1,721,001 research outputs found
Sustainable Infrastructure Monitoring for Security-Oriented Purposes
No full textAs computing and communication infrastructures have gained an ever-increasing role in everybody's life, guaranteeing their reliability has become a critical endeavor. In the face of threats that grow more and more sophisticated, we must turn our attention to the techniques that have the potential to match them and scale with the infrastructure complexity. The current trend in the telecommunication industry towards "softwarized infrastructures"by means of new technologies such as Software Defined Networking and Network Function Virtualization may provide a innovative and effective solutions from this point of view. In this work, we outline a network security monitoring architecture aimed at striking the best trade-off between effectiveness and efficiency. This result is achieved by exploiting the possibility, already enabled by state-of-the-art, yet well tested components for infrastructural orchestration, of dynamic instantiation and composition of functions. We conclude that efficient detection of some classes of network-based denial-of-service attacks is possible, and open the path to mitigation strategies that optimize the usage of resources by deploying and re-configuring them as needed in real-time
Packet Optical Networks for High Speed TCP-IP Backbones
No full textThis article presents a new proposal for TCP-IP backbone.The proposed architecture merges the flexibility in resource management of packet switching with the high capacity offered by full optical technology
Flock: A Live Migration Protocol for SDN Controllers
No full textAvailability is a fundamental operational challenge of any networked system. Software-Defined Networks (SDN) and Network Function Virtualization (NFV) systems are no exception. While extensive work exists on lightweight virtual machines live migration, and SDN controllers are claimed to be only logically centralized, specifications for a live controller migration protocol have not been written yet.In this paper, we propose the design and implementation of Flock, a live controller migration protocol that works independently from the underlying software-defined infrastructure, a feature lacking in every related solution. We also propose the controller-switch assignment problem and show that no pseudo-polynomial algorithm exists to solve it, unless P=NP. Our initial evaluation results with the Ryu controller show expected minimal protocol overhead
Inter-Routes Fairness Strategies Inspired by Trunk Reservation Technique
No full textElastic Optical Network (EON) has emerged as a solution to manage different kinds of services, improving network scalability and efficiency. However, EONs tend to present differences in service performance due to the uneven bandwidth requirements. In addition, uneven network performance among routes with different hop counts is a known issue, affecting not only optical networks or EONs, but also computer networks. We call this problem inter-routes unfairness. In this letter we propose strategies based on the trunk reservation technique to solve it. Our results show that it is possible to deal with the inter-routes unfairness problem. We believe that this kind of strategy opens opportunities to be applied for connections traveling longer and more loaded routes, that would lead to a minimum impact in the overall network performance
Load balancing in fixed-routing optical networks with weighted ordering heuristics
Full text linkIn this paper we show that the adoption of a simple weighted ordering heuristic strategy to find fixed shortest path routes in a topology can improve load-balancing and, consequently, network performance. We compared our fixed routing strategies against the k-shortest paths (k-SP) fixed-alternate routing strategy for three different mesh topologies considering fixed grid networks (FGNs) and elastic optical networks (EONs). The results show that our simple fixed routing strategies can improve network performance for an optical network system, even compared with the fixed alternate routing and always using the shortest path. Results also show that such easy strategies act mainly in longer routes, increasing their probability of use and balancing the link load distribution
Robust Nonlinear Control of Miniature Fixed-Wing UAVs
No full textThis work focuses on the problem of letting the longitudinal dynamics of a miniature fixed-wing aerial vehicle to track a desired reference trajectory robustly with respect to possible uncertainties and exogenous disturbances such as, in particular, wind. As a main novelty, the proposed stabilizing controller is based on a numerical model inversion in which the nonlinear aerodynamic model obtained from experimental data is taken directly into account. The effectiveness and limitations of the proposed controller with respect to other approaches based on different approximations of the aerodynamic coefficients are pointed out both from a methodological viewpoint and by means of numerical results obtained with realistic aerodynamic models
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
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
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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