I've reviewed this document as part of the transport area directorate's ongoing
effort to review key IETF documents.
These comments were written primarily for the transport area directors,
but are copied to the document's authors for their information and to allow
them to address any issues raised. When done at the time of IETF Last Call,
the authors should consider this review together with any other last-call
comments they receive.
Please always CC tsv-art@ietf.org if you reply to or forward this review.

This draft is basically ready for publication, but has nits that should be
fixed before publication.

Running https://tools.ietf.org/tools/idnits/idnits.pyht reports
* The abstract seems to contain references ([RFC7624]), which it shouldn't.
* Unused Reference: 'RFC4301'

The discussion of RFC 7871 in section 4 could be improved to allow readers
not knowing the EDNS0 option to get the point. Either provide an abstract
description or refer to RFC 6891.