[dns-operations] about the underline in hostname

David Conrad drc at virtualized.org
Thu May 29 16:48:07 UTC 2014


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:

"The ASCII label must consist entirely of letters (alphabetic characters a-z), or [a valid IDNA A-Label]"

> At any rate, given the state of the specs, I don't see cause for being
> rude when people ask questions about them.

I don't believe there is cause for being rude when people ask honest questions period.

> There is a document quality issue here. None of these specs would be
> published as a proposed standard today.

Very true. It is, in fact, somewhat difficult to come up with "the" DNS specs that define the DNS today. IIRC, there was an attempt in DNSEXT before it was shut down to try to address that, but it didn't attract significant interest.


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