3Com MSR 50 Series Configuration Manual page 1241

RPs. The BSR then floods the RP-Set to the entire IPv6 PIM-SM domain. Based on
the information in these RP-Sets, all routers (including the DRs) in the network can
calculate the location of the corresponding RPs.
An IPv6 PIM-SM domain can have only one BSR, but can have multiple
candidate-BSRs (C-BSRs). Once the BSR fails, a new BSR is automatically elected
from the C-BSRs through the bootstrap mechanism to avoid service interruption.
Similarly, multiple C-RPs can be configured in an IPv6 PIM-SM domain, and the
position of the RP corresponding to each IPv6 multicast group is calculated
through the BSR mechanism.
Figure 361 shows the positions of C-RPs and the BSR in the network.
Figure 361 BSR and C-RPs
C-RP
BSR message
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Embedded RP
The Embedded RP mechanism allows a router to resolve the RP address from an
IPv6 multicast address so that the IPv6 multicast group is mapped to an RP, which
can take the place of the statically configured RP or the RP dynamically calculated
based on the BSR mechanism. The DR does not need to know the RP address
beforehand. The mechanism is as follows.
At the receiver side:
■
1 A receiver host sends an MLD report to announce its joining an IPv6 multicast
group.
2 Upon receiving the MLD report, the receiver-side DR resolves the RP address
embedded in the IPv6 multicast address, and sends a join message to the RP.
At the IPv6 multicast source side:
■
1 Upon getting the IPv6 multicast address, the IPv6 multicast source starts sending
IPv6 multicast traffic to the IPv6 multicast group.
2 The source-side DR resolves the RP address embedded in the IPv6 multicast
address, and sends a register message to the RP by unicast.
IPv6 PIM-SM
BSR
C-RP
C-BSR
C-RP
IPv6 PIM Overview 1241