References of "Leduc, Guy"
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See detailTowards a Proposal for Datatypes in E-LOTOS
Jeffrey, Alan; Garavel, Hubert; Leduc, Guy ULg et al

Report (1995)

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See detailTime Extended LOTOS
Léonard, Luc; Leduc, Guy ULg

Report (1995)

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See detailA Group Communication Framework
Mathy, Laurent ULg; Leduc, Guy ULg; Bonaventure, Olivier et al

in Bauerfeld, Wulf; Spaniol, Otto; Williams, F. (Eds.) Broadband Islands '94: Connecting with the End-User (1994, June)

This paper presents a general architectural model for group communications which are communications that may involve more than two parties. The concept of group is presented and the concept of group ... [more ▼]

This paper presents a general architectural model for group communications which are communications that may involve more than two parties. The concept of group is presented and the concept of group association, which is an instance of group communication, is analysed. Those group associations are modeled as a set of basic components called multicast conversations. At the service boundery, new architectural concepts are introduced to identify a group association as well as its multicast conversations. Then, facilities to handle the group associations and the multicast conversations are defined and the properties of data transfer on a group association are examined. Finally, the paper deals with aspects of group management. [less ▲]

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See detailFailure-based Congruences, Unfair Divergences and New Testing Theory
Leduc, Guy ULg

in Vuong, Son; Chanson, Sam (Eds.) Protocol Specification, Testing and Verification, XIV (1994, June)

The testing equivalence 'te' that is used as a reference in verification and testing theory in LOTOS is not a congruence, and no explicit definition of the least congruence stronger than 'te' has been ... [more ▼]

The testing equivalence 'te' that is used as a reference in verification and testing theory in LOTOS is not a congruence, and no explicit definition of the least congruence stronger than 'te' has been found. The critical LOTOS context in which congruence is lost is the hiding context that creates divergence. In this paper we first survey this problem and present three known variants of 'te' that are congruences. Each of them, as well as 'te', is then related to a particular interpretation of divergences in terms of (un)fairness of divergences. The associated preorders that generate these equivalences are also presented. Based on these results, we propose a new testing theory based on unfair divergences. It defines new equivalence and conformance relations, as well as the associated canonical tester. We also prove that the least congruence stronger than this new testing equivalence is one of three presented failure-based congruences, which thus also deserves the label of testing congruence. [less ▲]

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See detailA Group Communication Framework
Mathy, Laurent ULg; Leduc, Guy ULg; Bonaventure, Olivier et al

Report (1994)

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See detailA formal definition of time in LOTOS
Leduc, Guy ULg; Léonard, Luc

Report (1994)

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See detailA Method for Applying LOTOS at an Early Design Stage and Its Application to the ISO Transport Protocol
Leduc, Guy ULg

in The OSI95 Transport Service with Multimedia Support (1994)

We propose a method applicable to the design of large and abstract LOTOS specifications. More precisely, this method explains how to generate a constrain-oriented specification which is an adequate ... [more ▼]

We propose a method applicable to the design of large and abstract LOTOS specifications. More precisely, this method explains how to generate a constrain-oriented specification which is an adequate abstract and modular starting point of a complex design process leading to implementation. It is illustrated on a substantial part of the ISO Transport Protocol class 4 which is considered as a complex and stable case study. Having proved the feasibility of the method on this protocol, it was then used to specify (parts of) the new transport protocol TPX of OSI95. [less ▲]

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See detailOn the Provision of a Fast Connect Facility in a Connection-Mode Transport Service
Leduc, Guy ULg; Danthine, André ULg

in The OSI95 Transport Service with Multimedia Support (1994)

A "fast connect" facility in a connection-mode service allows the calling service user to send service data units without waiting for the rount trip delay associated with the successful establishment of ... [more ▼]

A "fast connect" facility in a connection-mode service allows the calling service user to send service data units without waiting for the rount trip delay associated with the successful establishment of the connection. In this paper we investigate how such a fast connect facility can be added to a connection-mode transport service. Starting from the eXpress Transfer Protocol (XTP) which is at the origin of the concepr, we analyse the High Speed Transport Service (HSTS) and study how it can be improved by the introduction of a listening interaction at the called side. After having criticized these two transport facilities, we finally propose three possible models of the fast connect facility. The first one is the 4-primitive connection establishment from the Broadbant Transport Service (BTS) and the last ones are two 3-primitive connection establishment. [less ▲]

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See detailThe OSI95 Connection-Mode Transport Service
Baguette, Yves; Léonard, Luc; Leduc, Guy ULg et al

in The OSI95 Transport Service with Multimedia Support (1994)

We present the main features of the connection-mode service developed as a part of the entire OSI95 Enhanced Transport Service. This connection-mode service results from modifications and enhancements to ... [more ▼]

We present the main features of the connection-mode service developed as a part of the entire OSI95 Enhanced Transport Service. This connection-mode service results from modifications and enhancements to the standard ISO/IEC Connection-Mode Transport Service. Some of the enhancements are just mentioned in this paper for they are addressed in detail in companion papers. [less ▲]

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See detailThe Qos Enhancements in OSI95
Danthine, André ULg; Bonaventure, Olivier; Leduc, Guy ULg

in The OSI95 Transport Service with Multimedia Support (1994)

The new communication environment has brought new requirements on the qualities of service for which the present "best effort" semantics is inadequate. The response to this evolution goes through the ... [more ▼]

The new communication environment has brought new requirements on the qualities of service for which the present "best effort" semantics is inadequate. The response to this evolution goes through the definition of a new model of QoS for the lower layers. In the Òbest effortÓ model, when a service provider accepts a transmission with a given QoS, it does not commit itself to any duty about the way it will take account of this QoS. The "guaranteed" QoS requires resources reservation mechanisms which are not always available. We present in this paper a new semantics for the QoS. It allows a service user to express more accurately its requirements, and although it does not include yet a concept of guarantee of the result, the fact is that it assures the users that the provider will monitor the selected parameters and return some defined feedback about the way it succeeds in meeting their requirements. New negotiation rules have also been specified, which are consistent with the new semantics. An example illustrates the practical use of the notions we have introduced which are at the origin of the OSI95 transport service. [less ▲]

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See detailOSI95 Contributions to ISO/IEC and ETSI
Leduc, Guy ULg; Danthine, André ULg

in The OSI95 Transport Service with Multimedia Support (1994)

This paper summarizes the activities that were carried out within the standardization bodies ISO/IEC and ETSI during the two-year period of the OSI95 project. However it focuses mainly on the OSI95 ... [more ▼]

This paper summarizes the activities that were carried out within the standardization bodies ISO/IEC and ETSI during the two-year period of the OSI95 project. However it focuses mainly on the OSI95 contributions. [less ▲]

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See detailThe Tick-Tock Case Study for the Assessment of Timed FDT's
Léonard, Luc; Leduc, Guy ULg; Danthine, André ULg

in The OSI95 Transport Service with Multimedia Support (1994)

The initial purpose of this paper was to design a case study to assess LOTOS-T [MFV93] which is a temporal extension of LOTOS developed within the ESPRIT II OSI95 project. However, we think that it can be ... [more ▼]

The initial purpose of this paper was to design a case study to assess LOTOS-T [MFV93] which is a temporal extension of LOTOS developed within the ESPRIT II OSI95 project. However, we think that it can be useful for any proposed timed FDT. It consists of a protocol composed of two entities and an underlying service provider, whose behaviour is mainly based on various timing constraints such as time-out, isochronism, rate-control,... The selection of the mechanisms was guided by the two following characteristics: Realism: the selected mechanisms have been inspired by similar and existing protocol mechanisms or service facilities, even if we have tried to (over)simplify them in order to focus the case study on the timing constraints. Temporal modelling facilities: this means that the specificity and the variety of the timing constraints are intended to assess whether timed FDTs have enough power and flexibility to tackle a maximum number of aspects of timed behaviours. Of course, we do not pretend to have explored all possible timed behaviours which may exist in protocols. We have simply tried to cover a broad spectrum of them. [less ▲]

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See detailThe Connection Release Facilities in the OSI95 Transport Service
Baguette, Yves; Leduc, Guy ULg

in The OSI95 Transport Service with Multimedia Support (1994)

We explain in detail how the work carried out on the transport connection release aspects in the framework of the OSI95 Connection-Mode Transport Service has led to the introduction of a graceful ... [more ▼]

We explain in detail how the work carried out on the transport connection release aspects in the framework of the OSI95 Connection-Mode Transport Service has led to the introduction of a graceful transport connection release facility and, later on, to an enhancement of the existing ISO/IEC abrupt transport connection release facility. [less ▲]

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See detailBelgian-Spanish Proposal for a Time Extended LOTOS
Léonard, Luc; Leduc, Guy ULg; de Frutos, David et al

Report (1994)

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See detailAn Enhanced Version of Timed LOTOS and its Application to a Case study
Léonard, Luc; Leduc, Guy ULg

in Tenney, R. L.; Amer, P. D.; Uyar, M. U. (Eds.) FORMAL DESCRIPTION TECHNIQUES, VI (1993, October)

We propose here ET-LOTOS, a timed extension of LOTOS. It is an enhancement of Timed LOTOS that we presented at FORTE 92. We show how some simple modifications allow us to improve the expressiveness of our ... [more ▼]

We propose here ET-LOTOS, a timed extension of LOTOS. It is an enhancement of Timed LOTOS that we presented at FORTE 92. We show how some simple modifications allow us to improve the expressiveness of our former formalism. To assess ET-LOTOS, we apply it to the specification of a small case study. Finally, we show how the semantics of ET-LOTOS could be modified to easily define more powerful operators, if one ever had to. [less ▲]

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See detailComment rendre LOTOS apte à spécifier des systèmes temps réel ?
Leduc, Guy ULg; Léonard, Luc

in Dssouli, Rachida; Bochmann, Gregor (Eds.) Ingénierie des Protocoles (1993, September)

We explain and justify by examples our proposed timed extension of LOTOS. The examples cover protocol functions and service facilities that are frequently encountered in practice or are inspired by ... [more ▼]

We explain and justify by examples our proposed timed extension of LOTOS. The examples cover protocol functions and service facilities that are frequently encountered in practice or are inspired by existing ones, such as timers, watchdogs, delays, isochronism, multimedia, rate control, ... The semantics of the language is presented after, and its properties discussed more formally. We think that the systematic application of formal temporal techniques to this kind of examples is unavoidable to convince of the pertinence of the design choices. The practical effectiveness of a formalism is as important as the associated mathematical properties. [less ▲]

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See detailThe OSI95 Enhanced Transport Services
Baguette; Léonard, Luc; Leduc, Guy ULg et al

Report (1993)

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See detailQoS Enhancements and the new transport services
Danthine, André ULg; Bonaventure, Olivier; Baguette, Yves et al

in Onvural, R.; Nilsson, A. (Eds.) Local Area Network Interconnection (1993)

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See detailThe OSI 95 Connection-mode Transport Service-The Enhanced QoS
Danthine, André ULg; Baguette, Yves; Leduc, Guy ULg et al

in Danthine, André; Spaniol, Otto (Eds.) HIGH PERFORMANCE NETWORKING, IV (1992, December)

During the last ten years, tremendous changes have taken place in the communication environments. First, there has been a continuous increase in network performance that has led, for instance, to ... [more ▼]

During the last ten years, tremendous changes have taken place in the communication environments. First, there has been a continuous increase in network performance that has led, for instance, to increasingly high access data rates available in the lower layers. Furthermore, the changes in the offered network services have raised the issue of providing, at the transport level, services already provided at the subnetwork level, such as multicast or synchronous services for example. With the arrival of new applications, such as multimedia or client/server applications, a widening of the application requirements has also been observed. It is this evolving environment that has been at the origin of the ESPRIT II project OSI 95. An important task in the framework of this project is the definition of an enhanced Transport Service taking account of the aforementioned evolutions. The enhanced Transport Service specified for OSI 95 consists of several types of service. The paper presents the connection-mode Transport Service. We focus mainly on the following original features of our connection-mode service: a new semantics for QoS parameters and the associated negotiation and re-negotiation. [less ▲]

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