Administrative Scoping Overview - HP A5500 SI Switch Series Configuration Manual

Figure 44 RPT building at the multicast source side
Receiver
Host A
Source
Server A
As shown in
When a multicast source sends multicast packets to multicast group G, the DF in each network
4.
segment unconditionally forwards the packets to the RP.
The routers along the path from the source's directly connected router to the RP form an RPT branch.
5.
Each router on this branch adds a (*, G) entry to its forwarding table. The * means any multicast
source.
After a bidirectional RPT is built, multicast traffic is forwarded along the source-side RPT and receiver-side
RPT from sources to receivers.
NOTE:
If a receiver and a multicast source are at the same side of the RP, the source-side RPT and the receiver-
side RPT might meet at a node before reaching the RP. In this case, multicast packets are directly
forwarded by the node to the receiver, instead of by the RP.

Administrative scoping overview

Division of PIM-SM domains
Typically, a PIM-SM/BIDIR-PIM domain contains only one BSR, which is responsible for advertising RP-set
information within the entire PIM-SM/BIDIR-PIM domain. The information for all multicast groups is
forwarded within the network scope that the BSR administers. This is called a "non-scoped BSR
mechanism".
To implement refined management, you can divide a PIM-SM/BIDIR-PIM domain into one global-scope
zone and multiple administratively scoped zones—admin-scope zones. This is called an "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 through private group addresses.
RP
Source-side RPT
Multicast packets
Figure 44, the process of building a source-side RPT is relatively simple:
Source
Host C
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Server B
Receiver
Host B
Receiver