IETF Last Call Review of draft-ietf-v6ops-framework-md-ipv6only-underlay-23
review-ietf-v6ops-framework-md-ipv6only-underlay-23-genart-lc-bryant-2026-06-24-00

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Document: draft-ietf-v6ops-framework-md-ipv6only-underlay-23
Reviewer: Stewart Bryant
Review Date: 2026-06-24
IETF LC End Date: 2026-06-22
IESG Telechat date: Not scheduled for a telechat

Summary: I am reviewing from a GENART perspective and with this perspective I
think the text of the draft should reassure me that this unconditionally works
for any legitimate IPv4 protocol stack and any legitimate operation of that
protocol stack.

The draft adequately describes how an IPv4 packet is sent and delivered over an
IPv6 network at the network layer but IPv4/6 hosts have assumptions about the
network they are using at other layers of the protocol stack and there is no
in-depth exploration of the wider considerations. Hopefully these are addressed
in other similar mechanisms that I did not have time to explore, but I think
the general reader should be reassured in the body of the text.

Major issues:The draft has covered ICMP by asserting the presence of a
stateless translator, but I cannot but worry that the are a lot of other
assumptions built into an IPv4 protocol stack that may surface during
deployment. For example IPv6 has the assumption (for integrity reasons) that
UDP will have a checksum. IPv4 is acrostic on that and frequently sets CS = 0
and yet the draft seems to be silent on the consequences. I wonder if the draft
needs to be experimental until there is operational experience with the method.

Minor issues: None

Nits/editorial comments:There seems to be a minor confusion between Network
Operator and Network Provider in the text that needs examining. "service
continuity after IPv4 address exhaustion, network operators (NPs). I assume
this is just a typo.