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Conference Papers Year : 2021

Synchronization Modulo k in Dynamic Networks


We define the mod k-synchronization problem as a weakening of the Firing Squad problem, where all nodes fire not at the same round, but at rounds that are all equal modulo k. We propose an algorithm that achieves mod k-synchronization in any dynamic network where there exist – possibly several – fixed spanning stars within each period of Delta consecutive rounds. In other words, we require that there always exists a temporal path of length at most Delta between some fixed node gamma and every other node. As opposed to the perfect synchronization achieved in the Firing Squad problem, mod k-synchronization thus does not require any strong connectivity property in the network. In our algorithm, all the nodes "know'' Delta, but they ignore what nodes are the centers of the spanning stars. We also prove that if the bound Delta for guaranteeing fixed spanning stars exists but is unknown to the agents, then mod k-synchronization is impossible.All nodes in our algorithm fire in less that 6kn + 4k rounds after all nodes become active, but unfortunately use unbounded counters. We then propose a refinement of this algorithm so that it becomes finite state while maintaining the same time complexity. The correctness of our first algorithm has been formally established in the proof assistant Isabelle.
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hal-03451085 , version 1 (28-11-2022)



Louis Penet de Monterno, Bernadette Charron-Bost, Stephan Merz. Synchronization Modulo k in Dynamic Networks. SSS 2021 - International Symposium on Stabilizing, Safety, and Security of Distributed Systems, Nov 2021, Virtual Event, France. pp.425-439, ⟨10.1007/978-3-030-91081-5_28⟩. ⟨hal-03451085⟩
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