Subject: [EAI] ISSUE: draft-ietf-eai-utf8headers-07 - nested encoding

From: SM <[email-masked]>
Date: Thu, 20 Sep 2007 11:29:03 -0700

Hello,

In Section 4.2, it is mentioned that double encoding might happen in 
practice.  Quoting Section 6.4 of RFC 2045:

   "NOTE ON ENCODING RESTRICTIONS:  Though the prohibition against using
    content-transfer-encodings on composite body data may seem overly
    restrictive, it is necessary to prevent nested encodings, in which
    data are passed through an encoding algorithm multiple times, and
    must be decoded multiple times in order to be properly viewed.
    Nested encodings add considerable complexity to user agents:  Aside
    from the obvious efficiency problems with such multiple encodings,
    they can obscure the basic structure of a message.  In particular,
    they can imply that several decoding operations are necessary simply
    to find out what types of bodies a message contains.  Banning nested
    encodings may complicate the job of certain mail gateways, but this
    seems less of a problem than the effect of nested encodings on user
    agents.

It may be more efficient implementation-wise to prohibit double 
encoding to avoid several decoding operations.  The paragraph also 
mentions several other reasons for having such a restriction.

Regards,
-sm

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From: Harald Alvestrand <[email-masked]>
Date: Thu, 27 Sep 2007 14:56:45 +0200

I saw no response on this, and there might be a need for more text here.

I believe the WG came to consensus that allowing nested encodings was 
better than inventing new schemes for handling nested types - that's why 
I've lumped this together with the "content-header-encoding" idea of 
another message.

Tracker #1504 is assigned to this issue; please keep that in the subject 
line.