[AVTCORE] Re: BUNDLE question - relationship to PR-Answer?

[Jonathan Lennox <[e-mail]>]

>> The question is whether, if we get
>> Offer: BUNDLE(a, b)
>> PR-Answer: BUNDLE(a, b)
>> Answer: No bundle
> 
> I'm not familiar with the term "PR-Answer". I presume this comes from webrtc rather than sip. I'm thinking the sip-analog to this would be a reliable provisional response containing an answer. An exchange like that is probably an invalid use of offer/answer in sip. Specifically, once an answer is returned in a reliable provisional response to an offer in an INVITE it must remain unchanged in subsequent responses to that INVITE. (See section 2.2 of RFC 6337.)
> 
> It would be helpful to see more detail - the message bodies from the exchange.

See https://datatracker.ietf.org/doc/html/rfc8829#section-4.1.10 for a definition of a WebRTC provisional answer.

In particular, it’s notable that one of the use cases described there is the “serial forking” case, i.e. cases where in SIP various provisional answers would have arrived on different dialogs.

As such, I think for WebRTC there can't be any constraints imposed on what’s in the pr-answer vs. what’s in the final answer (or in a subsequent pr-answer), because they might be coming from entirely separate peers, and that’s an intended use case.


> 
> 	Thanks,
> 	Paul
> 
>> The AI claimed that 7.3.2 "moving a media description out of a bundle group" meant that the answer needed to be rejected, since you can't move something out of a bundle in an answer.
>> I claim that an answer in have-remote-pranswer state should override the pr-answer bundling.
>> Is there a valid use case for wanting the spec to be read the way I claim? (The code is more complex if we want that variant to work....)
>> Harald
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