65 results
Search Results
2. Interactive Consistency Algorithms Based on Authentication and Error-correcting Codes
- Author
-
Postma, André and Krol, Thijs
- Subjects
Computer Science::Cryptography and Security - Abstract
In this paper, a class of interactive consistency algorithms is described, based on authentication and error-correcting codes. These algorithms require considerably less data communication than existing algorithms, whereas the required number of modules and communication rounds meet the minimum bounds. The algorithms based on authentication and error-correcting codes are defined and proved on basis of a class of algorithms called the Authenticated Dispersed Joined Communication Algorithms.
- Published
- 1995
3. DNS Zones Revisited
- Author
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van Wanrooij, Ward, Pras, Aiko, and Delgado Kloos, Carlos
- Subjects
DNS ,redundancy ,Performance ,lame delegation ,METIS-225885 ,nameserver ,EWI-7777 ,IR-80036 ,Recommendation ,Reliability - Abstract
Recent research suggests that, due to misconfiguration, DNS reliability and performance is not always as good as it should be. This paper therefore investigates the correct configuration of DNS zones, by checking if main configuration requirements, recommendations and bestpractices rules have been followed. Our research shows that almost one out of four zones fail to pass one or more of our tests. Our study reveals an interesting correlation: if the number of name servers for a single zone exceeds a certain number, reliability and performance usually decreases.
- Published
- 2005
4. Extending the enterprise: An evaluation of ERP and EAI technologies within a Case Study organisation
- Author
-
Zahir Irani and Sharif, A. M.
- Abstract
It is widely understood that both Information Technology (IT) and Information Systems (IS), provide great benefits in improving the visibility of supply and value chains within and across organisational boundaries. Those enterprises which can realise the benefits of extending their core business processes outwards to clients and trading partners, will be able to create unique supply chain-dependent products and solutions. Thus, such business infrastructures have enabled organisations to expand and improve the effectiveness of their enterprise. One method to achieve this, has been to integrate Enterprise Resource Planning (ERP) systems with web-based and other IS systems, using Enterprise Application Integration (EAI) technologies. This paper seeks to investigate those factors which contributed to a case organisation’s extended enterprise experiences, by using extant ERP and EAI implementation IS evaluation criteria; and by placing the research results within the context of applicable IS research techniques in the area.
- Published
- 2006
5. A staff development program for promoting change in Higher Education teaching and learning practices
- Author
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Nilza Costa, Fernando Ramos, José Tavares, and Isabel Huet
- Subjects
Higher education ,ComputingMilieux_THECOMPUTINGPROFESSION ,business.industry ,Best practice ,Professional development ,Collaborative learning ,Staff development ,Teacher training ,Pedagogy ,Teaching and learning center ,ComputingMilieux_COMPUTERSANDEDUCATION ,The Internet ,Sociology ,Faculty development ,business ,Curriculum - Abstract
This paper presents and discusses a staff development program for faculty staff being carried at the University of Aveiro, aiming at providing academics with essential skills in areas such as teaching best practices, student-centered curriculum design, collaborative learning and the adoption of ICT/Internet technologies.
- Published
- 2006
6. The architecture of global ICT programmes : a case study of e - governance in Jordan
- Author
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Navarra, D.D., Faculty of Geo-Information Science and Earth Observation, and Department of Urban and Regional Planning and Geo-Information Management
- Subjects
ADLIB-ART-1461 ,PGM ,ADLIB-BOOK-667 - Published
- 2007
7. Stream Data Management Based on Integration of a Stream Processing Engine and Databases
- Author
-
Yousuke Watanabe and Hiroyuki Kitagawa
- Subjects
Stream processing ,Data stream management system ,Relational database management system ,Database ,Relational database ,Computer science ,Data stream mining ,Persistent data structure ,Architecture ,computer.software_genre ,Stream data ,computer - Abstract
Developments in network and sensor device technologies enable us to easily obtain real-world information, such as locations of moving objects, weather information, news, and stock prices. These data are continuously supplied, and they are regarded as data streams. Because of the dramatical increase of streaming data, their management and utilization has become more and more important. This paper describes a data stream management system named Harmonica. Harmonica employs an architecture combining our stream processing engine named stream-spinner and relational DBMSs. Based on the architecture, the system processes both continuous queries and traditional one-shot queries. Moreover, Harmonica supports continuous persistence requirements for streaming data as well as queries including selection, join, projection, and user-defined functions over data streams. Users can also specify continuous queries that integrate streaming data and persistent data stored in databases. Using the Harmonica API, users can develop a variety of applications coping with different continuous steaming data and data stored in databases. Our system can be deployed in network environments to achieve efficient and dependable distributed stream processing.
- Published
- 2007
8. An Optimum Vertical Handoff Decision Algorithm for UMTS-WiMAX
- Author
-
Gyekye-Nkansah, Y, Agbinya, JI, Pieter, K, Ana, PSN, and Mieso, D
- Subjects
ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS - Abstract
The integration of diverse but complementary cellular and wireless technologies in the next generation of wireless communication systems requires the design of intelligent vertical handoff decision algorithms to enable mobile users to seamlessly switch network access and experience uninterrupted service continuity anywhere and anytime. This paper provides an adaptive multiple attribute vertical handoff decision algorithm that enables wireless access network selection at a mobile terminal using fuzzy logic concepts and a genetic algorithm. A performance study using the integration of wireless wide area networks (WWANs) and wireless metropolitan area networks (WMANs) as an example shows that our proposed vertical handoff decision algorithm is able to determine when a handoff is required, and selects the best access network that is optimized to network conditions, quality of service requirements, mobile terminal conditions, user preferences, and service cost.
- Published
- 2008
9. An Optimum Vertical Handoff Decision Algorithm for UMTS-WiMAX
- Abstract
The integration of diverse but complementary cellular and wireless technologies in the next generation of wireless communication systems requires the design of intelligent vertical handoff decision algorithms to enable mobile users to seamlessly switch network access and experience uninterrupted service continuity anywhere and anytime. This paper provides an adaptive multiple attribute vertical handoff decision algorithm that enables wireless access network selection at a mobile terminal using fuzzy logic concepts and a genetic algorithm. A performance study using the integration of wireless wide area networks (WWANs) and wireless metropolitan area networks (WMANs) as an example shows that our proposed vertical handoff decision algorithm is able to determine when a handoff is required, and selects the best access network that is optimized to network conditions, quality of service requirements, mobile terminal conditions, user preferences, and service cost.
- Published
- 2008
10. An Optimum Vertical Handoff Decision Algorithm for UMTS-WiMAX
- Abstract
The integration of diverse but complementary cellular and wireless technologies in the next generation of wireless communication systems requires the design of intelligent vertical handoff decision algorithms to enable mobile users to seamlessly switch network access and experience uninterrupted service continuity anywhere and anytime. This paper provides an adaptive multiple attribute vertical handoff decision algorithm that enables wireless access network selection at a mobile terminal using fuzzy logic concepts and a genetic algorithm. A performance study using the integration of wireless wide area networks (WWANs) and wireless metropolitan area networks (WMANs) as an example shows that our proposed vertical handoff decision algorithm is able to determine when a handoff is required, and selects the best access network that is optimized to network conditions, quality of service requirements, mobile terminal conditions, user preferences, and service cost.
- Published
- 2008
11. A use case of service-based knowledge management for software development
- Author
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Eichner, Hannes, Micsik, András, Pataki, Máté, and Woitsch, Robert
- Subjects
QA75 Electronic computers. Computer science / számítástechnika, számítógéptudomány - Abstract
Large, international cooperative efforts pose high expectations for knowledge management support. In this paper we present a use case of a knowledge management solution in an inter-national research project, which offers several novel features applicable in other cases as well. The primary goals are to make the implicit knowledge explicit, to organize knowledge objects according to multiple criteria of multiple user roles and to serve this knowledge to users in an interactive way adapting Web 2.0 principles. A Knowledge Management System called the BREIN Roadmap has been realised applying service-based knowledge management using PROMOTE® supporting developers and externals who want to make use of the know-how and software components of the project.
- Published
- 2009
12. Public sector IT outsourcing: a framework for evaluating risk
- Author
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Scott, Murray
- Subjects
e-Government ,IT outsourcing risks ,Enterprise Agility ,Public procurement - Abstract
A recent trend has seen the significant growth of governments outsourcing IT projects to private sector partners. However, despite the high risk of failure in public sector IT projects, the literature on outsourcing risks predominately concentrates on the private sector. This exploratory study draws on a framework developed from IT outsourcing risks in the private sector and applies it to the public sector by carrying out a case study on three local governments in Ireland. This study seeks to identify some of the most important risk factors in an outsourcing strategy by taking into account the unique nature of the public sector in analysis. This study highlights the specific difficulties public sector organisations can experience in attempting to gain cost efficiencies from an outsourcing strategy, especially a complex procurement process, difficulties in requirements gathering, costly contract amendments and inflexible employment structures. The approach used by this paper provides a useful peer-reviewed
- Published
- 2010
13. Architecture of a communication middleware for VANET applications
- Author
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Luca Caviglione, Vittoria Gianuzzi, and Giuseppe Ciaccio
- Subjects
Middleware ,Vehicular ad hoc network ,biology ,Computer science ,business.industry ,Vehicular ad-hoc networks ,Wireless communications ,Distributed computing ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,computer.software_genre ,biology.organism_classification ,Acis ,Telecommunication computing ,Middleware (distributed applications) ,Architecture ,business ,computer ,Computer network - Abstract
As one of the main tasks of a project for developing an Advanced Cooperative Infomobility System (ACIS), we have devised and partly implemented a communication middleware for infomobility applications on vehicular ad-hoc networks (VANETs). In this paper we illustrate and motivate some of the architectural choices underlying the ACIS middleware. © 2011 IEEE.
- Published
- 2011
14. Gossip-based Resource Allocationfor Green Computing in Large Clouds
- Abstract
We address the problem of resource allocation in a large-scale cloud environment, which we formalize as that of dynamically optimizing a cloud configuration for green computing objectives under CPU and memory constraints. We propose a generic gossip protocol for resource allocation, which can be instantiated for specific objectives. We develop an instantiation of this generic protocol which aims at minimizing power consumption through server consolidation, while satisfying a changing load pattern. This protocol, called GRMP-Q, provides an efficient heuristic solution that performs well in most cases—in special cases it is optimal. Under overload, the protocol gives a fair allocation of CPU resources to clients. Simulation results suggest that key performance metrics do not change with increasing system size, making the resource allocation process scalable to well above 100,000 servers. Generally, the effectiveness of the protocol in achieving its objective increases with increasing memory capacity in the servers., QC 20110818
- Published
- 2011
15. Gossip-based Resource Allocationfor Green Computing in Large Clouds
- Abstract
We address the problem of resource allocation in a large-scale cloud environment, which we formalize as that of dynamically optimizing a cloud configuration for green computing objectives under CPU and memory constraints. We propose a generic gossip protocol for resource allocation, which can be instantiated for specific objectives. We develop an instantiation of this generic protocol which aims at minimizing power consumption through server consolidation, while satisfying a changing load pattern. This protocol, called GRMP-Q, provides an efficient heuristic solution that performs well in most cases—in special cases it is optimal. Under overload, the protocol gives a fair allocation of CPU resources to clients. Simulation results suggest that key performance metrics do not change with increasing system size, making the resource allocation process scalable to well above 100,000 servers. Generally, the effectiveness of the protocol in achieving its objective increases with increasing memory capacity in the servers., QC 20110818
- Published
- 2011
16. Gossip-based Resource Allocationfor Green Computing in Large Clouds
- Abstract
We address the problem of resource allocation in a large-scale cloud environment, which we formalize as that of dynamically optimizing a cloud configuration for green computing objectives under CPU and memory constraints. We propose a generic gossip protocol for resource allocation, which can be instantiated for specific objectives. We develop an instantiation of this generic protocol which aims at minimizing power consumption through server consolidation, while satisfying a changing load pattern. This protocol, called GRMP-Q, provides an efficient heuristic solution that performs well in most cases—in special cases it is optimal. Under overload, the protocol gives a fair allocation of CPU resources to clients. Simulation results suggest that key performance metrics do not change with increasing system size, making the resource allocation process scalable to well above 100,000 servers. Generally, the effectiveness of the protocol in achieving its objective increases with increasing memory capacity in the servers., QC 20110818
- Published
- 2011
17. Gossip-based Resource Allocationfor Green Computing in Large Clouds
- Abstract
We address the problem of resource allocation in a large-scale cloud environment, which we formalize as that of dynamically optimizing a cloud configuration for green computing objectives under CPU and memory constraints. We propose a generic gossip protocol for resource allocation, which can be instantiated for specific objectives. We develop an instantiation of this generic protocol which aims at minimizing power consumption through server consolidation, while satisfying a changing load pattern. This protocol, called GRMP-Q, provides an efficient heuristic solution that performs well in most cases—in special cases it is optimal. Under overload, the protocol gives a fair allocation of CPU resources to clients. Simulation results suggest that key performance metrics do not change with increasing system size, making the resource allocation process scalable to well above 100,000 servers. Generally, the effectiveness of the protocol in achieving its objective increases with increasing memory capacity in the servers., QC 20110818
- Published
- 2011
18. Gossip-based Resource Allocationfor Green Computing in Large Clouds
- Abstract
We address the problem of resource allocation in a large-scale cloud environment, which we formalize as that of dynamically optimizing a cloud configuration for green computing objectives under CPU and memory constraints. We propose a generic gossip protocol for resource allocation, which can be instantiated for specific objectives. We develop an instantiation of this generic protocol which aims at minimizing power consumption through server consolidation, while satisfying a changing load pattern. This protocol, called GRMP-Q, provides an efficient heuristic solution that performs well in most cases—in special cases it is optimal. Under overload, the protocol gives a fair allocation of CPU resources to clients. Simulation results suggest that key performance metrics do not change with increasing system size, making the resource allocation process scalable to well above 100,000 servers. Generally, the effectiveness of the protocol in achieving its objective increases with increasing memory capacity in the servers., QC 20110818
- Published
- 2011
19. PLM and design education: a collaborative experiment on a mechanical device
- Author
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Segonds, Frédéric, Maranzana, Nicolas, Veron, Philippe, Aoussat, Améziane, Laboratoire Conception de Produits et Innovation (LCPI), Arts et Métiers Sciences et Technologies, HESAM Université (HESAM)-HESAM Université (HESAM), Laboratoire des Sciences de l'Information et des Systèmes : Ingénierie Numérique des Systèmes Mécaniques (LSIS- INSM), Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences de l'Informatique et ses Interactions-Université de Provence - Aix-Marseille 1-Université Paul Cézanne - Aix-Marseille 3-Université de la Méditerranée - Aix-Marseille 2, HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)-HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM), and Université de la Méditerranée - Aix-Marseille 2-Université Paul Cézanne - Aix-Marseille 3-Université de Provence - Aix-Marseille 1-Institut National des Sciences de l'Informatique et ses Interactions-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Ingénierie assistée par ordinateur [Informatique] ,[INFO.INFO-IA]Computer Science [cs]/Computer Aided Engineering - Abstract
The authors would like to thanks Ms Andia Montes C. and Mr Nelson J. for their helpful suggestions received during this experiment; The shift from sequential to concurrent engineering has initiated changes in the way design projects are managed. In order to assist designers, numerous effective tools have been devised for collaborative engineering, which are also well suited to the business world. Faced with these new challenges, practices in design training must evolve to allow students to be mindful of these evolutions as well as to be able to manage projects in these new work environments. After presenting a state of the art of collaborative tools used in product design, our paper presents an experiment focusing on the codesign of a complex mechanical product. This experiment was carried out between two centers of the Arts et Metiers ParisTech School of Engineering, located in Paris and Angers. We analyze the results obtained in this experiment and discuss some ways to improve future projects for inter-centre training programs in design engineering.; The shift from sequential to concurrent engineering has initiated changes in the way design projects are managed. In order to assist designers, numerous effective tools have been devised for collaborative engineering, which are also well suited to the business world. Faced with these new challenges, practices in design training must evolve to allow students to be mindful of these evolutions as well as to be able to manage projects in these new work environments. After presenting a state of the art of collaborative tools used in product design, our paper presents an experiment focusing on the codesign of a complex mechanical product. This experiment was carried out between two centers of the Arts et Metiers ParisTech School of Engineering, located in Paris and Angers. We analyze the results obtained in this experiment and discuss some ways to improve future projects for inter-centre training programs in design engineering.
- Published
- 2011
20. Product Lifecycle Simulation Applying Semantic Data Management
- Author
-
Jaime Campos, Juha Kortelainen, and Erkki Jantunen
- Subjects
semantic web ,web services ,semantic ,product lifecycle ,data management ,simulation - Abstract
Product lifecycle simulation (PLCS) has been given ever more attention as the manufacturers are competing with the quality and lifecycle costs of their products. Especially, the need of companies to try to get a strong position in providing services for their products and thus to make themselves less vulnerable to changes in the market has led to high interest in PLCS. A short summary of current status of PLCS is presented especially related to the poor integration of data in product lifecycle management systems and in PLCS. The potential of applying semantic data management to solve these problems is thoroughly discussed in the light of recent development. A basic roadmap how the above-described problems could be tackled with open software solutions is presented. Finally, this paper reviews the emergent Web technologies such as the Semantic Web framework and the Web services.
- Published
- 2011
21. Product Lifecycle Simulation Applying Semantic Data Management
- Subjects
semantic web ,web services ,semantic ,product lifecycle ,data management ,simulation - Abstract
Product lifecycle simulation (PLCS) has been given ever more attention as the manufacturers are competing with the quality and lifecycle costs of their products. Especially, the need of companies to try to get a strong position in providing services for their products and thus to make themselves less vulnerable to changes in the market has led to high interest in PLCS. A short summary of current status of PLCS is presented especially related to the poor integration of data in product lifecycle management systems and in PLCS. The potential of applying semantic data management to solve these problems is thoroughly discussed in the light of recent development. A basic roadmap how the above-described problems could be tackled with open software solutions is presented. Finally, this paper reviews the emergent Web technologies such as the Semantic Web framework and the Web services.
- Published
- 2011
22. Transferring Information Security Risk to an Opponent: New Principles for Non-Financial Risk Transfer Treatments
- Published
- 2011
23. System reliability effects in wind turbine blades
- Abstract
Laminated composite sandwich panels have a layered structure, where individual layers have randomly varying stiffness and strength properties. The presence of multiple failure modes and load redistribution following partial failures are the reason for laminated composites to exhibit system behavior from reliability point of view. The present paper discusses the specifics of system reliability behavior of laminated composite sandwich panels, and solves an example system reliability problem for a glass fiber-reinforced composite sandwich structure subjected to in-plane compression.
- Published
- 2012
24. System reliability effects in wind turbine blades
- Abstract
Laminated composite sandwich panels have a layered structure, where individual layers have randomly varying stiffness and strength properties. The presence of multiple failure modes and load redistribution following partial failures are the reason for laminated composites to exhibit system behavior from reliability point of view. The present paper discusses the specifics of system reliability behavior of laminated composite sandwich panels, and solves an example system reliability problem for a glass fiber-reinforced composite sandwich structure subjected to in-plane compression.
- Published
- 2012
25. System reliability effects in wind turbine blades
- Abstract
Laminated composite sandwich panels have a layered structure, where individual layers have randomly varying stiffness and strength properties. The presence of multiple failure modes and load redistribution following partial failures are the reason for laminated composites to exhibit system behavior from reliability point of view. The present paper discusses the specifics of system reliability behavior of laminated composite sandwich panels, and solves an example system reliability problem for a glass fiber-reinforced composite sandwich structure subjected to in-plane compression.
- Published
- 2012
26. Dynamic resource allocation with management objectives - Implementation for an OpenStack cloud
- Abstract
We report on design, implementation and evaluation of a resource management system that builds upon OpenStack, an open-source cloud platform for private and public clouds. Our implementation supports an Infrastructure-as-a-Service (IaaS) cloud and currently provides allocation for computational resources in support of both interactive and computationally intensive applications. The design supports an extensible set of management objectives between which the system can switch at runtime. We demonstrate through examples how management objectives related to load-balancing and energy efficiency can be mapped onto the controllers of the resource allocation subsystem, which attempts to achieve an activated management objective at all times. The design is extensible in the sense that additional objectives can be introduced by providing instantiations for generic functions in the controllers. Our implementation monitors the fulfillment of the relevant management metrics in real time. Testbed evaluation demonstrates the effectiveness of our approach in a dynamic environment. It further illustrates the trade-off between closely meeting a specific management objective and the associated cost of VM live-migration., QC 20130129
- Published
- 2012
27. Energy efficient PONs with service delay guarantees
- Abstract
Passive Optical access Networks (PONs) are currently the major contributor to the energy consumption budget of fixed optical networks. In PON, the largest part of the energy consumption is due to the equipments at the customer premises. This paper proposes a method for maximizing energy savings while providing services with delay guarantees (i.e., frame delivery time and frame delay variation). The method combines service-based variable sleep period and a queueing theory model to compute the optimal sleep time. Simulation results prove the effectiveness of the method for a Poisson frame arrival process., QC 20150707
- Published
- 2012
28. Predicting response times for the Spotify backend
- Abstract
We model and evaluate the performance of a distributed key-value storage system that is part of the Spotify backend. Spotify is an on-demand music streaming service, offering low-latency access to a library of over 16 million tracks and serving over 10 million users currently. We first present a simplified model of the Spotify storage architecture, in order to make its analysis feasible. We then introduce an analytical model for the distribution of the response time, a key metric in the Spotify service. We parameterize and validate the model using measurements from two different testbed configurations and from the operational Spotify infrastructure. We find that the model is accurate - measurements are within 11% of predictions - within the range of normal load patterns. We apply the model to what-if scenarios that are essential to capacity planning and robustness engineering. The main difference between our work and related research in storage system performance is that our model provides distributions of key system metrics, while related research generally gives only expectations, which is not sufficient in our case., QC 20130129
- Published
- 2012
29. Predicting response times for the Spotify backend
- Abstract
We model and evaluate the performance of a distributed key-value storage system that is part of the Spotify backend. Spotify is an on-demand music streaming service, offering low-latency access to a library of over 16 million tracks and serving over 10 million users currently. We first present a simplified model of the Spotify storage architecture, in order to make its analysis feasible. We then introduce an analytical model for the distribution of the response time, a key metric in the Spotify service. We parameterize and validate the model using measurements from two different testbed configurations and from the operational Spotify infrastructure. We find that the model is accurate - measurements are within 11% of predictions - within the range of normal load patterns. We apply the model to what-if scenarios that are essential to capacity planning and robustness engineering. The main difference between our work and related research in storage system performance is that our model provides distributions of key system metrics, while related research generally gives only expectations, which is not sufficient in our case., QC 20130129
- Published
- 2012
30. Predicting response times for the Spotify backend
- Abstract
We model and evaluate the performance of a distributed key-value storage system that is part of the Spotify backend. Spotify is an on-demand music streaming service, offering low-latency access to a library of over 16 million tracks and serving over 10 million users currently. We first present a simplified model of the Spotify storage architecture, in order to make its analysis feasible. We then introduce an analytical model for the distribution of the response time, a key metric in the Spotify service. We parameterize and validate the model using measurements from two different testbed configurations and from the operational Spotify infrastructure. We find that the model is accurate - measurements are within 11% of predictions - within the range of normal load patterns. We apply the model to what-if scenarios that are essential to capacity planning and robustness engineering. The main difference between our work and related research in storage system performance is that our model provides distributions of key system metrics, while related research generally gives only expectations, which is not sufficient in our case., QC 20130129
- Published
- 2012
31. Predicting response times for the Spotify backend
- Abstract
We model and evaluate the performance of a distributed key-value storage system that is part of the Spotify backend. Spotify is an on-demand music streaming service, offering low-latency access to a library of over 16 million tracks and serving over 10 million users currently. We first present a simplified model of the Spotify storage architecture, in order to make its analysis feasible. We then introduce an analytical model for the distribution of the response time, a key metric in the Spotify service. We parameterize and validate the model using measurements from two different testbed configurations and from the operational Spotify infrastructure. We find that the model is accurate - measurements are within 11% of predictions - within the range of normal load patterns. We apply the model to what-if scenarios that are essential to capacity planning and robustness engineering. The main difference between our work and related research in storage system performance is that our model provides distributions of key system metrics, while related research generally gives only expectations, which is not sufficient in our case., QC 20130129
- Published
- 2012
32. Predicting response times for the Spotify backend
- Abstract
We model and evaluate the performance of a distributed key-value storage system that is part of the Spotify backend. Spotify is an on-demand music streaming service, offering low-latency access to a library of over 16 million tracks and serving over 10 million users currently. We first present a simplified model of the Spotify storage architecture, in order to make its analysis feasible. We then introduce an analytical model for the distribution of the response time, a key metric in the Spotify service. We parameterize and validate the model using measurements from two different testbed configurations and from the operational Spotify infrastructure. We find that the model is accurate - measurements are within 11% of predictions - within the range of normal load patterns. We apply the model to what-if scenarios that are essential to capacity planning and robustness engineering. The main difference between our work and related research in storage system performance is that our model provides distributions of key system metrics, while related research generally gives only expectations, which is not sufficient in our case., QC 20130129
- Published
- 2012
33. Vengeance is Mine: A Model of Emotional Appraisal and Computer Abuse
- Abstract
What factors drive individuals to abuse information systems? Better understanding of the roots behind this individual decision could provide opportunities to reduce computer abuse by reducing the presence of these factors. In this paper, we examine the effects of both organizational and personal factors on an individual’s computer abuse behavior. We develop our theoretical model based on abuse opportunity structure theory and literature on emotion theory. Specifically, we identify the organization abuse structure as an organizational factor and three personal factors (goal conduciveness, abuse positive affect, and morality) as personal factors. We investigate their effects on the assessments and decisions that individuals make about computer abuse. The results of a controlled laboratory experiment showed that the organization abuse structure affects these decisions through the assessment of goal conduciveness and abuse positive affect. Morality, however, was found to directly and indirectly affect an individual’s abuse intent. These results imply that security practices are subject to individual appraisals that raise emotions that are in turn conditioned by morality in specific ways. A technical evaluation of the practices is incomplete when absent of the individual appraisal.
- Published
- 2012
34. The Information Security Risk Estimation Engine: A Tool for Possibility Based Risk Assessment
- Abstract
Risk analysis methods help evaluate the costs of information security controls in relation to their benefits. Despite dramatic changes in the constellation of information security risks, the basic approach to these risk calculation methods remains unchanged. The fundamental mathematics underlying these methods is anchored to probability theory. Probability has the advantage of being widely known and conceptually simple. But it has a disadvantage in its grounding on expert estimates of frequency data because such data is often publicly unavailable. This paper proposes the use of possibility theory as an alternative grounding for information security risk calculations. Possibility theory assumes the data grounding will be estimations. The estimations include expert evaluations of both possibility and likelihood of risks. Using a design science research approach, we use possibility theory as the kernel theory in developing and evaluating a practical possibility-based risk estimation prototype. The results offer an expanded grounding to improve information security risk analysis through the use of a broader portfolio of distinct methodologies anchored to alternative mathematical theories of evidence.
- Published
- 2013
35. Can SPDY really make the web faster?
- Abstract
HTTP is a successful Internet technology on top of which a lot of the web resides. However, limitations with its current specification have encouraged some to look for the next generation of HTTP. In SPDY, Google has come up with such a proposal that has growing community acceptance, especially after being adopted by the IETF HTTPbis-WG as the basis for HTTP/2.0. SPDY has the potential to greatly improve web experience with little deployment overhead, but we still lack an understanding of its true potential in different environments. This paper offers a comprehensive evaluation of SPDY’s performance using extensive experiments. We identify the impact of network characteristics and website infrastructure on SPDY’s potential page loading benefits, finding that these factors are decisive for an optimal SPDY deployment strategy. Through exploring such key aspects that affect SPDY, and accordingly HTTP/2.0, we feed into the wider debate regarding the impact of future protocols.
- Published
- 2014
36. Understanding HTTP flow rates in cellular networks
- Abstract
Data traffic in cellular networks increased tremendously over the past few years and this growth is predicted to continue over the next few years. Due to differences in access technology and user behavior, the characteristics of cellular traffic can differ from existing results for wireline traffic. In this study we focus on understanding the flow rates and on the relationship between the rates and other flow properties by analyzing packet level traces collected in a large cellular network. To understand the limiting factors of the flow rates, we further analyze the underlying causes behind the observed rates, e.g.,network congestion, access link or end host configuration. Our study extends other related work by conducting the analysis from a unique dimension, the comparison with traffic in wired networks, to reveal the unique properties of cellular traffic. We find that they differ in variability and in the dominant rate limiting factors.
- Published
- 2014
37. AMSDL: A declarative language for adaptive monitoring control
- Author
-
Messaoud Aouadj, Emmanuel Lavinal, Michelle Sibilla, Thierry Desprats, Institut National Polytechnique de Toulouse - INPT (FRANCE), Centre National de la Recherche Scientifique - CNRS (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Université Toulouse - Jean Jaurès - UT2J (FRANCE), Université Toulouse 1 Capitole - UT1 (FRANCE), Service IntEgration and netwoRk Administration (IRIT-SIERA), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées, Université Toulouse III - Paul Sabatier (UT3), and Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
- Subjects
[INFO.INFO-AR]Computer Science [cs]/Hardware Architecture [cs.AR] ,Domain-specific language ,Java ,Computer science ,Control (management) ,Système d'exploitation ,Réseaux et télécommunications ,02 engineering and technology ,computer.software_genre ,Adaptive monitoring ,[INFO.INFO-NI]Computer Science [cs]/Networking and Internet Architecture [cs.NI] ,Software ,Architectures Matérielles ,Adaptive system ,0202 electrical engineering, electronic engineering, information engineering ,computer.programming_language ,Declarative programming ,Programming language ,business.industry ,020206 networking & telecommunications ,Expression (computer science) ,Domain specific language ,Systèmes embarqués ,[INFO.INFO-ES]Computer Science [cs]/Embedded Systems ,020201 artificial intelligence & image processing ,[INFO.INFO-OS]Computer Science [cs]/Operating Systems [cs.OS] ,Software engineering ,business ,computer ,Policy-based management - Abstract
International audience; More and more requirements are given on the ability to precisely control at run time the achievement of a network and communicating systems monitoring activity. This paper gives an overview of AMSDL (Adaptive Monitoring Strategy Description Language), which is a language under development dedicated at the expression of adaptive monitoring strategies. AMSDL will provide both the network managers and the software developers of autonomic modules with the capacity to easily declare, more than the resources to be managed, the logics that will govern the dynamic monitoring behavior according to the variations of functional, informational and operational requirements.
- Published
- 2015
38. How Dynamic is the ISPs Address Space? Towards Internet-Wide DHCP Churn Estimation
- Abstract
IP address counts are typically used as a surrogate metric for the number of hosts in a network, as in the case of ISP rankings based on botnet infected addresses. However, due to effects of dynamic IP address allocation, such counts tend to overestimate the number of hosts, sometimes by an order of magnitude. In the literature, the rate at which hosts change IP addresses is referred to as DHCP churn. Churn rates vary significantly within and among ISP networks, and such variation poses a challenge to any research that relies upon IP addresses as a metric. We present the first attempt towards estimating ISP and Internet-wide DHCP churn rates, in order to better understand the relation between IP addresses and hosts, as well as allow us to correct data relying on IP addresses as a surrogate metric. We propose an scalable active measurement methodology and then validate it using ground truth data from a medium-sized ISP. Next, we build a statistical model to estimate DHCP churn rates and validate against the ground truth data of the same ISP, estimating correctly 72.3% of DHCP churn rates. Finally, we apply our measurement methodology to four major ISPs, triangulate the results to another Internet census, and discuss the next steps to more precisely estimate DHCP churn rates., Multi Actor Systems, Technology, Policy and Management
- Published
- 2015
39. How Dynamic is the ISPs Address Space? Towards Internet-Wide DHCP Churn Estimation
- Abstract
IP address counts are typically used as a surrogate metric for the number of hosts in a network, as in the case of ISP rankings based on botnet infected addresses. However, due to effects of dynamic IP address allocation, such counts tend to overestimate the number of hosts, sometimes by an order of magnitude. In the literature, the rate at which hosts change IP addresses is referred to as DHCP churn. Churn rates vary significantly within and among ISP networks, and such variation poses a challenge to any research that relies upon IP addresses as a metric. We present the first attempt towards estimating ISP and Internet-wide DHCP churn rates, in order to better understand the relation between IP addresses and hosts, as well as allow us to correct data relying on IP addresses as a surrogate metric. We propose an scalable active measurement methodology and then validate it using ground truth data from a medium-sized ISP. Next, we build a statistical model to estimate DHCP churn rates and validate against the ground truth data of the same ISP, estimating correctly 72.3% of DHCP churn rates. Finally, we apply our measurement methodology to four major ISPs, triangulate the results to another Internet census, and discuss the next steps to more precisely estimate DHCP churn rates., Multi Actor Systems, Technology, Policy and Management
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- 2015
40. Multihomed mobile network architecture
- Abstract
IP mobility ensures network reachability and session continuity while IPv6 networks are on the move. In the Network Mobility (NEMO) model, the potential for NEMO Mobile Routers (MRs) to interconnect and extend Internet connectivity allows the formation Nested NEMO networks. With MANEMO, nested MRs can be efficiently interconnected in a tree-based structure with Internet access being maintained via a designated Gateway. However, this only supports single-homed Internet connectivity. With the span of wireless access technologies and the popularity of multi-interfaced devices, multihoming support in this scenario becomes critical. A Nested Mobile Network with heterogeneous available Internet access options would allow better overall network performance and optimal utilisation of available resources. In this paper, we present the Multihomed Mobile Network Architecture (MMNA), a comprehensive multihomed mobility solution. It provides a multihoming management mechanism for Gateway Discovery and Selection on top of a multihomed mobility model integrating different mobility and multihoming protocols. It enables a complex nested multihomed topology to be established with multiple gateways supporting heterogeneous Internet access. The results demonstrate that the proposed solution achieves better overall throughput, load sharing, and link failure recovery.
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- 2015
41. Spectrum Aware Virtual Coordinates Assignment and Routing in Multihop Cognitive Networks
- Abstract
We propose Spectrum Aware Virtual Coordinate (SAViC) for multi hop cognitive radio network (CRN) to facilitate geographic routing. The proposed virtual coordinates (VC) of any two secondary users reflect both geographic distance and opportunistic spectrum availability between them. As a result, geographic routing is able to detour the area affected by licensed users or cut through the area with more available spectrum. According to different spectrum occupation patterns of primary user, two versions of SAViC are designed based on the channel utility and primary user’s sojourning time respectively. Simulation shows the proposed virtual coordinate facilitates geographic routing to achieve high success rate of path construction. When duty cycle on the licensed channel is heterogeneous in the network, channel utility based virtual coordinate supports geographic routing to outperform a state-of-the-art geographic routing protocol by 40% on packet delivery ratio. When the channel utility is identical on each secondary node, and the sojourning time of primary users for secondary users are different from each other, SAViC based on primary user’s sojourning time achieves significantly shorter delay than other virtual coordinates., Qc 20150618
- Published
- 2015
- Full Text
- View/download PDF
42. Spectrum Aware Virtual Coordinates Assignment and Routing in Multihop Cognitive Networks
- Abstract
We propose Spectrum Aware Virtual Coordinate (SAViC) for multi hop cognitive radio network (CRN) to facilitate geographic routing. The proposed virtual coordinates (VC) of any two secondary users reflect both geographic distance and opportunistic spectrum availability between them. As a result, geographic routing is able to detour the area affected by licensed users or cut through the area with more available spectrum. According to different spectrum occupation patterns of primary user, two versions of SAViC are designed based on the channel utility and primary user’s sojourning time respectively. Simulation shows the proposed virtual coordinate facilitates geographic routing to achieve high success rate of path construction. When duty cycle on the licensed channel is heterogeneous in the network, channel utility based virtual coordinate supports geographic routing to outperform a state-of-the-art geographic routing protocol by 40% on packet delivery ratio. When the channel utility is identical on each secondary node, and the sojourning time of primary users for secondary users are different from each other, SAViC based on primary user’s sojourning time achieves significantly shorter delay than other virtual coordinates., Qc 20150618
- Published
- 2015
- Full Text
- View/download PDF
43. Spectrum Aware Virtual Coordinates Assignment and Routing in Multihop Cognitive Networks
- Abstract
We propose Spectrum Aware Virtual Coordinate (SAViC) for multi hop cognitive radio network (CRN) to facilitate geographic routing. The proposed virtual coordinates (VC) of any two secondary users reflect both geographic distance and opportunistic spectrum availability between them. As a result, geographic routing is able to detour the area affected by licensed users or cut through the area with more available spectrum. According to different spectrum occupation patterns of primary user, two versions of SAViC are designed based on the channel utility and primary user’s sojourning time respectively. Simulation shows the proposed virtual coordinate facilitates geographic routing to achieve high success rate of path construction. When duty cycle on the licensed channel is heterogeneous in the network, channel utility based virtual coordinate supports geographic routing to outperform a state-of-the-art geographic routing protocol by 40% on packet delivery ratio. When the channel utility is identical on each secondary node, and the sojourning time of primary users for secondary users are different from each other, SAViC based on primary user’s sojourning time achieves significantly shorter delay than other virtual coordinates., Qc 20150618
- Published
- 2015
- Full Text
- View/download PDF
44. Spectrum Aware Virtual Coordinates Assignment and Routing in Multihop Cognitive Networks
- Abstract
We propose Spectrum Aware Virtual Coordinate (SAViC) for multi hop cognitive radio network (CRN) to facilitate geographic routing. The proposed virtual coordinates (VC) of any two secondary users reflect both geographic distance and opportunistic spectrum availability between them. As a result, geographic routing is able to detour the area affected by licensed users or cut through the area with more available spectrum. According to different spectrum occupation patterns of primary user, two versions of SAViC are designed based on the channel utility and primary user’s sojourning time respectively. Simulation shows the proposed virtual coordinate facilitates geographic routing to achieve high success rate of path construction. When duty cycle on the licensed channel is heterogeneous in the network, channel utility based virtual coordinate supports geographic routing to outperform a state-of-the-art geographic routing protocol by 40% on packet delivery ratio. When the channel utility is identical on each secondary node, and the sojourning time of primary users for secondary users are different from each other, SAViC based on primary user’s sojourning time achieves significantly shorter delay than other virtual coordinates., Qc 20150618
- Published
- 2015
- Full Text
- View/download PDF
45. Spectrum Aware Virtual Coordinates Assignment and Routing in Multihop Cognitive Networks
- Abstract
We propose Spectrum Aware Virtual Coordinate (SAViC) for multi hop cognitive radio network (CRN) to facilitate geographic routing. The proposed virtual coordinates (VC) of any two secondary users reflect both geographic distance and opportunistic spectrum availability between them. As a result, geographic routing is able to detour the area affected by licensed users or cut through the area with more available spectrum. According to different spectrum occupation patterns of primary user, two versions of SAViC are designed based on the channel utility and primary user’s sojourning time respectively. Simulation shows the proposed virtual coordinate facilitates geographic routing to achieve high success rate of path construction. When duty cycle on the licensed channel is heterogeneous in the network, channel utility based virtual coordinate supports geographic routing to outperform a state-of-the-art geographic routing protocol by 40% on packet delivery ratio. When the channel utility is identical on each secondary node, and the sojourning time of primary users for secondary users are different from each other, SAViC based on primary user’s sojourning time achieves significantly shorter delay than other virtual coordinates., Qc 20150618
- Published
- 2015
- Full Text
- View/download PDF
46. Exploiting state information to support QoS in Software-Defined WSNs
- Author
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Sebastiano Milardo, Patrizia Livreri, Giacomo Morabito, Salvatore Faraci, Sergio Palazzo, Laura Galluccio, Paolo Di Dio, Di Dio, Paolo, Faraci, Salvatore, Galluccio, Laura, Milardo, Sebastiano, Morabito, Giacomo, Palazzo, Sergio, and Livreri, Patrizia
- Subjects
OpenFlow ,business.industry ,Service set ,Computer science ,Wireless network ,Wireless ad hoc network ,Computer Networks and Communications ,Distributed computing ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,020206 networking & telecommunications ,02 engineering and technology ,Settore ING-INF/01 - Elettronica ,Key distribution in wireless sensor networks ,0202 electrical engineering, electronic engineering, information engineering ,Mobile wireless sensor network ,020201 artificial intelligence & image processing ,Radio resource management ,business ,Wireless sensor network ,Computer network - Abstract
Software-Defined Networking (SDN) is a promising paradigm initially proposed for the wired networks which has the potential to change the way in which networks are designed and managed. Recently, its use has been extended to wireless infrastructure-less networks such as ad-hoc and wireless sensor networks. In this paper, we take inspiration from our previous work where a scheme that extends the SDN paradigm to WSNs - called SDN-WISE - was proposed. Differently from OpenFlow, SDN-WISE is stateful; accordingly in this paper we investigate how state can be used to support different levels of QoS in WSNs. In fact, state can be used to represent the level of congestion of a node and rules can be given to the nodes that set different drop probabilities for different flows depending on the level of congestion. By reporting their state, the sensor nodes can inform the Controller about their level of congestion; thus, the Controller can select and set alternative routes for traffic flows in order to mitigate congestion. Numerical results assess the effectiveness of the proposed scheme.
- Published
- 2016
47. Learning at the digital boundaries
- Abstract
The blurring of boundaries between work life and private life, between Spredsheets and Facebook, between societal and private means that we need to reconsider learning both in the perspective of adoption of technological change and, as diffusion of continuous innovation. Both organizations and technologies are undergoing fundamental changes that transform and create new challenges in the ways we work and learn. Many organizations today require continuous development and effective learning processes to meet the challenges of globalization and digitalization. The questions that need to be raised are what new skills need to be recruited, and how can the capabilities and functionality be distributed among a mixture of both human and technical "workforce"? In this position paper we discuss arguments for a future research agenda where new digital phenomena's are viewed from a"learning at the digital boundaries" perspective, taking into account different waves of digitalization and infrastructural challenges at the boundaries of organizational setting and private life.
- Published
- 2017
48. Sustainable technology results for sewage networks in smart cities
- Author
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Josep Casanovas, Yolanda Bolea, Antoni Grau, Ana-Puig Pey, Alberto Sanfeliu, Universitat Politècnica de Catalunya. Departament d'Enginyeria de Sistemes, Automàtica i Informàtica Industrial, Institut de Robòtica i Informàtica Industrial, Universitat Politècnica de Catalunya. Departament d'Estadística i Investigació Operativa, Universitat Politècnica de Catalunya. VIS - Visió Artificial i Sistemes Intel·ligents, Universitat Politècnica de Catalunya. MPI - Modelització i Processament de la Informació, and Universitat Politècnica de Catalunya. VIS - Visió Artificial i Sistemes Intel.ligents
- Subjects
0209 industrial biotechnology ,Engineering ,Emerging technologies ,Sewage ,02 engineering and technology ,Communications system ,Communication systems ,020901 industrial engineering & automation ,Ciutats digitals (Xarxes d'ordinadors) ,Aigües residuals ,11. Sustainability ,0202 electrical engineering, electronic engineering, information engineering ,Sustainable design ,Robòtica ,business.industry ,Sewer systems ,020206 networking & telecommunications ,Robotics ,Engineering management ,Sustainability ,Information and Communications Technology ,Electronic villages (Computer networks) ,Artificial intelligence ,business ,Informàtica::Robòtica [Àrees temàtiques de la UPC] ,Smart cities - Abstract
The objective of this paper is to explain the importance of research in wastewater transportation (sewage systems) using new technologies such as robotics systems and information and communication technologies. ECHORD++ (European Coordination Hub for Open Robotics Development) is a very useful tool to foster this research and to meet needs and solutions. In this paper, authors explain the tool as well as the methodology to promote robotics research in urban environments, and the on-going experience will demonstrate that huge advances are made in this field.
- Published
- 2017
49. Sustainable technology results for sewage networks in smart cities
- Abstract
The objective of this paper is to explain the importance of research in wastewater transportation (sewage systems) using new technologies such as robotics systems and information and communication technologies. ECHORD++ (European Coordination Hub for Open Robotics Development) is a very useful tool to foster this research and to meet needs and solutions. In this paper, authors explain the tool as well as the methodology to promote robotics research in urban environments, and the on-going experience will demonstrate that huge advances are made in this field., Peer Reviewed, Postprint (author's final draft)
- Published
- 2017
50. Towards Learning with Digital Artifacts
- Abstract
The digitalization of the workplace and society at large brings new challenges for the field of Information Systems. A better understanding of how we learn with digital artifacts in our daily routines is needed. This paper is a literature review of how workplace learning has been addressed within the field, bringing together workplace learning and IS. The aim is to provide an alternative perspective to further IFIP 8.6 as a working group, where the suggestion is to re-image the group towards learning with digital artifacts. IS should be the leading field addressing digitalization of society. However, so far learning theorists has not been fully utilized within IS in fostering our understanding of how digitalization affects society. We argue that there is a need to explicitly talk about learning in IS and suggest IFIP 8.6 to be that place, which could contribute to advancements in our IS field in general.
- Published
- 2017
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