Re: [idn] length restrictions on IDN label

[Mark.Andrews@isc.org]

> About presentation formats, you argument stands.
> UTF8 form of labels further can be URLEncoded with %xx sequences into
> tripled length of character streams.
> That means "56 x U+AC00 " can be converted into
> 56 x 3 (utf8) x 3 (URLencode) = 504 octets string.
> RFC1035 length restriction does not apply to presentation forms. This is
> your point. right?

	Yes.
 
> But, my question is about utf8 form as protocol elements (wire format
> for future
> application or DNS protocols), not as presentation forms.
> You can find that in IDNA section 6.3.
> Would you make another comments on that section ?

	Well if you use raw utf-8 today int the DNS you are limited to
	63 octets per label.  255 octets for a domain name.  As long as
	you continue to use the same label encoding you are limited to
	63 octets.  YMMV at levels other than the DNS.

	However 
 
> THanks.
> 
> Soobok Lee
> 
> 
> Mark.Andrews@isc.org wrote:
> 
> >	The restrictions have always derived from the DNS wire format.
> >	Each individual presentation format will have its own maximum
> >	number of octets however just because a string fits within
> >	that number of octets doesn't mean that it will be valid.
> >
> >	Invalid 
> >	0123456789012345678901234567890123456789012345678901234567891234
> >
> >	Valid
> >	\048\049\050\051\052\053\054\055\056\057\048\049\050\051\052\053
> >
> >	Both of the above presentation strings are 64 octets long.  Only
> >	one is a legal label, both are < 252 octets that you would have
> >	to allow to convert a arbitary label from wire format to
> >	to RFC 1034 presentation format.  Similar things will happen
> >	with UTF-8 as a presentation format.  Only after you have attempted
> >	to covert to wire format can you determine if a arbitarty string
> >	of UTF-8 characters that is less than the maximum number of octets
> >	long will fit.
> >
> >	Mark
> > 
> >
> 
> 
> 
--
Mark Andrews, Internet Software Consortium
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PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews@isc.org