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RE: [Sip] Support for Multipart/MIME - when is it allowed to use alternative?

"Christer Holmberg (JO/LMF)" <christer.holmberg@ericsson.com> Wed, 30 May 2007 08:07 UTC

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Subject: RE: [Sip] Support for Multipart/MIME - when is it allowed to use alternative?
Date: Wed, 30 May 2007 10:07:01 +0200
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From: "Christer Holmberg (JO/LMF)" <christer.holmberg@ericsson.com>
To: Dan Wing <dwing@cisco.com>, Paul Kyzivat <pkyzivat@cisco.com>, "Gonzalo Camarillo (JO/LMF)" <gonzalo.camarillo@ericsson.com>
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Hi,

I don't think we should try to specify in detail when one is allowed to
use alternative, and one is not allowed, but instead refer to other
specifications for specific content types, and say that an
implementation shall reject the message if alternative is used in a
wrong way (based on those other specs).

I think our main focus should be to describe the expected protocol level
behavior of a SIP entity when receiving alternative.

Do we have the same issue with mixed, btw? I assume there COULD be cases
where the same content type can be used with mixed?

Regards,

Christer 



> -----Original Message-----
> From: Dan Wing [mailto:dwing@cisco.com] 
> Sent: 29. toukokuuta 2007 22:38
> To: 'Paul Kyzivat'; Gonzalo Camarillo (JO/LMF)
> Cc: 'Francois Audet'; sip@ietf.org; Christer Holmberg (JO/LMF)
> Subject: RE: [Sip] Support for Multipart/MIME
> 
> Paul Kyzivat wrote: 
> ...
> > >    OPEN ISSUE 2: we know that we do not want two SDPs in a 
> > > 'multipart/
> > >    alternative', but is this valid generally with any 
> content type?
> > >    Would it be possible to provide two alternative body 
> parts using 
> > > the
> > >    same format and, thus, the same content type but in, say, 
> > > different
> > >    languages?
> > 
> > Its my understanding that the distinction is based on which can be 
> > understood, relative to Content-Type. It isn't apparent to me that 
> > making this decision based on other attributes is valid. 
> For one thing 
> > the parts are supposed to be ordered by increasing 
> richness.  If they 
> > differed by language this wouldn't be true.
> 
> Multipart/alternative is the best we have, though.  And who 
> is to say that image/jpeg is richer than image/gif, or that 
> english is richer than latin?  
> 
> Anyway, the following RFCs standardize the use of 
> Content-Language and refer to using multipart/alternative 
> when providing support for multiple
> languages:
> 
>   http://tools.ietf.org/html/rfc3282
>   http://tools.ietf.org/html/rfc3066
> 
> -d
> 
> 


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