Re: [idn] Using the last DNS header bit

[Dan Oscarsson <Dan.Oscarsson@trab.se>]

>There are number of proposals in this working group suggesting to
>use this bit for expressing support for IDN. There will be deployment
>problems using this bit due to some old DNS software using this bit
>for non standardized behavior. This bit is being reserved for future
>use, in case we encounter a problem that is of extremely high importance 
>and where there is no way around it.

draft-ietf-dnsext-iana-dns-01.txt says that it is believed that current DNS
implementations ignore this bit.

>
>Most of the proposals that I have read can just as well use one of
>the EDNS extension functions, for instance the extended flags (there are 12 
>1-bit flags available).

Using EDNS gives an unacceptable overhead as older servers will
give an error response when using it. That is why the flag is needed
in the normal header. One can question why DNSSEC were allowed to
use up two of the three unused bits, DNSSEC could have used EDNS?
Considering that I have no doubt that IDNs are by far much more
important for most people on the planet, than DNSSEC.

The alternatives to using the unused bit in the header are using one
of the other bits only used in a response (not recommended by
draft-ietf-dnsext-iana-dns-01.txt) or the response code field.

   Dan