Setting an Interval for SPF Calculations

Context

When an OSPF LSDB changes, shortest paths must be recalculated. If a network changes frequently, shortest paths are recalculated frequently, heavily consuming system resources and degrading the network performance. To prevent this problem, you can configure an intelligent timer to set a proper interval for SPF calculations.

Procedure

Run system-view

The system view is displayed.
Run ospf [ process-id ]

The OSPF process view is displayed.
Run spf-schedule-interval { interval1 | intelligent-timer max-interval start-interval hold-interval | millisecond interval2 }

The interval for SPF calculations is set.
- The parameter interval1 specifies the interval for SPF calculations, in seconds.
- The parameter intelligent-timer indicates that an intelligent timer is used to set the interval for SPF calculations.
- The parameter max-interval specifies the maximum interval for SPF calculations, in milliseconds.
- The parameter start-interval specifies the initial interval for SPF calculations, in milliseconds.
- The parameter hold-interval specifies the hold interval for SPF calculations, in milliseconds.
- The parameter millisecond interval2 specifies the interval for SPF calculations, in milliseconds.
By default, an intelligent timer is enabled. After an intelligent timer is enabled, the default maximum interval for the SPF calculation is 10000 ms, the initial interval is 500 ms, and the hold interval is 1000 ms. The mechanism of the intelligent timer is as follows:
1. The initial interval for SPF calculations is specified by start-interval.
2. The interval for the nth (n ≥ 2) SPF calculation is equal to hold-interval x 2^(n-2).
3. When the interval specified by hold-interval x 2^(n-2) reaches the maximum interval specified by max-interval, the maximum interval is used for the subsequent three SPF calculations. Then, OSPF goes back to step 3.a and performs the SPF calculation at the initial interval specified by start-interval.