H3C S7500E Series Operation Manual page 703

Operation Manual – Multicast
H3C S7500E Series Ethernet Switches
The SSM model provides a solution for source-specific multicast. It maintains the
relationships between hosts and routers through IGMPv3.
In actual application, part of the PIM-SM technique is adopted to implement the SSM
model. In the SSM model, receivers know exactly where a multicast source is located
by means of advertisements, consultancy, and so on. Therefore, no RP is needed, no
RPT is required, there is no source registration process, and there is no need of using
the multicast source discovery protocol (MSDP) for discovering sources in other PIM
domains.
Compared with the ASM model, the SSM model only needs the support of IGMPv3 and
some subsets of PIM-SM. The operation mechanism of PIM-SSM can be summarized
as follows:
Neighbor discovery
DR election
SPT building
I. Neighbor discovery
PIM-SSM uses the same neighbor discovery mechanism as in PIM-DM and PIM-SM.
Refer to
II. DR election
PIM-SSM uses the same DR election mechanism as in PIM-SM. Refer to
III. Construction of SPT
Whether to build an RPT for PIM-SM or an SPT for PIM-SSM depends on whether the
multicast group the receiver is to join falls in the SSM group range (SSM group range
reserved by IANA is 232.0.0.0/8).
Figure 5-9 SPT establishment in PIM-SSM
Neighbor discovery.
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Chapter 5 PIM Configuration
DR election.