Synchronization protocols for reliable communication in fully distributed agent systems

In order to prevent misunderstandings within groups of interacting agents, it is necessary to ensure that the agents’ beliefs regarding the overall state of the interaction are consistent with each other at all times. In [7], Paurobally et al. proposed that these beliefs could be synchronized by adding a specialized protocol layer that incorporates protocols specifically designed to synchronize the agents’ beliefs. Here we define the problem that such protocols would need to solve in the worst case, and prove it to be insoluble. We then consider the possibility of synchronizing the beliefs of groups of agents if it is assumed that the communication layer notifies the sender of a message whenever that message is not successfully delivered. Paurobally et al. proved that this assumption allows agents’ beliefs to be synchronized in bilateral interactions. However, we prove that this assumption is insufficient to achieve belief synchronization in groups of three or more agents. Finally, we discuss the possibility of achieving adequate synchronization using probabilistic protocols.