HP VPN Firewall Appliances Appendix Protocol Reference

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Figure 59 Relationship in view of multicast group address ranges
As shown in Figure 59, 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 SSM model and the ASM model are opposites. Presently, 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 relationship 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 or RPT is required, no source registration process exists, and the MSDP is not needed for
discovering sources in other PIM domains.
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 PIM-DM and PIM-SM do. See "Neighbor
discovery."
DR election
PIM-SSM uses the same DR election mechanism as PIM-SM does. See "DR election."
Admin-scope 3
G3 address
Admin-scope 2
G2 address
Admin-scope 1
G1 address
Global-scope
G
−G1−G2 address