H3C Technologies H3C S7500E Series Switches - Manual (Page 361)

13-10
RPT establishment
Figure 13-5 RPT establishment in an IPv6 PIM-SM domain
As shown in Figure 13-5 , the process of building an RPT is as follows:
1) When a receiver joins IPv6 multicast group G, it uses an MLD report message to inform the
directly connected DR.
2) Upon getting the IPv6 multicast group G’s receiver information, the DR sends a join
message, which is hop by hop forwarded to the RP corresponding to the multicast group.
3) The routers along the path from the DR to the RP form an RPT branch. Each router on this
branch generates a (*, G) entry in its forwarding table. The * means any IPv6 multicast
source. The RP is the root, while the DRs are the leaves, of the RPT.
The IPv6 multicast data addressed to the IPv6 multicast group G flows through the RP, reaches
the corresponding DR along the established RPT, and finally is delivered to the receiver.
When a receiver is no longer interested in the IPv6 multicast data addressed to a multicast
group G, the directly connected DR sends a prune message, which goes hop by hop along the
RPT to the RP. Upon receiving the prune message, the upstream node deletes the interface
connected with this downstream node from the outgoing interface list and checks whether it has
receivers for that IPv6 multicast group. If not, the router continues to forward the prune
message to its upstream router.
Multicast source registration
The purpose of IPv6 multicast source registration is to inform the RP about the existence of the
IPv6 multicast source.