Re: [MMUSIC] Partial Offer/Partial Answer draft - MIME type value

[Christer Holmberg <[e-mail]>]

Hi,

>> The draft says that one will use the "application/sdpfrag" MIME type value for POFs and PANs.
>>
>> What about using "application/sdp" - ie the same MIME type value as for "normal" SDP Offers and Answers? From a SDP syntax perspective it should not be a problem - any SDP parser will be able to parse a POF/PAN.
>>
>> An entity that does not support POF/PAN would probably trigger an error. BUT, maybe that is good: It could be a mechanism to verify that all SDP processing/inspecting 
>> entities along the signaling path actually support the mechanism. At least for SIP I can't think of any other mechanism to do that (we can't use Proxy-Require).
>>
>> Comments?
>
> It isn't the same as SDP. The SDP fragments aren't syntactically valid SDP - they are missing some mandatory fields.
>
> Conceivably the POF/PAN stuff could require more, so that they are syntactically valid SDP. But do we want to?
>
> And required processing is semantically different. If it were the same content type then some other means would be required to indicate that it is being used for POF/PAN, not offer/answer.

Well, for that there are many alternatives: SDP attribute, Content-XXX parameter, etc.

> Adam isn't talking about that part. In sip, that could be done via content-disposition.

Content-Disposition does not apply to intermediaries. So, a proxy that only understands application/sdp (e.g. for gate control purpose) will not even look at the C-D header field value for other bodies. And, unless such proxy understands POF/PAN, there may not be any media passing through...

Regards,

Christer




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