3,109,941 research outputs found
A peer-to-peer infrastructure for resilient web services
No full textThis work is funded by GR/M78403 “Supporting Internet Computation in Arbitrary Geographical Locations” and GR/R51872 “Reflective Application Framework for Distributed Architectures”, and by Nuffield Grant URB/01597/G “Peer-to-Peer Infrastructure for Autonomic Storage Architectures”This paper describes an infrastructure for the deployment and use of Web Services that are resilient to the failure of the nodes that host those services. The infrastructure presents a single interface that provides mechanisms for users to publish services and to find hosted services. The infrastructure supports the autonomic deployment of services and the brokerage of hosts on which services may be deployed. Once deployed, services are autonomically managed in a number of aspects including load balancing, availability, failure detection and recovery, and lifetime management. Services are published and deployed with associated metadata describing the service type. This same metadata may be used subsequently by interested parties to discover services. The infrastructure uses peer-to-peer (P2P) overlay technologies to abstract over the underlying network to deploy and locate instances of those services. It takes advantage of the P2P network to replicate directory services used to locate service instances (for using a service), Service Hosts (for deployment of services) and Autonomic Managers which manage the deployed services. The P2P overlay network is itself constructed using novel Web Services-based middleware and a variation of the Chord P2P protocol, which is self-managing
Analysis of current middleware used in peer-to-peer and grid implementations for enhancement by catallactic mechanisms
No full textThis deliverable describes the work done in task 3.1, Middleware analysis: Analysis of current middleware used in peer-to-peer and grid implementations for enhancement by catallactic mechanisms from work package 3, Middleware Implementation. The document is divided in four parts: The introduction with application scenarios and middleware requirements, Catnets middleware architecture, evaluation of existing middleware toolkits, and conclusions. -- Die Arbeit definiert Anforderungen an Grid und Peer-to-Peer Middleware Architekturen und analysiert diese auf ihre Eignung für die prototypische Umsetzung der Katallaxie. Eine Middleware-Architektur für die Umsetzung der Katallaxie in Application Layer Netzwerken wird vorgestellt.Grid Computing
A Survey of Peer-to-Peer Architectures for Service Oriented Computing
No full textPeer-to-peer file sharing has become popular for many kinds of resource location and distribution applications including file sharing, distributed computation, multi-media messaging and content distribution. Peer-to-peer approaches also have significant potential for supporting large scale, decentralised service oriented computing. This chapter discusses each class of contemporary P2P architecture in turn and discusses the suitability of each architecture class for supporting service oriented computing. Future trends in peer-to-peer architectures are then discussed and multi-layer peer-to-peer architectures are highlighted as a promising platform for supporting service oriented computing. This chapter then concludes with a discussion of outstanding issues that must be addressed before peer-to-peer architectures can offer adequate support for service oriented computing
Rede peer-to-peer para imagem médica
No full textMestrado em Engenharia de Computadores e TelemáticaNos últimos anos, a imagem médica em formato digital tem sido uma
ferramenta cada vez mais importante quer para o diagnóstico médico quer
para o auxílio ao tratamento. Assim, equipamentos de aquisição digital e
repositórios de imagem médica são cada vez mais comuns em instituições de
saúde, podendo até haver mais que um repositório numa instituição. No
entanto, esta proliferação de repositórios leva a que a informação esteja
dispersa nos vários locais. Esta dispersão da informação juntamente com as
diferenças no armazenamento entre instituições são claros obstáculos à
pesquisa e acesso integrado a essa informação. Esta dissertação visa o
estudo da tecnologia Peer-to-Peer de forma a minimizar os problemas
associados à dispersão e heterogeneidade da informação.In the last years, digital medical imaging has been an increasingly important
tool for both medical diagnostic and treatment assistance. Therefore, digital
image acquisition equipments and medical imaging repositories are more and
more common in a healthcare institution, being possible even more than one
repository in one institution. However, this proliferation of repositories leads to
dispersion of data between many places. This data dispersion associated with
differences in the data storage between institutions are evident obstacles to
the search for medical data. This dissertation aims to the study of the Peer-to-
Peer technology in order to minimize the problems related to the dispersion
and heterogeneity of medical data
Use of context-awareness in mobile peer-to-peer networks
No full textMobile ad-hoc network are an emerging research field due to the potential range of applications that they support and for the problems they present due to their dynamic nature. Peer-to-peer is an example of a class of applications that have recently been deployed on top of ad-hoc networks. In this paper we propose an approach based on context-awareness to allow peer-to-peer applications to exploit information on the underlying network context to achieve better performance and better group organization. Information such as availability of resources, battery power, services in reach and relative distances can be used to improve the routing structures of the peer-to-peer network, thus reducing the routing overhead
Peer Support Workers’ Experience of an Intentional Peer Support Scheme on an Acute Psychiatric Ward
No full textThis paper reports on a study which formed part of a multi-perspective evaluation of an Intentional Peer Support scheme within an adult acute psychiatric inpatient setting. The objectives of the evaluation were twofold. Firstly, to explore the experience of Peer Support Workers (PSW) in their new role and, secondly, to examine the extent to which peer support may contribute towards recovery-based practice within the context of the NHS.
PSWs were recruited by a mental health charity for the purpose of the scheme within an inner city borough. The study employed a qualitative methodology. Two focus groups were conducted with PSWs. The findings highlighted that participants described both positive aspects, such as personal growth and adaptation, and challenges in relation to their new role as PSW. Initial challenges, particularly around working relationships with staff, were subsequently overcome during the study period. These findings contribute towards developing an evidence base for the value of the Intentional Peer Support services within the context of recovery-based NHS mental health services
Attrition Defenses for a Peer-to-Peer Digital Preservation System
No full textIn peer-to-peer systems, attrition attacks include both traditional, network-level denial of service attacks as well as application-level attacks in which malign peers conspire to waste loyal peers' resources. We describe several defenses for LOCKSS, a peer-to-peer digital preservation system, that help ensure that application-level attacks even from powerful adversaries are less effective than simple network-level attacks, and that network-level attacks must be intense, wide-spread, and prolonged to impair the system.
Peer Review for Journals: Evidence on Quality Control, Fairness, and Innovation
No full textI reviewed the published empirical evidence concerning journal peer review, which consisted of 68 papers, all but three published since 1975. Peer review improves quality, but its use to screen papers has met with limited success. Current procedures to assure quality and fairness seem to discourage scientific advancement, especially important innovations, because findings that conflict with current beliefs are often judged to have defects. Editors can use procedures to encourage the publication of papers with innovative findings such as invited papers, early-acceptance procedures, author nominations of reviewers, results-blind reviews, structured rating sheets, open peer review, and, in particular, electronic publication. Some journals are currently using these procedures. The basic principle behind the proposals is to change the decision from whether to publish a paper to how to publish itpeer review, journals, publications
A Sybilproof Indirect Reciprocity Mechanism for Peer-to-Peer Networks
No full textAlthough direct reciprocity (Tit-for-Tat) contribution systems have been successful in reducing free-loading in peer-to-peer overlays, it has been shown that, unless the contribution network is dense, they tend to be slow (or may even fail) to converge [1]. On the other hand, current indirect reciprocity mechanisms based on reputation systems tend to be susceptible to sybil attacks, peer slander and whitewashing.In this paper we present PledgeRoute, an accounting mechanism for peer contributions that is based on social capital. This mechanism allows peers to contribute resources to one set of peers and use this contribution to obtain services from a different set of peers, at a different time. PledgeRoute is completely decentralised, can be implemented in both structured and unstructured peer-to-peer systems, and it is resistant to the three kinds of attacks mentioned above.To achieve this, we model contribution transitivity as a routing problem in the contribution network of the peer-to-peer overlay, and we present arguments for the routing behaviour and the sybilproofness of our contribution transfer procedures on this basis. Additionally, we present mechanisms for the seeding of the contribution network, and a combination of incentive mechanisms and reciprocation policies that motivate peers to adhere to the protocol and maximise their service contributions to the overlay
Parallelisation for data-intensive applications over peer-to-peer networks
No full textIn Data Intensive Computing, properties of the data that are the input for
an application decide running performance in most cases. Those properties include
the size of the data, the relationships inside data, and so forth. There is a
class of data intensive applications (BLAST, SETI@home, Folding@Home and
so on so forth) whose performances solely depend on the amount of input data.
Another important characteristic of those applications is that the input data can be
split into units and these units are not related to each other during the runs of the
applications. This characteristic helps this class of data intensive applications to
be parallelised in the way where the input data is split into units and application
runs on different computer nodes for certain portion of the units. SETI@home and
Folding@Home have been successfully parallelised over peer-to-peer networks.
However, they suffer from the problems of single point of failure and poor scalability.
In order to solve these problems, we choose BLAST as our example data
intensive applications and parallelise BLAST over a fully distributed peer-to-peer
network.
BLAST is a popular bioinformatics toolset which can be used to compare
two DNA sequences. The major usage of BLAST is searching a query of sequences
inside a database for their similarities so as to identify whether they are
new. When comparing single pair of sequences, BLAST is efficient. However,
due to growing size of the databases, executing BLAST jobs locally produces
prohibitively poor performance. Thus, methods for parallelising BLAST are
sought.
Traditional BLAST parallelisation approaches are all based on clusters.
Clusters employ a number of computing nodes and high bandwidth interlinks between
nodes. Cluster-based BLAST exhibits higher performance; nevertheless,
clusters suffer from limited resources and scalability problems. Clusters are expensive, prohibitively so when the growth of the sequence database are taken into
account. It involves high cost and complication when increasing the number of
nodes to adapt to the growth of BLAST databases. Hence a Peer-to-Peer-based
BLAST service is required.
This thesis demonstrates our parallelisation of BLAST over Peer-to-Peer
networks (termed ppBLAST), which utilises the free storage and computing resources
in the Peer-to-Peer networks to complete BLAST jobs in parallel. In order
to achieve the goal, we build three layers in ppBLAST each of which is responsible
for particular functions. The bottom layer is a DHT infrastructure with the
support of range queries. It provides efficient range-based lookup service and
storage for BLAST tasks. The middle layer is the BitTorrent-based database distribution.
The upper layer is the core of ppBLAST which schedules and dispatches
task to peers. For each layer, we conduct comprehensive research and the
achievements are presented in this thesis.
For the DHT layer, we design and implement our DAST-DHT. We analyse
balancing, maximum number of children and the accuracy of the range query.
We also compare the DAST with other range query methodology and state that if
the number of children is adjusted to more two, the performance of DAST overcomes
others. For the BitTorrent-like database distribution layer, we investigate
the relationship between the seeding strategies and the selfish leechers (freeriders
and exploiters). We conclude that OSS works better than TSS in a normal situation
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