Re: [idn] draft about <draft-ietf-idn-uname-01.txt>

["Adam M. Costello" <amc@cs.berkeley.edu>]

It is already permissible (I think) for DNS servers to perform more
complex matching than the usual case-insensitive ASCII matching.  For
example, a DNS server implementation could support master file entries
whose keys are regular expressions, and it could compare incoming
requests to those patterns.  For example, it could allow:

foo-?(two|2)   A   1.2.3.4

to be used as shorthand for:

foo2      A   1.2.3.4
footwo    A   1.2.3.4
foo-2     A   1.2.3.4
foo-two   A   1.2.3.4

Similarly, if a DNS server implementation wants to perform
simplified/traditional Chinese matching, or matching of names encoded
in alternate charsets, isn't it already allowed to do so?  Is there any
need to standardize this?

Note that using such a feature will cause problems at higher layers,
because clients won't know the matching rules.  For example, if I
follow a link to www.foo2.net, and later follow a different link to
www.foo-two.net, the link will not be colored as visited.  If I tell
my browser to accept cookies from foo2.net, it won't know to also
accept cookies from foo-two.net.  Same problem with SSL certificates.
Therefore it would probably be desirable to deal with extended matching
not only in the DNS server but also at higher layers.  In these
examples, one might want the HTTP server to redirect requests from the
alternate server names to a single preferred server name.

AMC