I have been asked to review this document on behalf of the OPS directorate.  This document describes the applicability of p2mp BFD to VRRPv3.  It also defines an extension to VRRPv3 to support bootstrapping a p2mp BFD session.  For the most part, I found the document clear, but there were a couple of issues I had describing the BFD traffic flow and operational process.

First, in section 3, there is a statement: "The Active router, configured to use p2mp BFD to support faster convergence of VRRP, starts transmitting BFD control packets with VRID  as a source IP address..."  I think you mean a virtual IPvX address (or Active router IP) as the source as the VRID is just an 8-bit value.  Below you do seem to indicate that the source should be a virtual IP when a Backup changes to Active.

Also in Section 3, there is text that reads:

Backup router detects the failure of the Active router, it re-
evaluates its role in the VRID .  As a result, the Backup router may
become the Active router of the given VRID or continue as a Backup
router.

I feel the use of VRID here is also wrong (or at least confusing).  My understanding of VRID is just that 8-bit value for the ID of the Virtual Router.  To me it would be clearer if both instances of VRID in the text above were replaced with Virtual Router.

As a nit, in Section 1, you have text:

Bidirectional Forwarding Detection (BFD) [RFC5880] had been
originally defined detect 

I think that should read "originally defined to detect".