This reminds me of an objection I had a long time ago. If you send an
ASCII message to an EBCDIC site, the message will say that it's in
ASCII (charset=us-ascii), but it will say that in EBCDIC! (The
gateway automatically converts to EBCDIC, but it doesn't make the
corresponding change to the charset parameter.
Background:
The most popular of these systems (in terms of message load to and
from the Internet) are the collection of hosts and networks known
collectively as "BITNET". It is characterized by not having one
gateway, but many gateways (on many different platforms) and a lot of
hosts that are dual-homed with both Internet (TCP/IP) and BITNET (NJE)
connections. The network uses EBCDIC as its canonical transport encoding
for email, but, at this stage, there are more ASCII-ish hosts on the
network than EBCDIC ones. The structure of the gateway system is such
that it is common for mail to go in by one route (gateway) but for
addresses generated by "reply" commands to go back by another, and this
situation applies in both directions (original message BITNET-> Internet
and original message Internet-> BITNET).
The situation with MIME is, to put it mildly, perceived of as a disaster
and a complete refutation of the hypothesis that MIME can operate
transparently, with no change to MTAs or gateways. There is some
feeling on the BITNET side of things (articulated so far mostly in the
mode of hotheads and flamers) that IETF has been totally irresponsible
to turn this thing loose with the claim that it has no transport
implications and that the problems it has caused already are grounds for
scrapping MIME and starting over (I'm just reporting here, not
expressing agreement with feelings nearly that strong).
I am aware of three proposed realistic and comprehensive solutions to
emerge so far:
(i) changing the base transport of that network from EBCDIC to ASCII
(ii) changing the gateways to recognize MIME messages and sending
them, and them only, specially-encoded, without character translation.
(iii) Recognizing MIME messages at the gateways and bouncing some or
all of them as undeliverable to BITNET hosts.
While these options may be feasible (!), they are not consistent with
statements about being transport-transparent, nor about ones about
avoiding disruption to the installed base.
But maybe some of
those gateways have now been updated to take MIME into account. Or
perhaps the UAs in those environments have been updated to take this
issue into account. Does anyone know of such changes?)
While I'm aware of some attempts to locally minimize the impact of
these problems (especially on the ASCII machines on BITNET), the
official gateways have not been changed, nor have any of the widely-
available UAs or mail-based applications software on the EBCDIC
platforms.
Because a host may receive mail passed through any of several
different gateways, having UAs compensate ("take the issue into
account") is not practical unless either all gateways behave the same
way--which might include extending or modifying MIME to canonically
document what was done so that UAs could act accordingly.
Because the gateways are not centrally administered (and because the
description of the collection of administratively separate, but
protocol-sharing, networks involved as "Cooperating" is a statement of
hope and intent but occasionally not fact) plans that would require
flag-day switchover of either gateways or UAs are non-starters.
Many years of effort have gone into making the BITNET mail
environment transparently interoperable with the Internet one in this
many-gateway and dual-homed-host environment, even if those efforts have
not always been completely successful. One of the traditional tests for
the level of interoperability expected was that one should be able to
perform a "remail" or "forward" operation without worrying about which
of the parties involved (originator, first recipient/ forwarder, final
recipient) were on which side of the gateways or, of course, which
gateways were in use. Prior to MIME, this worked. At this point, we
have EBCDIC floating around BITNET labelled as ASCII and some ASCII
floating around there and labelled as ASCII (mostly on individual
hosts). It is probably only a matter of time before we have EBCDIC on
the Internet labelled ASCII and multipart MIME messages floating around
that have all parts labelled as ASCII but that are actually mixed.
Fairly unattractive situation, really.
john