Why BFD used in core network?

BFD provides a consistent failure detection method for network administrators, in addition to fast forwarding path failure detection. Because the network administrator can use BFD to detect forwarding path failures at a uniform rate, rather than the variable rates for different routing protocol hello mechanisms, network profiling and planning will be easier, and reconvergence time will be consistent and predictable.

BUT

BFD Resource Demands

• The number of BFD sessions on each linecard or router can impact how well BFD scales for you. -Each unique platform has its own limits.
• Bundled interfaces supporting min tx/rx of250ms or2 seconds have been seen.
• In some cases, BFD instances on a router may need to be operated on the route-processor depending on the implementation (non-adjacency based BFD sessions).
• Test your platform first before deploying BFD. Attempt to put load on the RP or LC CPU with your configured settings. This can be done by:
• Executing CPU-heavy commands
• Flooding packets to TTL expire on the destination