H3C S3610-28P Operation Manual page 824

Operation Manual – Multicast Protocol
H3C S3610&S5510 Series Ethernet Switches
Source
Figure 7-2 MSDP peering relationships
The process of implementing inter-domain multicast delivery by leveraging MSDP
peers is as follows:
1) When the multicast source in PIM-SM 1 sends the first multicast packet to
multicast group G, DR 1 encapsulates the multicast data within a register
message and sends the register message to RP 1. Then, RP 1 gets aware of the
information related to the multicast source.
2) As the source-side RP, RP 1 creates SA messages and periodically sends the SA
messages to its MSDP peer. An SA message contains the source address (S), the
multicast group address (G), and the address of the RP which has created this SA
message (namely RP 1).
3) On MSDP peers, each SA message is subject to a reverse path forwarding (RPF)
check and multicast policy–based filtering, so that only SA messages that have
arrived along the correct path and passed the filtering are received and forwarded.
This avoids delivery loops of SA messages. In addition, you can configure MSDP
peers into an MSDP mesh group so as to avoid flooding of SA messages between
MSDP peers.
4) SA messages are forwarded from one MSDP peer to another, and finally the
information of the multicast source traverses all PIM-SM domains with MSDP
peers (PIM-SM 2 and PIM-SM 3 in this example).
5) Upon receiving the SA message create by RP 1, RP 2 in PIM-SM 2 checks
whether there are any receivers for the multicast group in the domain.
If so, the RPT for the multicast group G is maintained between RP 2 and the
receivers. RP 2 creates an (S, G) entry, and sends an (S, G) join message hop by
MSDP peers
Multicast packets
SA message
Join message
Register message
DR 1
RP 1
PIM-SM 1
Receiver
RP 2
PIM-SM 4
PIM-SM 3
7-4
Chapter 7 MSDP Configuration
DR 2
PIM-SM 2
RP 3