333
mappings between IPv6 multicast groups and RPs. The BSR then encapsulates the RP-set in the bootstrap
messages it periodically originates and floods the bootstrap messages (BSMs) to the entire IPv6 PIM-SM
domain.
Figure 89 BSR and C-RPs
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Bootstrap message
IPv6 PIM-SM
BSR
C-RP
C-RP
C-RP
C-BSR
Based on the information in the RP-sets, all routers in the network can calculate the location of the
corresponding RPs based on the following rules:
1. The C-RP with the highest priority wins.
2. If all the C-RPs have the same priority, their hash values are calculated through the hashing
algorithm. The C-RP with the largest hash value wins.
3. If all the C-RPs have the same priority and hash value, the C-RP that has the highest IP address wins.
The hashing algorithm used for RP calculation is Value (G, M, C
i
) = (1103515245 * ( (1103515245 *
(G & M) + 12345) XOR C
i
) + 12345) mod 2
31
.
Table 12 Values in the hashing algorithm
Value Descri
tion
Value Hash value.
G
The digest from the exclusive-or (XOR) operation between the 32-bit segments of the
IPv6 multicast group address. For example, if the IPv6 multicast address is
FF0E:C20:1A3:63::101, G = 0xFF0E0C20 XOR 0x01A30063 XOR 0x00000000
XOR 0x00000101.
M Hash mask length
C
i
The digest from the exclusive-or (XOR) operation between the 32-bit segments of the C-
RP IPv6 address. For example, if the IPv6 address of the C-RP is 3FFE:B00:C18:1::10,
C
i
= 0x3FFE0B00 XOR 0x0C180001 XOR 0x00000000 XOR 0x00000010.
& Logical operator of “and”.
XOR Logical operator of “exclusive-or”.
mod Modulo operator, which gives the remainder of an integer division.
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