The Experts below are selected from a list of 24 Experts worldwide ranked by ideXlab platform

Carlo Marchetti - One of the best experts on this subject based on the ideXlab platform.

  • Fully distributed three-tier active Software Replication
    IEEE Transactions on Parallel and Distributed Systems, 2006
    Co-Authors: Carlo Marchetti, Roberto Baldoni, Sara Tucci-piergiovanni, A. Virgillito
    Abstract:

    Keeping strongly consistent the state of the replicas of a Software service deployed across a distributed system prone to crashes and with highly unstable message transfer delays (e.g., the Internet), is a real practical challenge. The solution to this problem is subject to the FLP impossibility result, and thus there is a need for "long enough" periods of synchrony with time bounds on process speeds and message transfer delays to ensure deterministic termination of any run of agreement protocols executed by replicas. This behavior can be abstracted by a partially synchronous computational model. In this setting, before reaching a period of synchrony, the underlying network can arbitrarily delay messages and these delays can be perceived as false failures by some timeout-based failure detection mechanism leading to unexpected service unavailability. This paper proposes a fully distributed solution for active Software Replication based on a three-tier Software architecture well-suited to such a difficult setting. The formal correctness of the solution is proved by assuming the middle-tier runs in a partially synchronous distributed system. This architecture separates the ordering of the requests coming from clients, executed by the middle-tier, from their actual execution, done by replicas, i.e., the end-tier. In this way, clients can show up in any part of the distributed system and replica placement is simplified, since only the middle-tier has to be deployed on a well-behaving part of the distributed system that frequently respects synchrony bounds. This deployment permits a rapid timeout tuning reducing thus unexpected service unavailability

  • asynchronous active Replication in three tier distributed systems
    Pacific Rim International Symposium on Dependable Computing, 2002
    Co-Authors: Roberto Aldoni, Carlo Marchetti, Tucci S Piergiovanni
    Abstract:

    The deployment of server replicas of a service across an asynchronous distributed system (e.g., Internet) is a real practical challenge. This target cannot be indeed achieved by classical Software Replication techniques (e.g., passive and active Replication) as these techniques usually rely on group communication toolkits that require server replicas to run over a partially synchronous distributed system to solve the underlying agreement problem. This paper proposes a three-tier architecture for Software Replication that encapsulates the need of partial synchrony in a specific Software component of a mid-tier to free replicas and clients from the need of underlying partial synchrony assumptions. Then we propose how to specialize the mid-tier in order to manage active Replication of server replicas.

  • active Software Replication through a three tier approach
    Symposium on Reliable Distributed Systems, 2002
    Co-Authors: Roberto Baldoni, Carlo Marchetti, Alessandro Termini
    Abstract:

    A Replication logic is the set of protocols and mechanisms implementing a Software Replication technique. A three-tier approach to Replication consists in separating the Replication logic from both clients and replicated servers by embedding such logic in a middle-tier In this paper we first introduce the fundamental concepts underlying three-tier Replication. This approach has two main practical advantages: (i) it allows to maintain consistency among the state of server replicas deployed within an asynchronous distributed system and (ii) it supports very thin clients. Then we present the Interoperable Replication Logic (IRL) architecture, which is a Fault Tolerant CORBA compliant infrastructure exploiting a three-tier approach to replicate stateful deterministic CORBA objects. In this context, we illustrate the three-tier Replication protocol currently implemented in our IRL prototype and a performance analysis that shows the feasibility of the three-tier approach to Software Replication.

Roberto Baldoni - One of the best experts on this subject based on the ideXlab platform.

  • Fully distributed three-tier active Software Replication
    IEEE Transactions on Parallel and Distributed Systems, 2006
    Co-Authors: Carlo Marchetti, Roberto Baldoni, Sara Tucci-piergiovanni, A. Virgillito
    Abstract:

    Keeping strongly consistent the state of the replicas of a Software service deployed across a distributed system prone to crashes and with highly unstable message transfer delays (e.g., the Internet), is a real practical challenge. The solution to this problem is subject to the FLP impossibility result, and thus there is a need for "long enough" periods of synchrony with time bounds on process speeds and message transfer delays to ensure deterministic termination of any run of agreement protocols executed by replicas. This behavior can be abstracted by a partially synchronous computational model. In this setting, before reaching a period of synchrony, the underlying network can arbitrarily delay messages and these delays can be perceived as false failures by some timeout-based failure detection mechanism leading to unexpected service unavailability. This paper proposes a fully distributed solution for active Software Replication based on a three-tier Software architecture well-suited to such a difficult setting. The formal correctness of the solution is proved by assuming the middle-tier runs in a partially synchronous distributed system. This architecture separates the ordering of the requests coming from clients, executed by the middle-tier, from their actual execution, done by replicas, i.e., the end-tier. In this way, clients can show up in any part of the distributed system and replica placement is simplified, since only the middle-tier has to be deployed on a well-behaving part of the distributed system that frequently respects synchrony bounds. This deployment permits a rapid timeout tuning reducing thus unexpected service unavailability

  • active Software Replication through a three tier approach
    Symposium on Reliable Distributed Systems, 2002
    Co-Authors: Roberto Baldoni, Carlo Marchetti, Alessandro Termini
    Abstract:

    A Replication logic is the set of protocols and mechanisms implementing a Software Replication technique. A three-tier approach to Replication consists in separating the Replication logic from both clients and replicated servers by embedding such logic in a middle-tier In this paper we first introduce the fundamental concepts underlying three-tier Replication. This approach has two main practical advantages: (i) it allows to maintain consistency among the state of server replicas deployed within an asynchronous distributed system and (ii) it supports very thin clients. Then we present the Interoperable Replication Logic (IRL) architecture, which is a Fault Tolerant CORBA compliant infrastructure exploiting a three-tier approach to replicate stateful deterministic CORBA objects. In this context, we illustrate the three-tier Replication protocol currently implemented in our IRL prototype and a performance analysis that shows the feasibility of the three-tier approach to Software Replication.

  • Software Replication in three tiers architectures is it a real challange
    IEEE Computer Society Workshop on Future Trends of Distributed Computing Systems, 2001
    Co-Authors: Roberto Baldoni, C Marchetti
    Abstract:

    This paper is a first attempt to study the problem of handling Software Replication in three tiers architectures. In particular a study based on synchronization and communication patterns imposed by Replication is presented. We show how the complexity of the Replication scheme is affected by the deterministic (or not) behavior of the members of the backtier We also give two generic synchronization and communication patterns used in two and three tiers Replication. Well-known schemes such us active and passive Replication are particular instances of these generic patterns.

A. Virgillito - One of the best experts on this subject based on the ideXlab platform.

  • Fully distributed three-tier active Software Replication
    IEEE Transactions on Parallel and Distributed Systems, 2006
    Co-Authors: Carlo Marchetti, Roberto Baldoni, Sara Tucci-piergiovanni, A. Virgillito
    Abstract:

    Keeping strongly consistent the state of the replicas of a Software service deployed across a distributed system prone to crashes and with highly unstable message transfer delays (e.g., the Internet), is a real practical challenge. The solution to this problem is subject to the FLP impossibility result, and thus there is a need for "long enough" periods of synchrony with time bounds on process speeds and message transfer delays to ensure deterministic termination of any run of agreement protocols executed by replicas. This behavior can be abstracted by a partially synchronous computational model. In this setting, before reaching a period of synchrony, the underlying network can arbitrarily delay messages and these delays can be perceived as false failures by some timeout-based failure detection mechanism leading to unexpected service unavailability. This paper proposes a fully distributed solution for active Software Replication based on a three-tier Software architecture well-suited to such a difficult setting. The formal correctness of the solution is proved by assuming the middle-tier runs in a partially synchronous distributed system. This architecture separates the ordering of the requests coming from clients, executed by the middle-tier, from their actual execution, done by replicas, i.e., the end-tier. In this way, clients can show up in any part of the distributed system and replica placement is simplified, since only the middle-tier has to be deployed on a well-behaving part of the distributed system that frequently respects synchrony bounds. This deployment permits a rapid timeout tuning reducing thus unexpected service unavailability

Alessandro Termini - One of the best experts on this subject based on the ideXlab platform.

  • active Software Replication through a three tier approach
    Symposium on Reliable Distributed Systems, 2002
    Co-Authors: Roberto Baldoni, Carlo Marchetti, Alessandro Termini
    Abstract:

    A Replication logic is the set of protocols and mechanisms implementing a Software Replication technique. A three-tier approach to Replication consists in separating the Replication logic from both clients and replicated servers by embedding such logic in a middle-tier In this paper we first introduce the fundamental concepts underlying three-tier Replication. This approach has two main practical advantages: (i) it allows to maintain consistency among the state of server replicas deployed within an asynchronous distributed system and (ii) it supports very thin clients. Then we present the Interoperable Replication Logic (IRL) architecture, which is a Fault Tolerant CORBA compliant infrastructure exploiting a three-tier approach to replicate stateful deterministic CORBA objects. In this context, we illustrate the three-tier Replication protocol currently implemented in our IRL prototype and a performance analysis that shows the feasibility of the three-tier approach to Software Replication.

Sara Tucci-piergiovanni - One of the best experts on this subject based on the ideXlab platform.

  • Fully distributed three-tier active Software Replication
    IEEE Transactions on Parallel and Distributed Systems, 2006
    Co-Authors: Carlo Marchetti, Roberto Baldoni, Sara Tucci-piergiovanni, A. Virgillito
    Abstract:

    Keeping strongly consistent the state of the replicas of a Software service deployed across a distributed system prone to crashes and with highly unstable message transfer delays (e.g., the Internet), is a real practical challenge. The solution to this problem is subject to the FLP impossibility result, and thus there is a need for "long enough" periods of synchrony with time bounds on process speeds and message transfer delays to ensure deterministic termination of any run of agreement protocols executed by replicas. This behavior can be abstracted by a partially synchronous computational model. In this setting, before reaching a period of synchrony, the underlying network can arbitrarily delay messages and these delays can be perceived as false failures by some timeout-based failure detection mechanism leading to unexpected service unavailability. This paper proposes a fully distributed solution for active Software Replication based on a three-tier Software architecture well-suited to such a difficult setting. The formal correctness of the solution is proved by assuming the middle-tier runs in a partially synchronous distributed system. This architecture separates the ordering of the requests coming from clients, executed by the middle-tier, from their actual execution, done by replicas, i.e., the end-tier. In this way, clients can show up in any part of the distributed system and replica placement is simplified, since only the middle-tier has to be deployed on a well-behaving part of the distributed system that frequently respects synchrony bounds. This deployment permits a rapid timeout tuning reducing thus unexpected service unavailability