Re: [idn] length restrictions on IDN label

[Soobok Lee <lsb@postel.co.kr>]

2002-10-14 ¿ù 23:29, Erik Nordmark :
 
> 
> But perhaps IDNA should be more clear that there is a length issue for
> such future work. For instance, would adding a sentence at the end of
> this paragraph be helpful?
> 	If a signaling system which makes negotiation possible between old and
> 	new DNS clients and servers is standardized in the future, the encoding
> 	of the query in the DNS protocol itself can be changed from ACE to
> 	something else, such as UTF-8. The question whether or not this should
> 	be used is, however, a separate problem and is not discussed in this
> 	memo.
> E.g. "Such work would have to take into account the length limit for IDNs
> as specified in this document".
> 
> It might also be useful to make the IDNA specification more clear about
> the length limit and its implications somewhere in the document.
> Strawman:
> 	The length limit for internationalized labels is the limit
> 	of at most 63 octets of output from ToASCII. The design
> 	of the Punycode encoding is such that some sequences of up to 63 Unicode
> 	code points result in ToASCII output of 63 or less octets, but
> 	all possible Unicode strings of 64 code points result in ToASCII
> 	output of 64 or more octets.
> 
> 	Implementation Note:
> 		Depending on the local encoding the software uses for
> 		Unicode this can correspond to a lot more than 63 octets.
> 		Similarely, the total length of a IDN expressed in the local
> 		encoding can significantly exceed 255 octets.
> 
>   Erik
> 

This clarification will really help.  Thanks.

Soobok Lee