3,413 research outputs found
Active architecture for pervasive contextual services
International Workshop on Middleware for Pervasive and Ad-hoc Computing MPAC 2003), ACM/IFIP/USENIX International Middleware Conference (Middleware 2003), Rio de Janeiro, Brazil This work was supported by the FP5 Gloss project IST2000-26070, with partners at Trinity College Dublin and Université Joseph Fourier, and by EPSRC grants GR/M78403/GR/M76225, Supporting Internet Computation in Arbitrary Geographical Locations, and GR/R45154, Bulk Storage of XML Documents.Pervasive services may be defined as services that are available "to any client (anytime, anywhere)". Here we focus on the software and network infrastructure required to support pervasive contextual services operating over a wide area. One of the key requirements is a matching service capable of as-similating and filtering information from various sources and determining matches relevant to those services. We consider some of the challenges in engineering a globally distributed matching service that is scalable, manageable, and able to evolve incrementally as usage patterns, data formats, services, network topologies and deployment technologies change. We outline an approach based on the use of a peer-to-peer architecture to distribute user events and data, and to support the deployment and evolution of the infrastructure itself.Peer reviewe
Active architecture for pervasive contextual services
Pervasive services may be defined as services that are available to any client (anytime, anywhere). Here we focus on the software and network infrastructure required to support pervasive contextual services operating over a wide area. One of the key requirements is a matching service capable of assimilating and filtering information from various sources and determining matches relevant to those services. We consider some of the challenges in engineering a globally distributed matching service that is scalable, manageable, and able to evolve incrementally as usage patterns, data formats, services, network topologies and deployment technologies change. We outline an approach based on the use of a peer-to-peer architecture to distribute user events and data, and to support the deployment and evolution of the infrastructure itself
Evaluation of an awareness distribution mechanism: a simulation approach
In distributed software engineering, the role of informal communication is frequently overlooked. Participants simply employ their own ad-hoc methods of informal communication. Consequently such communication is haphazard, irregular, and rarely recorded as part of the project documentation. Thus, a need for tool support to facilitate more systematic informal communication via awareness has been identified. The tool proposed is based on the provision of awareness support that recognises the complete context of the evolution of software artefacts rather than single events.
Peer-to-Peer (P2P) networking has been successfully
employed to develop various distributed software engineering support tools. However, there are scalability problems inherent in naive P2P networks. To this end a semantic overlay network organisation algorithm has been developed and tested in simulation prior to deployment as part of a forthcoming awareness extension to the Eclipse environment.
The simulation verified that the self-organisation algorithm was suitable for arranging a P2P network, but several unexpected behaviours were observed. These included
wandering nodes, starved nodes, and local maxima. Each
of these problems required modification of the original algorithm design to solve or ameliorate them
Stochastic Analysis of a Churn-Tolerant Structured Peer-to-Peer Scheme
We present and analyze a simple and general scheme to build a churn
(fault)-tolerant structured Peer-to-Peer (P2P) network. Our scheme shows how to
"convert" a static network into a dynamic distributed hash table(DHT)-based P2P
network such that all the good properties of the static network are guaranteed
with high probability (w.h.p). Applying our scheme to a cube-connected cycles
network, for example, yields a degree connected network, in which
every search succeeds in hops w.h.p., using messages,
where is the expected stable network size. Our scheme has an constant
storage overhead (the number of nodes responsible for servicing a data item)
and an overhead (messages and time) per insertion and essentially
no overhead for deletions. All these bounds are essentially optimal. While DHT
schemes with similar guarantees are already known in the literature, this work
is new in the following aspects:
(1) It presents a rigorous mathematical analysis of the scheme under a
general stochastic model of churn and shows the above guarantees;
(2) The theoretical analysis is complemented by a simulation-based analysis
that validates the asymptotic bounds even in moderately sized networks and also
studies performance under changing stable network size;
(3) The presented scheme seems especially suitable for maintaining dynamic
structures under churn efficiently. In particular, we show that a spanning tree
of low diameter can be efficiently maintained in constant time and logarithmic
number of messages per insertion or deletion w.h.p.
Keywords: P2P Network, DHT Scheme, Churn, Dynamic Spanning Tree, Stochastic
Analysis
Diffusive capture processes for information search
We show how effectively the diffusive capture processes (DCP) on complex
networks can be applied to information search in the networks. Numerical
simulations show that our method generates only 2% of traffic compared with the
most popular flooding-based query-packet-forwarding (FB) algorithm. We find
that the average searching time, , of the our model is more scalable than
another well known $n$-random walker model and comparable to the FB algorithm
both on real Gnutella network and scale-free networks with $\gamma =2.4$. We
also discuss the possible relationship between and , the second
moment of the degree distribution of the networks
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