After thinking more about the draft, I think it is
purposelessly hostile against innocent operators and
end users who are suffering between people filtering
ICMP and people insisting on PMTUD.
Today, innocent operators often clear DF bit and
end users are happy with it, because, today, probability
of accidental ID match is small enough.
However, as the ID specifies:
>> Originating sources MAY set the IPv4 ID field of atomic datagrams
to any value.
>> IPv4 datagram transit devices MUST NOT clear the DF bit.
people insisting on PMTUD are now authorized to set ID always
zero, trying to discourage ICMP filtering and DF bit clearing.
But, as people filtering ICMP won't stop doing so and if
operators can do nothing other than clearing DF, it is
end users who suffers.
Then, end users may actively act against PMTUD and/or IETF.
Masataka Ohta