Register and register-stop messages

The DR sends register messages to the RP for a directly connected source. The register message informs the RP of a new source, causing the RP to send join or prune messages back toward the DR of the source, which forwards the data down the RP tree after it obtains the data natively. After the receiver DR obtains the first packet, it switches to the shortest-path tree (SPT) and continues receiving data through the SPT path.

The DR stops sending encapsulated packets to the RP after it receives a register-stop message. This traffic stops without delay because the RP sends a register-stop message immediately after it receives the first multicast data packet, and joins the shortest-path tree.