Converters in Multistage Optical Packet Switches
No full textThis paper describes a multistage switch based on the broadcast-and-select principle. It implements shared per node wavelength conversion for contention resolution in optical packet-switched networks. A novel scheduling algorithm is proposed to control packet forwarding in synchronous context. An analytical model is provided to calculate the packet loss probability related to the multistage configuration. Results show how the sharing of wavelength converters impacts on node performance, and provide a meaningful support for cost-performance benchmarking studies
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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