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Re: back by popular demand - a DNS calculator

John C Klensin <john-ietf@jck.com> Fri, 15 February 2013 23:17 UTC

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Date: Fri, 15 Feb 2013 18:17:27 -0500
From: John C Klensin <john-ietf@jck.com>
To: Joe Touch <touch@isi.edu>
Subject: Re: back by popular demand - a DNS calculator
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--On Friday, February 15, 2013 14:10 -0800 Joe Touch
<touch@isi.edu> wrote:

> Let's just say that there doesn't appear to be disagreement
> that the DNS can handle a-z/0-9/'-'.
> 
> Other values _may or may not_ be permitted or handled opaquely
> in the lookup, AFAICT. It remains a question AFAICT.

Joe,

Except for IDNs (or labels starting with "xn--" more
specifically), for which there are special rules, it appears to
me that the spec is _extremely_ clear that a lookup operation
that fails to deal with those "other values" in labels
--including even properly-escaped embedded "." characters -- is
unambiguously non-conforming.

There should be no "AFACIT" about it, much less a question.

Whether or not it is a good idea to use such labels and in what
contexts is a different matter.

   john

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