Инструкции По Установке для 3com S7906E

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PIM-SM builds SPTs through SPT switchover more economically than PIM-DM does through the “flood 

and prune” mechanism. 

PIM-SM uses a similar assert mechanism as PIM-DM does. For details, refer to 

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. 

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.