Network RADIUS SARL Kloud Services Cisco Systems, Inc Aalyria Technologies Ciena Corporation This document describes a new BFD Authentication mechanism, Meticulous Keyed ISAAC. This mechanism can be used to authenticate BFD packets with less CPU time cost than using MD5 or SHA1, with the tradeoff of decreased security. This mechanism cannot be used to signal state changes, but it can be used as an authenticated signal to maintain a session in the the "Up" state. This document updates RFC 5880.