Ipv6 Bidir-Pim Overview - HP A8800 Configuration Manual

register messages, the RP abstracts 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 whole process
involves three issues as follows:
• The DR at the source side and the RP need to implement complicated encapsulation and
de-encapsulation of IPv6 multicast packets.
IPv6 multicast packets are delivered along a path that is not necessarily the shortest one.
•
When the IPv6 multicast traffic increases, a great burden is added to the RP, increasing the risk of
•
failure.
To solve the 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:
1. The RP initiates an SPT switchover process
The RP can periodically check the passing-by IPv6 multicast packets. Once 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.
For more information about the SPT switchover initiated by the RP, see
registration."
2. The receiver-side DR initiates an SPT switchover process
Upon discovering that the traffic rate exceeds a configurable threshold, 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.
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.
When the IPv6 multicast packets travel to the router where the RPT and the SPT deviate, the
router 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). Thus, SPT switchover is completed.
Finally, IPv6 multicast data is directly sent from the source to the receivers along the SPT.
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 the 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 may 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.
IPv6 BIDIR-PIM is suitable for networks with dense multicast sources and dense receivers.
382
"Multicast source