[asterisk-users] 180 Ringing with SDP

[Jared Smith]

On 6/18/07, Douglas Garstang <DGarstang at interainc.com> wrote:
> We're dialing a disconnected number via Level 3's vector network, and are
> receiving this. The response has SDP in it. Apparently, Level 3 is playing
> early media. Asterisk doesn't seem to know what to do with SDP in a 180
> RINGING, and just plays ringing. What am I missing here? How can Asterisk
> see there's SDP, early media, in the response and act accordingly?

I could be totally off base here, but it's my understanding that a 180
is telling Asterisk to generate ringing on it's side, and that a 183
(with SDP) would tell Asterisk that the call is progressing and that
it should play the early media specified in the SDP.  I'm sure someone
there's probably someone on the list who is more intimate with the
details of SIP that can enlighten us further on the subtle differences
between the 180 and 183 provisional responses.

-Jared