--On Tuesday, May 07, 2013 08:08 -0700 Ned Freed
<ned(_dot_)freed(_at_)mrochek(_dot_)com> wrote:
Maybe things have changed, but, if one actually believes the
robustness principle, then, in the case Geoff cites, Exchange
is simply non-conforming -- not because the spec prohibits
rejecting on the basis of a fine distinction about IPv6
formats, but because doing so is unnecessary, inconsistent
with the robustness principle, and, arguably, plain silly.
I'm afraid I'm going to have to disagree here. If you look at
RFC 5321 and are unaware of the history of how the text came
about, it gives the definite appearance of going out of its
way to ban the use of :: to replace a single 0. A reasonable
interpretation is therefore that such forms are disallowed for
a reason.
I hadn't looked at the syntax (as you know, the other part of
that history of how the text came about is that I didn't write
it or even make an effort to check it carefully). But, having
now done so, you are completely correct.
It's fine to be tolerant of stuff the relevant standard doesn't
allow but doesn't call out explicitly. But that's not the case
here.
Of course, we have lots of implementations that allow things on
input that the standard explicitly prohibits and we rarely spend
much time complaining about them. I suppose that tolerance for
bare LF is among the most common examples.
In any case, if you want to "fix" this, we could change RFC
5321 to accept this form. But as Mark Andrews points out, you
can't make it legal to send such forms without breaking
interoperability. I suppose we could make the change and
recycle at proposed, but that seems rather extreme to fix what
is in fact a nonissue.
Agreed
I'll also point out that this has diddley-squat to do with
formal verification processes. Again as Mark Anrdrews points
out, we deployed something with a restriction that
subsequently turned out to be unnecessary, and now we're stuck
with it. Indeed, had formal verification processes been
properly used, they would have flagged any attempt to change
this as breaking interoperability.
Also agreed.
best,
john