Reliable multicast protocols exploit the tree topology of the underlying network by arranging the recipients into a logical tree that roughly copies the network topology. The sender of data packets is the root of the tree. Each node is responsible for delivering the data packets to its direct descendants.

Each node sends a local acknowledgement when it has received a data packet and an aggregate acknowledgement when it has received aggregate acknowledgements from all its direct descendants. The local acknowledgement is used for flow control. The aggregate acknowledgement is used for forgetting the data packet.