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The User Datagram Protocol (UDP) and other similar protocols send the application data from the source machine to the destination machine inside segments, without foreseeing nor allowing for any type of control on the transmission or success metrics. These protocols are very convenient for e.g. real time data transmission. But when the reliability of the transmitted data is critical, other protocols termed as connection-oriented, allow for full control of the data transmission process, assuring that the received data is an exact copy of the transmitted data, e.g. the case of the Transmission Control Protocol (TCP). To sustain the increased functionality and features of the connection-oriented protocol, a set of mechanisms is implemented based on some specific fields of the segment header. These mechanisms result in a significant overhead in terms of the increased number of transmitted packets. This may further translate into significant delays, because of the additional number of switching and routing tasks, and eventually, because of more complex communications procedures, such as e.g. transmission window resizing, and of course, acknowledgement and sequence numbers updating. The two extremes of these communication modalities, one that has no control at all, and the other one that allows for full control, have resulted in the creation of an intermediate protocol that allows for a limited degree of knowledge on how successful a transmission was, and even for an eventual reordering of the segments that arrive out of sequence. This paper presents simulation results that confirm the efficiency of the new almost-reliable UDP protocol, termed Keyed User Datagram Protocol (or KUDP) for transmission of data that includes the ability to identify which packets were lost and to reorder packets that were received out-of-sequence, and points future tasks to be pursued in this research., Comment: 5 pages, 4 figures

MANIAC Challenge raises a problem of game theory, different players strategies intertwine and the success of any player is dependent on the actions of all players in the system. A truly fair scenario is when all the strategies are identical, all the nodes co-operate and they all equally share the rewards and risks that come with every transfer. A successful strategy is one that tries to diverge from the equilibrium to maximize its own gains and it manages to do so. We propose the wolf-pack strategy. Unlike standard game-theory based strategies, our strategy does not penalize the nodes that diverge from fairness or from equilibrium, as we believe most nodes will do so in an attempt to get an advantage over the other nodes. The wolf-pack strategy will try to always find the most successful node or nodes and penalize them. We believe that just like in nature, a number of small predators can take down the bigger, more profitable ones. Furthermore during the Challenge we test two different strategies that provide completely opposite results. These offer a clear picture of what the best strategy is and the problems of the current system., Comment: Published in: E. Baccelli, F. Juraschek, O. Hahm, T. C. Schmidt, H. Will, M. W\"ahlisch (Eds.), Proc. of 3rd MANIAC Challenge, Berlin, Germany, July 27 - 28, 2013, arXiv:1401.1163, Jan. 2014

Mobile Advertisement is a location-aware dissemination solution built on top of a vehicular ad-hoc network. We envision a network of WiFi access points that dynamically disseminate data to clients running on the car's smart device. The approach can be considered an alternative to the static advertisement billboards and can be useful to business companies wanting to dynamically advertise their products and offers to people driving their car. The clients can subscribe to information based on specific topics. We present design solutions that use access points as emitters for transmitting messages to wireless-enabled devices equipped on vehicles. We also present implementation details for the evaluation of the proposed solution using a simulator designed for VANET application. The results show that the application can be used for transferring a significant amount of data even under difficult conditions, such as when cars are moving at increased speeds, or the congested Wi-Fi network causes significant packet loss., Comment: Please cite this as "Ciprian Dobre, George Cristian Tudor, Mobile Advertisement in Vehicular Ad-Hoc Networks, in Proc. of 16th Annual Conference on Web Technology, New Media, Communications and Telematics Theory, Methods, Tools and Applications (Euromedia'2011), London, UK, 2011, pp. 43-49, ISBN: 978-90-77381-61-7, EUROSIS-ETI"

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., Comment: Please cite this as "Ciprian Dobre, Florin Pop, Valentin Cristea, A Simulation Model for Evaluating Distributed Systems Dependability, 23rd annual European Simulation and Modelling Conference (ESM'2009), 2009, pp. 62-69, ISBN: 978-90-77381-52-6, EUROSIS-ETI"

Please cite this as "Lorina Negreanu, Cristian Giumale, Alexandru Agache, Mihnea Muraru, Matei Popovici, Ciprian Dobre, A Formal Approach for the Development of Service-Oriented Applications, in Proc. of 18th International Conference on Control Systems and Computer Science (CSCS-18), Bucharest, Romania, 2011, pp. 804-810, ISSN: 2066-4451, Politehnica Press", Comment: This article has been withdrawn by the author due to copyright incompatibilities raised by the original publisher. The author(s) ask all interested readers to contact either the authors, or check directly the Proceedings published by the Politehnica Press

Mobile devices integrating wireless short-range communication technologies make possible new applications for spontaneous communication, interaction and collaboration. An interesting approach is to use collaboration to facilitate communication when mobile devices are not able to establish direct communication paths. Opportunistic networks, formed when mobile devices communicate with each other while users are in close proximity, can help applications still exchange data in such cases. In opportunistic networks routes are built dynamically, as each mobile device acts according to the store-carry-and-forward paradigm. Thus, contacts between mobile devices are seen as opportunities to move data towards destination. In such networks data dissemination is done using forwarding and is usually based on a publish/subscribe model. Opportunistic data dissemination also raises questions concerning user privacy and incentives. Such problems are addressed differently by various opportunistic data dissemination techniques. In this paper we analyze existing relevant work in the area of data dissemination in opportunistic networks. We present the categories of a proposed taxonomy that captures the capabilities of data dissemination techniques used in such networks. Moreover, we survey relevant data dissemination techniques and analyze them using the proposed taxonomy., Comment: Please cite this as "Radu Ciobanu, Ciprian Dobre, Data Dissemination in Opportunistic Networks, in Proc. of 18th International Conference on Control Systems and Computer Science (CSCS-18), Bucharest, Romania, 2011, pp. 529-536, ISSN: 2066-4451, Politehnica Press"

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., Comment: 17th International Conference on Control Systems and Computer Science (CSCS 17), Bucharest, Romania, May 26-29, 2009. Vol. 1, pp. 407-414, ISSN: 2066-4451

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.

In this paper we present a system for monitoring and controlling dynamic network circuits inside the USLHCNet network. This distributed service system provides in near real-time complete topological information for all the circuits, resource allocation and usage, accounting, detects automatically failures in the links and network equipment, generate alarms and has the functionality to take automatic actions. The system is developed based on the MonALISA framework, which provides a robust monitoring and controlling service oriented architecture, with no single points of failure., Comment: 17th International Conference on Control Systems and Computer Science (CSCS 17), Bucharest, Romania, May 26-29, 2009. Vol. 1, pp. 155-161, ISSN: 2066-4451

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., Comment: Proceedings of 17th International Conference on Control Systems and Computer Science (CSCS 17), Bucharest, Romania, May 26-29, 2009. Vol. 1, pp. 453-460, ISSN: 2066-4451

We present a distributed agent based system used to monitor, configure and control complex, large scale data transfers in the Wide Area Network. The Localhost Information Service Agent (LISA) is a lightweight dynamic service that provides complete system and applications monitoring, is capable to dynamically configure system parameters and can help in optimizing distributed applications. As part of the MonALISA (Monitoring Agents in A Large Integrated Services Architecture) system, LISA is an end host agent capable to collect any type of monitoring information, to distribute them, and to take actions based on local or global decision units. The system has been used for the Bandwidth Challenge at Supercomputing 2006 to coordinate global large scale data transfers using Fast Data Transfer (FDT) application between hundreds of servers distributed on major Grid sites involved in processing High Energy Physics data for the future Large Hadron Collider experiments., Comment: Proc. of 16th International Conference on Control Systems and Computer Science (CSCS-16), pp. 64-68, Bucharest, Romania, ISBN: 978-973-718-741-3

Grid computing has gained an increasing importance in the last years, especially in the academic environments, offering the possibility to rapidly solve complex scientific problems. The monitoring of the Grid jobs has a vital importance for analyzing the system's performance, for providing the users an appropriate feed-back, and for obtaining historical data which may be used for performance prediction. Several monitoring systems have been developed, with different strategies to collect and store the information. We shall present here a solution based on MonALISA, a distributed service for monitoring, control and global optimization of complex systems, and LISA, a component application of MonALISA which can help in optimizing other applications by means of monitoring services. The advantages of this system are, among others, flexibility, dynamic configuration, high communication performance., Comment: Proc. of the 15th International Conference on Control Systems and Computer Science (CSCS-15), Bucharest, Romania, 2005, pp. 127-130, ISBN: 973-8449-89-8

This paper discusses the latest generation of the MONARC (MOdels of Networked Analysis at Regional Centers) simulation framework, as a design and modelling tool for large scale distributed systems applied to HEP experiments. A process-oriented approach for discrete event simulation is well-suited for describing concurrent running programs, as well as the stochastic arrival patterns that characterize how such systems are used. The simulation engine is based on Threaded Objects (or Active Objects), which offer great flexibility in simulating the complex behavior of distributed data processing programs. The engine provides an appropriate scheduling mechanism for the Active objects with support for interrupts. This approach offers a natural way of describing complex running programs that are data dependent and which concurrently compete for shared resources as well as large numbers of concurrent data transfers on shared resources. The framework provides a complete set of basic components (processing nodes, data servers, network components) together with dynamically loadable decision units (scheduling or data replication modules) for easily building complex Computing Model simulations. Examples of simulating complex data processing systems are presented, and the way the framework is used to compare different decision making algorithms or to optimize the overall Grid architecture and/or the policies that govern the Grid's use., Comment: Buletinul Stiintific al Universitatii "Politehnica" din Timisoara, Romania, Seria Automatica si Calculatoare, Periodica Politechnica, Transactions on Automatic Control and Computer Science Vol.49 (63), 2004, ISSN 1224-600X Special issue on 3rd Edition of RoEduNet International Conference, Timisoara, Romania, 2004

This paper discusses the latest generation of the MONARC (MOdels of Networked Analysis at Regional Centers) simulation framework, as a design and modeling tool for large scale distributed systems applied to HEP experiments. The simulation of Grid architectures has a vital importance in the future deployment of Grid systems for providing the users an appropriate feed-back. We present here an example of simulating complex data processing systems and the way the framework is used to optimize the overall Grid architecture and/or the policies that govern the Grid's use., Comment: in Proc. of 15th International Conference on Control Systems and Computer Science (CSCS-15), pp. 131-135, 2005, Bucharest, Romania, Ed. Politehnica Press, ISBN: 973-8449-89-8

Distributed computing is increasingly being viewed as the next phase of Large Scale Distributed Systems (LSDSs). However, the vision of large scale resource sharing is not yet a reality in many areas - Grid computing is an evolving area of computing, where standards and technology are still being developed to enable this new paradigm. Hence, in this paper we analyze the current development of middleware tools for LSDS, from multiple perspectives: architecture, applications and market research. For each perspective we are interested in relevant technologies used in undergoing projects, existing products or services and useful design issues. In the end, based on this approach, we draw some conclusions regarding the future research directions in this area.

Failure detection is a fundamental building block for ensuring fault tolerance in large scale distributed systems. There are lots of approaches and implementations in failure detectors. Providing flexible failure detection in off-the-shelf distributed systems is difficult. In this paper we present an innovative solution to this problem. Our approach is based on adaptive, decentralized failure detectors, capable of working asynchronous and independent on the application flow. The proposed solution considers an architecture for the failure detectors, based on clustering, the use of a gossip-based algorithm for detection at local level and the use of a hierarchical structure among clusters of detectors along which traffic is channeled. The solution can scale to a large number of nodes, considers the QoS requirements of both applications and resources, and includes fault tolerance and system orchestration mechanisms, added in order to asses the reliability and availability of distributed systems.

The overall performance of a distributed system is highly dependent on the communication efficiency of the system. Although network resources (links, bandwidth) are becoming increasingly more available, the communication performance of data transfers involving large volumes of data does not necessarily improve at the same rate. This is due to the inefficient usage of the available network resources. A solution to this problem consists of data transfer scheduling techniques, which manage and allocate the network resources in an efficient manner. In this paper we present several online and offline data transfer optimization techniques, in the context of a centrally controlled distributed system.