Ipv6 Bidir-Pim Overview - HP FlexNetwork 7500 Series Configuration Manual

For more information about the switchover to SPT initiated by the RP, see
source
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The receiver-side DR initiates the switchover to SPT:
The receiver-side DR periodically checks the forwarding rate of the multicast packets that the
IPv6 multicast source S sends to the IPv6 multicast group G. If the forwarding rate exceeds the
specified threshold, the DR initiates the switchover to SPT as follows:
a. The receiver-side DR sends an (S, G) source-specific join message toward the IPv6
multicast source. The routers along the path create an (S, G) entry in their forwarding table
to constitute an SPT branch.
b. When the multicast packets reach the router where the RPT and the SPT branches, the
router drops the multicast packets that travel along the RPT. It then sends a prune message
with the RP bit toward the RP.
c. After receiving the prune message, the RP forwards it toward the IPv6 multicast source
(supposed only one receiver exists). Thus, the switchover to SPT is completed. The
subsequent IPv6 multicast packets for the IPv6 multicast group travel along the SPT from
the IPv6 multicast source to the receiver hosts.
With the switchover to SPT, IPv6 PIM-SM builds SPTs more economically than IPv6 PIM-DM does.
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 a multi-side video conference, multiple receivers of an
IPv6 multicast group might be interested in the IPv6 multicast data from multiple IPv6 multicast
sources. 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 addresses the problem. Derived from IPv6 PIM-SM, IPv6 BIDIR-PIM builds and
maintains a bidirectional RPT, which is rooted at the RP and connects the IPv6 multicast sources and
the receivers. Along the bidirectional RPT, the IPv6 multicast sources send IPv6 multicast data to the
RP, and the RP forwards the data to the receivers. Each router along the bidirectional RPT needs to
maintain only one (*, G) entry, saving system resources.
IPv6 BIDIR-PIM is suitable for a network with dense IPv6 multicast sources and receivers.
Neighbor discovery
IPv6 BIDIR-PIM uses the same neighbor discovery mechanism as IPv6 PIM-SM does. For more
information, see
RP discovery
IPv6 BIDIR-PIM uses the same RP discovery mechanism as IPv6 PIM-SM does. For more
information, see
and an RPF neighbor is the address of the next hop to the RP.
In IPv6 PIM-SM, an RP must be specified with a real IPv6 address. In IPv6 BIDIR-PIM, an RP can be
specified with a virtual IPv6 address, which is called the "rendezvous point address (RPA)." The link
corresponding to the RPA's subnet is called the "rendezvous point link (RPL)." All interfaces
connected to the RPL can act as the RPs, and they back up one another.
DF election
On a subnet with multiple multicast routers, duplicate multicast packets might be forwarded to the RP.
To address this issue, IPv6 BIDIR-PIM uses a designated forwarder (DF) election mechanism to
elect a unique DF on each subnet. Only the DFs can forward IPv6 multicast data to the RP.
DF election is not necessary for an RPL.
registration."
"Neighbor discovery."
"RP discovery." In IPv6 BIDIR-PIM, an RPF interface is the interface toward an RP,
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"IPv6 multicast