how did the idna theory start?

Abdulrahman I. ALGhadir aghadir at
Mon Jul 2 07:50:09 CEST 2012

Oh, this argument raised a question in my mind:

Why the EAI stopped using IDNA as solution of downgrading and it went to use fully UNICODE? Isn't the same concerns apply on it?
What I mean updating the email protocols will require to update the existence legacy machines, wouldn't be wiser to use IDNA to avoid the updating part,

Also, it is a bit confusing when there are multiple of solutions are used to solve this issue? Who knows other protocol might come up with new one isn't better to fix it on one method like using IDNA but instead of using the prefix XN-- use different prefix for different mapping based on the protocol needs?

-----Original Message-----
From: John C Klensin [mailto:klensin at] 
Sent: 1/Jul/2012 7:42 PM
To: Abdulrahman I. ALGhadir; Patrik Fältström
Cc: idna-update at
Subject: RE: how did the idna theory start?

--On Sunday, July 01, 2012 12:31 +0000 "Abdulrahman I. ALGhadir"
<aghadir at> wrote:

> The second point makes sense.

Two observations:

(1) The first point makes sense unless we were all willing to deal with a delay of possibly decades.  New ways of doing things in the DNS to which actual resolvers and servers have to adapt take a _very_ long time to deploy, with no workarounds until
they do.   It has taken IDNA much longer to deploy than anyone
expected then, but the workarounds exist and it is possible to adapt on an application-by-application basis.  There are problems even then; see RFC 6055.

(2) While Patrik is exactly correct about the second, if you (or
others) want to ask this question, I think there is something
else that is worth repeating.   I believe that, although we
reached the right conclusion,  we underestimated, and often continue to underestimate, the complexity of comparisons of
Unicode strings.   It is really tempting and easy to say "just
use Unicode" or even "just use UTF-8", without appreciating that, as soon as the requirements involve issues more complex than simple display, meeting expectations about how and why strings should match get extremely complicated.  IMO, IDNA goes about as far as is possible and gets it right within the limits of the DNS, but lots of people don't want to accept those limits (or are unable to understand them), leading to interminable discussions about character mapping (not just as a forward compatibility issue), "variants", various type of synonyms, the appropriateness of transliterations and translations of other strings, etc.


> -----Original Message-----
> From: idna-update-bounces at 
> [mailto:idna-update-bounces at] On Behalf Of Patrik 
> F?ltstr?m Sent: 1/Jul/2012 9:21 AM
> To: Abdulrahman I. ALGhadir
> Cc: idna-update at
> Subject: Re: how did the idna theory start?
> On 1 jul 2012, at 07:43, Abdulrahman I. ALGhadir wrote:
>> What is the main reason for not supporting the UNICODE in the DNS 
>> protocol and to not use the hack-and-slash current way to solve this 
>> issue?
> Because of mainly two reasons:
> 1. Backward compatibility with ascii domain names where domain names 
> are in use in protocols.
> 2. The problematic part of IDNA is not the encoding, but the choice 
> what characters to allow etc. If we one day need a completely 
> different version of IDNA, then we can use a different prefix than 
> "xn--" and still we have not destroyed the complete Unicode name 
> space.
>    Patrik
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