Introduction To Bsr Admin-Scope Regions In Pim-Sm - H3C S7500E Series Operation Manual

Operation Manual – Multicast
H3C S7500E Series Ethernet Switches
3) The subsequent multicast data from the multicast source travels along the
established SPT to the RP, and then the RP forwards the data along the RPT to
the receivers. When the multicast traffic arrives at the RP along the SPT, the RP
sends a register-stop message to the source-side DR by unicast to stop the
source registration process.
VI. Switchover from RPT to SPT
Initially, multicast traffic flows along an RPT from the RP to the receivers. Because the
RPT is not necessarily the tree that has the shortest path, upon receiving the first
multicast packet along the RPT (by default), or when detecting that the multicast traffic
rate reaches a configurable threshold (if so configured), the receiver-side DR initiates
an RPT-to-SPT switchover process, as follows:
1) First, the receiver-side DR sends an (S, G) join message hop by hop to the
multicast source. When the join message reaches the source-side DR, all the
routers on the path have installed the (S, G) entry in their forwarding table, and
thus an SPT branch is established.
2) Subsequently, the receiver-side DR sends a prune message hop by hop to the RP.
Upon receiving this prune message, the RP forwards it toward the multicast
source, thus to implement RPT-to-SPT switchover.
After the RPT-to-SPT switchover, multicast data can be directly sent from the source to
the receivers. PIM-SM builds SPTs through RPT-to-SPT switchover more economically
than PIM-DM does through the "flood and prune" mechanism.
VII. Assert
PIM-SM uses exactly the same assert mechanism as PIM-DM does. Refer to Assert.

5.1.5 Introduction to BSR Admin-scope Regions in PIM-SM

I. 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.
To implement refined management and group-specific services, a PIM-SM domain can
be divided into one global scope zone and multiple BSR administratively scoped
regions (BSR admin-scope regions).
Specific to particular multicast groups, the BSR administrative scoping mechanism
effectively lessens the management workload of a single-BSR domain and provides
group-specific services.
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Chapter 5 PIM Configuration