Dear Authors,
I've got a question on how the proposed mechanism to use Authentication only 
for the state transition signaling affects the state machine. Consider BFD 
implementation that uses HW-assistance. BFD control packets with NUL Auth TLV 
can easily be validated in the HW but those that have real Authentication may 
require a punt and processing out of the fast path. Authenticated packet to be 
validated must pass authentication verification and that may happen much later. 
If we imagine, though it is a stretch, that the next two packets get lost or 
corrupted, then we may have false negative because validation of the 
authenticated packet is outside of the normal validation path.
Or consider another scenario when validation fails because of the 
Authentication. Should this have immediate impact on the state machine? If not, 
the new state will be learnt from the very next BFD control packet, which is 
not authenticated as I understand the proposal. Then what is the benefit of 
sending state change with Authentication?

                Regards,
                                Greg

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