This document has been reviewed as part of the transport area review team'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 and WG to allow them to address any issues raised and also to the IETF discussion list for information. When done at the time of IETF Last Call, the authors should consider this review as part of the last-call comments they receive. Please always CC tsv-art@ietf.org if you reply to or forward this review. The only transport issue in this document involves the need to generate ICMP messages using IPv4 source addresses based on the offending IPv4 datagram, over interfaces intended to forward using IPv6 addresses. This is sufficiently covered in Section 3. There are two minor nits: - Section 3 refers to RFC7600 Section 22; it should refer to R-22 (the requirement number) in Section 4.8 of that RFC. - the word "since" throughout the doc (5 instances) may be more accurately expressed as "because" (indicating a logical consequence, rather than temporal precedence)