2005
Journal article
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A hierarchical radio resource management framework for integrating WLANs in cellular networking environments
Karetsos Gt, Kyriazakos Sa, Groustiotis E, Di Giandomenico F, Mura I
Over the last few years wireless local area networking (WLAN) has become a very important technology that offers high-speed communication services to mobile users in indoor environments. WLAN technology offers some very attractive characteristics such as high data rates, increased QoS capabilities, and low installation costs which has made many professionals claim that it will be the main opponent of IMT- 2000, despite the enormous effort needed for the specification and implementation of 3G systems. However, WLANs also present many important constraints related mainly to their restricted coverage capabilities. On the other hand, 3G systems are deployed gradually and carefully since their business prospects have not been validated yet and it is expected that 2G and 2G+ cellular systems will continue to play an important role for at least five more years. Thus, today's wireless networking environment is in fact a conglomeration of all these technologies for which there is a strong need for cooperation. In this article we describe a heterogeneous wireless networking environment together with its features and user requirements. We explain the importance of the existence of WLANs and describe a framework and system architecture that support seamless integration of WLAN in heterogeneous cellular networking environments, focusing on support for efficient resource provision and management.Source: IEEE WIRELESS COMMUNICATIONS, vol. 12 (issue 6), pp. 11-17
DOI: 10.1109/mwc.2005.1561940
Metrics:
Karetsos Gt, Kyriazakos Sa, Groustiotis E, Di Giandomenico F, Mura I
Over the last few years wireless local area networking (WLAN) has become a very important technology that offers high-speed communication services to mobile users in indoor environments. WLAN technology offers some very attractive characteristics such as high data rates, increased QoS capabilities, and low installation costs which has made many professionals claim that it will be the main opponent of IMT- 2000, despite the enormous effort needed for the specification and implementation of 3G systems. However, WLANs also present many important constraints related mainly to their restricted coverage capabilities. On the other hand, 3G systems are deployed gradually and carefully since their business prospects have not been validated yet and it is expected that 2G and 2G+ cellular systems will continue to play an important role for at least five more years. Thus, today's wireless networking environment is in fact a conglomeration of all these technologies for which there is a strong need for cooperation. In this article we describe a heterogeneous wireless networking environment together with its features and user requirements. We explain the importance of the existence of WLANs and describe a framework and system architecture that support seamless integration of WLAN in heterogeneous cellular networking environments, focusing on support for efficient resource provision and management.Source: IEEE WIRELESS COMMUNICATIONS, vol. 12 (issue 6), pp. 11-17
DOI: 10.1109/mwc.2005.1561940
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IEEE Wireless Communications 
| CNR IRIS | ieeexplore.ieee.org | CNR IRIS
2005
Conference article
Restricted
Evaluation of the impact of congestion on service availability of GPRS infrastructures
Lollini P, Bondavalli A, Di Giandomenico F
This paper deals with the congestion analysis of a GPRS infrastructure composed by a number of adjacent cells partially overlapped. We consider that one cell can be affected by an outage and we perform a transient analysis to evaluate the effectiveness of applying a specific class of resource management techniques for congestion treatment. The classical availability analysis is here enhanced taking into account the important congestion phenomenon following outages and its impact on user's perceived QoS, both in each cell and in the overall GPRS network. In order to efficiently solve the large and complex model capturing the network's behavior, we introduce a resolution technique in which the solution of the entire model is constructed on the basis of the solutions of the individual sub-models.
Lollini P, Bondavalli A, Di Giandomenico F
This paper deals with the congestion analysis of a GPRS infrastructure composed by a number of adjacent cells partially overlapped. We consider that one cell can be affected by an outage and we perform a transient analysis to evaluate the effectiveness of applying a specific class of resource management techniques for congestion treatment. The classical availability analysis is here enhanced taking into account the important congestion phenomenon following outages and its impact on user's perceived QoS, both in each cell and in the overall GPRS network. In order to efficiently solve the large and complex model capturing the network's behavior, we introduce a resolution technique in which the solution of the entire model is constructed on the basis of the solutions of the individual sub-models.
2005
Conference article
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Quantitative evaluation of distributed algorithms using the Neko framework: the NekoStat extension
Falai L, Bondavalli A, Di Giandomenico F
In this paper we present NekoStat, an extension of the Neko tool. Neko is a Java framework and a communication platform that permits rapid prototyping of distributed applications; it provides tools to organize the applications using a layered architecture, with the network(s) at the bottom of the architecture. Neko is also a communication platform that allows sending and receiving of generic Java objects. Distributed systems realized within the Neko framework can be exercised both on real networks and on simulated ones, without changes in the application code. We constructed an extension to plain Neko, called NekoStat; it permits attainment of quantitative evaluations of distributed systems. In the paper we describe this extension; we motivate the development of NekoStat, we describe the design and finally we illustrate its usage through a case study, which highlights the usefulness of NekoStat.
Falai L, Bondavalli A, Di Giandomenico F
In this paper we present NekoStat, an extension of the Neko tool. Neko is a Java framework and a communication platform that permits rapid prototyping of distributed applications; it provides tools to organize the applications using a layered architecture, with the network(s) at the bottom of the architecture. Neko is also a communication platform that allows sending and receiving of generic Java objects. Distributed systems realized within the Neko framework can be exercised both on real networks and on simulated ones, without changes in the application code. We constructed an extension to plain Neko, called NekoStat; it permits attainment of quantitative evaluations of distributed systems. In the paper we describe this extension; we motivate the development of NekoStat, we describe the design and finally we illustrate its usage through a case study, which highlights the usefulness of NekoStat.
2003
Journal article
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Service level availability estimation of GPRS
Porcarelli S, Di Giandomenico F, Bondavalli A, Barbera M, Mura I
The General Packet Radio Service (GPRS) extends the Global System Mobile Communication (GSM), by introducing a packet-switched transmission service. This paper analyses the GPRS behavior under critical conditions. In particular, we focus on outages, which significantly impact the GPRS dependability. In fact, during outage periods the cumulative number of users trying to access the service grows proportionally over time. When the system resumes its operations, the overload caused by accumulated users determines a higher probability of collisions on resources assignment and therefore a degradation of the overall QoS. This paper adopts a Stochastic Activity Network modeling approach for evaluating the dependability of a GPRS network under outage conditions. The major contribution of this study lies in the novel perspective the dependability study is framed in. Starting from a quite classical availability analysis, the network dependability figures are incorporated into a very detailed service model that is used to analyze the overload effect GPRS has to face after outages, gaining deep insights on its impact on user's perceived QoS. The result of this modeling is an enhanced availability analysis, which takes into account not only the bare estimation of unavailability periods, but also the important congestion phenomenon following outages that contribute to service degradation for a certain period of time after operations resume.Source: IEEE TRANSACTIONS ON MOBILE COMPUTING, vol. 2 (issue 3), pp. 233-247
DOI: 10.1109/tmc.2003.1233529
Metrics:
Porcarelli S, Di Giandomenico F, Bondavalli A, Barbera M, Mura I
The General Packet Radio Service (GPRS) extends the Global System Mobile Communication (GSM), by introducing a packet-switched transmission service. This paper analyses the GPRS behavior under critical conditions. In particular, we focus on outages, which significantly impact the GPRS dependability. In fact, during outage periods the cumulative number of users trying to access the service grows proportionally over time. When the system resumes its operations, the overload caused by accumulated users determines a higher probability of collisions on resources assignment and therefore a degradation of the overall QoS. This paper adopts a Stochastic Activity Network modeling approach for evaluating the dependability of a GPRS network under outage conditions. The major contribution of this study lies in the novel perspective the dependability study is framed in. Starting from a quite classical availability analysis, the network dependability figures are incorporated into a very detailed service model that is used to analyze the overload effect GPRS has to face after outages, gaining deep insights on its impact on user's perceived QoS. The result of this modeling is an enhanced availability analysis, which takes into account not only the bare estimation of unavailability periods, but also the important congestion phenomenon following outages that contribute to service degradation for a certain period of time after operations resume.Source: IEEE TRANSACTIONS ON MOBILE COMPUTING, vol. 2 (issue 3), pp. 233-247
DOI: 10.1109/tmc.2003.1233529
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IEEE Transactions on Mobile Computing | CNR IRIS | CNR IRIS
2005
Contribution to book
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A modular approach for model-based dependability evaluation of a class of systems
Porcarelli S, Di Giandomenico F, Lollini P, Bondavalli A
Modeling for dependability and performance evaluation has proven to be a useful and versatile approach in all the phases of the system life cycle. Indeed, a widely used approach in performability modeling is to describe the system by state space models (like Markov models). However, for large systems, the state space of the system model may result extremely large, making it very hard to solve. Taking advantage of the characteristics of a particular class of systems, this paper develops a methodology to construct an efficient, scalable and easily maintainable architectural model for such class, especially tailored to dependability analysis. Although limited to the class considered, the proposed methodology shows very attractive because of its ability to master complexity, both in the model design phase and, then, in its solution. A representative case study is also included.
Porcarelli S, Di Giandomenico F, Lollini P, Bondavalli A
Modeling for dependability and performance evaluation has proven to be a useful and versatile approach in all the phases of the system life cycle. Indeed, a widely used approach in performability modeling is to describe the system by state space models (like Markov models). However, for large systems, the state space of the system model may result extremely large, making it very hard to solve. Taking advantage of the characteristics of a particular class of systems, this paper develops a methodology to construct an efficient, scalable and easily maintainable architectural model for such class, especially tailored to dependability analysis. Although limited to the class considered, the proposed methodology shows very attractive because of its ability to master complexity, both in the model design phase and, then, in its solution. A representative case study is also included.
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CNR IRIS | CNR IRIS | link.springer.com
2008
Book
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Architecting dependable systems V - Preface
De Lemos R, Di Giandomenico F, Gacek C, Muccini H, Vieira M
This is the fifth book in a series on Architecting Dependable Systems we started six years ago that brings together issues related to software architectures and the dependability of systems. This book includes expanded and peer-reviewed papers based on the selected contributions to two workshops, and a number of invited papers written by recognized experts in the area. The two workshops were: the Workshop on Architecting Dependable Systems (WADS) organized at the 2007 International Conference on Dependable Systems and Networks (DSN 2007), and the Third Workshop on the Role of Software Architecture for Testing and Analysis organized as part of a federated conference on Component-Based Software Engineering and Software Architecture (CompArch 2007).DOI: 10.1007/978-3-540-85571-2
Metrics:
De Lemos R, Di Giandomenico F, Gacek C, Muccini H, Vieira M
This is the fifth book in a series on Architecting Dependable Systems we started six years ago that brings together issues related to software architectures and the dependability of systems. This book includes expanded and peer-reviewed papers based on the selected contributions to two workshops, and a number of invited papers written by recognized experts in the area. The two workshops were: the Workshop on Architecting Dependable Systems (WADS) organized at the 2007 International Conference on Dependable Systems and Networks (DSN 2007), and the Third Workshop on the Role of Software Architecture for Testing and Analysis organized as part of a federated conference on Component-Based Software Engineering and Software Architecture (CompArch 2007).DOI: 10.1007/978-3-540-85571-2
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CNR IRIS | CNR IRIS | link.springer.com
2009
Journal article
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A decomposition-based modeling framework for complex systems
Lollini P, Bondavalli A, Di Giandomenico F
Stochastic model-based approaches are widely used for performability evaluation of complex software/hardware systems. Many techniques have been developed to mitigate the complexity of the associated models, but most of them are domain-specific, and they support the analysis of a limited class of systems. This paper provides a contribution in the definition of a general modeling framework that adopts three different types of decomposition techniques to deal with model complexity. First, a functional decomposition is applied at the system-level, thus identifying a set of subsystems, called entities, each one performing a function with respect to the validation objectives. The entities can interact with each other through some dependency relations that state how the behavior of each entity can affect the other(s). Then a temporal decomposition is used to divide the system's lifetime in a sequence of phases such that two consecutive phases have at least one different dependency relation. Last, a model-level decomposition produces a set of separate sub-models that can be solved in isolation, passing some intermediate results between them, if and when required. This modeling framework has been applied to analyze a General Packet Radio Service (GPRS) mobile telephone system. The purpose of this case-study is to demonstrate the applicability of the framework, in terms of its computational complexity, and the accuracy of the obtained results. The proposed approach provides results sufficiently accurate, though it induces some acceptable approximation. Moreover, it significantly reduces the computational complexity with respect to solving the whole non-decomposed model, and shows only a slight increase in complexity with respect to the ad-hoc solution technique specifically developed for the GPRS case-study.Source: IEEE TRANSACTIONS ON RELIABILITY, vol. 58 (issue 1), pp. 20-33
DOI: 10.1109/tr.2008.2011663
Metrics:
Lollini P, Bondavalli A, Di Giandomenico F
Stochastic model-based approaches are widely used for performability evaluation of complex software/hardware systems. Many techniques have been developed to mitigate the complexity of the associated models, but most of them are domain-specific, and they support the analysis of a limited class of systems. This paper provides a contribution in the definition of a general modeling framework that adopts three different types of decomposition techniques to deal with model complexity. First, a functional decomposition is applied at the system-level, thus identifying a set of subsystems, called entities, each one performing a function with respect to the validation objectives. The entities can interact with each other through some dependency relations that state how the behavior of each entity can affect the other(s). Then a temporal decomposition is used to divide the system's lifetime in a sequence of phases such that two consecutive phases have at least one different dependency relation. Last, a model-level decomposition produces a set of separate sub-models that can be solved in isolation, passing some intermediate results between them, if and when required. This modeling framework has been applied to analyze a General Packet Radio Service (GPRS) mobile telephone system. The purpose of this case-study is to demonstrate the applicability of the framework, in terms of its computational complexity, and the accuracy of the obtained results. The proposed approach provides results sufficiently accurate, though it induces some acceptable approximation. Moreover, it significantly reduces the computational complexity with respect to solving the whole non-decomposed model, and shows only a slight increase in complexity with respect to the ad-hoc solution technique specifically developed for the GPRS case-study.Source: IEEE TRANSACTIONS ON RELIABILITY, vol. 58 (issue 1), pp. 20-33
DOI: 10.1109/tr.2008.2011663
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IEEE Transactions on Reliability | CNR IRIS | ieeexplore.ieee.org | CNR IRIS
2005
Journal article
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A modeling methodology for hierarchical control systems and its application
Lollini P, Bondavalli A, Di Giandomenico F
Current and future computerized systems and infrastructures are going to be based on the layering of different systems, designed at different times, with different technologies and components and difficult to integrate. Control systems and resource management systems are increasingly employed in such large and heterogeneous environment as a parallel infrastructure to allow an efficient, dependable and scalable usage of the system components. System complexity comes out to be a paramount challenge to solve from a number of different viewpoints, including dependability modeling and evaluation. Key directions to deal with system complexity are abstraction and hierarchical structuring of the system functionalities. This paper addresses the issue of an efficient dependability evaluation by a model-based approach of hierarchical control and resource management systems. We exploited the characteristics of this specific, but important, class of systems and derived a modeling methodology that is not only directed to build models in a compositional way, but it also includes some capabilities to reduce their solution complexity. The modeling methodology and the resolution technique are then applied to a case study consisting of a resource management system developed in the context of the ongoing European project CAUTION++. The results obtained are useful to understand the impact of several system component factors on the dependability of the overall system instance.
Lollini P, Bondavalli A, Di Giandomenico F
Current and future computerized systems and infrastructures are going to be based on the layering of different systems, designed at different times, with different technologies and components and difficult to integrate. Control systems and resource management systems are increasingly employed in such large and heterogeneous environment as a parallel infrastructure to allow an efficient, dependable and scalable usage of the system components. System complexity comes out to be a paramount challenge to solve from a number of different viewpoints, including dependability modeling and evaluation. Key directions to deal with system complexity are abstraction and hierarchical structuring of the system functionalities. This paper addresses the issue of an efficient dependability evaluation by a model-based approach of hierarchical control and resource management systems. We exploited the characteristics of this specific, but important, class of systems and derived a modeling methodology that is not only directed to build models in a compositional way, but it also includes some capabilities to reduce their solution complexity. The modeling methodology and the resolution technique are then applied to a case study consisting of a resource management system developed in the context of the ongoing European project CAUTION++. The results obtained are useful to understand the impact of several system component factors on the dependability of the overall system instance.
2004
Conference article
Restricted
Congestion analysis during outage, congestion treatment and outage recovery for simple GPRS networks
Lollini P, Bondavalli A, Di Giandomenico F, Porcarelli S
This paper deals with congestion analysis of a simple GPRS network composed by two cells partially overlapping. In particular, we consider that one of the two cells is affected by an outage and we analyze the effectiveness of applying a class of congestion treatment techniques that ultimately results in a switching of users from the congested cell to the other one. For this purpose, we introduce a modelling technique to support a proper calibration of the parameters involved in a reconfiguration action, in order to successfully treat the congestion phenomenon. The effectiveness of a reconfiguration action is evaluated in terms of indicators that represent the Quality of Service (QoS) perceived by the users in the congested and adjacent cells.
Lollini P, Bondavalli A, Di Giandomenico F, Porcarelli S
This paper deals with congestion analysis of a simple GPRS network composed by two cells partially overlapping. In particular, we consider that one of the two cells is affected by an outage and we analyze the effectiveness of applying a class of congestion treatment techniques that ultimately results in a switching of users from the congested cell to the other one. For this purpose, we introduce a modelling technique to support a proper calibration of the parameters involved in a reconfiguration action, in order to successfully treat the congestion phenomenon. The effectiveness of a reconfiguration action is evaluated in terms of indicators that represent the Quality of Service (QoS) perceived by the users in the congested and adjacent cells.
2004
Conference article
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Model-based evaluation of a radio resource management system for wireless
Porcarelli S, Di Giandomenico F, Bondavalli A, Lollini P
This paper focuses on dependability analysis of an interoperable platform for radio resource management and mobility support in multiple radio environments. The emphasis is on reliability and availability issues, which unavoidably need to be addressed to some extent to cope with malfunctions in such complex environment. With reference to the European project CAUTION++, which aims to build a capacity and network management platform for increased utilization of present and future wireless systems, means to help system design and verification w.r.t dependability requirements are here presented. For this purpose, we introduce and apply a modelling technique based on Petri nets in order to compare different architectural fault tolerant solutions. This evaluation is carried out in terms of the probability of correct/incorrect emission and correct/incorrect omission of a reconfiguration action decided by the CAUTION++ system.
Porcarelli S, Di Giandomenico F, Bondavalli A, Lollini P
This paper focuses on dependability analysis of an interoperable platform for radio resource management and mobility support in multiple radio environments. The emphasis is on reliability and availability issues, which unavoidably need to be addressed to some extent to cope with malfunctions in such complex environment. With reference to the European project CAUTION++, which aims to build a capacity and network management platform for increased utilization of present and future wireless systems, means to help system design and verification w.r.t dependability requirements are here presented. For this purpose, we introduce and apply a modelling technique based on Petri nets in order to compare different architectural fault tolerant solutions. This evaluation is carried out in terms of the probability of correct/incorrect emission and correct/incorrect omission of a reconfiguration action decided by the CAUTION++ system.
2003
Conference article
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Dependability Issues in Radio Resource Management of Wireless Systems
Di Giandomenico F, Porcarelli S, Lollini P, Bondavalli A
This paper focuses on resource management and mobility support in multiple radio environments. The emphasis is on dependability issues, which unavoidably need to be addressed to some extent to cope with malfunctions in such complex environment. With reference to the European project CAUTION++, which aims to build a capacity and network management platform for increased utilization of present and future wireless systems, dependability requirements, as well as means to help designing and verifying that such dependability requirements are fulfilled, are here discussed.
Di Giandomenico F, Porcarelli S, Lollini P, Bondavalli A
This paper focuses on resource management and mobility support in multiple radio environments. The emphasis is on dependability issues, which unavoidably need to be addressed to some extent to cope with malfunctions in such complex environment. With reference to the European project CAUTION++, which aims to build a capacity and network management platform for increased utilization of present and future wireless systems, dependability requirements, as well as means to help designing and verifying that such dependability requirements are fulfilled, are here discussed.
2005
Conference article
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NekoStat extension for Neko: quantitative evaluation of distributed algorithms
Falai L, Bondavalli A, Di Giandomenico F
In this paper we present NekoStat, an extension to the Neko tool. Neko is a Java framework and a communication platform that permits rapid prototyping of distributed applications. Distributed systems realized within the Neko framework can be exercised both on real networks and on simulated ones, without changes in the application code. We realized an extension to standard Neko, called NekoStat; it permits to obtain quantitative evaluations of systems implemented using Neko.
Falai L, Bondavalli A, Di Giandomenico F
In this paper we present NekoStat, an extension to the Neko tool. Neko is a Java framework and a communication platform that permits rapid prototyping of distributed applications. Distributed systems realized within the Neko framework can be exercised both on real networks and on simulated ones, without changes in the application code. We realized an extension to standard Neko, called NekoStat; it permits to obtain quantitative evaluations of systems implemented using Neko.
2005
Conference article
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QoS analysis of a UMTS cell with different service classes
Lollini P, Bondavalli A, Di Giandomenico F
Service (QoS) of a Universal Mobile Telecommunication System (UMTS) cell. Among UMTS characteristics, we focus the attention on two aspects strictly related with the identified QoS measures: the random-access procedure and the admission control strategy. Using a model-based approach, we model and evaluate a UMTS cell under several service classes, thus providing useful insights on the perception of the QoS both from the users'perspective and from the mobile telephone operators'one.
Lollini P, Bondavalli A, Di Giandomenico F
Service (QoS) of a Universal Mobile Telecommunication System (UMTS) cell. Among UMTS characteristics, we focus the attention on two aspects strictly related with the identified QoS measures: the random-access procedure and the admission control strategy. Using a model-based approach, we model and evaluate a UMTS cell under several service classes, thus providing useful insights on the perception of the QoS both from the users'perspective and from the mobile telephone operators'one.
2006
Conference article
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Critical utility infrastructural resilience
Dondossola G, Deconinck G, Di Giandomenico F, Donatelli S, Kaaniche M, Verissimo P
The paper refers to CRUTIAL , CRitical UTility InfrastructurAL Resilience, a European project within the research area of Critical Information Infrastructure Protection, with a specific focus on the infrastructures operated by power utilities, widely recognized as fundamental to national and international economy, security and quality of life. Such infrastructures faced with the recent market deregulations and the multiple interdependencies with other infrastructures are becoming more and more vulnerable to various threats, including accidental failures and deliberate sabotage and malicious attacks. The subject of CRUTIAL research are small scale networked ICT systems used to control and manage the electric power grid, in which artifacts controlling the physical process of electricity transportation need to be connected with corporate and societal applications performing management and maintenance functionality. The peculiarity of such ICT-supported systems is that they are related to the power system dynamics and its emergency conditions. Specific effort need to be devoted by the Electric Power community and by the Information Technology community to influence the technological progress in order to allow commercial intelligent electronic devices to be effectively deployed for the protection of citizens against cyber threats to electric power management and control systems. A well-founded know-how needs to be built inside the industrial power sector to allow all the involved stakeholders to achieve their service objectives without compromising the resilience properties of the logical and physical assets that support the electric power provision.
Dondossola G, Deconinck G, Di Giandomenico F, Donatelli S, Kaaniche M, Verissimo P
The paper refers to CRUTIAL , CRitical UTility InfrastructurAL Resilience, a European project within the research area of Critical Information Infrastructure Protection, with a specific focus on the infrastructures operated by power utilities, widely recognized as fundamental to national and international economy, security and quality of life. Such infrastructures faced with the recent market deregulations and the multiple interdependencies with other infrastructures are becoming more and more vulnerable to various threats, including accidental failures and deliberate sabotage and malicious attacks. The subject of CRUTIAL research are small scale networked ICT systems used to control and manage the electric power grid, in which artifacts controlling the physical process of electricity transportation need to be connected with corporate and societal applications performing management and maintenance functionality. The peculiarity of such ICT-supported systems is that they are related to the power system dynamics and its emergency conditions. Specific effort need to be devoted by the Electric Power community and by the Information Technology community to influence the technological progress in order to allow commercial intelligent electronic devices to be effectively deployed for the protection of citizens against cyber threats to electric power management and control systems. A well-founded know-how needs to be built inside the industrial power sector to allow all the involved stakeholders to achieve their service objectives without compromising the resilience properties of the logical and physical assets that support the electric power provision.
2001
Conference article
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Analysis and estimation of the quality of service of group communication protocols
Coccoli A, Bondavalli A, Di Giandomenico F
QoS (defined as a proper set of quantitative characteristics) analysis is a necessary step for the early verification and validation of an appropriate design, and for taking design decisions about the most rewarding choice, in relation with user requirements. In this paper, we describe an analytical approach for the evaluation of the QoS offered by a family of group communication protocols in a wireless environment, and use experimental data for feeding our models. Specific indicators have been defined and evaluated, which capture the main characteristics of the protocols and of the environment, focusing our attention on performance and dependability attributes. The defined models account for the correlation among successive packet transmissions due to fading and users mobility. The main purpose of our analysis is to provide a fast, cost effective, and formally sound way to further analyze and understand the protocol behavior and its environment.
Coccoli A, Bondavalli A, Di Giandomenico F
QoS (defined as a proper set of quantitative characteristics) analysis is a necessary step for the early verification and validation of an appropriate design, and for taking design decisions about the most rewarding choice, in relation with user requirements. In this paper, we describe an analytical approach for the evaluation of the QoS offered by a family of group communication protocols in a wireless environment, and use experimental data for feeding our models. Specific indicators have been defined and evaluated, which capture the main characteristics of the protocols and of the environment, focusing our attention on performance and dependability attributes. The defined models account for the correlation among successive packet transmissions due to fading and users mobility. The main purpose of our analysis is to provide a fast, cost effective, and formally sound way to further analyze and understand the protocol behavior and its environment.
2001
Conference article
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Analysis of the effects of outages on the quality of service of GPRS network systems
Tataranni F, Porcarelli L, Di Giandomenico F, Bondavalli A
The General Packet Radio Service (GPRS) extends the Global System Mobile Communications (GSM) by addressing packet-oriented traffic. Availability is the most important dependability requirement for such Comunication Systems as GPRS. Focusing on the contention phase, where users compete for channel reservation, this paper analyses the GPRS with the objective to understand its behaviour under critical conditions, as determined by periods of outages, which significantly impact on the resulting dependability. In fact, during outages (service unavailability), users tying to access the service accumulate, leading to an overload of the system. When the system resumes its operations, the accuniulated users determine a higher probability of collisions on resources assignment (and therefore a degradation of the QoS perceived by the users). Our analysis, performed using a simulation approach, allowed to gain insights on the impact of outages on the QoS and of the overload that GPRS systems have to face after outages.
Tataranni F, Porcarelli L, Di Giandomenico F, Bondavalli A
The General Packet Radio Service (GPRS) extends the Global System Mobile Communications (GSM) by addressing packet-oriented traffic. Availability is the most important dependability requirement for such Comunication Systems as GPRS. Focusing on the contention phase, where users compete for channel reservation, this paper analyses the GPRS with the objective to understand its behaviour under critical conditions, as determined by periods of outages, which significantly impact on the resulting dependability. In fact, during outages (service unavailability), users tying to access the service accumulate, leading to an overload of the system. When the system resumes its operations, the accuniulated users determine a higher probability of collisions on resources assignment (and therefore a degradation of the QoS perceived by the users). Our analysis, performed using a simulation approach, allowed to gain insights on the impact of outages on the QoS and of the overload that GPRS systems have to face after outages.
2001
Conference article
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Modeling and analysis of the behavior of GPRS systems
Tataranni F, Porcarelli S, Di Giandomenico F, Bondavalli A, Simoncini L
The General Packet Radio Service (GPRS) has recently become a standard to extend the services provided by the Global System for Mobile Communications (GSM). GPRS addresses packet-oriented traffic, by allowing a more efficient usage of the radio resources with a consequent improvement in the QoS of subscribers. This paper focuses on a preliminary evaluation of dependability and performance figures of the GPRS, by analyzing its behavior during the contention phase where users compete for the channel reservation. The presented work constitutes the first step towards the analysis of the GPRS under critical conditions, as determined by periods of outages, which significantly impact on the dependability, of the GPRS itself. In fact, outages imply service unavailability, with a consequent accumulation of users actively waiting for making a service request, leading to a higher probability of collisions on requests (and therefore a degradation of the QoS perceived by the users) when the system comes back up again. Here, some analyses have been performed, using a simulation approach, to gain insights on appropriate settings for the GPRS, at varying values of internal and external system conditions.
Tataranni F, Porcarelli S, Di Giandomenico F, Bondavalli A, Simoncini L
The General Packet Radio Service (GPRS) has recently become a standard to extend the services provided by the Global System for Mobile Communications (GSM). GPRS addresses packet-oriented traffic, by allowing a more efficient usage of the radio resources with a consequent improvement in the QoS of subscribers. This paper focuses on a preliminary evaluation of dependability and performance figures of the GPRS, by analyzing its behavior during the contention phase where users compete for the channel reservation. The presented work constitutes the first step towards the analysis of the GPRS under critical conditions, as determined by periods of outages, which significantly impact on the dependability, of the GPRS itself. In fact, outages imply service unavailability, with a consequent accumulation of users actively waiting for making a service request, leading to a higher probability of collisions on requests (and therefore a degradation of the QoS perceived by the users) when the system comes back up again. Here, some analyses have been performed, using a simulation approach, to gain insights on appropriate settings for the GPRS, at varying values of internal and external system conditions.
2001
Conference article
Metadata Only Access
Towards optimal database maintenance in wireless communication systems
Chohra A., Di Giandomenico F., Porcarelli L., Bondavalli A.
Chohra A., Di Giandomenico F., Porcarelli L., Bondavalli A.
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CNR IRIS
2001
Conference article
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Tuning of database audits to improve scheduled maintenance in communication systems
Porcarelli S, Di Giandomenico F, Chohra A, Bondavalli A
To ensure the consistency of database subsystems involved in communication systems (e.g., telephone systems), appropriate scheduled maintenance policies are necessary. Audit operations, consisting in periodic checks and recovery actions, are typically employed in databases to cope with run time faults which may affect the dependability and quality of service of the overall system. This paper aims at investigating on appropriate tuning of audit operations, so as to find optimal balances between contrasting requirements, namely satisfactory database availability and low overhead due to audits. For this purpose, a methodology to analyse the behaviour of the database under scheduled maintenance is here suggested. Analytical models, essentially based on Deterministic and Stochastic Petri Nets (DSPN), are defined and analysed, in terms of dependability indicators. A sensitivity analysis wrt to the most affecting internal and external parameters is also performed on a case study.
Porcarelli S, Di Giandomenico F, Chohra A, Bondavalli A
To ensure the consistency of database subsystems involved in communication systems (e.g., telephone systems), appropriate scheduled maintenance policies are necessary. Audit operations, consisting in periodic checks and recovery actions, are typically employed in databases to cope with run time faults which may affect the dependability and quality of service of the overall system. This paper aims at investigating on appropriate tuning of audit operations, so as to find optimal balances between contrasting requirements, namely satisfactory database availability and low overhead due to audits. For this purpose, a methodology to analyse the behaviour of the database under scheduled maintenance is here suggested. Analytical models, essentially based on Deterministic and Stochastic Petri Nets (DSPN), are defined and analysed, in terms of dependability indicators. A sensitivity analysis wrt to the most affecting internal and external parameters is also performed on a case study.
2002
Conference article
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Analyzing quality of service of GPRS network systems from a user's perspective
Porcarelli S, Di Giandomenico F, Bondavalli A
With reference to the General Packet Radio Service (GPRS), an extension of the Global System Mobile Communication (GSM) addressing packet-oriented traffic, this paper contributes to the analysis on the service accomplishment level perceived by GPRS users. The proposed modeling approach builds separately the GPRS and user models; the focus is on the GPRS access random procedure on one side, and different classes of users behavior on the other side. The overall model is obtained composing the basic submodels. Quantitative analysis, performed using a simulation approach, is carried out, showing the impact of users characteristics and network load on identified indicators expressing the QoS as perceived by users
Porcarelli S, Di Giandomenico F, Bondavalli A
With reference to the General Packet Radio Service (GPRS), an extension of the Global System Mobile Communication (GSM) addressing packet-oriented traffic, this paper contributes to the analysis on the service accomplishment level perceived by GPRS users. The proposed modeling approach builds separately the GPRS and user models; the focus is on the GPRS access random procedure on one side, and different classes of users behavior on the other side. The overall model is obtained composing the basic submodels. Quantitative analysis, performed using a simulation approach, is carried out, showing the impact of users characteristics and network load on identified indicators expressing the QoS as perceived by users