A Scalable Multicast Architecture for One-to-many Telepresentations

We have developed a scalable reliable multicast architecture for delivering one-to-many telepresentations. In contrast to audio and video, which are often transmitted unreliably other media, such as slides, images and animations require reliability. Our approach transmits the data in two layers. One layer is for session-persistent data, with reliability achieved by FEC alone, using the Fcast protocol. The other layer is for dynamic data, with reliability achieved using the ECSRM protocol, which combines FEC with NACK suppression. Our approach is scalable to large heterogeneous receiver sets, and supports late-joining receivers. We have implemented our approach in a multicast version of PowerPoint, a graphical slide presentation tool.