The DR sends join and prune messages from a receiver toward an RP for the group to either join the shared tree or remove (prune) a branch from it. A single message contains both a join and a prune list. This list includes a set of source addresses that indicate the shortest-path trees or the shared trees that the host wants to join. The DR sends join and prune messages hop-by-hop to each PIM router on the path to the source or the RP.