A Group Communication Framework

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 ▲]

On the Provision of a Fast Connect Facility in a Connection-Mode Transport Service

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 ▲]

The Qos Enhancements in OSI95

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 ▲]

The Tick-Tock Case Study for the Assessment of Timed FDT's

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 ▲]

The OSI95 Enhanced Transport Services

Report (1993)

The OSI 95 Connection-mode Transport Service-The Enhanced QoS

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 ▲]