Mark Andrews Mark_Andrews at
Tue Dec 5 05:55:15 UTC 2006

> Hello, 
> I've been looking into IDNA a bit lately and unfortunately I think most IDNA
>  libraries may have a bug.  I'm looking for some feedback on this to see if 
> I am wrong or if the libraries do in fact have a bug.  The primary reason I 
> question whether this is a bug or not is it seems everyone has the same bug.
> IDNA encoding is performed on a label by label basis.  First the domain name
>  must be broken down into labels and then each label encoded in turn.  Most 
> IDNA libraries don't seem to account for dots embedded within a label.
> For example assuming "test\" were actually a name that neede
> d IDNA encoding to be valid ASCII it should be broken down into the labels "
> test\.me", "example", "com" and the root label, right?  But from my review o
> f at least 3 different IDNA libraries it appears they would break this down 
> improperly to "test\", "me", "example", "com" and the root label.  Isn't tha
> t a bug?  Wouldn't the IDNA ASCII name be invalid as a result?
> If it is a bug, should it be fixed or is it a matter of everyone made the sa
> me mistake so don't fix it because at least we are all compatible?  What doe
> s this mean then for domains with dots within a label?
> Thanks - your feedback is greatly appreciated.
> Rob

	What you describe would be a bug at first glance.
	Report the bug to the various implementors.

Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at

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