H3C S5500-EI Configuration Manual page 162

Figure 47 RPT building at the receiver side
Receiver
Host A
Source
Server A
Join message
Receiver-side RPT
Multicast packets
As shown in Figure 47, the process for building a receiver-side RPT is similar to that for building an RPT
in PIM-SM:
When a receiver joins multicast group G, it uses an IGMP message to inform the directly
1.
connected router.
After getting the receiver information, the router sends a join message, which is forwarded hop by
2.
hop to the RP of the multicast group.
The routers along the path from the receiver's directly connected router to the RP form an RPT
3.
branch, and each router on this branch adds a (*, G) entry to its forwarding table. The * means
any multicast source.
When a receiver is no longer interested in the multicast data addressed to multicast group G, the directly
connected router sends a prune message, which goes hop by hop along the reverse direction of the RPT
to the RP. After receiving the prune message, each upstream node deletes the interface connected to the
downstream node from the outgoing interface list and checks whether it has receivers in that multicast
group. If not, the router continues to forward the prune message to its upstream router.
RP
143
Source
Server B
Receiver
Host B
Receiver
Host C