HP 4800G Series Configuration Manual page 1015

Multicast source registration
The purpose of IPv6 multicast source registration is to inform the RP about the existence of the IPv6
multicast source.
Figure 1-6 IPv6 multicast source registration
As shown in Figure 1-6, the IPv6 multicast source registers with the RP as follows:
1) When the IPv6 multicast source S sends the first IPv6 multicast packet to IPv6 multicast group G,
the DR directly connected with the multicast source, upon receiving the multicast packet,
encapsulates the packet in a register message, and sends the message to the corresponding RP
by unicast.
2) When the RP receives the register message, it extracts the multicast packet from the register
message and forwards the multicast IPv6 multicast packet down the RPT, and sends an (S, G) join
message hop by hop toward the IPv6 multicast source. Thus, 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 DR at the IPv6 multicast source side is the root, while the RP is
the leaf, of the SPT.
3) The subsequent IPv6 multicast data from the IPv6 multicast source travels along the established
SPT to the RP, and 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.
The RP is configured to initiate an SPT switchover as described in this section. Otherwise, the DR at the
IPv6 multicast source side keeps encapsulating IPv6 multicast data in register messages and the
registration process will not stop unless no outgoing interfaces exist in the (S, G) entry on the RP.
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