Late join algorithms for distributed interactive applications

Distributed interactive applications such as shared whiteboards and multiplayer games often support dynamic groups where users may join and leave at any time. A participant joining an ongoing session has missed the data that have previously been exchanged by the other session members. It is therefore necessary to initialize the application instance of the latecomer with the current state. In this paper, we propose a late join algorithm for distributed interactive applications that provides such an initialization of applications. The algorithm is scalable and robust and can be easily adapted to the needs of different applications by means of late join policies. The behavior of the late join algorithm and the impact of design alternatives are investigated in detail by means of an extensive simulation study. This study also shows that an improper handling of the late join problem can cause very high application and network load.