3Com MSR 50 Series Configuration Manual page 1242

1242 C 74: IP 6 PIM C
HAPTER V ONFIGURATION
RPT establishment
Figure 362 RPT establishment in an IPv6 PIM-SM domain
Source
Server
RPT
Join message
IPv6 multicast packets
As shown in Figure 362, the process of building an RPT is as follows:
1 When a receiver joins an 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 its link with this downstream node from the outgoing
interface list and checks whether it itself 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.
RP
Host A
Receiver
DR
Host B
DR
Receiver
Host C