29 research outputs found
DHash table
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2006.Includes bibliographical references (p. 123-132) and index.DHash is a new system that harnesses the storage and network resources of computers distributed across the Internet by providing a wide-area storage service, DHash. DHash frees applications from re-implementing mechanisms common to any system that stores data on a collection of machines: it maintains a mapping of objects to servers, replicates data for durability, and balances load across participating servers. Applications access data stored in DHash through a familiar hash-table interface: put stores data in the system under a key; get retrieves the data. DHash has proven useful to a number of application builders and has been used to build a content-distribution system [31], a Usenet replacement [115], and new Internet naming architectures [130, 129]. These applications demand low-latency, high-throughput access to durable data. Meeting this demand is challenging in the wide-area environment. The geographic distribution of nodes means that latencies between nodes are likely to be high: to provide a low-latency get operation the system must locate a nearby copy of the data without traversing high-latency links.(cont.) Also, wide-area network links are likely to be less reliable and have lower capacities than local-area network links: to provide durability efficiently the system must minimize the number of copies of data items it sends over these limited capacity links in response to node failure. This thesis describes the design and implementation of the DHash distributed hash table and presents algorithms and techniques that address these challenges. DHash provides low-latency operations by using a synthetic network coordinate system (Vivaldi) to find nearby copies of data without sending messages over high-latency links. A network transport (STP), designed for applications that contact a large number of nodes, lets DHash provide high throughput by striping a download across many servers without causing high packet loss or exhausting local resources. Sostenuto, a data maintenance algorithm, lets DHash maintain data durability while minimizing the number of copies of data that the system sends over limited-capacity links.by Frank Dabek.Ph.D
Large-Scale Indexing, Discovery, and Ranking for the Internet of Things (IoT)
Network-enabled sensing and actuation devices are key enablers to connect real-world objects to the cyber world. The Internet of Things (IoT) consists of the network-enabled devices and communication technologies that allow connectivity and integration of physical objects (Things) into the digital world (Internet). Enormous amounts of dynamic IoT data are collected from Internet-connected devices. IoT data are usually multi-variant streams that are heterogeneous, sporadic, multi-modal, and spatio-temporal. IoT data can be disseminated with different granularities and have diverse structures, types, and qualities. Dealing with the data deluge from heterogeneous IoT resources and services imposes new challenges on indexing, discovery, and ranking mechanisms that will allow building applications that require on-line access and retrieval of ad-hoc IoT data. However, the existing IoT data indexing and discovery approaches are complex or centralised, which hinders their scalability. The primary objective of this article is to provide a holistic overview of the state-of-the-art on indexing, discovery, and ranking of IoT data. The article aims to pave the way for researchers to design, develop, implement, and evaluate techniques and approaches for on-line large-scale distributed IoT applications and services
Introducing the new paradigm of Social Dispersed Computing: Applications, Technologies and Challenges
[EN] If last decade viewed computational services as a utility then surely
this decade has transformed computation into a commodity. Computation
is now progressively integrated into the physical networks in
a seamless way that enables cyber-physical systems (CPS) and the
Internet of Things (IoT) meet their latency requirements. Similar to
the concept of ¿platform as a service¿ or ¿software as a service¿, both
cloudlets and fog computing have found their own use cases. Edge
devices (that we call end or user devices for disambiguation) play the
role of personal computers, dedicated to a user and to a set of correlated
applications. In this new scenario, the boundaries between
the network node, the sensor, and the actuator are blurring, driven
primarily by the computation power of IoT nodes like single board
computers and the smartphones. The bigger data generated in this
type of networks needs clever, scalable, and possibly decentralized
computing solutions that can scale independently as required. Any
node can be seen as part of a graph, with the capacity to serve as a
computing or network router node, or both. Complex applications can
possibly be distributed over this graph or network of nodes to improve
the overall performance like the amount of data processed over time.
In this paper, we identify this new computing paradigm that we call
Social Dispersed Computing, analyzing key themes in it that includes
a new outlook on its relation to agent based applications. We architect
this new paradigm by providing supportive application examples that
include next generation electrical energy distribution networks, next
generation mobility services for transportation, and applications for
distributed analysis and identification of non-recurring traffic congestion
in cities. The paper analyzes the existing computing paradigms
(e.g., cloud, fog, edge, mobile edge, social, etc.), solving the ambiguity
of their definitions; and analyzes and discusses the relevant foundational
software technologies, the remaining challenges, and research
opportunities.Garcia Valls, MS.; Dubey, A.; Botti, V. (2018). Introducing the new paradigm of Social Dispersed Computing: Applications, Technologies and Challenges. Journal of Systems Architecture. 91:83-102. https://doi.org/10.1016/j.sysarc.2018.05.007S831029
Hydrodynamics-Biology Coupling for Algae Culture and Biofuel Production
International audienceBiofuel production from microalgae represents an acute optimization problem for industry. There is a wide range of parameters that must be taken into account in the development of this technology. Here, mathematical modelling has a vital role to play. The potential of microalgae as a source of biofuel and as a technological solution for CO2 fixation is the subject of intense academic and industrial research. Large-scale production of microalgae has potential for biofuel applications owing to the high productivity that can be attained in high-rate raceway ponds. We show, through 3D numerical simulations, that our approach is capable of discriminating between situations where the paddle wheel is rapidly moving water or slowly agitating the process. Moreover, the simulated velocity fields can provide lagrangian trajectories of the algae. The resulting light pattern to which each cell is submitted when travelling from light (surface) to dark (bottom) can then be derived. It will then be reproduced in lab experiments to study photosynthesis under realistic light patterns