In message <alpine.OSX.2.11.1608092140330.1678@ary.local>, "John R Levine"
writes:
RFC2671/RFC6891 has
Z
Set to zero by senders and ignored by receivers, unless modified
in a subsequent specification.
which resulted in 2% of deployed nameservers just copying reserved
bits to the reply or 3% of nameservers not answering because a
reserved bit is set.
I suppose, but how many of the people who wrote the broken code would have
paid attention if it said YOU MUST SET THE BIT TO ZERO AND THEN IGNORE IT
YOU MORON.
We will never know.
"MUST be set to zero by senders and MUST be ignored by receivers,
unless modified in a subsequent specification." would have caught
those that scan for MUST, SHOULD and MAYs.
At the moment we have draft-ietf-dnsop-no-response-issue-03 to try
and clean up the mess out there. I'm waiting on Tim for promised
feedback before I publish -04.
Mark
Regards,
John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
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Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: marka(_at_)isc(_dot_)org