Ubicast: An Enhanced Application-Level Multicast Protocol

This paper presents Ubicast, an enhanced application- level multicast protocol. Ubicast is built upon Pastry, a scalable and self-organizing peer-to-peer substrate overlay, and leverages its merits of reliable application-level routing and object location. Ubicast is mainly applied to such real-time multimedia applications with QoS heterogeneousness as multimedia streaming service, video-on-demand. The paper makes two contributions to the study of application-level multicast: (1) Ubicast extends traditional degree-bound model and satisfies nodes’ heterogeneous QoS requirements to provide customizable multicast services. It tries to minimize the delay radius of the multicast tree, while meeting different bandwidth requirements. (2) Priority Joining Algorithm is proposed to limit the number of nodes that a participant needs to probe. The join cost is decreased substantially to guarantee the scalability for a potentially large network topology. Simulation and experimental analysis confirm the performance improvement of Ubicast which is especially suited for small sized multicast groups.