[asterisk-users] [External] 180 Ringing missing

[Alex Hermann]

On dinsdag 1 december 2020 13:22:17 CET Floimair Florian wrote:
> If you have 183 Session progress, there is no need to send 180 Ringing
> (especially not AFTER 183 Session progress), as you already have
> early media instead. Having both is actually a bit misleading IMHO.

I disagree (and I think rfc3261 agrees).  How would the caller know if 
the callee has been alerted if he doesn't receive the 180?

183 and 180 have different meaning. 180 indicates the callee is being 
alerted. An 183 has no such meaning but is often used to setup early 
media (although any 1xx can do that). 180 and 183 are not mutually 
exclusive and in fact form a full matrix of possible and useful states. 
There can be early media without any phone ringing (announcement), 
ringing without early media (caller is expected to generate a ringback 
tone itself), no early media nor ringing and finally early media and 
ringing simultaneous.

Especially automata calling will want to know the difference.

Of course, a generated ringback tone by the caller should be stopped 
when media is received.

Asterisk should indicate to the caller the same state it received from 
the callee.
-- 
Alex Hermann