Using n-trees for scalable event ordering in peer-to-peer games

Abstract

We are concerned with the fundamental problem of event ordering in multiplayer peer-to-peer games. Event ordering, even without faults, requires all-to-all message passing with at least two rounds of communication \cite{keidar01}. Multiplayer games add real-time constraints to this scenario. To meet this challenge, we develop an event scoping mechanism that uses N-Trees for event propagation. Unlike traditional application-layer multicast, N-Trees organize peers by their application-level scope of interest, instead of by their delay-based shortest-path tree. This organization allows peers which are close by in the virtual world to order events without needing to communicate with other peers that are farther away. We show the asymptotic analysis of N-Trees indicates that they will perform well for scalable peer-to-peer event ordering. We also provide an analysis of N-Trees in comparison to other distributed architectures for peer-to-peer games.