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OmniAccess 5740 Unified Services Gateway CLI Configuration Guide
Alcatel-Lucent
LSA G
ROUP PACING WITH MULTIPLE TIMERS
This problem is solved by configuring each LSA to have its own timer. For
example, each LSA gets refreshed every 30 minutes, independent of other LSAs;
so the CPU is used only when necessary.
Refreshing LSAs at frequent, random intervals requires the router to send many
packets, which uses up the bandwidth. Therefore, the router delays the LSA
refresh function for an interval of time. The accumulated LSAs constitute a group,
which is then refreshed and sent out in one packet or more. Thus, the refresh
packets are paced, as are the checksumming and aging.
E
XAMPLE
ALU(config-router ospf 1)# timers lsa-group-pacing 100
T
O REDUCE LSA FLOODING
By design, OSPF requires LSAs to be refreshed as they expire after 3600
seconds. Some implementations have tried to improve the flooding by reducing
the frequency to refresh from 30 minutes to about 50 minutes.
This solution reduces the amount of refresh traffic but requires at least one refresh
before the LSA expires. The OSPF flooding reduction solution works by reducing
unnecessary refreshing and flooding of already known and unchanged
information.
E
XAMPLE
ALU(config-if GigabitEthernet3/0)# ip ospf flood-reduction
Command (in RCM) Description
timers lsa-group-pacing <10-1800> Changes the group pacing of
LSAs.
The default lsa-group pacing
interval is 60 seconds.
Command (in ICM) Description
ip ospf flood-reduction
Suppresses the unnecessary flooding of
LSAs in stable topologies.
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