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. General issues: - I have an issue with using RFC 2119 language in informative RFCs, as it is unclear what normative language means in informative documents. However, I understand that there is legacy from older documents in particular, but not limited to, RFC 7084. - The document is in parts hard to read, even for someone who has a background in IPv4/IPv6 transition. E.g. Section 1, 2nd paragraph, about what IP version is used where. A figure could help here. Issues: - Remove the DEFAULT word and replace it with default. It is very confusing to add capital letters normative language here. - Section 5: UPnP This section is posing requirements in an IETF document that incorporates non-IETF standards for a matter that is solely a recommendation. Can this be MUST at all? - Section 6: Code Considerations This section is a collection of unfounded points without any hard proof that the numbers are correct and tangible. Either there is a hard example on required changes and added code size or remove it. This is an engineering document and not a marketing document, isn't it? Thanks, Martin Stiemerling