Accton Technology ES4626 - Manual (Page 694)

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When multicast source S sends a multicast packet to multicast group G, the PIM-SM
multicast router directly connected to it will take charge of sealing the multicast packet
into registered message and unicast it to corresponding RP. If there are more than one
PIM-SM multicast routers on a network segment, then DR (Designated Router) takes
charge of forwarding the multicast packet.
(3) SPT Switch
Once the multicast router finds that the rate of the multicast packet from RP with
destination address G exceeds threshold, the multicast router will send Join message to
the upper lever nodes in the source direction, which results in the switch from RPT to
SPT.
2. Preparation before PIM-SM configuration
(1) Configuration Candidate RP
More than one RPs (candidate RP) are permitted in PIM-SM network and each
C-RP (Candidate RP) takes charge of forwarding multicast packets with destination
address in a certain range. To configure more than one candidate RPs can achieve RP
load balancing. There is no master or slave difference among RPs. All multicast routers
work out the RP corresponded with certain multicast group based on the same algorithm
after receiving the candidate RP message announced by BSR.
Note that one RP can serve more than one multicast groups, even all multicast
groups. But each multicast group can only correspond with one unique RP at any
moment. It can’t correspond with more RPs at the same time.
(2) BSR Configuration
As the management core of PIMSM network, BSR is in charge of collecting
messages sent by candidate RPs and broadcast them..
There may be only one BSR within a network. However, there may be several
candidate BSRs to be configured. With such arrangement, once a BSR fails, another
may be switched to. C-BSR determines BSR through automatic selection.
As a result of continuous development of IPv6 network, it has the network
environment of nonsupport IPv6 multicast sometimes, so it needs to do the IPv6
multicast operation by tunnel. Therefore, our PIM-DM6 supports configuration on
configure tunnel, and passes through nonsupport IPv6 multicast network by single cast
packet of IPv4 encapsulation.
17.2.2 PIM-SM Configuration Task List
1、 Start PIM-SM (Required)
2、 Configure PIM-SM auxiliary parameters (Optional）
（ 1） Configure PIM-SM interface parameters
1) Configure PIM-SM hello message interval time