For example, monitoring MPLS LSPs involves piggybacking session establishment on LSP-Ping packets.
Protocols that support some form of adjacency setup, such as OSPF, IS-IS, BGP or RIP may also be used to bootstrap a BFD session.
In demand mode, no Hello packets are exchanged after the session is established; it is assumed that the endpoints have another way to verify connectivity to each other, perhaps on the underlying physical layer.
When this function is active, a stream of Echo packets is sent, and the other endpoint then sends these back to the sender via its forwarding plane.
BFD's operation in conjunction with Open Shortest Path First (OSPF) and IS-IS protocols has also been outlined in RFC 5881.