Re: [MMUSIC] Offer/Answer PT Questions - text proposal

Christer Holmberg <christer.holmberg@ericsson.com> Wed, 02 March 2016 16:38 UTC

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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Roman Shpount <roman@telurix.com>, Paul Kyzivat <pkyzivat@alum.mit.edu>
Thread-Topic: [MMUSIC] Offer/Answer PT Questions - text proposal
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Date: Wed, 02 Mar 2016 16:38:10 +0000
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Subject: Re: [MMUSIC] Offer/Answer PT Questions - text proposal
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Hi,

…

>The problem is that if you have multiple O/A exchanges happening in rapid succession, you can get
>RTP packets for any of the previous O/A exchanges. This means you can have a new RTP session
>being set up for any of the recent O/A exchanges. Unless you have an additional way to demultiplex,
>such as using a different local transport, ssrc or mid, you will need to map the received RTP packet
>to a particular O/A exchange. The only way left is PT.

Which means that PT bindings, once they have been signalled, will “survive” subsequent O/A transactions, meaning that a given PT value must not be bound to another codec in a subsequent O/A. Which is what I believe the current 3264 text says – the question was whether it’s per SDP session or per direction within the SDP session.

Regards,

Christer