ietf-822
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Re: Internationalization of the Internet

1994-11-20 23:02:12
That paragraph
simply RESTATES, in terms of the MIME content-type, the definition that
was already made in RFC 822.

Read RFC 822 again. We have designed ISO-2022-JP, which is NOT US-ASCII,
10 years ago with full understanding on RFC 822.

Make no mistake.  The use of ISO-2022-JP DOES violate RFC 822.
RFC 822 specifies ASCII.  ISO-2022-JP, as you say, is NOT ASCII.

ASCII, not ASCII graphic characters, which does include ESC, which is
NET-ASCII. If the issue is not clear to you see other documents (for
example for ftp) on how NET-ASCII is.

ISO-2022-JP was very carefully engineered to not cause problems with MTAs and
user agents that expect ASCII, and it's a fine piece of work.  But strictly
speaking, its use is NOT allowed by the RFC 822 specification.

See extended BNF in RFC 822:

     CHAR        =  <any ASCII character>        ; (  0-177,  0.-127.)

     CTL         =  <any ASCII control           ; (  0- 37,  0.- 31.)
                     character and DEL>          ; (    177,     127.)

Few people would blame anyone for violating RFC 822 by using ISO-2022-JP, in
part because it is so well designed.  But it's another matter entirely to
insist that MIME should be backward compatible with such nonstandard usage.

Yes, MIME default should be US-ASCII.

                                                        Masataka Ohta