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DES-7200 Configuration Guide Chapter 4 OSPF
Configuration
4-26
4.2.17.4 Configuring the LSA to Send the
packet updates
To avoid the impacts on network devices caused by the flooding of a number of
update packets, the feature of LSP packet update is introduced. By controlling the
inter-packet spacing between substantive update packets, the LSAs to be flooded
during this period can be collected, so that these LSAs can be sent with the least
number of packets. Meanwhile, the CPU resources can be saved to handle other
tasks and the system performance can be optimized.
When there are excessive LSAs on the network and the device is suffering from
excessive loads, the "transmit-time" and "transmit-count" shall be properly
configured to control the number of LS-UPD packets flooded on the network.
When the load of CPU and network bandwidth is not too high, you can reduce
"transmit-time" and increase "transmit-count" in order to accelerate network
convergence. In routing process configuration mode, the user can execute the
following commands to configure LSA to send packet updates:
Command Function
DES-7200# configure terminal
Enter global configuration mode.
DES-7200(config)# router ospf 1
Enter routing protocol configuration mode.
DES-7200(config-router)# timers
pacing lsa-transmit transmit-time
transmit-count
(Optional) Configure LSA to send packet
updates.
DES-7200 (config-if)# end
Return to privileged mode.
DES-7200 # write
Save configurations.
4.2.17.5 Configuring the LSA to Send the
packet updates
To prevent multiple events from triggering the same LSAs within a short time and
consuming excess CPU resources, OSPF protocol has defined the minimum time
interval of "MinLSInterval" for LSA generation, with default value being 5 seconds.
During this time, the same LSA instances cannot be generated repeatedly. The
purpose for configuring this interval is to prevent frequent LSA oscillation from
causing impacts to the network. However, such a limit will slow down LSA
generation and fail to advertise the changes in network topology.
To quickly respond to the changes in network topology and avoid excessively
frequent route calculation, we can use rate-limiting algorithm to dynamically
change the interval for LSA generation. The command of "timers throttle lsa all"
has three parameters: initial interval, hold interval and maximum interval, which
allow the system to automatically adjust the interval for LSA generation according
to the extent of frequent changes in network topology. Generally, "delay-time" is