Re: [DNSOP] draft-liman-tld-names-04

[Tony Finch <[e-mail]>]

On Tue, 16 Nov 2010, Andrew Sullivan wrote:
>
> Define what you mean by "normative text".

Normative text specifies requirements. (This is the usual meaning of the
word.) Text in "DISCUSSION" sections is not normative. RFC 1123 section
1.3.1 says:

         Under many of the individual topics in this document, there is
         parenthetical material labeled "DISCUSSION" or
         "IMPLEMENTATION".  This material is intended to give
         clarification and explanation of the preceding requirements
         text.  It also includes some suggestions on possible future
         directions or developments.

Therefore the "will be alphabetic" phrase is not a requirement, it's part
of an explanation of how the syntax works in practice.

> But the argument has been that the Discussion segment amounts to a
> constraint on the protocol, or anyway may well have been interpreted
> that way in running code.  We don't know.

This is why you need to be clear about the layering. If this constraint
had been implemented in low-level non-policy code then IDNA TLDs would not
work.

There is quite a lot of policy enforcement code that has detailed
knowledge of which TLDs are valid, and that is perfectly fine because it
is operating at the policy layer not the protocol syntax layer, and is
obliged to keep up with changes in allocation policy.

> So I read the document as trying to relax that rule just exactly enough
> to allow A-labels in the TLDs, without relaxing everything.

I believe that no requirement needs to be relaxed to allow A-labels. A
clarification might be helpful.

What this document does is introduce new syntactic restrictions, by
specifying policy-layer stuff as protocol syntax.

> There's probably some heuristic software out there that checks the
> top-most label, looks for a digit in the first character, and treats the
> set of labels as an IP address if there is one.

That is blatantly broken. There is no need for any heuristic to tell IP
addresses and host names apart. This kind of code should be mocked, not
accommodated.

> Even if I don't like it, the top level is different from other levels in
> the DNS, and we need to be careful there.

Careful is for policy not mechanism.

Tony.
-- 
f.anthony.n.finch  <[e-mail]>  http://dotat.at/
HUMBER THAMES DOVER WIGHT PORTLAND: NORTH BACKING WEST OR NORTHWEST, 5 TO 7,
DECREASING 4 OR 5, OCCASIONALLY 6 LATER IN HUMBER AND THAMES. MODERATE OR
ROUGH. RAIN THEN FAIR. GOOD.