Retour au site du LAAS-CNRS

Abstract

In this paper, we propose a refinement-based adaptation approach for the architecture of distributed group communication support applications. Unlike most of previous works, our approach reaches implementable, context-aware and dynamically adaptable architectures. To model the context, we manage simultaneously four parameters that influence Qos provided by the application. These parameters are: the available bandwidth, the exchanged data communication priority, the energy level and the available memory for processing. These parameters make it possible to refine the choice between the various architectural configurations when passing from a given abstraction level to the lower level which implements it. Our approach allows the importance degree associated with each parameter to be adapted dynamically. To implement adaptation, we switch between the various configurations of the same level, and we modify the state of the entities of a given configuration when necessary. We adopt the direct and mediated Producer/Consumer architectural styles and graphs for architecture modelling. In order to validate our approach we elaborate a simulation model.

Abstract

Adaptation of deployment is required for maintaining the Quality of Service (QoS) in Service Oriented Architectures (SOA). Dy- namic reconfiguration of SOA is proposed here to to cope with adapta- tion in reaction to or in prediction of QoS degradation. Handling such an issue needs to detect and to identify the deficiency source, and to reconfigure the architecture implementing service composition. System reconfiguration constitutes a complex activity acting on distributed soft- ware entities, and requires to be implemented by correct model-based approaches. We show in this paper how graph grammars can be used to design policy-driven reconfiguration mechanisms of architectures and to rule running applications using reconfiguration laws. We describe how coordinated architectural actions and reconfiguration policies are used to maintain QoS at runtime.

Mots-Clés / Keywords

Abstract

The need for on-demand QoS support for communications over satellite is of primary importance for distributed multimedia applications. This is particularly true for the return link which is often a bottleneck due to the large set of end-users accessing a very limited uplink resource. Facing this need, Demand Assignment Multiple Access (DAMA) is a classical technique that allows satellite operators to offer various types of services, while managing the resources of the satellite system efficiently. Tackling the quality degradation and delay accumulation issues that can result from the use of these techniques, this paper proposes an instantiation of the Application Layer Framing (ALF) approach, using a cross-layer interpreter (xQoS-Interpreter). The information provided by this interpreter is used to manage the resource provided to a terminal by the satellite system in order to improve the quality of multimedia presentations from the end users point of view. Several experiments are carried out for different loads on the return link. Their impact on QoS is measured through different application as well as network level metrics.

Mots-Clés / Keywords

Abstract

This paper presents an approach that aims to provide Quality of Services (QoS) over heterogeneous Internet domains. The goal is to install and to manage QoS inside each domain and to ensure it on the end to end data path. QoS is a key requirement representing a significant infrastructure upgrade for future networks. Our proposal relies on the multi-service, multi-technology model based on Bandwidth Broker, entity in charge of controlling a given domain. It introduces a concept able to provide QoS in a set of domains using an inter domain signaling protocol as well as dynamic provisioning schemes that optimize resource usage. The approach is independent of the intra-domain routing protocol. Moreover it is independent of the underlying technology and imposes minimal constraints leaving a maximum degree of freedom for users and domains providers to implement specific internal solutions. The efficiency of the solution is shown through extensive simulations.

Mots-Clés / Keywords