I note the IETF last call was issued for rev. 2. That
revision no longer exists, hence I reviewed rev. 3.
This document specification of a "User Principal Name",
I believe, is inadequate.
The I-D indicates that a user_principal_name is a sequence of
0 to 65535 bytes in the form of user(_at_)domain(_dot_) However,
such a form implies the value is a character string,
but there is no mention of what character set/encoding
is used here. I would think interoperability
requires both client and server to have a common
understand of what character set/encoding is to
be used. Additionally, there is no discussion
of UPN matching. Are byte sequences that differ
only due to use of different Unicode normalizations
to be consider the same or differ? Are values
case sensitive or not? etc..
The domain_name field suffers not only from the
above problem, but is flawed due to use of the
outdated "preferred name syntax" of RFC 1034.
This syntax doesn't allow domains such as
123.example. The text should likely reference
the RFC 1123 which updates the "preferred name
syntax" for naming hosts.
Could the IESG / RFC editor please reject any request to
publish a document which use the '"preferred name syntax"
of RFC 1034'.
RFC 952 as modified by RFC 1123 which was the the intent
of this section of RFC 1034.
For mail domains it was RFC 821 as modified by RFC 1123
(even though RFC 1123 fails to mention RFC 821). If it
didn't apply you could send mail to the address records
for 3com.com but not to the MX records and I don't think
that was ever the intent.
Domain name, hostname and mail domain are not interchangable
concepts. There are too many RFCs which incorrectly
interchange these concepts which leads to lots of confusion.
The latter to are very restriced subsets* of the first.
Additionally, no mention of how International
domain names (IDNs) are to be handled.
If we restrict to RFC 952 as modified by RFC 1123 then IDN
comes into play.
That doesn't help with the user side however unless we
apply the mailbox translation for the DNS.
I recommend ABNF be used to detail the syntax
of each of these fields and that the I-D detail
how values of these fields are to be compared.
Additionally, the I-D should discuss how IDNs
are to be handled.
-- Kurt
* Hostnames that are 254 and 255 characters long cannot be
expressed in the DNS.
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: Mark_Andrews(_at_)isc(_dot_)org
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