HP 6125G HP 6125G & 6125G/XG Blade Switches IP Multicast Configuration - Page 123

PIM-SSM overview, Neighbor discovery, DR election, SPT building

Page 123 highlights

In Figure 43, the admin-scoped zones 1 and 2 have no intersection, but the admin-scoped zone 3 is a subset of the admin-scoped zone 1. The global-scoped zone serves all the multicast groups that are not covered by the admin-scoped zones 1 and 2, that is, G−G1−G2 in this case. PIM-SSM overview The source-specific multicast (SSM) model and the any-source multicast (ASM) model are opposites. Presently, the ASM model includes the PIM-DM and PIM-SM modes. You can implement the SSM model by leveraging part of the PIM-SM technique. It is also called "PIM-SSM." 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 IGMPv3 or PIM-SM technique is adopted to implement the SSM model. In the SSM model, receivers locate a multicast source by means of advertisements, consultancy, and so on. No RP is needed, no RPT is required, no source registration process exists, and the multicast source discovery protocol (MSDP) is not needed for discovering sources in other PIM domains. In PIM-SSM, the term "channel" refers to a multicast group, and the term "channel subscription" refers to a join message. The working mechanism of PIM-SSM is summarized as follows: • Neighbor discovery • DR election • SPT building Neighbor discovery PIM-SSM uses the same neighbor discovery mechanism as in PIM-DM and PIM-SM. See "Neighbor discovery." DR election PIM-SSM uses the same DR election mechanism as in PIM-SM. See "DR election." SPT building The decision to build an RPT for PIM-SM or an SPT for PIM-SSM depends on whether the multicast group the receiver will join falls into the SSM group range (SSM group range reserved by IANA is 232.0.0.0/8). 112

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112
In
Figure 43
, the admin-scoped zones 1 and 2 have no intersection, but the admin-scoped zone 3
is a subset of the admin-scoped zone 1. The global-scoped zone serves all the multicast groups that
are not covered by the admin-scoped zones 1 and 2, that is, G
G1
G2 in this case.
PIM-SSM overview
The source-specific multicast (SSM) model and the any-source multicast (ASM) model are opposites.
Presently, the ASM model includes the PIM-DM and PIM-SM modes. You can implement the SSM model
by leveraging part of the PIM-SM technique. It is also called "PIM-SSM."
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 IGMPv3 or PIM-SM technique is adopted to implement the SSM model. In
the SSM model, receivers locate a multicast source by means of advertisements, consultancy, and so on.
No RP is needed, no RPT is required, no source registration process exists, and the multicast source
discovery protocol (MSDP) is not needed for discovering sources in other PIM domains.
In PIM-SSM, the term "channel" refers to a multicast group, and the term "channel subscription" refers to
a join message.
The working mechanism of PIM-SSM is summarized as follows:
Neighbor discovery
DR election
SPT building
Neighbor discovery
PIM-SSM uses the same neighbor discovery mechanism as in PIM-DM and PIM-SM. See "
Neighbor
discovery
."
DR election
PIM-SSM uses the same DR election mechanism as in PIM-SM. See "
DR election
."
SPT building
The decision to build an RPT for PIM-SM or an SPT for PIM-SSM depends on whether the multicast group
the receiver will join falls into the SSM group range (SSM group range reserved by IANA is
232.0.0.0/8).