Resource sharing in peer-to-peer environments with selfish participants suffers from the free-riding phenomenon unless the environment provides appropriate countermeasures. We present a concept for a distributed deskt...
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Resource sharing in peer-to-peer environments with selfish participants suffers from the free-riding phenomenon unless the environment provides appropriate countermeasures. We present a concept for a distributed desktop grid which promotes fairness and inhibits free-riding. It contains a shared-history reputation mechanism designed for use in dynamic peer-to-peer systems. In simulations based on real-world network delay and workload information, we show that our concept offers a considerable speedup over non-distributed computation while effectively thwarting free-riding. Moreover, we assess the benefits of self-organizing super-peer overlays for Desktop Grids.
Scalability constitutes a key property in Peer-to-Peer environments. One way to foster this property is the introduction of super-peers, a concept which has gained widespread acceptance in recent years. We solve the p...
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Scalability constitutes a key property in Peer-to-Peer environments. One way to foster this property is the introduction of super-peers, a concept which has gained widespread acceptance in recent years. We solve the problem of selecting super- peers in a distributed, scalable, self-organized way, supported by network coordinates. To this end, we present an exact optimization model and introduce a distributed algorithm that addresses the problem in a decentralized fashion. By means of simulation using actual Internet distance measurements, we demonstrate the savings in communication cost attainable by our super-peer topology construction and maintenance scheme.
Scalability constitutes a property of particular interest when investigating Peer-to-Peer overlay behavior. Recent advances that improve scalability include super-peer infrastructures and network coordinates. To this ...
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Scalability constitutes a property of particular interest when investigating Peer-to-Peer overlay behavior. Recent advances that improve scalability include super-peer infrastructures and network coordinates. To this end, we introduce a lightweight simulation framework that focuses on Peer-to-Peer topology construction supported by network coordinates and optionally, super-peers. One of the design goals has been a straightforward way to re-use simulation code in practical applications. We illustrate the utility of our simulation framework by means of a comprehensive application case study that compares different network coordinates generation mechanisms in the context of a distributed super-peer topology construction effort.
In this paper we present a multilevel approach for the static routing and wavelength assignment (RWA) problem. The RWA deals with the problem of assigning paths and wavelengths to requests in optical communication net...
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In this paper we present a multilevel approach for the static routing and wavelength assignment (RWA) problem. The RWA deals with the problem of assigning paths and wavelengths to requests in optical communication networks. The multilevel approach is a general solution strategy involving stepwise coarsening the original problem instance, solving a simplified instance and expanding the solution back to the original size. We propose both a multilevel-inspired construction heuristic and a multilevel algorithm using iterated local search for refinement. These algorithms significantly improve previous approaches regarding time consumption and solution quality for large instances.
Network coordinates facilitate delay estimation in largescale networks. In particular, they support the creation of peer-to-peer-based desktop grid overlay structures. Landmark-based approaches to computing such coord...
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ISBN:
(纸本)9780769529172;0769529178
Network coordinates facilitate delay estimation in largescale networks. In particular, they support the creation of peer-to-peer-based desktop grid overlay structures. Landmark-based approaches to computing such coordinates have gained widespread acceptance in recent years. Several of these approaches produce coordinates by solving sequences of nonlinear unconstrained optimization problems. Apparently, Simplex Downhill has been the preferred method for solving such problems in the network coordinates context. In this paper, we propose a replacement for this algorithm. Our method works more accurately than Simplex Downhill and refrains from imposing additional requirements on the objective function.
We are interested in improving risk and reliability analysis of complex systems where our knowledge of system performance is provided by large simulation codes, and where moreover input parameters are known only impre...
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We are interested in improving risk and reliability analysis of complex systems where our knowledge of system performance is provided by large simulation codes, and where moreover input parameters are known only imprecisely. Such imprecision lends itself to interval representations of parameter values, and thence to quantifying our uncertainty through Dempster-Shafer or Probability Bounds representations on the input space. In this context, the simulation code acts as a large "black box" function f, transforming one input Dempster-Shafer structure on the line into an output random interval f(A). Our quantification of output uncertainty is then based on this output random interval.. If some properties of f are known, then some information about f(A) can be determined. But when f is a pure black box, we must resort to sampling approaches. We present the basic formalism of a Monte Carlo approach to sampling a functionally propagated general random set, as opposed to a random interval. We show that the results of straightforward formal definitions are mathematically coherent, in the sense that bounding and convergence properties are achieved.
Novel algorithms for determining optimal routes through a packet-switched, LEO satellite communications system having inter-linked satellites are presented. These algorithms have their foundations in the field of diff...
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Novel algorithms for determining optimal routes through a packet-switched, LEO satellite communications system having inter-linked satellites are presented. These algorithms have their foundations in the field of differential geometry and a version of these algorithms has been implemented in the Iridium system. The implementation resulted in a multiple of an order of magnitude performance enhancement as well as a bound on the computational complexity (thus facilitating scalability).
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