HP 6125XLG - Relationship Among PIM Protocols

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Figure 43 SPT building in PIM-SSM
As shown in Figure 43, Host B and Host C are receivers. They send IGMPv3 report messages to their DRs
to express their interest in the multicast information that the multicast source S sends to the multicast group
G.
After receiving a report message, the DR first checks whether the group address in this message is in the
SSM group range and does the following:
• If the group address is in the SSM group range, the PIM-SSM service is provided.
The DR sends a subscribe message toward the multicast source. All routers along the path from the
DR to the source create an (S, G) entry to build an SPT. The SPT is rooted at the multicast source S
and has the receivers as its leaves.
• If the group address is not in the SSM group range, the PIM-SM service is provided.
The receiver-side DR sends a (*, G) join message to the RP, and the multicast source registers with
the source-side DR.
In PIM-SSM, the term "channel" refers to a multicast group, and the term "subscribe message" refers to
a join message.
Relationship among PIM protocols
In a PIM network, PIM-DM cannot run together with PIM-SM, BIDIR-PIM, or PIM-SSM. However, PIM-SM,
BIDIR-PIM, and PIM-SSM can run together. Figure 44
shows how the device selects one protocol from
among them for a receiver trying to join a group.
Source
Server
Host A
Host B
Host C
Receiver
Receiver
Multicast packets
SPT
Subscribe message
DR
DR
RP