H3C LS-3100-52P-OVS-H3 Operation Manual page 958

optimize the topological structure of the RPT, multiple candidate RPs (C-RPs) can be configured in a
PIM-SM domain, among which an RP is dynamically elected through the bootstrap mechanism. Each
elected RP serves a different multicast group range. For this purpose, a bootstrap router (BSR) must be
configured. The BSR serves as the administrative core of the PIM-SM domain. A 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 to avoid service interruption.
An RP can serve multiple multicast groups or all multicast groups. Only one RP can serve a given
multicast group at a time.
A device can serve as a C-RP and a C-BSR at the same time.
As shown in Figure 1-4, each C-RP periodically unicasts its advertisement messages (C-RP-Adv
messages) to the BSR. A C-RP-Adv message contains the address of the advertising C-RP and the
multicast group range it serves. The BSR collects these advertisement messages and chooses the
appropriate C-RP information for each multicast group to form an RP-set, which is a database of
mappings between multicast groups and RPs. The BSR then encapsulates the RP-set in the bootstrap
messages it periodically originates and floods the bootstrap messages to the entire PIM-SM domain.
Figure 1-4 BSR and C-RPs
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 has the highest IP address wins.
The hashing algorithm used for RP calculation is: Value (G, M, C
& M) + 12345) XOR C
algorithm.
31
) + 12345) mod 2 . The table below gives the meanings of the values in this
i
) = (1103515245 * ( (1103515245 * (G
i
1-7