1,721,261 research outputs found
Shaping opportunistic networks
No full textThis paper deals with the problem of identifying and managing overlay topologies in opportunistic networks. To make this possible, we define the concept of “link” in an opportunistic network, which cannot be represented as a simple communication connection between two nodes at a given instant (as in classic MANETs). Rather, links represent contacts among nodes arising during a (non-instantaneous) time interval. With this definition in view, opportunistic networks can be seen as evolving graphs. The interesting thing is that it becomes possible to control the way nodes manage contacts and build overlays based on some desired overlay topology. This is an important result, since the statistical characteristics of the topology allow estimating the ability of the opportunistic network to spread contents. An experimental assessment based on a trace-driven simulation employing different types of datasets (ranging from urban dense networks to very sparse ones) confirms the viability of the proposed approach
On the Degree Distribution of Faulty Peer-to-Peer Overlay Networks
No full textThis paper presents an analytical approach to model fault-tolerance in P2P overlays, represented as complex networks. We define a distributed protocol for managing the overlay and reacting to node faults; peers try to maintain a desired degree and make (accept) requests for creating links only if their actual degree is lower than their desired degree. Based on the protocol, evolution equations are defined and manipulated by resorting to generating functions. Obtained outcomes provide insights on the nodes' degree probability distribution. We study different networks, characterized by three specific desired degree distributions, i.e.~fixed desired degree, random graphs and power law. All these networks are assessed via the analytical tool and simulation as well. Results show that based on the provided mathematical model, it is possible to properly tune the average attachment rate at peers so as they are enabled to maintain their own desired degree
Associate Editor for the Journal of Grid and Distributed Computing
No full textThe Journal of Grid and Distributed Computing, ISSN: 2249-7056 (Print) & E-ISSN: 2249–7064 (Online), aims to publish all the latest and outstanding research articles, reviews and letters in all areas of Grid and Distributed Computing. Each issue contains a series of timely, in-depth written articles by leaders in the field, covering a wide range of the integration of multidimensional challenges of research including integration issues of Grid and Distributed Computing
On the Degree Distribution of Opportunistic Networks
No full textThis paper presents an analytical approach to model opportunistic networks, with mobile devices that may concurrently employ multiple networks. By modeling these systems as complex networks, it is possible to obtain information on the degree probability distribution of nodes. Such a metric provides insights on the connectivity of the opportunistic network. The analytical tool is assessed via simulation
Cheating Detection Through Game Time Modeling: A Better Way to Avoid Time Cheats in P2P MOGs?
No full textCheating is a key issue in online games. Whatever the rules that govern a game, some players will always be tempted to break or elude these rules so as to gain an unfair advantage over other players. Mitigation schemes are thus needed in online gaming platforms. However, it is widely recognized that typical cheating prevention schemes introduce complications and overheads in the distributed game system, which may seriously jeopardize the online gaming experience. It turns out that, often, detecting the cheaters, instead of preventing the cheats, could represent a viable solution,
especially for time cheats. We present a general framework able to model game time advancements in P2P online games. Based on this framework, time cheat detection schemes can be easily devised,
which monitor the communication patterns among peers and do not affect the performances of the game system. To provide evidence of our claim, we present in this paper two different time cheats,
namely fast rate cheat and look-ahead cheat, and discuss on practicable methods to detect them. Simulation results confirm the viability of the proposed approach
Editorial Board for ISRN Epidemiology
No full textISRN Epidemiology is a peer-reviewed, open access journal that publishes original research articles, review articles, and clinical studies in all areas of epidemiology.
ISRN Epidemiology is part of the ISRN series of peer-reviewed, open access journals that are designed to provide a fast peer review process for all submitted manuscripts. Every ISRN journal is collaboratively run by a relatively large, international Editorial Board of experts in the subject area of the journal
Modeling Faulty, Unstructured P2P Overlay
No full textUnstructured peer-to-peer systems represent viable candidates for supporting distributed applications with frequent node failures.
This paper presents a framework to study the reliability of evolving overlay networks in presence of faulty nodes. We focus on the node degree distribution, an important metric to understand whether the topology of the overlay can be maintained in presence of peer churns. From the degree distribution, other metrics can be estimated such as the diameter of the net. Two protocols are considered, which differ in the way peers attach to other nodes. Numerical results are compared with those obtained through simulation. They confirm that the proposed model can be factually exploited to adapt the peers' behavior and preserve the desired topology of the overlay
Gossiping for Resource Discovering: an Analysis based on Complex Network Theory
No full textThis paper analyzes the adoption of unstructured P2P overlay networks to build resource discovery services. We consider a simple distributed communication protocol, which is based on gossip and on the local knowledge each node has about resources hold by its neighbors. In particular, upon reception (or generation) of a novel query, a node relays the message to those neighbors that have resources whose profile matches the query. Moreover, the node gossips the query to other remaining neighbors, so that the query can be disseminated through the overlay. A mathematical analysis is provided to estimate the number of nodes receiving the query (and consequently, the portion of query hits), based on the network topology, resource availability and gossip probability. Results show that the use of unstructured networks, coupled with simple dissemination protocols, represent a viable approach to build P2P resource discovery systems
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
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