Subject: Re: [EAI] Proposal for Alternate ABNF (was: Consensus Issue #6: current metalanguage model acceptable?)

From: John C Klensin <[email-masked]>
Date: Sun, 23 Jan 2011 05:58:50 -0500

--On Saturday, January 22, 2011 22:54 +0000 Shawn Steele
<[email-masked]> wrote:

>> I can live with this approach.  If it is adopted, I'll help
>> sort out the domain name part.
> 
> As mentioned, IMO, the domain part should "just" say UTF-8 as
> well, though it's fair to point out the dependencies on
> existing RFCs that define DNS.  DNS is a bit trickier than the
> other headers because we explicitly want to disallow the
> punycode I think, and require UTF-8 U-Labels instead.

Shawn,

I know that you want to "disallow" punycode.  In a perfect
world, I would too, and that is part of what
draft-iab-idn-encoding is about.  But, realistically, while we
can try to discourage its use, banning it is just impractical
given that A-labels conform to the RFC 1035 "preferred syntax",
the syntax requirements of RFCs 5321 and 5322, and even the
rather careful rules in RFC 5892 about what does and does not
need to be checked on lookup.

    john

---

From: Shawn Steele <[email-masked]>
Date: Mon, 24 Jan 2011 02:56:13 +0000

Yes, it's legal for the existing RFCs, however the existing RFCs don't allow the use of MAIL FROM UTF8SMTP.  Presumably it could be a requirement that if you're using the EAI RFC, then punycode could be illegal.

At the very least u-labels should be a SHOULD.

-Shawn

 
http://blogs.msdn.com/shawnste

________________________________________
From: John C Klensin [[email-masked]]
Sent: Sunday, January 23, 2011 2:58 AM
To: Shawn Steele; [email-masked]
Subject: Re: [EAI] Proposal for Alternate ABNF (was: Consensus Issue #6: current metalanguage model acceptable?)

Shawn,

    john

---

From: John C Klensin <[email-masked]>
Date: Sun, 23 Jan 2011 22:48:24 -0500

--On Monday, January 24, 2011 02:56 +0000 Shawn Steele
<[email-masked]> wrote:

> Yes, it's legal for the existing RFCs, however the existing
> RFCs don't allow the use of MAIL FROM UTF8SMTP.  Presumably it
> could be a requirement that if you're using the EAI RFC, then
> punycode could be illegal.
> 

I don't see any problem with a SHOULD.   But the ability to use
an A-label anywhere that a U-label is permitted is fairly
fundamental to the IDNA design.  Unless you want to get the WG
into the business of updating IDNA itself -- IMO, a bad idea and
probably outside charter-- I don't see any practical way to go
beyond a SHOULD.  Note that, while we avoided RFC 2119 language
(consistent with the IESG decision to process 4952bis as
Informational), the Framework document already essentially has
the SHOULD.  In Section 7.1 of draft-eai-frmwrk-4952bis-10,
general principle (1), we have:

	When the local part of the address includes characters
	outside the ASCII character repertoire, use of
	ASCII-compatible encoding (ACE) [RFC3492] [RFC5890] in
	the domain part is discouraged to promote consistent
	processing of characters throughout the address.

"strongly discouraged" is pretty clear.  

And, slipping on my co-chair hat for a moment, since 4952bis has
successfully been through WG and IETF Last Call and IESG
signoff, in the absence of significant new issues, I consider
this a settled matter that is not subject to further debate or
discussion.  Whatever text appears in 5336bis/5335bis needs to
be consistent with that principle, but that should be an
editorial matter, not a substantive one.

    john