Add to ORKGWe propose a new synchronization protocol devised to support multiplayer online games (MOGs) over peer-to-peer architectures. The dissemination of game events is performed through an overlay network. Peers are kept synchronized thanks to an optimistic mechanism which is able to drop obsolete events (i.e., events that lose their importance as the game goes on) and to allow different processing orders for non-correlated events (i.e., events which do not represent competing actions in the virtual world). To allow a fast identification of obsolete events, a gossip protocol is added to the synchronization mechanism, which is in charge of spreading in background information on generated game events. Results coming from extensive simulations conf...