[asterisk-users] 180 Ringing with SDP

[Alex Balashov]

On Mon, 18 Jun 2007, Jared Smith wrote:

> 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.

   A cursory interpretation of the RFC suggests that 180 Ringing is a
message designed solely to convey ringback, and that it is the payload
of the 183 response that may be used to convey additional details
about the nature of the call's progress.  Therefore, a 180 would be an
inappropriate vehicle for early media SDP information.

   21.1.5 183 Session Progress

    The 183 (Session Progress) response is used to convey information
    about the progress of the call that is not otherwise classified.  The
    Reason-Phrase, header fields, or message body MAY be used to convey
    more details about the call progress.

-- Alex


--
Alex Balashov
Evariste Systems
Web    : http://www.evaristesys.com/
Tel    : +1-678-954-0670
Direct : +1-678-954-0671