You are designing a core MPLS-based network with a single OSPF area with no external routes. Which two mechanisms can be used to improve convergence time during a failure? (Choose two.)

Incremental SPF (iSPF) recalculates only the subtree of the shortest path tree affected by a topology change rather than running a full Dijkstra computation. This significantly reduces CPU processing time in larger areas and allows OSPF to install updated routes much faster after a link or node failure.

Route filtering controls which prefixes are advertised or accepted by a router but has no effect on how quickly the network detects failures or recalculates paths after a topology change.

Graceful restart is designed to maintain forwarding state while the control plane restarts, and it suppresses reconvergence from neighbors during the restart window - this actually delays convergence from a neighbor's perspective rather than accelerating it.

BFD sends rapid hello packets at millisecond intervals independent of OSPF timers, detecting link failures far faster than OSPF dead-interval expiration. Upon detecting a failure BFD immediately signals OSPF to trigger SPF, dramatically reducing the time from failure to route reconvergence.