reverse path broadcast (RPB)

Reverse PathBroadcast (RPB) is an improvement of RPF. RPB not only evaluates the shortest path with respect to the interface where the multicast packets are received, but also influences the forwarding of the data to the interface of the router. As a result, the multicast packets are only forwarded to the interfaces where the next router in the reverse direction is on the shortest path to the data source. In order to make the forwarding decision, routers must be aware of the shortest paths. TRPB routing is an extension of RPB routing. It ensures that multicast packets do not reach subnets where there are no current group members.

RPF and RPB are broadcast procedures, since the structure of the group is not taken into account in any way when the distribution tree is built.