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

Paul Kyzivat <pkyzivat@alum.mit.edu> Tue, 21 April 2026 20:04 UTC

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

On 4/21/26 2:03 AM, Harald Alvestrand wrote:
> I recently tangled with an AI about how to interpret RFC 8843 (BUNDLE) 
> in the presence of PR-Answer.

You are raising this question on an RFC where you are an author?!

> 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.

	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
> 
> _______________________________________________
> Audio/Video Transport Core Maintenance
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