You are working on a network design for Customer A. This design should consider fast convergence features, and it was agreed that BFD should be used for faster link-transition detection. Which three o

The BFD echo function is designed to operate alongside asynchronous mode, where control packets are still exchanged between peers. In echo mode, the local system sends echo packets looped back by the remote forwarding plane while control packets continue at a reduced rate.

BFD control packets are still required even when echo function is active - the echo function reduces their transmission rate but does not eliminate them, as they are needed to maintain the session state machine.

The echo function is configurable on a per-direction basis, allowing operators to enable it in one direction without affecting the other. This flexibility lets administrators tune BFD detection behavior independently for each link endpoint.

Echo packets traverse the remote system's actual data-plane forwarding path before returning to the originator, which validates that the remote forwarding hardware is functioning correctly. This is a key advantage over pure asynchronous mode, which only exercises the control path between the two BFD peers.

Enabling the echo function allows the rate of BFD control packets to be decreased, not increased, because echo packets assume the fast failure-detection role and control packets are only needed for session maintenance.