Ipv6 Bidir-Pim Overview - HP A5500 SI Switch Series Configuration Manual

multicast group in register messages and sends these messages to the RP. Upon receiving these register
messages, the RP extracts the multicast data and sends the multicast data down the RPT to the DRs at the
receiver side. The RP acts as a transfer station for all IPv6 multicast packets. The process involves the
following issues:
The DR at the source side and the RP need to implement complicated encapsulation and de-
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encapsulation of IPv6 multicast packets.
IPv6 multicast packets are delivered along a path that might not be the shortest one.
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An increase in IPv6 multicast traffic burdens the RP, increasing the risk of failure.
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To solve these issues, IPv6 PIM-SM allows an RP or the DR at the receiver side to initiate an SPT
switchover process when the traffic rate exceeds the threshold.
The RP initiates an SPT switchover process.
1.
The RP can periodically check the passing-by IPv6 multicast packets. If it finds that the traffic rate
exceeds a configurable threshold, the RP sends an (S, G) join message hop by hop toward the IPv6
multicast source to establish an SPT between the DR at the source side and the RP. Subsequent IPv6
multicast data travels along the established SPT to the RP.
NOTE:
For more information about the SPT switchover initiated by the RP, see
The receiver-side DR initiates an SPT switchover process.
2.
Upon receiving the first IPv6 multicast packet, the receiver-side DR initiates an SPT switchover process as
follows:
The receiver-side DR sends an (S, G) join message hop by hop toward the IPv6 multicast source.
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When the join message reaches the source-side DR, all the routers on the path have created the (S,
G) entry in their forwarding table, and thus an SPT branch is established.
When the IPv6 multicast packets travel to the router where the RPT and the SPT deviate, the router
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drops the multicast packets received from the RPT and sends an RP-bit prune message hop by hop
to the RP. Upon receiving this prune message, the RP sends a prune message toward the IPv6
multicast source—suppose only one receiver exists—to implement the SPT switchover.
IPv6 multicast data is directly sent from the source to the receivers along the SPT.
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IPv6 PIM-SM builds SPTs through SPT switchover more economically than IPv6 PIM-DM does through the
flood-and-prune mechanism.
Assert
IPv6 PIM-SM uses a similar assert mechanism as IPv6 PIM-DM does. For more information, see "Assert."

IPv6 BIDIR-PIM overview

In some many-to-many applications, such as multi-side video conference, there might be multiple
receivers interested in multiple IPv6 multicast sources simultaneously. With IPv6 PIM-DM or IPv6 PIM-SM,
each router along the SPT must create an (S, G) entry for each IPv6 multicast source, consuming a lot of
system resources. IPv6 BIDIR-PIM is introduced to address this problem. Derived from IPv6 PIM-SM, IPv6
BIDIR-PIM builds and maintains bidirectional RPTs, each of which is rooted at an RP and connects IPv6
multiple multicast sources with multiple receivers. Traffic from the IPv6 multicast sources is forwarded
through the RP to the receivers along the bidirectional RPT. In this case, each router needs to maintain
only a (*, G) multicast routing entry, saving system resources.
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"Multicast source registration."