RE: [Sip] Support for Multipart/MIME

["Dan Wing" <[e-mail]>]

> >Using the same port number on multiple m= lines has been, and 
> >continues to be, a direct violation of several SDP 
> >specifications.  Even the SDP grouping specification 
> >explicitly calls this out as illegal.
> 
> Yes. But in the multipart/alternative example I gave you (and which is
> ilustrated in a simple form below) would have 3 individual SDP bodies,
> and the same port number would not be used within a single 
> SDP bodies. 
> 
> But, the same port number would be used in each indivudual 
> SDP body, and as far as I know there is no specification which 
> forbids that.
> 
> -----boundary
> 
> m=audio 9999 audio_x
> m=video 7777 video_x
> 
> -----boundary
> 
> m=video 7777 video_y
> 
> -----boundary
> 
> m=audio 9999 audio_y
> 
> -----boundary--

This can be expressed with MMUSIC's capabilities negotiation, though -- and
can be expressed better than with multipart/alternative because MMUSIC's
capability negotiation defines preferences of each m= and each a= line,
whereas multipart/alternative can only ever allow simple "take all of this
SDP" or "take none of this SDP".

(With the specific example you show, of course, you don't even need MMUSIC's
capabilities negotiation -- an answerer that doesn't support video (or
doesn't support audio) can already indicate that in its SDP answer.)

-d


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