Networked games can be seen as forerunners of all kinds of participatory entertainment applications delivered through the Internet. Physically dispersed players are immersed in a common virtual environment where they interact in real time. When a user performs an action, other users must be made aware of that action. Otherwise, there is a discrepancy in the perceptions of participants about the overall state of the virtual world. This discrepancy could lead to undesirable and sometimes paradoxical outcomes. In particular, first-person shooter, and to a lesser extent role-playing games impose stringent constraints on responsiveness and consistency. Disciplines Physical Sciences and MathematicsPublication Details

This article evaluates network and server infrastructure requirements to support real-time flows associated with networked entertainment applications. These include the state information flow to update the status of the virtual environment and immersive communication flows such as voice, video, gesture, and haptics communication. The article demonstrates that scaling these applications to large geographical spreads of participants requires distribution of computation to meet the latency constraints of the applications. This latency-driven distribution of computation is essential even when there are no limitations on the availability of computational resources in one location. The article provides detailed results on distributed server architectures for two of these real-time flows, state information and immersive voice communication. It also identifies a generic set of requirements for the underlying network and server infrastructure to support these applications and propose a new design, called switched overlay networks, for this purpose.

Playability and fairness are crucial elements of an enjoyable online game experience. The unavoidable propagation time introduced by the geographical distance between participants can deteriorate the game responsiveness and playability. Also, differences in these delays can provide unfair advantages and/or disadvantages to different players. This paper explores the causal relationships between propagation time, inconsistencies, playability and fairness in online multiplayer games. It clearly defines causes of unfairness and introduces a theoretical quantification supported by an experimental technique to evaluate it in simulations. It also demonstrates through simulations the impact of changes in network architecture and topology on playability and fairness. Disciplines Physical Sciences and Mathematics Publication DetailsThis article was originally published as: Brun, J, Safaei, Abstract-Playability and fairness are crucial elements of an enjoyable online game experience. The unavoidable propagation time introduced by the geographical distance between participants can deteriorate the game responsiveness and playability. Also, differences in these delays can provide unfair advantages and/or disadvantages to different players. This paper explores the causal relationships between propagation time, inconsistencies, playability and fairness in online multiplayer games. It clearly defines causes of unfairness and introduces a theoretical quantification supported by an experimental technique to evaluate it in simulations. It also demonstrates through simulations the impact of changes in network architecture and topology on playability and fairness.

The selection of servers within the network affect both the participants' playability and the overall game fairness. This paper defines the concept of critical response time and uses it as the objective function for the server selection optimization problem we formulate and solve for small topologies.An approximate heuristic solution usable for large networks is introduced and its performance compared to the calculable lower bound of the critical response time. In our simulations, the heuristic converges towards a close to optimum critical response time. We also compare this solution to central server selection strategies and show that it outperforms them, both in terms of playability and fairness.