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Microsoft Lync - CCM 8.6 - Voice Gateway - delayed call establishment

Unanswered Question
Aug 13th, 2013
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Hi,

I have a call establishement problem, the call flow is like this:


Lync client ---- Lync Server ---- SIP TRUNK ---- CCM8.6 ---- Voice gateway


After the client calls outside number the calling party can hear the called party but the called one cannot hear anything. And at this time lync still says calling after 40-50 seconds lync says call is established and the called one start hearing the calling one. What can cause this delay?


Thanks

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Jonathan Schulenberg Tue, 08/13/2013 - 05:59
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    2017 IP Telephony

It sounds like SDP exchange is not finishing. One possible cause is a lack of PRACK if delay offer/early media. We would need to see the SIP messaging from an example call to answer definitively. Also, what protocol is in use between CUCM and the voice gateway? What is the PSTN circuit?



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