H3C Technologies H3C S3600 Series Switches - Manual (Page 434)

5-3
z Intermediate MSDP peer: an MSDP peer with multicast remote MSDP peers, like RP 2. An
intermediate MSDP peer forwards SA messages received from one remote MSDP peer to other
remote MSDP peers, functioning as a relay of multicast source information.
2) MSDP peers created on common PIM-SM routers (other than RPs)
Router A and Router B are MSDP peers on common multicast routers. Such MSDP peers just forward
received SA messages.
An RP is dynamically elected from C-RPs. To enhance network robustness, a PIM-SM network typically
has more than one C-RP. As the RP election result is unpredictable, MSDP peering relationships
should be built among all C-RPs so that the winner C-RP is always on the "MSDP interconnection map”,
while loser C-RPs will assume the role of common PIM-SM routers on the “MSDP interconnection
map”.
Implementing inter-domain multicast delivery by leveraging MSDP peers
As shown in Figure 5-2 , an active source (Source) exists in the domain PIM-SM 1, and RP 1 has
learned the existence of Source through multicast source registration. If RPs in PIM-SM 2 and PIM-SM
3 also wish to know the specific location of Source so that receiver hosts can receive multicast traffic
originated from it, MSDP peering relationships should be established between RP 1 and RP 3 and
between RP 3 and RP 2 respectively.
Figure 5-2 MSDP peering relationships
RP 1
DR 1
Source
PIM-SM 1
PIM-SM 3
PIM-SM 2
PIM-SM 4
RP 3
RP 2
DR 2
MSDP peers
SA message
Join message
Multicast packets
Register message
Receiver
The process if implementing inter-domain multicast delivery by leveraging MSDP peers is as follows: