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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:
1.
The directly connected DR sends a prune message, which goes hop by hop along the RPT to
the RP.
2.
After receiving the prune message, the upstream node deletes the interface connected with this
downstream node from the outgoing interface list and determines 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
In IPv6 multicast source registration, the multicast source informs the RP of its existence.
Figure 121 IPv6 multicast source registration
As shown in
, 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. Then, it sends the message to the
corresponding RP by unicast.
3.
When the RP receives the register message, it does the following:
a.
It extracts the multicast packet from the register message and forwards the multicast IPv6
multicast packet down the RPT.
b.
It 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 traffic arrives at the RP along the SPT, the RP sends a register-stop
message to the source-side DR by unicast to stop the source registration process.
