Re: [MMUSIC] IANA registration of the "image" media type in SDP

[Flemming Andreasen <[e-mail]>]

On 4/1/11 3:56 AM, Magnus Westerlund wrote:
>
> Gonzalo Salgueiro skrev 2011-03-31 15:52:
> > Almost a year ago Kevin Fleming and I had this discussion. We ran into
> > this issue in the course of working with the ITU-T on a SIP Forum FoIP
> > TG initiated contribution to T.38. When updating references from RFC
> > 2327  to RFC 4566, we came across the fact that in RFC 2327 the
> > possible values for the 'media' type are documented as sharing the name
> > space with the top-level media content types in the MIME (RFC 2048)
> > registry, whereas in RFC 4566 this statement does not appear. RFC 4566
> > does contain language that would appear to include such top-level media
> > content types as valid 'media' types in SDP, but also establishes a new
> > SDP-specific 'media' type registry. The MIME top-level media content
> > registry *does* have a registration for 'image'. As you correctly note,
> > IANA does not appear to have
> > actually created an SDP media type registry (and populated it with
> > the values from RFC 4566). As a result of this we intended to write the
> > I-D for consideration by MMUSIC to register the 'image' media type for
> > SDP. We'll happily submit this if the group agrees.
> >
>
> Isn't it simpler to just point at the media types registry in general.
> Not indicate which of the existing media types that might or might not
> be used in SDP.
>
I was thinking the same thing, but there is the question of the 
"control" and "data" media types in the original SDP spec (RFC 2327) as 
noted in RFC 4566 and pointed out by Colin. Note that in the other 
direction, we also have more media types than currently defined in SDP 
(e.g. "multipart"). It would also be a change to RFC 4566, that 
effectively undoes a change from RFC 2327.

Maybe Colin can clarify further, but in looking closer at RFC 4566 
Section 5.14, and more specifically the text for the <fmt> part, there 
is text saying that media type registrations should define the packet 
format when the transport is UDP. In other words, there are additional 
considerations above and beyond the media type registration procedure 
from RFC 4288 as far as I can tell.


> That way you don't have to change the SDP specification
> if anyone creates a new top media level type.
>
We don't need to change the SDP specification, but we do need to add a 
new registration to the SDP media types registry. Considering that 
top-level media types don't appear too often, that does seem manageable.

Thanks

-- Flemming [as an individual]




> Cheers
>
> Magnus Westerlund
>
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