Also known as End System or Peer-to-Peer Multicast.

High bandwidth multi-source multicast among widely distributed nodes is a critical capability for a wide range of important applications including audio and video conferencing, multi-party games and content distribution. Throughout the last decade, a number of research projects have explored the use of Multicast as an efficient and scalable mechanism to support such group communication applications. Multicast decouples the size of the receiver set from the amount of state kept at any single node and potentially avoids redundant communication in the network.

The limited deployment of IP Multicast, a best effort network layer multicast protocol, has led to considerable interest in alternate approaches that are implemented at the application layer, using only end-systems. In an overlay or end-system multicast approach participating peers organize themselves into an overlay topology for data delivery. Each edge in this topology corresponds to a unicast path between two end-systems or peers in the underlying Internet. All multicast-related functionality is implemented at the peers instead of at routers, and the goal of the multicast protocol is to construct and maintain an efficient overlay for data transmission.

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