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Thread: 183 Session Progress

  1. #1
    Join Date
    Oct 2002
    Posts
    20

    Question 183 Session Progress

    What's it mean when the PRI gateway returns TRYING, but no RINGING or OK - it just returns 183 Session Progress?

    11:27:14.939_9747[106c]:SIPEngine::SIPTransport::recv(): remote=86.254.60.10, message=
    SIP/2.0 183 Session Progress
    Via: SIP/2.0/UDP 85.213.60.2
    From: "NBT Voicemail" <sip:8474182833@85.213.60.6>;tag=9723
    To: <sip:918002472676@86.254.60.10>;tag=68490974-2126
    Date: Fri, 30 Jul 2004 16:27:14 GMT
    Call-ID: 9b287134f810c5ba9f620cedd96557d0@85.213.60.2
    Server: Cisco-SIPGateway/IOS-12.x
    CSeq: 1 INVITE
    Allow-Events: telephone-event
    Content-Type: application/sdp
    Content-Disposition: session;handling=required
    Content-Length: 204

    v=0
    o=CiscoSystemsSIP-GW-UserAgent 1900 2762 IN IP4 86.254.60.10
    s=SIP Call
    c=IN IP4 86.254.60.10
    t=0 0
    m=audio 17740 RTP/AVP 18 0
    a=rtpmap:18 G729/8000
    a=fmtp:18 annexb=yes
    a=rtpmap:0 PCMU/8000

    Only happens on a particular 800 number. All other 800 and other calls are fine. (The 800 number works when called from your cell phone.)

    Thanks,
    Barry

  2. #2
    Join Date
    Nov 2002
    Location
    Indianapolis
    Posts
    271
    It's possible for a gateway to transmit audio (an IVR for example) before a call goes connected. It indicates this (early media) with a 183 Session Progress message that contains SDP. IC will setup the audio path to the gateway 'early' and pass the audio but only if delayed media is disabled on the SIP line.

    Regards,
    Mike

  3. #3
    Join Date
    Oct 2002
    Posts
    20

    Smile

    Got it. Thanks Mike!
    Barry

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