# OSPF SPF Scheduling and Throttling

**URL:** https://forum.networklessons.com/t/ospf-spf-scheduling-and-throttling/1948
**Category:** Lessons Discussion
**Created:** [July 20, 2017, 2:20pm UTC](https://forum.networklessons.com/t/ospf-spf-scheduling-and-throttling/1948 "2017-07-20T14:20:11Z")
**Posts on this page:** 1
**Showing post:** 5

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### Author: ![lagapidis](https://cdn-forum.networklessons.com/user_avatar/forum.networklessons.com/lagapidis/32/4949_2.png) [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [August 28, 2021, 4:31am UTC](https://forum.networklessons.com/t/ospf-spf-scheduling-and-throttling/1948/5 "2021-08-28T04:31:20Z")

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Hello Narad

The OSPF SPF scheduling and throttling feature is used to keep an OSPF topology stable in the event that there is a continuous inflow of LSAs, causing continuous recalculation of the SPF algorithm.

The `spf-hold` value is the **initial amount of time** to wait between one SPF calculation and the next. Every time a new LSA is received before `sfp-hold` has elapsed, this value doubles, so it waits longer before running the SPF calculation again. You can see this clearly in the diagrams in the lesson.

Now imagine that you keep getting LSAs all the time. This `spf-hold` value will continue to double. It could potentially continue to double forever, reaching values of several minutes or hours!! This doubling must have a limit, and that’s where the `spf-max-wait` value comes in. The `spf-hold` value, as it doubles, will hit a maximum of `spf-max-wait`, and will not double further, but will remain at that maximum. The original `spf-hold` value is reset only if `spf-max-wait` has elapsed without any new incoming LSAs.

I hope this has been helpful!

Laz

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