Interoperability and updates

Erik van der Poel erikv at
Fri May 9 19:46:51 CEST 2008

Hi Paul,

I agree with much of what you said. However, in the long run, I
believe zone operators at all levels of the DNS will eventually settle
on a set of common practices that not only adhere to the "protocol"
that we are refining in this working group, but also take into account
the display restrictions that the clients develop. Some clients may
refuse to display labels that mix scripts. Some may even refuse to
display characters outside the user's familiar set (my long-stated

But whatever the clients decide to do on the display side, the zone
operators will have to gravitate toward labels that can be displayed
adequately, because ultimately, interoperability is not about
machine-to-machine communication -- it is about human-to-human

Having said that, the 4 drafts being considered in this working group
(plus your helpful mini-draft) do not really have display issues in
scope. They only address registration and lookup. We may wish to
consider starting another doc that begins to discuss the display
issues, but maybe not in this working group, or not this year

I also note that you haven't really addressed my proposal that clients
be allowed to look up *any* Punycode label, whether or not it is a
legal A-label in any version of IDNA and Unicode. Are you suggesting
that it is OK for IDNA-unaware software to look up Punycode labels,
but it is not OK for IDNA-aware software to look up Punycode labels
that are not legal A-labels, even if they receive the Punycode label
on the wire, from a 3rd party? What kind of interoperability is that?


On Fri, May 9, 2008 at 9:16 AM, Paul Hoffman <phoffman at> wrote:
> At 8:40 AM -0700 5/9/08, Erik van der Poel wrote:
> > We are only trying to maintain or achieve interoperability. If we
> > cannot get the representatives of the bigger players to agree, then
> > it's hard to achieve interoperability, right? Sorry if some of my
> > wording is deemed arrogant -- I'm just an engineer with ideas for
> > interoperability.
> >
>  The IETF has a long history of wrestling with the question of
> interoperability, agreement among the parties who care, enforcement,
> resistance, and updates. Different people in the IETF (we are people, not a
> monolithic organization) have different views about the best way to write a
> standard to get the greatest interoperability. Some of those differences of
> opinion are very relevant in the current discussion.
>  My view for IDNAbis (and IDNA2003) is that if the standard does not say
> that software that does a lookup needs to follow the rules for allowed and
> disallowed characters, meaningful interoperability will not be possible.
> Without lookup validation, registries will make mistakes (or possibly
> intentional mistakes) and then leave them in place with impunity. The reason
> we have had such good interoperability in IDNA2003 is the fact that most/all
> major software refuses to get to names that go against the standard.
>  This view makes updating the standard harder due to the already-discussed
> issues of delay in software updates. However, those issues are just as
> present if the standard does not require checking for lookup but does
> require checking for display. Programs that display IDNs need to be updated
> as often as those checking them before sending out queries. Thus, the
> standard does not gain any flexibility for updates unless both sides are
> made optional. A standard that only proposed limits on what could be
> registered would lead to near-zero interoperability due to the high number
> of mistakes that would be made.
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