[dns-operations] about the underline in hostname

Phillip Hallam-Baker phill at hallambaker.com
Thu May 29 16:54:33 UTC 2014

Sorry, hit send rather than reply all just then

On Thu, May 29, 2014 at 12:48 PM, David Conrad <drc at virtualized.org> wrote:
> Phillip,
> On May 29, 2014, at 8:17 AM, Phillip Hallam-Baker <phill at hallambaker.com> wrote:
>> And that is a problem because all numeric names are valid DNS hostnames.
> Not really. An all numeric string is a valid DNS _label_, however not all collections of DNS labels that make up a domain name are valid as a hostname. Specifically, RFC 1123 states (four paragraphs down from the bit you quoted):
>                          [...] However, a valid host name can never
>            have the dotted-decimal form #.#.#.#, since at least the
>            highest-level component label will be alphabetic.
> This implies that ICANN can't delegate an all-numeric TLD, and in fact, ICANN (in section, sub-section 1.2.1 of the Applicant's Guide Book) states:

I am rather worried when specifications rely on what is implied rather
than what is stated.

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