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One of the most important design goals of current peer-to-peer (P2P) technology is to be able to offer its service to an arbitrary large number of users. Discrete event simulation is often applied to quantitatively and qualitatively evaluate the performance and scalability of such systems before they are deployed. However, the number of users, processes and events which can be simulated is limited...
Component-based grid applications have complex deployment models. Performance-sensitive decisions should be taken by automatic tools. Such tools must match developer knowledge on component performance with QoS requirements on the applications, in order to find deployment plans that satisfy a service level agreement (SLA). This paper presents a steady state performance model that can be employed to...
The ongoing process of globalization leads to a huge demand for highly scalable applications that are able to deal with millions of participants distributed all over the world. Peer-to-peer (P2P) technology enables an arbitrary large number of users to participate in distributed services like content distribution or collaboration tools. In order to verify a new protocol's performance and scalability...
Detailed knowledge of macromolecular structure is essential for the understanding of how the cellular machines work. Rigid body fitting is the common way to interpret the information contained in a 3D electron microscope (3DEM) medium-low resolution map in terms of its available atomic structural components. This fitting process, termed multi-resolution docking, consists in localizing atomic resolution...
Wireless sensor networks (WSNs) are commonly used for continuously monitoring applications. Data gathering and in-network processing are techniques to efficiently gather the information from sensor nodes. Usually, these techniques have been analyzed taking into account a global knowledge of the system in order to select the best path to gather the information or to establish a routing function. In...
We investigate the dynamics of a distributed video proxy-cache system that is able to adapt the number of running nodes depending on conditions like client request patterns, network load etc. Since we've already examined the split operation used to expand the system by adding new nodes, we explore in detail two operations (hibernate and shut down) used to reduce the number of active nodes. Also, several...
This paper deals with the design and implementation of a parallel software system based on differential evolution for the registration of images, and with its testing on two bidimensional remotely sensed images on mosaicking problem. Registration is carried out by finding the most suitable affine transformation in terms of maximization of the mutual information between the first image and the transformation...
Information security is a key requirement in emerging networked scenarios, which typically involve a large variety of heterogeneous, often resource-constrained devices. Providing security to this emerging class of distributed applications raises a number of new challenges. This paper discusses such challenges with respect to two key security services, namely public key certification and digital timestamping,...
Nowadays, one of the most active areas of research in computer graphics is focused on improving the performance of global illumination methods. In this paper we present a new parallel method for hierarchical radiosity computation. Contrary to usual solutions in the literature our approach carries out an effective partitioning and distribution of the input geometry among the processors. Thus, the memory...
For resource discovery in social networks, people can directly contact some acquaintances that have knowledge about the resources they are looking for. However, in current peer-to-peer networks, peer nodes lack capabilities similar to social networks, making it difficult to route queries efficiently. In this paper, we present a social-like system (Social-P2P) for resource discovery by mimicking human...
In the process of developing P2P systems simulation has proved to be an essential tool for the evaluation of existing and conceived P2P systems. So far, in practice there has been a clear separation between a simulation model of a P2P system and a real P2P system that operates on a real physical network. This separation hinders the transition of models to real systems and the evaluation of already...
Grid computing has become a driving force of scientific computing. By combining the resources of distributed computing centers under a unified management and offering their computing power (nearly) as seamless as electrical power, grid computing is seen as an important step to solve large scale-out problems. Storage grids and storage clusters try to transfer this idea into the storage domain: By combining...
Failure detection protocols - an important building block of fault-tolerant distributed systems - are often described by their authors making use of informal pseudo-codes of their own devising. Often these pseudo-codes use syntactical constructs that are not available in COTS programming languages such as C or C++. This translates into informal descriptions that require ad hoc interpretations and...
This paper presents an evaluation of two families of ring-based algorithms implementing the eventually perfect failure detector class (diamPscr). The evaluation is based on two kinds of performance parameters: communication efficiency, which refers to the number of links that carry messages forever, and quality of service, which includes the capability of the failure detector for providing right answers...
This paper presents a modified leader election algorithm for complete networks without sense of direction. The original algorithm, introduced by Villadangos et al. in (2005), had the aim of reducing the number of exchanged messages in order to select a leader. However, the original O(n) algorithm fails to choose a leader on several occasions. A modified algorithm, which eliminates the problems that...
Heterogeneous distributed computing platforms continue to require substantial effort in terms of software installation and management for efficient use, often necessitating manual intervention by resource providers and end-users. In this paper we propose a novel model of resource sharing that is a viable alternative to that commonly adopted in the grid community. Our model shifts the resource virtualization...
Java has become a popular paradigm in software development. It is widely used in embedded systems and network computing because of its excellent robustness, modularity and security. Its built-in garbage collection automatically reclaims unused memory space. Current generational garbage collector works well with programs containing massive shortlived objects. However, the existence of hot-mature (i...
Skeletal systems exploit algorithmical skeletons technology to provide the user very high level, efficient parallel programming environments. They have been recently demonstrated to be suitable for highly distributed architectures, such as workstation clusters, networks and grids. However, when using skeletal system for grid programming care must be taken to secure data and code transfers across nondedicated,...
The scalability has remained a challenge in the design of distributed publish/subscribe systems. In this paper we propose a novel solution to address this problem in content-based pub/sub systems on top of distributed hash table. The main objective is to ensure an appropriate amount of rendezvous point nodes in the system, as well as maintain an even load distribution among them. An attribute-vector...
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