Today's Multi-player Online Games (MOGs) are challenged by infrastructure requirements because of their server-centric nature. Peer-to-peer overlay networks are an interesting alternative if they can implement the set of functions that are traditionally performed by centric game servers. In this paper, we propose a Zoned Federation Model (ZFM) to adapt MOGs to peer-to-peer overlay networks. We also introduce the concept of zone and zone owner to MOGs. A zone is some part of the whole game world, and a zone owner is a game sever of a specific zone. According to the demands of the game program, each node actively changes its role to a zone owner. By dividing the whole game world into several zones, workloads of the centric game server can be distributed to a federation of zones. In order to reduce response latency overhead on data exchanges between a zone owner and its clients, we limit the use of a Distributed Hash Table(DHT) to the rendezvous point of each zone; actual data exchanges are carried out through direct TCP connection between a zone owner and its members. We also use the DHT as backup storage media to cope with the resignation of a zone owner. We have implemented this zoned federation model as a middle layer between the game program and the DHT, and we evaluate our implementation with a prototypical multi-player game. Evaluation results indicate that our approach enables game creators to design scalable MOGs on the peer-to-peer environment with a short response latency which is acceptable for MOGs.