# About configuring shortest path first (SPF) scheduling

SPF scheduling (throttling) can be configured in intervals of seconds to potentially delay SPF calculations when the network is unstable or there is a change in topology. It provides a granularity of one to four seconds between SPF calculations as opposed to the current default of five seconds.

The interval for the SPF calculations is dynamically chosen, based on the frequency of topology changes in the network. The chosen interval is within user-specified ranges of values. When the network topology is unstable, SPF throttling calculates SPF scheduling intervals that are longer, until the topology is again stable.

It is guaranteed that no SPF will be calculated within the SPF currently in effect, however, it is not guaranteed that the SPF will be calculated at the exact expiration of the timer if there have been updates. The timer may be delayed due to system constraints.