Pim-ssm overview, Neighbor discovery, Dr election – H3C Technologies H3C S12500 Series Switches User Manual
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Figure 47 Relationship between admin-scoped zones and the global-scoped zone in group
address ranges
In
, the group address ranges of admin-scoped 1 and 2 have no intersection, whereas
the group address range of admin-scoped 3 is a subset of the address range of admin-scoped 1.
The group address range of the global-scoped zone covers all the group addresses other than
those of all the admin-scoped zones. That is, the group address range of the global-scoped zone
is G-G1-G2. A supplementary relationship exists between the global-scoped zone and all the
admin-scoped zones in terms of group address ranges.
PIM-SSM overview
The source-specific multicast (SSM) model and the any-source multicast (ASM) model are opposites.
Currently, the ASM model includes the PIM-DM and PIM-SM modes. The SSM model can be
implemented 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.
Therefore, 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.
The operating mechanism of PIM-SSM is summarized as follows:
•
Neighbor discovery
•
DR election
•
SPT building
In PIM-SSM, the term "channel" refers to a multicast group, and the term "channel subscription" refers to
a join message.
Neighbor discovery
PIM-SSM uses the same neighbor discovery mechanism as in PIM-DM and PIM-SM. See "
DR election
PIM-SSM uses the same DR election mechanism as in PIM-SM. See "
."
Admin-scope 3
G3 address
Admin-scope 2
G2 address
Admin-scope 1
G1 address
Global-scope
G
−
G1
−
G2 address