Multiplayer network games have become increasingly popular over the past decade and their popularity continues to grow as more vendors release this genre of games over social media or as expansions to single-player games. A very prominent category of multiplayer games is the so-called Massively Multiplayer Online Games (MMOGs), which allow a large number of players to play within a virtual world. Successful examples are World of Warcraft , Eve Online  and Lord of the Rings Online .
The idea behind most MMOGs is that of a large virtual world, consisting of thousands of players at any given time, which allows for player interaction and story lines in order to fulfill a quest. In many cases, these quests are designed to be difficult for a single player to undertake, thus forcing players to form groups and solve them together.
Online games present quite different challenges to other distributed application domains (e.g., ecommerce). However, the basic problems remain of gaining scalability and ensuring correctness of execution .
The most common model used by the majority of vendors of MMOGs is the server-client model. In this model, the clients i.e. the players connect to the server and send data to it. The server in-turn processes all the requests it receives from the clients and broadcasts the results that occur in the game world back to clients. As the number of clients grows, scalability is achieved by employing server clusters. In addition to broadcasting results, the server is also responsible for: managing player positions in the virtual world, manage the AI and non-player characters in the world, and securely save each player’s characters and their traits.
An optional model being widely proposed for deploying MMOGs is the peer-to-peer model as it allows for scalability at a lower cost to the vendor. The peer-to-peer model uses connectivity between participants in a network and their cumulative bandwidth rather than conventional centralized resources. It does not have the notion of clients or servers, but only equal peer nodes that simultaneously function as both clients and servers to the other nodes on the network. They are well known for their use in file sharing networks.
The aim of this paper is to propose a hybrid of the existing server-client model with a modified peer-to-peer distributed algorithm that addresses some of the challenges faced by MMOGs. It enables players to share a single game world without any kind of restrictions on movement to hot spots within the world. It also dynamically allocates resources to deal with flocking (movement of many players to one area) without compromising performance and at the same time providing consistent level of operation.
This hybrid model will offer security for the players by storing the account information, avatar information and allowing authentication through a centralized server, while providing flexibility, scalability and load balancing through a...