122 research outputs found
A dynamically adaptive, unstructured multicast overlay
No full textThe simplicity of multicast as a communication primitive belies its broad utility as a building block for distributed applications. Nevertheless, creating and maintaining multicast structures can be challenging, particularly when networks are transient and/or dynamic. We introduce a new unstructured multi-source multicast (UMM) overlay approach that we argue is less complex than, but as efficient as, current state-of-the-art solutions based either on structured overlays or on running full routing protocols at the overlay level. UMM builds a base overlay independently from the routing mechanisms employed to route messages. On top of this base overlay, it selects distribution trees for each multicast source by first flooding the base overlay and then using the implicit information contained in duplicated messages to select and filter out redundant tunnels. Simple heuristics are used to maintain and evolve both the base overlay and the multicast distribution trees in response to changes in the set of overlay participants or in underlying network conditions. We experiment on a 65-node PlanetLab deployment and on ModelNet emulated distributed platforms to quantify the overheads associated with UMM operation and to explore its performance and adaptability to changes in the underlying network conditions
A problem-specific fault-tolerance mechanism for asynchronous, distributed systems
No full textThe idle computers on a local area, campus area, or even wide area network represent a significant computational resource—one that is, however, also unreliable, heterogeneous, and opportunistic. We describe an algorithm that allows branch-and-boundproblems to be solved in such environments. In designing this algorithm, we faced two challenges: (1) scalability, to effectively exploit the variably sized pools of resources available, and (2) fault tolerance, to ensure the reliability of services. We achieve scalability through a fully decentralized algorithm, in which the dynamically available resources are managed through a membership protocol. We guarantee fault tolerance in the sense that the loss of up to all but one resource will not affect the quality of the solution. For propagating information reliably, we use epidemic communication for both the membership protocol and the fault-tolerance mechanism. We have developed a simulation framework that allows us to evaluate design alternatives. Results obtained in this framework suggest that our techniques can execute scalably and reliably. 1
Control y automatización mediante MATLAB de un banco de calibración e instrumentación asociada
No full textEn este trabajo se lleva a cabo la automatización de un banco de calibración de cinco grados
de libertad, que permita realizar movimientos de manera programada y automática para
captar y almacenar las señales recibidas en los sensores, procedentes de un emisor, en las
diferentes posiciones y orientaciones. Esta información, tras ser procesada, permitirá caracterizar el comportamiento y determinar los parámetros de los sensores. La automatización
de movimientos, del control de la emisión y de la captura de señales procedentes de los
sensores se realizan con MATLAB, donde también se podrán procesar, en el futuro, las señales obtenidas para obtener la caracterización de los sensores bajo estudio.This work involves the automation of a calibration bench of five degrees of freedom is carried
out, which allows to perform movements in a programmed and automatic way to capture
and store the signals received in the sensors, coming from an emitter located in different
positions and orientations. This information, after being processed, will allow to characterize the behavior and determine the parameters of the sensors. The automation of movements, emission control and capture of signals coming from the sensors are carried out with
MATLAB, where the signals obtained can also be processed in the future to obtain the characterization of the sensors under study.Grado en Ingeniería en Tecnologías de Telecomunicació
A Problem-Specific Fault-Tolerance Mechanism for Asynchronous, Distributed Systems
No full textThe idle computers on a local area, campus area, or even wide area network represent a signi cant computational resource|one that is, however, also unreliable, heterogeneous, and opportunistic. This type of resource has been used eectively for embarrassingly parallel problems but not for more tightly coupled problems. We describe an algorithm that allows branch-and-bound problems to be solved in such environments. In designing this algorithm, we faced two challenges: (1) scalability, to eectively exploit the variably sized pools of resources available, and (2) fault tolerance, to ensure the reliability of services. We achieve scalability through a fully decentralized algorithm, by using a membership protocol for managing dynamically available resources. However, this fully decentralized design makes achieving reliability even more challenging. We guarantee fault tolerance in the sense that the loss of up to all but one resource will not aect the quality of the solution. F..
P2P Systems Meet Mobile Computing: A Community-Oriented Software Infrastructure for Mobile Social Applications
No full textThe widespread adoption of powerful mobile evices creates an unprecedented potential for innovative mobile applications that can enhance users\u27 social interactions. The current centralized mobile system and service architectures do not allow large-scale dynamic interactions be tween mobile devices, as required by these applications. This paper proposes Mobius, a decentralized solution that supports mobile social applications via a two-tier software infrastructure. In Mobius, a socially-aware peer-to-peer tier provides community-oriented data and persistent services for the mobile tier that runs the applications. © 2008 IEEE
A Heterophily-Based Polarization Measure for Multi-community Networks
No full textThis work proposes a heterophily-based metric for quantifying polarization in social networks where multiple ideological, antagonistic communities coexist. This metric captures node-level polarization and is built on user’s affinity towards other communities rather than their own. Node-level values can then be aggregated at the community, network, or sub-network level, providing a more detailed map of polarization. We tested our metric on the Polblogs network, White Helmets Twitter interaction network with two communities and the VoterFraud2020 domain network with five communities. We also tested our metric on dK-random graphs to verify that it results in low polarization scores, as expected. Finally, we compared our metric with two widely used polarization measures: Guerra’s polarization index and RWC.</p
G.: Filecules in High-Energy Physics: Characteristics and Impact on Resource Management
No full textGrid computing has reached the stage where deployments are mature and many collaborations run in production mode. Mature Grid deployments offer the opportunity for revisiting and perhaps updating traditional beliefs related to workload models, which in turn leads to the reevaluation of traditional resource management techniques. This paper analyzes usage patterns in a typical Grid community, a large-scale data-intensive scientific collaboration in high-energy physics. We focus mainly on data usage, since data is the major resource for this class of applications. Our observations led us to propose a new abstraction for resource management in scientific data analysis applications: we define a filecule as a group of files that is always used together. We show that filecules exist and present their characteristics. The existence of filecules suggests a new granularity for data management, which, if incorporated in design, can significantly outperform the traditional solutions for data caching, replication and placement based on single-file granularity. We reason about the impact of filecules on resource management and show compelling evidence for using this abstraction when designing data management services.
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