[asterisk-dev] sip message 183 and ringback

[Klaus Darilion]

183 means that early media is available. Thus, the party who sent the 
183 should also send media (e.g. ringback or busy tones).

If a client sends 180 Ringing only, the ringback will be produced by the 
caller.

regards
klaus

dima wrote:
> Hello everyone.
> Please, could anyone explaing, if a 183 "Session in progress" message is
> the only thing needed for generating ringback? Another question is where
> do those ringbacks come from (who generates them?).
> I'm having a wierd problem of not having ringback when dialing some
> particular numbers (asterisk 1.2.18).
> Thanks in advance
> 
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