Catálogo de publicaciones - libros

This work presents a workflow-based computational resource broker whose main functions are matching available resources with user requests and considering network information statuses during matchmaking. The resource broker provides an interface for accessing available and appropriate resources via user credentials. We use the Ganglia and NWS tools to monitor resource status and network-related information, respectively. We also report on using the Globus Toolkit to construct a grid platform called the TIGER project that integrates the distributed resources of five universities in Taichung, Taiwan, where the resource broker was developed. The proposed broker provides secure, updated information about available resources and serves as a link to the diverse systems available in the Grid.

Sharing huge databases in distributed systems is inherently difficult. As the amount of stored data increases, data localization techniques become no longer sufficient. A more efficient approach is to rely on compact database summaries rather than raw database records, whose access is costly in large distributed systems. In this paper, we propose PeerSum, a new service for managing summaries over shared data in large P2P and Grid applications. Our summaries are synthetic, multidimensional views with two main virtues. First, they can be directly queried and used to approximately answer a query without exploring the original data. Second, as semantic indexes, they support locating relevant nodes based on data content. Our main contribution is to define a summary model for P2P systems, and the algorithms for summary management. Our performance evaluation shows that the cost of query routing is minimized, while incurring a low cost of summary maintenance.

In Taiwan, a community of educational and research organizations interested in Grid computing technologies founded a Grid computing platform, called Taiwan UniGrid. Taiwan UniGrid consists of three primary portions: Computational Grid, Data Grid, and Web Portal. In this paper, we present the development of a virtual data storage system for Taiwan UniGrid. In addition to developing basic data storage functions, we identify three main requirements of the current development: high-performance data transfer, data sharing and single sing-on. For these requirements, we come up with three corresponding features in our data storage system: Self-Adaptation for high-performance data transfer, forming user groups and specifying admission control for data sharing, and adopting GSI authentication to enable single sing-on. Besides, we also develop a Java-based graphic user interface of the storage system that allows Grid users to manage data transparently as using local file systems.

In the last years several Grid Virtual Organizations -VOs- have been proliferating, each one usually installing its own Certification Authority and thus giving birth to a large set of different and possibly untrusted security domains. Nevertheless, despite the fact that the adoption of Grid Certification Authorities (CAs) has partially solved the problem of identification and authentication between the involved parties, and that Public Key Infrastructure (PKI) technologies are mature enough, we cannot make the same assumptions when untrusted domains are involved. In this paper we propose an architecture to face the problem of secure interoperability among untrusted Grid-domains. Our approach is based on building a dynamic federation of CAs, formed thorough the quantitative and automatic evaluation of their Certificate Policies. In this paper we describe the proposed architecture and its integration into Globus Toolkit 4.

This paper proposes an application level multicast approach called (TCMM) to distribute live media streams to a large number of users efficiently. In TCMM, transmissions of media data are controlled by two independent relay protocols in a collaborative manner. One protocol here is used to help a peer to identify its neighbor peers using the location information while the other one is used to deliver of media stream among the peers. The two protocols organize all peers into two graphs with different topologies that the communications can benefit a lot from the hybrid control topology. We have studied the performance of TCMM approach using different simulation cases. The experimental results have shown that the broadcasting performance of TCMM can achieve that of a well constructed mesh network while it can adapt more dynamic and irregular network environment. We also see that the penalty of introducing two protocols is rarely low which implies the high scalability of TCMM.

We present in this paper the recent developments done in P2P-MPI, a grid middleware, concerning the fault management, which covers fault-tolerance for applications and fault detection. P2P-MPI provides a transparent fault tolerance facility based on replication of computations. Applications are monitored by a distributed set of external modules called failure detectors. The contribution of this paper is the analysis of the advantages and drawbacks of such detectors for a real implementation, and its integration in P2P-MPI. We pay especially attention to the reliability of the failure detection service and to the failure detection speed. We propose a variant of the binary round-robin protocol, which is more reliable than the application execution in any case. Experiments on applications of up to 256 processes, carried out on Grid’5000 show that the real detection times closely match the predictions.

Heterogeneous wireless sensor network (heterogeneous WSN) consists of sensor nodes with different ability, such as different computing power and sensing range. Compared with homogeneous WSN, deployment and topology control are more complex in heterogeneous WSN. In this paper, a deployment and topology control method is presented for heterogeneous sensor nodes with different communication and sensing range. It is based on the irregular sensor model used to approximate the behavior of sensor nodes. Besides, a cost model is proposed to evaluate the deployment cost of heterogeneous WSN. According to experiment results, the proposed method can achieve higher coverage rate and lower deployment cost for the same deployable sensor nodes.

Wireless sensor networks consist of sensor nodes that are deployed in a large area and collect information from a sensor field. Since the nodes have very limited energy resources, the energy consuming operations such as data collection, transmission and reception must be kept to a minimum. Low Energy Adaptive Clustering Hierarchy (LEACH) is a cluster based communication protocol where cluster-heads (CH) are used to collect data from the cluster nodes and transmit it to the remote base station. In this paper we propose two extensions to LEACH. Firstly, nodes are evenly distributed during the cluster formation process, this is accomplished by merging multiple overlapping clusters. Secondly, instead of each CH directly transmitting data to remote base station, it will do so via a CH closer to the base station. This reduces transmission energy of cluster heads. The combination of above extensions increases the data gathering at base station to 60% for the same amount of sensor nodes energy used in LEACH.

Due to the high availability of the Internet, many large cross-organization collaboration projects, such as SourceForge, grid systems etc., have emerged. One of the fundamental requirements of these collaboration efforts is a storage system to store and exchange data. This storage system must be highly scalable and can efficiently aggregate the storage resources contributed by the participating organizations to deliver good performance for users. In this paper, we propose a storage system, Collaborative File Repository (CFR), for large scale collaboration projects. CFR uses peer-to-peer techniques to achieve scalability, efficiency, and ease of management. In CFR, storage nodes contributed by the participating organizations are partitioned according to geographical regions. Files stored in CFR are automatically replicated to all regions. Furthermore, popular files are duplicated to other storage nodes of the same region. By doing so, data transfers between users and storage nodes are confined within their regions and transfer efficiency is enhanced. Experiments show that our replication can achieve high efficiency with a small number of duplicates.

Sensor network deployment and its maintenance are very challenging due to hostile and unpredictable nature of environments. The field coverage of a wireless sensor network (WSN) can be enhanced and consequently network lifetime can be prolonged by optimizing the sensor deployment with a finite number of sensors. In this paper, we propose an energy-efficient fuzzy optimization algorithm (EFOA) for movement assisted self-deployment of sensor networks based on three descriptors – energy, concentration and distance to neighbors. The movement of each sensor node is assumed relatively limited to further reduce energy consumption. The existing next-step move direction formulas are improved to be more realistic. We also propose a network maintenance strategy in the post-deployment phase based on the sensor node importance level ranking. Simulation results show that our approach not only achieves fast and stable deployment but also greatly improves the network coverage and energy efficiency as well as prolongs the lifetime.