3Com S7906E - Switch, Руководство по настройке

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PIM-SM builds SPTs through SPT switchover more economically than PIM-DM does through the “flood
and prune” mechanism.
Assert
PIM-SM uses a similar assert mechanism as PIM-DM does. For details, refer to Assert .
Introduction to Administrative Scoping in PIM-SM
Division of PIM-SM domains
Typically, a PIM-SM domain contains only one BSR, which is responsible for advertising RP-set
information within the entire PIM-SM domain. The information for all multicast groups is forwarded
within the network scope administered by the BSR. We call this non-scoped BSR mechanism.
To implement refined management, a PIM-SM domain can be divided into one global scope zone and
multiple administratively scoped zones (admin-scope zones). We call this administrative scoping
mechanism.
The administrative scoping mechanism effectively releases stress on the management in a single-BSR
domain and enables provision of zone-specific services using private group addresses.
Admin-scope zones are divided specific to multicast groups. The boundary of the admin-scope zone is
formed by zone border routers (ZBRs). Each admin-scope zone maintains one BSR, which serves
multicast groups within a specific range. Multicast protocol packets, such as assert messages and
bootstrap messages, for a specific group range cannot cross the admin-scope zone boundary. Multicast
group ranges served by different admin-scope zones can overlap. A multicast group is valid only within
its local admin-scope zone, functioning as a private group address.
The global scope zone maintains a BSR, which serves the multicast groups that do not belong to any
admin-scope zone.
Relationship between admin-scope zones and the global scope zone
The global scope zone and each admin-scope zone have their own C-RPs and BSRs. These devices
are effective only in their respective admin-scope zones. Namely, BSR election and RP election are
implemented independently within each admin-scope zone. Each admin-scope zone has its own
boundary. The multicast information cannot cross this border in either direction. A better understanding
of the global scope zone and admin-scope zones should be based on two aspects: geographical space
and group address range.
1) Geographical space
Admin-scope zones are logical zones specific to particular multicast groups. The multicast packets of
these multicast groups are confined within the local admin-scope zone and cannot cross the boundary
of the zone.