State-of-the-art in Application Layer Multicast Research

Multicast provides an efficient way for one-to-many and multi-party communication. It is a key technique for the next-generation Internet applications. The conventional work on multicast emphasizes on providing multicast mechanism in IP protocol layer. However, the deployment of IP multicast is constrained by the modification to the op- erational Internet infrastructure and is hampered by a lot of unsolved technical problems. In the recent two years, the research trend on Peer-to-Peer (P2P) gives new light on multicast, and Application Layer Multicast (ALM) begins to attract wide attention. ALM protocols organize a set of hosts into an overlay tree for data delivery and all multicast related functions are implemented within end system. The shift of multicast functions from routers to hosts has the potential to address most problems associated with IP multicast, but also presents new challenges. This paper analy- ses the characteristics of ALM research from distributed system perspective, describes the technologies and difficulties involved in ALM design, and summarizes current work and progress.