HP A6600 Configuration Manual page 175

Source-side MSDP peer—The MSDP peer nearest to the multicast source (Source), typically the
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source-side RP, like RP 1. The source-side RP creates SA messages and sends the messages to its
remote MSDP peer to notify the MSDP peer of the locally registered multicast source information. A
source-side MSDP peer must be created on the source-side RP. Otherwise it will not be able to
advertise the multicast source information out of the PIM-SM domain.
Receiver-side MSDP peer—The MSDP peer nearest to the receivers, typically the receiver-side RP,
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like RP 3. After receiving an SA message, the receiver-side MSDP peer resolves the multicast source
information carried in the message and joins the SPT rooted at the source across the PIM-SM
domain. When multicast data from the multicast source arrives, the receiver-side MSDP peer
forwards the data to the receivers along the RPT.
Intermediate MSDP peer—An MSDP peer with multicast remote MSDP peers, like RP 2. An
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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.
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.
In a PIM-SM network running the BSR mechanism, the 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 must be built among all C-RPs so that the winner C-RP is
always on the "MSDP interconnection map", and loser C-RPs will assume the role of common PIM-SM
routers on the "MSDP interconnection map".
Implementing inter-domain multicast delivery
As shown in
the existence of Source through multicast source registration. If RPs in PIM-SM 2 and PIM-SM 3 also seek
the specific location of Source so that receiver hosts can receive multicast traffic that originated from it,
MSDP peering relationships must be established between RP 1 and RP 3 and between RP 3 and RP 2
respectively.
Figure 51, an active source (Source) exists in the domain PIM-SM 1, and RP 1 has learned
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