Reliable broadcast is a fundamental building block in fault-tolerant distributed systems. It consists of a basic primitive that provides agreement among processes of the system on the delivery of each broadcast message, i.e., either none or all correct processes deliver the message, despite failures of processes. In this work, we propose a reliable broadcast solution on top of VCube, assuming that the system is asynchronous. VCube is an autonomic monitoring layer that organizes processes on a hypercube-like overlay which provides several logarithmic properties even in the presence of processes failures. We consider that processes can fail by crashing, do not recover, and faults are eventually detected by all correct processes. The protocol tolerates false suspicions by sending additional messages to suspected processes but logarithmic properties of the algorithm are still kept. Experimental results show the efficiency of the proposed solution compared to an one-to-all strategy.

The failure detector abstraction has been used to solve agreement problems in asynchronous systems prone to crash failures, but so far it has mostly been used in static and complete networks. This paper aims to adapt existing failure detectors in order to solve agreement problems in unknown, dynamic systems. We are specifically interested in the k-set agreement problem. The problem of k-set agreement is a generalization of consensus where processes can decide up to k different values. Although some solutions to this problem have been proposed in dynamic networks, they rely on communication synchrony or make strong assumptions on the number of process failures. In this paper we consider unknown dynamic systems modeled using the formalism of Time-Varying Graphs, and extend the definition of the existing ΠΣx,y failure detector to obtain the ΠΣ ⊥,x,y failure detector, which is sufficient to solve k-set agreement in our model. We then provide an implementation of this new failure detector using connectivity and message pattern assumptions. Finally, we present an algorithm using ΠΣ ⊥,x,y to solve k-set agreement.

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Este trabalho apresenta a versão preliminar de uma solução hierárquica para a difusão confiável de mensagens com base na topologia virtual mantida pelo VCube. A topologia é construída e adaptada dinamicamente com base nas informações de falhas obtidas de um sistema não confiável de monitoramento. As mensagens são propagadas por uma árvore geradora criada dinamicamente sobre os enlaces mantidos pelo VCube. Os processos podem falhar por crash sem recuperação e uma falha é detectada por todos os processos corretos em um tempo finito. Mensagens diferenciadas são utilizadas para tratar falsas suspeitas geradas pela execução em ambiente assíncrono.