[SR-Users] Send UPDATE to inform changes in SDP

[Alex Balashov]

I would instead redirect my focus to why A is dropping the call in this situation. It shouldn't be doing that.

Per the standards, the first SDP answer must be the final SDP answer (absent an update or reinvite) *of that endpoint*. There's no rule saying that must be true of the dialog as a whole. 

-- Alex

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Sent via mobile, please forgive typos and brevity.