User’s Guide FUJITSU PSWITCH
December/2018 97
three consecutive missed messages. Therefore, it could take 90 seconds for the DR
to failover. If the query interval is lowered to 1 second, then the DR failover time is
reduced to 3 seconds. A too-low value for the hello message interval is not
recommended, as it would be taxing on the CPU.
3.1.3.9.2. PIM Join/Prune Interval Tuning
PIM-SM sends periodic Join/Prune messages to its upstream (RPF) routers to keep
the multicast channel alive. This value may need to be turned down (using the ip
pim join-prune interval command) in scenarios to help faster PIM-SM convergence.
Keep in mind that this would be taxing on the CPU.
3.1.3.9.3. Multicast Traffic Recovery Time
In general, the multicast traffic recovery time is dominated by the time required to
reconstruct the unicast routing table. If possible, the unicast routing protocol
parameters should be tuned to allow rapid detection of topology changes and
prompt updating of the routing table. PIM generally generates a high control load
during the recovery time, and this is directly proportional to the number of
multicast route entries (mostly receivers) that need to be recovered.
3.1.3.9.4. Source Specific Multicast (PIM-SSM)
Protocol Independent Multicast─Source Specific Multicast (PIM-SSM) is a subset of
PIM-SM and is used for one-to-many multicast routing applications, such as audio
or video broadcasts. PIM-SSM does not use shared trees. PIM-SSM defines a
"channel" identified by an (S,G) pair. S is a specific source address and G is
multicast destination address in the SSM range. Channel subscriptions are
supported using an group management protocol such as IGMPv3 or MLDv2. Default
SSM group address is 232.0.0.0/8 for IPv4 multicast and ff3x::/32(exclude ff30, ff31
and ff35) for IPv6 multicast. Both RP and SSM configuration can coexist on a single
router, but it should not configure in the same group address.
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