Regarding change #3645 "[protocol] Use case sensitive compression when responding to queries. [RT #34737]"

Bjørn Mork bjorn at mork.no
Thu Jan 8 10:30:08 UTC 2015


Hello,

I see on 
https://deepthought.isc.org/article/AA-01113/0/Case-Insensitive-Response-Compression-May-Cause-Problems-With-Mixed-Case-Data-and-Non-Conforming-Clients.html
that you are seeking feedback about issues related to this change.

FYI: I just got a report about some TV set-top boxes having problems as
a result of this change.  The report included a packet dump showing a
"working" DNS reply (matching case in query/answer, with compression)
and a "non-working" reply (different casing in query and answer, no
compression).

That's unfortunately all the details I can give at this point.

I'd also like to point to RFC4343, which AFAICS makes it clear that the
behaviour prior to change #3645 *is* allowed:

<quote>
4. Case on Input and Output

   While ASCII label comparisons are case insensitive, [STD13] says case
   MUST be preserved on output and preserved when convenient on input.
   However, this means less than it would appear, since the preservation
   of case on output is NOT required when output is optimized by the use
   of indirect labels, as explained below.
</quote>

Using the "no-case-compress" ACL will most likely solve any problems,
but maybe it should default to "all"?



Bjørn


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