1,721,135 research outputs found
Editorial for Computer Networks special issue on "Measurement-based optimization of P2P networking and applications"
No full textOn the Analysis of Internet Paths with DisNETPerf, a Distributed Paths Performance Analyzer
Full text linkpeer reviewedTraceroute is the most widely used Internet path analysis tool today to study the topology of the Internet and to diagnose routing failures as well as poor performance events. A major limitation of traceroute when the destination is not controllable by the user is its inability to measure reverse paths, i.e., the path from any given destination back to the source. This is a major drawback for ISPs, who need to understand the performance of the Internet paths connecting popular services (e.g., YouTube and Facebook) to their customers. Even if public servers and distributed measurement platforms can provide partial reverse path visibility through ad-hoc measurements, there is still a need for a structured approach capable of analyzing the performance of Internet paths connecting any pair of nodes (servers, routers, hosts, etc.). While the problem of reverse traceroute has been addressed in the past, proposed techniques rely on IP address spoofing – which might lead to security concerns, and assume the availability of certain route-tracking options –, which might not be available. In this paper, we introduce and evaluate DisNETPerf, a new tool which provides exactly the same type of information as traceroute, but for paths connecting arbitrarily selected nodes. DisNETPerf works by firstly locating probes (i.e., measurement points) that are the closest to a given target node, using them to perform traceroute measurements from the target point-of-view to a given destination for path performance monitoring and troubleshooting purposes. We propose two techniques for probe location, and demonstrate that the reverse path (from server to users) can be measured with very high accuracy in certain scenarios. We also analyze relevant characteristics of Internet paths and distributed measurement platforms, which reinforce the applicability and relevance of DisNETPerf in current Internet
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Construction topologiquement avertie d'overlays sans structure sur des réseaux ad hocs
Full text linkThe number of electronic devices, equipped with a wireless interface hasexploded over the last decades. Unfortunately, their usage is often restricted to the connection to a wired infrastructure, even for local communications.That is quite surprising as the research area of infrastructureless, or ad hoc, networks has flourished for years. The literature on ad hoc networks is very rich, but their usage almost inexistent. Potential users have plenty of solutions at hand, but do not exploit them.Even if ad hoc networks allow us to get rid of the infrastructure, theystill require an implicit agreement on the solution to use. Nevertheless, it isvery dicult to pick in the rich panel of protocols the best one, that would fit any ad hoc user in any ad hoc network. As an example, it has beendemonstrated, for the routing, that each protocol has definite advantagesand disadvantages, in every different scenario, and is well suited for certainsituations.Yet, a salient feature of ad hoc networks is precisely that the panel ofsituations is very large. The ad hoc network conditions are influenced bythe number of ad hoc users, their relative positions, their capabilities, their mobility pattern, the applications they use, the traffic load and type, and so forth. Moreover, the users may themselves be heterogeneous, with different hardware and software capabilities, mobile behaviour and communication needs. Hence, there is a particular need in ad hoc networking for flexible techniques.We contribute to this problem by studying the feasibility of overlay routing and giving some hints in that direction.We explain how the overlay members can avoid the expensive process ofbuilding an overlay topology, before using their customised routing application.The rationale exploits the broadcast nature of ad hoc networks, and isqualified as a Reactive Overlay Approach. We also detail an elementary reactive overlay routing application and test it, by simulations, in a variety of conditions, including the network and overlay densities. This performance study shows the feasibility and the efficiency of overlay routing applications developed according to the Reactive Overlay Approach. It also evidences the impact of using an appropriate value for the neighbourhood range, defined as the maximum number of hops between two overlay neighbours.Hence, we detail the critical neighbourhood range (CNR) problem, which, in short, consists in determining the minimum neighbourhood range value that generates a connected overlay. We solve it in the asymptotic case, i.e. when the number of nodes in the underlay or the size of the field tends to infinity. The mathematical results are interesting in the sense that they can be useful for a better understanding of the interaction between various typical characteristics of a connected overlay topology on an ad hoc network.However, the theoretical, asymptotic, CNR is not adequate in practice.We thus also explore heuristics for estimating the CNR. We present a simpleprotocol which estimates an appropriate neighbourhood range for overlayrouting applications. For the purpose of its evaluation, we define generalperformance criteria based on overlay flooding. Namely, these are the deliverypercentage, bandwidth consumption and time duration of flooding onthe overlay.The main drawback of the Reactive Overlay Approach is the amount ofbandwidth consumed during the flooding of overlay route requests. Hence,we also consider the Proactive Overlay Approach, which consists in buildingthe overlay topology before the emission of any overlay broadcast message, and maintaining it. We compare the quality of various overlay topologies in the static case. We finally describe and evaluate the Overlay Topology Control (OTC) protocol, that maintains, in a mobile context, the overlay topology as close as possible to the overlay topology evaluated as the best.The main objection that would arise against overlay routing on ad hocnetworks is that the ad hoc nodes do generally own poor resources and thatoverlay routing consumes them even more than native routing.The feasibility study we conducted with the reactive approach and theevaluation of OTC, designed in the context of the proactive overlay approach, confirm that the consumption of resources must be handled carefully.Nevertheless, they show that this problem is not insurmountable
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