Subject: [Sip] MIME: binary data

From: "Christer Holmberg (JO/LMF)" <[email-masked]>
Date: Wed, 30 May 2007 13:10:29 +0200

Hi,

When I was looking at RFC3204 I found the following text in chapter 3
(note the 2 last sentences):

"ISUP and QSIG messages are composed of arbitrary binary data that is
transparent to SIP processing. The best way to encode these is to use
binary encoding. This is in conformance with the restrictions imposed on
the use of binary data for MIME (RFC 2045 [3]). It should be noted that
the rules mentioned in the RFC 2045 apply to Internet mail messages and
not to SIP messages. Binary has been preferred over Base64 encoding
because the latter would only result in adding bulk to the encoded
messages and possibly be more costly in terms of processing power."

Now, if this text is not specific to ISUP and QSIG, but to binary data
in general, I think it needs to be documented in Gonzalo's draft.
Because, it seems to be one example of where we "override" the generic
MIME rules (I haven't check, but the text says that some rules in
RFC2045 does not apply to SIP...). 

Regards,

Christer

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From: [email-masked]
Date: Wed, 30 May 2007 14:59:17 -0400

From: "Christer Holmberg (JO/LMF)" <[email-masked]>

Well, we probably should document it.  But SIP is not an exception,
*e-mail* is, as far as I can tell from scanning through 2045:

   Mail transport for unencoded 8bit data is defined in RFC 1652.  As of
   the initial publication of this document, there are no standardized
   Internet mail transports for which it is legitimate to include
   unencoded binary data in mail bodies.  Thus there are no
   circumstances in which the "binary" Content-Transfer-Encoding is
   actually valid in Internet mail.  However, in the event that binary
   mail transport becomes a reality in Internet mail, or when MIME is
   used in conjunction with any other binary-capable mail transport
   mechanism, binary bodies must be labelled as such using this
   mechanism.

Dale

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From: Dean Willis <[email-masked]>
Date: Wed, 30 May 2007 19:21:27 -0500

> *e-mail* is, as far as I can tell from scanning through 2045:

See RFC 3030 - SMTP Service Extensions for Transmission of Large and  
Binary MIME Messages.

--
Dean