183 Session Progress

[BarryL]

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

[MikeSz]

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

[BarryL]

Got it. Thanks Mike!
Barry