TOPCOM: Topology-Aware Reliable Group Communication in Geographically Large-Scale Systems

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The goal of the project is twofold: in first place, it intends to implement and test a mature distribution of the Navigators' protocols and, in second place, to contribute to the validation the Ensemble framework. Since there are several technical differences between the protocol designed by the Navigators and the protocols currently implemented in Ensemble, this experiment will emphasize the generic aspects of the framework and reveal its potential limitations. The project will gather feedback from protocol implementors in order to improve the framework and, hopefully, to support other research groups in adopting Ensemble for their projects.


The project pretends to mature some of the topological protocols previously developed by the team and to test their implementation in the Ensemble platform. It also intends to study novel architectures to support the implementation and execution of configurable protocol stacks.

Approach and Methods

The project intends to develop and evaluate prototypes and use the experience gained to refine the models, algorithms, protocols and implementations.

Progress and Results

Part of the project was dedicated to the implementation of a Light-Weight Groups Layer in the Ensemble system. This experiment helped to get insights on the tradeoffs involved in the design of a platform to implement and execute configurable protocol stacks.

The project also investigated the developemnt of a protocol composition framework able to support inter-QoS constraints. A prototype of this platform, called Appia, has been implemented.


  • Alexandre Pinto, Hugo Miranda, Luís Rodrigues, “Light-Weight Groups: an implementation in Ensemble”, in in Proceedings of the Ersads 2001, European Research Seminar on Advances in Distributed Systems, 14-18 May 2001, Bertinoro (Forlì), Italy., May 2001.

  • Miguel Antunes, Hugo Miranda, António Rito Silva, Luís Rodrigues, Jorge Martins, “Separating Replication from Distributed Communication: Problems and Solutions”, in in Proceedings of the International Workshop on Distributed Dynamic Multiservice Architectures (DDMA), in conjunction with the 21st International Conference on Distributed Computing Systems (ICDCS-21) April 16-19, 2001, pp 103-108Phoenix, Arizona, USA, Apr. 2001.

  • João Rodrigues, Hugo Miranda, João Ventura, Luís Rodrigues, “The design of RTAppia”, in in Proceedings of the Sixth IEEE International Workshop on Object-oriented Real-Time Dependable Systems, Rome, 8-10 January 2001., Jan. 2001.

  • Luís Rodrigues, Katherine Guo, Paulo Verissimo, Kenneth P. Birman, “A Dynamic Light-Weight Group Service”, in Journal of Parallel and Distributed Computing Vol. 60, No. 12, December 2000, pp 1449-1479. Academic Press., Dec. 2000.

  • J. Pereira, Luís Rodrigues, R. Oliveira, “Semantically Reliable Multicast Protocols”, in in Proceedings of the 19th IEEE Symposium on Reliable Distributed Systems, pp. 60-69, Nurnberg, Germany, October 2000., Oct. 2000.

  • Luís Rodrigues, K. Guo, “Partitionable Light-Weight Groups”, in Proceedings of the 20th IEEE International Conference on Distributed Computing Systems, Taipe, Taiwan, Apr. 2000.

  • Luís Rodrigues, R. Baldoni, E. Anceaume, M. Raynal, “Deadline-Constrained Causal Order”, in In Proceedings of the The 3rd IEEE International Symposium on Object-oriented Real-time distributed Computing, Newport Beach, California, USA, March, 2000., Mar. 2000.

  • Luís Rodrigues, Rachid Guerraoui, A. Schiper, “Scalable Atomic Multicast”, in Proceedings of the Seventh International Conference on Computer Communications and Networks (IC3N'98), Lafayette, Louisiana, USA, 12-15 October, 1998, Oct. 1998.

  • Katherine Guo, Luís Rodrigues, “Dynamic Light-Weight Groups”, in Proceedings of the 17th IEEE International Conference on Distributed Computing Systems. Baltimore, Maryland, USA, May, 1997, May 1997.

  • Luís Rodrigues, Katherine Guo, António Sargento, Robert van Renesse, Brad Glade, Paulo Verissimo, Kenneth P. Birman, “A Transparent Light-Weight Group Service”, in Proceedings of the 15th IEEE Symposium on Reliable Distributed Systems. Niagara-on-the-Lake, Canada, October, 1996, Oct. 1996.


Navigators - TOPCOM project
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