No case change in DNS (was: Re: Mapping and Variants)

Jaap Akkerhuis jaap at
Sat Mar 7 11:22:41 CET 2009

    At 03:27 09/03/07, Andrew Sullivan wrote:
    Hello Andrew,
    Can you shed some light on the "don't change case"
    provision in RFC 1034?
    In my understanding, it would make very much sense during
    registration. It could also make sense for the eventuality
    that some parts of the DNS don't do case-equivalent lookup.
    (Don't know whether there is currently such a case.)

As you say, there is currently not such a case and it is very
unlikely that this will ever happen. Some registries do map the
case (of US-ASCII names) uniformly storing domain names in their
databases and/or zone files. If you look at the .com zone file,
you'll note the all names are upper case while in the .nl zone file
the names are lower case. The original difference in case the
registrant might have made is very likely lost.  As example, the
name "NLnetLabs" is just "nlnetlabs" in the .nl zone file (and whois
information) and would have become "NLNETLABS" in the .com file.

So it is just the other way around.  The "don't change case" provision
was apparently never followed in the context of the registry system
but only in the DNS protocol.


PS. I've always assumed this provision was in the protocol because
at the time its was defined there were systems around with different
character sets and encoding around. I seems to remember that there
were quite some systems which knew about the difference in upper and
lower case, but rendered all character in only one case. So making
names case ignorant and mapping them to a single form for internal
use made some sense.

Isn't this also observed in one of Johns documents?

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