[dns-operations] Questions on DNS Flag day 2020 proposal

Dave Lawrence tale at dd.org
Thu Jul 4 18:44:59 UTC 2019

Tony Finch writes:
> You cannot apply RFC 2119 pedantry when reading older RFCs. Especially
> when reading RFC 1035 you will be more correct if you treat "should"
> as having the force of MUST unless you have clear evidence otherwise.

Definitely agree with the first bit, insofar as it has to be
intrinsically true that you can't use 2119 to interpret RFCs that
predated it. I wonder how it is that you have come to the conclusion
that a pre-2119 "should" has the force of "MUST".  Is this supported
by other documentation to that effect, or only a personally held
opinion?  Either way it must also be noted that ...

> Also you can't ignore updates to RFCs; in particular the part of RFC 1035
> you are quoting is amended by RFC 1123 (STD3) and RFC 7766.

1123 section made it quite explicit that DNS/TCP was a SHOULD,
which seems to provide "clear evidence otherwise" that 1035 didn't
mean it as a MUST either.  7766 was in necessary in very large part to
address that very issue.

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