Definitions limit on label length in UTF-8
vint at google.com
Wed Sep 16 13:47:33 CEST 2009
better to count two things:
1. length in Unicode code points
2. length in Punycoded ASCII octets.
On Sep 16, 2009, at 7:24 AM, jean-michel bernier de portzamparc wrote:
> why not to count in "punycode points", i.e. the number of bytes of
> the transcoded text + four for the header ?
> 2009/9/15 Shawn Steele <Shawn.Steele at microsoft.com>
> That's fine, I was just curious :)
> -----Original Message-----
> From: Vint Cerf [mailto:vint at google.com]
> Sent: Monday, September 14, 2009 14:58
> To: Shawn Steele
> Cc: idna-update at alvestrand.no
> Subject: Re: Definitions limit on label length in UTF-8
> no i am counting in code points regardless of how expressed - is that
> a reasonably metric?
> On Sep 14, 2009, at 3:58 PM, Shawn Steele wrote:
> > You're suggesting some smaller # of Unicode characters? Are you
> > counting in UTF-16?
> > -Shawn
> > -----Original Message-----
> > From: Vint Cerf [mailto:vint at google.com]
> > Sent: Monday, September 14, 2009 12:42
> > To: Shawn Steele; idna-update at alvestrand.no
> > Subject: Re: Definitions limit on label length in UTF-8
> > Expressing limits in unicode characters (code points) regardless of
> > coding
> > scheme seems like a useful way to offer insight for implementers. V
> > ----- Original Message -----
> > From: idna-update-bounces at alvestrand.no <idna-update-bounces at alvestrand.no
> > >
> > To: idna-update at alvestrand.no <idna-update at alvestrand.no>
> > Sent: Mon Sep 14 12:59:08 2009
> > Subject: Definitions limit on label length in UTF-8
> > FWIW: I think that UTF-8 should NOT be a limit for Punycode. How an
> > app (or
> > OS) encodes a decoded Punycode string internally is up to them. I
> > doubt
> > we'd express such limits in GB-18030 or EUC-JP?
> > The only case I can think of for a UTF-8 limit is in the event
> > someone made
> > a UTF-8 clean DNS in the future. However an ASCII punycode label is
> > clearly
> > not the same thing, even if it represents a similar string.
> > In practice, all imposing a UTF-8 length limit does is to break
> > IDNA2003
> > further, make it harder to code, and a little more error-prone.
> > -Shawn
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