HP VPN Firewall Appliances Appendix Protocol Reference

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When a receiver is no longer interested in the IPv6 multicast data addressed to the multicast group G, the
directly connected DR sends a prune message, which goes hop-by-hop along the RPT to the RP.
After receiving the prune message, the upstream node deletes the interface connected with this
downstream node from the outgoing interface list and examines 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 IPv6 multicast source uses the registration process to inform the RP of its existence.
Figure 72 IPv6 multicast source registration
As shown in Figure 72, the IPv6 multicast source registers with the RP as follows:
1. The IPv6 multicast source S sends the first IPv6 multicast packet to IPv6 multicast group G.
2. After receiving the multicast packet, the DR that directly connects to the multicast source
encapsulates the packet in a register message, and then unicasts the message to the
corresponding RP.
3. When the RP receives the register message, it does the following
a. Extracts the multicast packet from the register message.
b. Forwards the multicast IPv6 multicast packet down the RPT.
c. Sends an (S, G) join message hop-by-hop toward the IPv6 multicast source.
The routers along the path from the RP to the IPv6 multicast source form an SPT branch. Each router
on this branch generates an (S, G) entry in its forwarding table. The source-side DR is the root of
the SPT, and the RP is the leaf of the SPT.
4. The subsequent IPv6 multicast data from the IPv6 multicast source travels along the established SPT
to the RP. Then, the RP forwards the data along the RPT to the receivers. When the IPv6 multicast
data arrives at the RP along the SPT, the RP unicasts a register-stop message to the source-side DR
to stop the source registration process.