Call not disconnect

Unanswered Question
Jun 15th, 2010


I have call manager 7.1.3, MGCP voice gateway 2921 & ip phone 7911 & 6921.

I have observed that when IP phone A calls to IP phone B or any PSTN number. During the call if IP phone A will get power off, then also opposite phone will still remain connected undefined period of time. This call will disconnect only if opposite user will disconnect the call manually.

IP phone A calls to IP phone B. During the call if LAN cable of the IP phone A will get disconnect, still on both phones it will show connected. After some time on IP phone A it will show connected with meassage "Features disable".

This behaviour i have observed with CUCM version 4.1, 6.1, 7.1.3.

Is this the default behaviour of all CUCM ?



I have this problem too.
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Jonathan Schulenberg Tue, 06/15/2010 - 05:23

Yes. The phones are sending RTP traffic over UDP. The lack of packets does not tear down the call by itself.

I believe it is possible to achieve this call teardown scenario if there is a PSTN gateway involved and you configure RTCP properly. The absense of RTCP traffic from the IP phone for a defined period of time can be used to trigger a call teardown.

doshinimit Tue, 06/15/2010 - 05:38

Hi Jonathan,

Thanks for your support.

What about IP phone to IP phone calling on LAN in which PSTN gateway not involved ?



Jonathan Schulenberg Tue, 06/15/2010 - 05:44

No and that's unavoidable IMO. UCM cannot issue a call teardown because there is no way to be sure that it is not UCM that has lost communication, not the two phones. Example: If you have a three-site WAN with UCM at Site A, and the call between site B and C. If Site A looses WAN connectivity, or a provider error causes the route between A and B to go down, the phones would still be able to send RTP to one another even though UCM has lost contact with one of the phones.

The phones would need to deal with a mid-call loss of RTCP as the gateway can be configured to; however, AFAIK the phone firmware doesn't do this. I haven't tested this scenario but most of the TNP firmware deals with RTCP as an auxiliary and very much optional signaling protocol.


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