R3303-HP HSR6800 Routers IP Multicast Configuration Guide

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Figure 93 IPv6 multicast source registration
As shown in Figure 93, 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 sends the message to the corresponding
RP by unicast.
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 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.
NOTE:
In this section, the RP is configured to initiate a switchover to SPT. If the RP is not confi
g
ured with switchover
to SPT, the DR at the IPv6 multicast source side keeps encapsulating multicast data in register messages,
and the registration process will not stop unless no out
g
oin
g
interfaces exist in the (S, G) entry on the RP.
Switchover to SPT
In an IPv6 PIM-SM domain, an IPv6 multicast group corresponds to one RP and one RPT. Before a
switchover to SPT occurs, the source-side DR encapsulates all multicast data destined to the multicast
group in register messages and sends these messages to the RP. After receiving these register messages,
the RP extracts the multicast data and sends the multicast data down the RPT to the receiver-side DRs. The
RP acts as a transfer station for all IPv6 multicast packets. The whole process involves the following issues: