--On Wednesday, 02 April, 2003 11:23 -0500 Keith Moore
<moore(_at_)cs(_dot_)utk(_dot_)edu> wrote:
Sounds like you both are arguing that the DNS has become
"embedded" and the applications that use IP are unusable
without a working DNS.
as a practical matter, this was true even in IPv4. yes, you
can often use address literals in either v4 or v6 apps, but
this isn't practical for ordinary users on an ordinary basis.
and in both v4 and v6, several essential apps (e.g. email, the
web) have explicit dependencies on DNS. yes you can use
address literals in email addresses and URLs but there is no
assurance that an email address or URL with an address literal
is equivalent to the same address or URL with a domain instead
of the address. Both email and the web define their resources
in relation to a DNS name, not relative to a host or address.
At least in the case of email, it is important to be precise
about this, because we have a clear evolutionary trend:
(i) RFC 2821 can be read (and was intended to be read)
to prohibit the use of an address literal in a HELO or
EHLO command unless the relevant host has no DNS name.
(sections 3.6, 4.1.1.1, 4.1.4)
(ii) The use of address literals is described as a
mechanism to bypass a barrier, not one for normal use
(RFC2821, section 4.1.3)
(iii) On the other hand, the address literal "should"
still be provided in the From clause of a Received
field. Received field information is expected to not be
picked up by other software and protocols, but the
inclusion of address information there is very
leak-friendly.
Contrast this with RFC 821, which doesn't seem to strongly argue
that explicit address use is undesirable.
of course it is possible to write apps that do not use DNS,
but this is rarely done.
Yep. And as pointed out earlier, we have pushed back strongly
against such protocol proposals and implementations.
john