At 16:15 +0900 11/22/05, JINMEI Tatuya /
=?ISO-2022-JP?B?GyRCP0BMQEMjOkgbKEI=?= wrote:
Hmm, so the gtld server returns a glue record for which it does not
have the authority in the answer section. While it does not
necessarily seem invalid according to RFC2181 (which prohibits an
authoritative server from returning an authoritative answer as
non-authoritative data, but doesn't say anything about the content of
the answer section), it's still annoying as we see now...
This is something I've personally labelled a "hybrid answer" on the
namedroppers list. (Meaning it's my term, no group has vetted it.)
The expected response in the situation is a referral - everything in
the response you see but with a ANCOUNT=0 and no records in the
ANSWER section. The message is a hybrid referral-cache response.
There is a historical reason for this hybrid. Smoothing over a ton
of details, older resolvers were not capable of handling the number
of "restarts" needed to look up a reverse map (for instance). By
slipping in the A record in the hybrid answer, these resolvers were
able to do reverse map lookups.
There's nothing syntactically wrong with the response. It is
possible to see an answer that not authoritative (no AA) without the
recursion available bit on (no RA). The semantic is "I've learned
this for some other reason and I'll tell you, but don't expect me to
look it up for you otherwise." In this case, the answer was obtained
through the registration process.
I'm not surprised that this hybrid isn't covered by specifications,
it came from an operational observation. The situation spurring this
kind of message was a weakness in a software design (not a bug per
se). The design weakness has been corrected in later versions of
software, but, as usual, there's no accounting for some folks'
failure to upgrade.
--
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Edward Lewis +1-571-434-5468
NeuStar
3 months to the next trip. I guess it's finally time to settle down and
find a grocery store.
.
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