Bidirectional Forwarding Detection (BFD)

Bidirectional Forwarding Detection (BFD) is a network protocol used to detect link failure between two nodes. This is great features used for link detection as it even detect failure for you on Layer-1 where mostly detection is not possible like on VC, tunnels, MPLS-LSP, Ethernet etc.

When BFD session is establishes between two nodes, & if there are more than twlo links exists b/w that two nodes so BFD can be used to monitor the session for these two nodes. BFD does not have a discovery mechanism, sessions must be explicitly configured between endpoints. For example, on Huawei NE40E, we can do like:

bfd to-NameOfNode-001 bind peer-ip default-ip interface GigabitEthernet1/1/1
discriminator local 809
discriminator remote 908
min-tx-interval 60
min-rx-interval 60
process-interface-status
commit

BFD may &/or can be used on many different transport mechanisms and layers. For this it needs to be encapsulated by whatever transport it uses. For example, MPLS-LSP, OSPF, IS-IS Protocols that support some form of adjacency setup.

BFD can be used in either asynchronous mode and demand mode.

I hope this will be informative for you.

Cheers :)