Re: [rtcweb] The meaning of SDP_PRANSWER

Justin Uberti <juberti@google.com> Tue, 24 April 2012 03:02 UTC

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From: Justin Uberti <juberti@google.com>
Date: Mon, 23 Apr 2012 23:02:11 -0400
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To: Henry Lum <Henry.Lum@genesyslab.com>
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Cc: rtcweb@ietf.org
Subject: Re: [rtcweb] The meaning of SDP_PRANSWER
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It's needed to indicate to the offerer that the answer is not final; any
resources associated with the offer should not yet be released.

One example where this may be useful is when using RTCP mux; the initial
answer may indicate that mux is to be used, but the final answer may come
from a different endpoint and choose not to use mux. Using SDP_PRANSWER
allows the offerer to honor the second answer, since the RTCP transport is
not discarded by the first answer.

On Mon, Apr 16, 2012 at 11:52 AM, Henry Lum <Henry.Lum@genesyslab.com>wrote;wrote:

>  It’s unclear to me what the purpose of SDP_PRANSWER is really for and
> why it needs to be there. Originally I thought it was meant for early
> media, but section 6.1.4 paragraph 3 says that it should not result in
> starting of media transmission. Is there a reason to provide an answer
> before media is ready to be transmitted? There are separate handles for
> processing ICE candidates so I don’t see a need to have provisional
> answers. ****
>
> ** **
>
> I am not proposing PRANSWER for handling early media though, since I
> believe early media is more of an application level issue (it’s more like
> late-billing on the application side) and should be considered as a
> separate offer/answer if needed.****
>
> ** **
>
> Regards,****
>
> Henry ****
>
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