[vip] Suggested meta-questions to think about

[Cary Karp]

Quoting Andrew:

> .., many people do not realise that there is no strict technical 
> restriction at all of what eight bit octet you can put in your zone. 
> DNS labels are made of octets.  If you want, in your zone, to put
> any series of bits you like in there, you can do so. This means that
> you could just plop UTF-8 directly into the zone; and some people
> have done this.  But, the RFCs (STD 13) also say that it would be
> better to stick to the hostname rules ("letter, digit, hyphen").  So,
> in the TLD space, we have mostly stuck to this, for maximum
> interoperability on the Internet.  The closer you are to the root,
> the more conservative you need to be, since things will break
> otherwise.

The root is not just constrained by the hostname rule. To ensure that a
domain name cannot be confused with a numerical IP address, RFC 1123
requires that "at least the highest-level component label will be
alphabetic". Strictly speaking, this bars the ASCII-encoded form of an
IDN TLD label (the "A-label") from the root (since every A-label
contains hyphens and many also include digits). The necessary
clarification of what is meant by "alphabetic", explicitly to permit the
inclusion of A-labels in the root, is provided in
<http://tools.ietf.org/html/draft-liman-tld-names-04>.

(Since that draft recently expired, I assume subsequent action has been
taken to address the underlying issue. ??)

/Cary