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

[Roman Shpount <[e-mail]>]

On Fri, Feb 26, 2016 at 12:20 PM, Paul Kyzivat <[e-mail]>
wrote:

>
> The session remains, and so the PT bindings remain. But the O/A rules are
> negotiating which of those are to be used going forward. If the new offer
> no longer mentions some PTs that were previously bound, then it is saying
> that it doesn't want to receive them any more.
>
> It is becoming clear to me that it will be necessary to define PT bindings
> - what they are, when they are established, when they are forgotten, and
> the scope within which they live. Each participant will need to know these
> bindings, and they must agree on them, except for well defined signaling
> delays. I guess this is a lot like an RTP session, except that it is tied
> to O/A signaling.
>

One other thing to keep in mind is that RTP session creation and tear down
is not time synchronized with O/A. End point might still be receiving media
packets for the previous RTP session after O/A completes. If O/A happen
often enough, several O/A exchanges can complete while old RTP sessions
established by old O/A exchanges are still running. PT should uniquely
identify codec profile for all of them. In case of SIP, O/A exchanges
typically take more time then RTP session setup/tear down, so keeping track
of the last two O/A exchanges is typically enough.

Regards,
_____________
Roman Shpount