Assert, Bidir-pim overview, Neighbor discovery – H3C Technologies H3C S12500 Series Switches User Manual
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To solve the issues, PIM-SM allows an RP or the DR at the receiver side to initiate the following switchover
to SPT process:
1.
The RP initiates a switchover to SPT process.
After receiving the first multicast packet, the RP sends an (S, G) join message hop by hop toward
the multicast source to establish an SPT between the DR at the source side and the RP. The
subsequent multicast data from the multicast source travels along the established SPT to the RP.
For more information about the switchover to SPT initiated by the RP, see "
."
2.
The receiver-side DR initiates a switchover to SPT process.
After receiving the first multicast packet, the receiver-side DR initiates a switchover to SPT process,
as follows:
{
The receiver-side DR sends an (S, G) join message hop by hop toward 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.
{
When the 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. After receiving this prune message, the RP sends a prune message toward the
multicast source (suppose only one receiver exists). Thus, switchover to SPT is completed.
{
Multicast data is directly sent from the source to the receivers along the SPT.
PIM-SM builds SPTs through switchover to SPT more economically than PIM-DM does through the
flood-and-prune mechanism.
Assert
PIM-SM uses a similar assert mechanism as PIM-DM does. For more information, see "
BIDIR-PIM overview
In some many-to-many applications, such as multi-side video conference, there might be multiple
receivers interested in multiple multicast sources simultaneously. With PIM-DM or PIM-SM, each router
along the SPT must create an (S, G) entry for each multicast source, consuming a lot of system resources.
BIDIR-PIM addresses the problem. Derived from PIM-SM, BIDIR-PIM builds and maintains bidirectional
RPTs, each of which is rooted at an RP and connects multiple multicast sources with multiple receivers.
Traffic from the multicast sources is forwarded through the RPs to the receivers along the bidirectional RPTs.
Each router needs to maintain only one (*, G) multicast routing entry, saving system resources.
BIDIR-PIM is suitable for networks with dense multicast sources and dense receivers.
The operating mechanism of BIDIR-PIM is summarized as follows:
•
Neighbor discovery
•
RP discovery
•
DF election
•
Bidirectional RPT building
Neighbor discovery
BIDIR-PIM uses the same neighbor discovery mechanism as PIM-SM does. For more information, see
"