Fault-tolerant group membership protocols using physical robot messengers

In this paper, we consider a distributed system that consists of a group of teams of worker robots that rely on physical robot messengers for the communication between the teams. Unlike traditional distributed systems, there is a finite amount of messengers in the system, and thus a team can send messages to other teams only when some messenger robot is available locally. It follows that a careful management of the messengers is necessary to avoid the starvation of some teams. Concretely, the paper proposes algorithms to provide group membership and view synchrony among robot teams. We look at the problem in the face of failures, in particular when a certain number of messenger robots can possibly crash.