IDNA 2008 Question Re: "Confusable" Characters in Domain Names

J-F C. Morfin jfc at
Thu Nov 4 03:55:49 CET 2010


The question is quite confusing. So let us go through it step by step. As,

At 18:58 03/11/2010, Vint Cerf wrote:
>If your browser is operating under purely idna2008 rules the lookup 
>should fail. But some implementations

that you may also use on your own, same computer...

>may permit the lookup without verfying the legality of the 
>characters in the lookup string. V

and resolve differently.

1. Let us try it

on my ISP, which does not seem to offer a good 404 commercial 
replacement, if I enter €.com:

- Firefox: "Firefox ne peut trouver le serveur 'adresse 
<>". - Cannot find the host at 
address <> (please note: "address")

- Explorer: echoes €.com as, says that IE did not find 
the €.com page and suggests to  either access the hm.-com page or to 
search on Google, which also does not know "€", so back to Explorer 
for a second try and this time the suggestion is for "", and 
the final resolution is the <> page of H&M 
(please note: "page").

- Chrome: it states that it was unable to find the page 
(please note: "page") and proposes for me to access either:,,, or to search Google for... "lzg".

With  I reach a "€ - euro - €" website accompanied by Google ads.
With I reach a portal selling me plenty of 
exciting domain names, including £££.net and €
With xn--ozg: I get a Bad Request (Invalid Hostname) from an unknown 
When I google "lzg", I get 534,000 results.

- nslookup (prompt): my Internet box states that  "" is a 
non-existent domain (please note; "domain")

- ftp .com: the computer responds "unknown host" (please note: "host"),


2. What's the reason for these exotic answers?

There are at least three reasons:

2.1. IDNA2003 permitted possibilities that are supported differently 
by browsers (as tested above).

2.2. IDNA2008 purposely has a _no_ response to your question. 
IDNA2008 is only for the Internet side, and not for the user side. 
The user side is suggested (for information) to follow the 
indications of RFC 5895.

2.3. The IDNA concept of Internationalizing Domain Names in 
Applications (IDNA), as shown by the example above, is an 
architectural error on the user side. However, this error is in 
operation, so we needed to continue supporting it, to decide and 
document an alternative, to protect the Internet from it, and to 
transition from it. IDNA2008 protects the Internet in stating as to 
which Internet domain names labels are accepted by the Internet DNS. 
To document an architectural replacement (on the user side) is 
simpler now the Internet side is stabilized, but also much more 
complex because the IETF can only document SHOULDs outside of the 
Internet scope, i.e. in this case on the user side.

This means that now the IAB is to decide and document the IETF 
SHOULDs in that area (RFC under finalization). Several architectural 
possibilities can be considered as far as the user side MUSTs could 
be documented. Thereafter, the question of who would organize an 
authoritative documentation of these possibilities arises. As RFC 
5895 puts it: this is an unusual case.


Now, for your information, outside of the now closed WG/IDNABis but 
still probably subject to ISOC Copyright, we (IUsers) are working on 
exploring, testing, and authoritatively documenting one of these 
possibilities called the "ML-DNS", i.e. MultiLayer-DNS. I will 
describe it in an I_D when it has been finaly released as public 
domain (this copyright issue does not help ...).

I announced, from the very onset of the IDNABis work, as soon as the 
today still prevailing limits were self-imposed by the Chairs 
(previous WG/IDNA and WG/IDNAbis) that I would build-it on top of 
IDNA2008. It was possible for the IDNA2008 to be consensually agreed 
because the RFC 5895 proposed text in turn removed conflicts with the 
ML-DNS project. Once this was clarified (a fundamental change in the 
way the Internet supports diversity, any diversity), I made sure 
through an Appeal procedure that neither the IESG nor the IAB opposed 
that limitation to the IETF scope.

This clarified the IUser community area. It results from IDNA2008 and 
from the digital convergence [the Internet as an intertechnology 
network]. This is the area where any Intelligent Use of every 
possible digital system, including the Internet Use Interfacing 
(IUI), leads to the necessary respect of the IETF MUSTs. As far as 
the Internet is concerned, these MUSTs are world digital ecosystem 
network AREs, that no-Internet MUST can dispute.

In the ML-DNS, "€.com" may be given a meaning. However, that meaning,
(1) will be the same for every network and user application on your computer;
(2) will not conflict with IDNA 2008 on the Internet part of the 
World Digital Ecosystem Network;
(3) will be supported along the same rules by every IUser's ML-DNS. 
Please ensure to note that "same rules" does not necessarily mean " 
same IP resolution".


><mailto:idna-update-bounces at>idna-update-bounces at 
><<mailto:idna-update-bounces at>idna-update-bounces at>
>To: <mailto:idna-update at>idna-update at 
><<mailto:idna-update at>idna-update at>
>Sent: Wed Nov 03 13:14:55 2010
>Subject: IDNA 2008 Question Re: "Confusable" Characters in Domain Names
>Dear List Members,
>I am a little unclear what impact the IDNA 2008 policy will have on
>domain name registrant's who have a domain that does not fall under
>the policy's permissible code-points, particularly symbol-based domain
>The IDNA 2008 protocol clearly explains what code point are permissible,
>but what (in practice) will it mean if someone types in e.g. €.com in their
>browser under IDNA 2008?
>I do realise that an error message may be displayed, but will IDNA 2008
>allow the domain name registrant to satisfy the user's query by forwarding
>them on to a different (legal) domain name?
>I will hope to hear any replies on this matter.
>John Daw
>Idna-update mailing list
>Idna-update at
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