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As IRL design has changed over time, we classify papers on IRL into two disjoint classes: We also present the results of our investigations on CORBA Portable Interceptors: R. Baldoni, C.Marchetti, S.Tucci Piergiovanni Abstract:"The deployment of server replicas of a given 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. This paper proposes a threetier architecture for software replication that encapsulates the need of partial synchrony in a specific software component of a mid-tier to free replicas (end-tier) and clients (client-tier) 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." Download : R. Baldoni, C.Marchetti, S.Tucci Piergiovanni Abstract:"The synchronization among thin, independent and concurrent processes in an open distributed system is a fundamental issue in current architectures (e.g. middlewares, three-tier architectures etc.). “Independent process” means no message has to be exchanged among the processes to synchronize themselves and “open” means that the number of processes that require to synchronize changes along the time. In this paper we present the speci.cation of a sequencer service that allows independent processes to get a sequence number that can be used to label successive operations (e.g. to allow a set of independent and concurrent processes to get a total order on these labelled operations). Moreover, we propose an implementation of the sequencer service in the timed asynchronous model along with its correctness proof." R. Baldoni, C.Marchetti, A.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 mid-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. Finally a detailed description of an IRL prototype developed in our department is proposed along with an extensive performance analysis." Download : R. Baldoni, C.Marchetti, A. Virgillito Abstract:"Cooperative information systems are characterized by distribution, high heterogeneity and scale. Therefore they require interoperable, dependable services on top of which the development of cooperative application can take place. This paper studies, in the context of the Unitary Network of the Italian Public Administration, the problem of increasing the availability of the services exported by a cooperating entity through interoperable middleware. In particular we show how a Fault Tolerant CORBA compliant system, namely the Interoperable Replication Logic (IRL), can be used to increase such availability by building a replicated cooperative gateway that wraps enterprise cooperative applications." Download : .pdf R. Baldoni, C.Marchetti, R.Panella, L.Verde Abstract:"The handling of Interoperable Object Group References (IOGRs) is one of the basic building block of any FT-CORBA compliant platform. In this paper we introduce two basic components: IOGRManager, a tool to create, update, browse IOGRs, and an Object-Request-GateWay (ORGW), a CORBA compliant client request interceptor, which allows clients running on non-FT-Corba compliant ORBs to transparently interact with replicated objects residing on FT-CORBA-compliant platforms. Both components have been developed in the context of Interoperable Replication Logic (IRL) project which investigates the impact of three tiers architectures on software replication." C.Marchetti, A.Virgillito, R. Baldoni Abstract:"In this paper we present the design of IRL (Interoperable Replication Logic), a FT-CORBA compliant platform that provides transparent client-server interactions and server failovers to application clients by using a set of replicated CORBA objects (IRL components). As cooperation among IRL components is carried out using standard CORBA invocations, IRL allows deployments of CORBA server objects and IRL components over ORBs from distinct vendors satisfying the interoperability property." C.Marchetti, R. Baldoni, A.Virgillito, F.Zito, Abstract:"In this paper we present the failure management system of IRL (Interoperable Replication Logic) which is a FT-CORBA platform that provides transparent/server interactions and server failovers to application clients by using a set of replicated CORBA objects (IRL components). The IRL failure management system includes two basic mechanisms, failure detection and recovery. Each of these mechanisms follows a service stack approach (i) to reduce as many as possible the impact of the services in terms of network traffic and (ii) to use the same services both for application objects and for IRL components." C.Marchetti, L.Verde, R.Baldoni, Abstract:"Interceptors are a mean to add specific network-oriented capabilities (such as authentication, flow control, caching etc.) to a distributed application which runs over a middleware without changing either the application code or the middleware's one. However, interceptors could be non-intuitive and this could in turn limit their use on a large scale. In this paper we present results of an investigation on CORBA portable interceptors in Java on various CORBA platforms. This study includes the identification of the basic mechanisms provided by an interceptor, of their limitations, a proxy-based technique to overcome some of these limitations and a performance analysis. We also release fragments of Java code used for experiments on Interceptor." Download Extended Version (submitted for publication): .pdf .ps C.Marchetti, M.Mecella, A.Virgillito, R.Baldoni, Abstract:"The Replication Logic is a set of protocols, mechanisms and services that allow a CORBA system to handle object replication. In this paper we present a specific implementation of a Replication Logic, namely Interoperable Replication Logic (IRL), which exhibits nice properties like non-intrusion (i.e., the replication logic is built "above" the ORB) and interoperability (i.e., a client can reside on an ORB while server replicas reside on other, possibly distinct, ORBs). We compare IRL to other CORBA systems implementing replication logic such as Eternal, OGS, DOORS, Isis+Orbix, etc." C.Marchetti, A. Virgillito, M.Mecella, R.Baldoni, Abstract:"Integrating autonomous enterprise systems allows the cooperation among entities belonging to distinct systems. As an example, this problem shows up when integrating software services of large departments and organizations of the Public Administration of a country. This paper studies, in the context of the Unitary Network of the Italian Public Administration, the problem of increasing the availability of services exported by an autonomous enterprise system towards others. In particular we show how a fault tolerant CORBA system, namely the Interoperable Replication Logic (IRL), can be used to increase such an availability by building a replicated cooperative gateway that wraps enterprise applications." C.Marchetti, M.Mecella, R.Baldoni, Abstract:"The Common Object Request Broker Architecture (CORBA) is one of the most popular standard for middleware platforms based on object technology. CORBA shields distributed applications from the heterogeneity of the bare distributed system. Till recently CORBA did not address the fault tolerance issue which is actually one of the core aspects of distributed applications running upon an heterogeneous environment. As a consequence, in the last few years many research proposals have appeared in the literature to add reliability and availability to CORBA applications. This paper first analyzes the advantages and drawbacks of such proposals and shows that none of them completely exploits the platform independence provided by CORBA. Then it proposes a novel CORBA-compliant approach, which differs in allowing the deployment of a dependable infrastructure in heterogeneous environments." |
