Working Principle - H3C S9500 Series Operation Manual

Operation Manual – MSDP
H3C S9500 Series Routing Switches
By initiating registration and RPT joining to the nearest RP, MSDP implements RP load
sharing. Once an RP turns invalid, its original registered source and receivers will
select another nearest RP, implementing redundant RP backup.
In addition, MSDP only accepts the SA messages from the correct paths and excludes
redundant SA messages through RPF check mechanism, and prevents the flooding of
SA messages among MSDP peers by configuring Mesh Group.

1.1.2 Working Principle

I. Identifying multicast source and receiving multicast data
As shown in
relationship between them. Domain 3 contains a group member.
Figure 1-1 MSDP working principles (I)
When the multicast source in domain 1 sends data to the multicast group, the working
process of the member in domain 3, from discovering the multicast source to receiving
data from the source, includes the following:
The multicast source in PIM-SM domain 1 begins to send datagram.
The DR connected to the multicast source encapsulates the datagram into a Register
packet and forward it to the RP in domain 1.
The RP in domain 1 decapsulates the packet and forwards it along the RPT to all the
members within the domain. The domain members can choose whether to switch to the
SPT.
The RP in domain 1 generates an SA message for the MSDP peers (the RPs in
PIM-SM domain 2 and domain 3). The SA message contains multicast source IP
address, multicast group address and the address of the RP that generates the
Figure 1-1, the RPs of PIM-SM domains 1, 2 and 3 establish peer
1-2
Chapter 1 MSDP Configuration
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