I am an assigned INT directorate reviewer for draft-ietf-bier-ping. These comments were written primarily for the benefit of the Internet Area Directors. Document editors and shepherd(s) should treat these comments just like they would treat comments from any other IETF contributors and resolve them along with any other Last Call comments that have been received. For more details on the INT Directorate, see https://datatracker.ietf.org/group/intdir/about/

This is a relatively well-written document and I only have a few nits. Happy to chat about these, if needed.

# Section 3.1

## It is inferred that the OAM Message Length is specifying the length in bytes/octets. May be good to specify the units for all length fields.
## QTF/RTF - There are multiple NTP timestamp formats. It appears that this document wants implementors to use the long (64-bit) NTP timestamp. Would be useful to be explicit. There is good guidance in RFC 8877 for specifying the use of timestamps.
## Sender's Handle - A forward pointer to Section 4.3 where guidance on setting this field is specified would be useful.

# Section 3.3.4

## The text describing the Downstream Mapping TLV is a bit confusing. The field descriptions under Figure 7 reference the DA Length and the DIA Length, which are not fields shown in Figure 7. It would be useful to define those separately from the TLV fields since they are derived from the Address Type.

# Operational considerations - The security considerations seem reasonable for this type of function, but there is no guidance given on the potential response explosion that can occur when a sender requests replies from a large number of BFERs. What advice can you give to operators on the use of this OAM technique so they don't cause operational issues?