when I call from a IP phone to the pstn user (for example a mobile network), I want to hear the PSTN ringtone before the callee responds (answer, reject … ).
Something like that is no longer guaranteed. You typically play your own ringtone, unless the other side uses “early media” and “early media” works. When you hear some kind of ringtone, then this is how your system reacts to some SIP replies. Sometimes you may not hear anything at all for a couple of seconds.
With ARI, I believe you would have to put them into an early media bridge. (Or just answer the call, for the inbound side, prematurely.)
As the previous answer says, the trend is away from using early media for ringback. Especially given that the PSTN is moving to using SIP/RTP internally, it is a waste of bandwidth for which the caller isn’t being charged.
Hi, thanks for your reply,
As you said, I tried to answer the call before the callee answered. Now, another problem occurs. Error 422 occurs when trying to add a callee channel to a bridge. How can I add Channel In Stasis Application?