Difference Between 180 Ringing and 183 Session Progress

Difference Between 180 Ringing and 183 Session Progress

In general, ringing is controlled via two Informational Responses in SIP: the 180 Ringing and the 183 Session Progress.

The main difference between them, is the 180 Ringing message instructs the UA to create the dial-tone locally, whereas the 183 Session Progress contains an SDP, which allows for regional ring-back and carrier announcements as well.

Typically 183 contains SDP and is used to play media before the call is connected

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a) 180 Ringing

   The UA receiving the INVITE is trying to alert the user. This

   response MAY be used to initiate local ringback.

b) 183 Session Progress

   The 183 (Session Progress) response is used to convey information

   about the progress of the call that is not otherwise classified.

https://supportforums.cisco.com/t5/ip-telephony/difference-between-180-ringing-and-183-session-progress/td-p/2413632