@techreport{ietf-sip-183-00,
    number =    {draft-ietf-sip-183-00},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-ietf-sip-183/00/},
    author =    {Jonathan Rosenberg and Henning Schulzrinne and Matthew Cannon and Steve Donovan and Adam Roach},
    title =     {{SIP 183 Session Progress Message}},
    pagetotal = 26,
    year =      1999,
    month =     oct,
    day =       22,
    abstract =  {This document describes a proposed extension to SIP {[}1{]}. This exten- sion adds the 183 Session Progress response and a new header to indi- cate why a SDP message body is included in a 18x message. The introduction of the 183 informational response message would allow a called user agent to indicate to the calling user agent whether or not the calling user agent should apply local alerting for the session. The existing 180 Ringing message would indicate that the calling user agent has the option of providing local alerting (and generally should). The 183 Session Progress message would indi- cate that the calling user agent should not provide local alerting. In additionally, the calling user agent may be called on to establish a media session to be used by the called user agent to indicate the status of the session setup request as part of the indicated media stream. The indication of whether or not to play early media to the calling user would be controlled with a new Session header included in the 183 message.},
}