numeric (ascii) labels (was: Re: draft-liman-tld-names-00.txt and bidi)

John C Klensin klensin at
Tue Mar 10 07:11:48 CET 2009

--On Monday, March 09, 2009 22:34 -0400 Vint Cerf
<vint at> wrote:

> eric,
> given the need to program something to answer the question
> "could this dotted thing possibly be interpreted as an IP
> address" and the alternative "this could not possibly be an IP
> address because it is not all-numeric" I would incline towards
> what I think is the easier to program and not very restrictive
> choice that simply says:
> 1. no TLD can be all-numeric ASCII
> 2. leading (and trailing ?) digits are disallowed in labels
> I gather you favor allowing all-numeric TLD labels. How does
> the rest of the WG see this?


I'm clearly not the "rest of the WG".  However, there is a
reason why Jon wrote "alphabetic" in 1123 when he could have
written "won't be anything that can be confused with IPv4
addresses" or "the original no-leading-digit restriction is not
changed for TLD names".  While they involve more words, the
latter options would not have been any harder to write than what
was written.

The reason was to avoid any possible confusion with addresses
--not confusion after applying a series of rules, but confusion
at all.

But, more important for this WG, it seems to me that we have
verified that A-labels cannot contain trailing digits.  Beyond
that, where RFC 1123 should be modified at all is a problem for
DNSOPS (or some other WG), but certainly not for this one.  And
the policy matter about what should be permitted at the top
level within the constraints set by 1123 or an update to it is
an ICANN problem.    We have documents posted that are not
getting adequate review and discussion, in part, I believe,
because endless speculation on this sort of topic is much more
amusing.  Could you, as WG Chair, please rule this discussion
out of order and ask people to take it off the list?

Just my personal opinion, but, if we were making more focused
attention on the WG's documents, I'd feel a lot better about
these many excursions into the weeds.


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