Florin Pop

Publications

• A Simulation Model for Evaluating Distributed Systems Dependability

  Ciprian Dobre, Florin Pop, Valentin Cristea

  02/2012;

  In this paper we present a new simulation model designed to evaluate the dependability in distributed systems. This model extends the MONARC simulation model with new capabilities for capturing reliability, safety, availability, security, and maintainability requirements. The model has been implemen... [more] In this paper we present a new simulation model designed to evaluate the dependability in distributed systems. This model extends the MONARC simulation model with new capabilities for capturing reliability, safety, availability, security, and maintainability requirements. The model has been implemented as an extension of the multithreaded, process oriented simulator MONARC, which allows the realistic simulation of a wide-range of distributed system technologies, with respect to their specific components and characteristics. The extended simulation model includes the necessary components to inject various failure events, and provides the mechanisms to evaluate different strategies for replication, redundancy procedures, and security enforcement mechanisms, as well. The results obtained in simulation experiments presented in this paper probe that the use of discrete-event simulators, such as MONARC, in the design and development of distributed systems is appealing due to their efficiency and scalability.

• A Simulation Model for Evaluating Distributed Systems Dependability

  Ciprian Dobre, Florin Pop, Valentin Cristea

  CoRR. 01/2012; abs/1202.2551.

• Reputation Based Selection for Services in Cloud Environments

  O. Achim, F. Pop, V. Cristea

  Network-Based Information Systems (NBiS), 2011 14th International Conference on; 10/2011

  Distributed environments hosting specific and dedicated computing resources are serving nowadays more and more scientific and commercial applications. Finding the right resource in distributed environments in term of performance is not an obvious task. This paper is addressing the issue of selecting... [more] Distributed environments hosting specific and dedicated computing resources are serving nowadays more and more scientific and commercial applications. Finding the right resource in distributed environments in term of performance is not an obvious task. This paper is addressing the issue of selecting the right service deployed in a distributed environment for any applications or workflow engines that need access to best service's endpoint in term of performance. The service selection is made according with a reputation function, defined in this paper. The reputation function considers the execution cost as a performance criterion. The experimental results highlight the behavior of proposed reputation function and the comparison with other reputation functions. The papers present the possibility of enhancing the proposed solution in a real environment represented by a workflow engine based on Business Process Execution Language (BPEL).

• An Architectural Model for a Grid based Workflow Management Platform in Scientific Applications

  Alexandru Costan, Florin Pop, Corina Stratan, Ciprian Dobre, Catalin Leordeanu, Valentin Cristea

  06/2011;

  With recent increasing computational and data requirements of scientific applications, the use of large clustered systems as well as distributed resources is inevitable. Although executing large applications in these environments brings increased performance, the automation of the process becomes mo... [more] With recent increasing computational and data requirements of scientific applications, the use of large clustered systems as well as distributed resources is inevitable. Although executing large applications in these environments brings increased performance, the automation of the process becomes more and more challenging. While the use of complex workflow management systems has been a viable solution for this automation process in business oriented environments, the open source engines available for scientific applications lack some functionalities or are too difficult to use for non-specialists. In this work we propose an architectural model for a grid based workflow management platform providing features like an intuitive way to describe workflows, efficient data handling mechanisms and flexible fault tolerance support. Our integrated solution introduces a workflow engine component based on ActiveBPEL extended with additional functionalities and a scheduling component providing efficient mapping between tasks and available resources.

• Models and Techniques for Ensuring Reliability, Safety, Availability and Security of Large Scale Distributed Systems

  Valentin Cristea, Ciprian Dobre, Florin Pop, Corina Stratan, Alexandru Costan, Catalin Leordeanu

  06/2011;

  17th International Conference on Control Systems and Computer Science (CSCS 17), Bucharest, Romania, May 26-29, 2009. Vol. 1, pp. 401-406, ISSN: 2066-4451.... [more] 17th International Conference on Control Systems and Computer Science (CSCS 17), Bucharest, Romania, May 26-29, 2009. Vol. 1, pp. 401-406, ISSN: 2066-4451.

• Intelligent strategies for DAG scheduling optimization in Grid environments

  Florin Pop, Valentin Cristea

  06/2011;

  The paper presents a solution to the dynamic DAG scheduling problem in Grid environments. It presents a distributed, scalable, efficient and fault-tolerant algorithm for optimizing tasks assignment. The scheduler algorithm for tasks with dependencies uses a heuristic model to optimize the total cost... [more] The paper presents a solution to the dynamic DAG scheduling problem in Grid environments. It presents a distributed, scalable, efficient and fault-tolerant algorithm for optimizing tasks assignment. The scheduler algorithm for tasks with dependencies uses a heuristic model to optimize the total cost of tasks execution. Also, a method based on genetic algorithms is proposed to optimize the procedure of resources assignment. The experiments used the MonALISA monitoring environment and its extensions. The results demonstrate very good behavior in comparison with other scheduling approaches for this kind of DAG scheduling algorithms.

• DistHash: A robust P2P DHT-based system for replicated objects

  Ciprian Dobre, Florin Pop, Valentin Cristea

  06/2011;

  Over the Internet today, computing and communications environments are significantly more complex and chaotic than classical distributed systems, lacking any centralized organization or hierarchical control. There has been much interest in emerging Peer-to-Peer (P2P) network overlays because they pr... [more] Over the Internet today, computing and communications environments are significantly more complex and chaotic than classical distributed systems, lacking any centralized organization or hierarchical control. There has been much interest in emerging Peer-to-Peer (P2P) network overlays because they provide a good substrate for creating large-scale data sharing, content distribution and application-level multicast applications. In this paper we present DistHash, a P2P overlay network designed to share large sets of replicated distributed objects in the context of large-scale highly dynamic infrastructures. We present original solutions to achieve optimal message routing in hop-count and throughput, provide an adequate consistency approach among replicas, as well as provide a fault-tolerant substrate.

• Towards an IO intensive Grid application instrumentation in MedioGRID

  Dacian Tudor, Florin Pop, Valentin Cristea, Vladimir Cretu

  06/2011;

  Obtaining high performance in IO intensive applications requires systems that support reliable fast transfer, data replication, and caching. In this paper we present an architecture designed for supporting IO intensive applications in MedioGRID, a system for real-time processing of satellite images,... [more] Obtaining high performance in IO intensive applications requires systems that support reliable fast transfer, data replication, and caching. In this paper we present an architecture designed for supporting IO intensive applications in MedioGRID, a system for real-time processing of satellite images, operating in a Grid environment. The solution ensures that applications which are processing geographical data have uniform access to data and is based on continuous monitoring of the data transfers using MonALISA and its extensions. The MedioGRID architecture is also built on Globus, Condor and PBS and based on this middleware we aim to extract information about the running systems. The results obtained in testing MedioGRID system for large data transfers show that monitoring system provides a very good view of system evolution.

• Decentralized Trust Management in Peer-to-Peer Systems.

  Andreea Visan, Florin Pop, Valentin Cristea

  10th International Symposium on Parallel and Distributed Computing, ISPDC 2011, Cluj-Napoca, Romania, July 6-8, 2011; 01/2011

• Load-Balancing Metric for Service Dependability in Large Scale Distributed Environments.

  Florin Pop, Marius-Viorel Grigoras, Ciprian Dobre, Ovidiu-Marian Achim, Valentin Cristea

  Scalable Computing: Practice and Experience. 01/2011; 12.

• Reputation Based Selection for Services in Cloud Environments.

  Ovidiu-Marian Achim, Florin Pop, Valentin Cristea

  The 14th International Conference on Network-Based Information Systems, NBiS 2011, Tirana, Albania, September 7-9, 2011; 01/2011

• Modelling Requirements for Enabling Meta-scheduling in Inter-Clouds and Inter-Enterprises.

  Nik Bessis, Stelios Sotiriadis, Valentin Cristea, Florin Pop

  2011 Third International Conference on Intelligent Networking and Collaborative Systems (INCoS), Fukuoka, Japan, November 30 - Dec. 2, 2011; 01/2011

• Using Bio-inspired Models to Design Peer-to-Peer Overlays.

  Bogdan Ghit, Florin Pop, Valentin Cristea

  2011 International Conference on P2P, Parallel, Grid, Cloud and Internet Computing, 3PGCIC 2011, Barcelona, Catalonia, Spain, October 26-28, 2011; 01/2011

• A Virtualization-based Approach to Dependable Service Computing.

  Ciprian Dobre, Florin Pop, Valentin Cristea, Ovidiu-Marian Achim

  Scalable Computing: Practice and Experience. 01/2011; 12.

• HIGA: Hybrid Immune - Genetic Algorithm for Dependent Task Scheduling in Large Scale Distributed Systems.

  Mihai Istin, Florin Pop, Valentin Cristea

  10th International Symposium on Parallel and Distributed Computing, ISPDC 2011, Cluj-Napoca, Romania, July 6-8, 2011; 01/2011

• Bio-Inspired Techniques for Resources State Prediction in Large Scale Distributed Systems.

  Andreea Visan, Mihai Istin, Florin Pop, Valentin Cristea

  IJDST. 01/2011; 2:1-18.

• Epidemic-Style Global Load Monitoring in Large-Scale Overlay Networks

  B. Ghit, F. Pop, V. Cristea

  P2P, Parallel, Grid, Cloud and Internet Computing (3PGCIC), 2010 International Conference on; 12/2010

  Peer-to-peer systems are highly dynamic systems, with permanent changes in their configurations, as peers may join and leave the system with no restriction or control. This makes monitoring an important element for several applications, especially for fault management: fault detection and fault reco... [more] Peer-to-peer systems are highly dynamic systems, with permanent changes in their configurations, as peers may join and leave the system with no restriction or control. This makes monitoring an important element for several applications, especially for fault management: fault detection and fault recovery. As the system may have a large number of nodes, we need a scalable algorithm, able to guarantee a fast convergence no matter what the structure of the network is. Epidemic-style or gossip-based algorithms offer solutions for various topics in large-scale distributed systems. Even though they present many advantages due to their property of continuously spreading the information across the system in a reactive and proactive fashion, several problems such as the total number of messages exchanged between peers and the number of rounds required for ensuring the convergence of the algorithm appear. In this paper we present a gossip-based algorithm for monitoring large-scale distributed systems and we analyze its efficiency in a simulated environment provided by OverSim.

• Decomposition Based Algorithm for State Prediction in Large Scale Distributed Systems

  Mihai Istin, Andreea Visan, Florin Pop, Valentin Cristea

  Parallel and Distributed Computing (ISPDC), 2010 Ninth International Symposium on; 08/2010

  Prediction represents an important component of resource management, providing information about the future state, utilization and availability of resources. We propose a new prediction algorithm inspired from the decomposition of a complex wave into simpler waves with fixed frequencies (similar to ... [more] Prediction represents an important component of resource management, providing information about the future state, utilization and availability of resources. We propose a new prediction algorithm inspired from the decomposition of a complex wave into simpler waves with fixed frequencies (similar to Fourier decomposition). The partial results obtained from this decomposition stage are combined using approaches inspired from artificial intelligence models. The experimental results for different system parameters, used in Alice experiment, highlight the great improvement, discussed in terms of error reduction, offered by this new prediction algorithm. The tests were made using real-time monitoring data provided by a system monitoring tool, in the case of one-step and multi-step ahead prediction. The prediction's results can be used by the resource management systems in order to improve the scheduling decisions, assuring the load balancing and optimizing the resource utilization.

• Digital certificate management for document workflows in E-government services

  Florin Pop, Ciprian Dobre, Decebal Popescu, Vlad Ciobanu, Valentin Cristea

  EGOV'10: Proceedings of the 9th IFIP WG 8.5 international conference on Electronic government; 01/2010

• An adaptive scheduling approach in distributed systems

  Alexandra Olteanu, Florin Pop, Ciprian Dobre, Valentin Cristea

  ICCP '10: Proceedings of the Proceedings of the 2010 IEEE 6th International Conference on Intelligent Computer Communication and Processing; 01/2010