IMS Users Fail to Make Outgoing Calls Through the SoftCo

Publication Date:  2015-07-14 Views:  173 Downloads:  0
Issue Description
Network: PBX----PRI----SoftCo----SBC----IMS

When an IMS user makes a call to a user on another PBX through the SoftCo, the call is disconnected when the called party picks up the phone.
Handling Process
Step 1 Obtain onsite SoftCo logs from usam/ccm/pri/sip/siptk/sipsignal.

Step 2 View the logs. According to the logs, the IMS disconnects the call when receiving the correct 183 message from the SoftCo.

Step 3 Contact IMS engineers. The IMS engineers advise that the SoftCo report the 180 message instead of the 183 message if the RBT service is enabled on the core network because the 183 message will cause a processing exception.

Step 4 Analyze the SoftCo logs. According to the logs, the Alerting message sent from the PRI trunk carries a progress indicator, instructing the PBX to provide a ringback tone. It is not recommended that the ringback tone be played to avoid this problem. However, PBX engineers indicate that the PBX cannot be modified.

Step 5 Modify the SoftCo to avoid this problem:

     1)  The SoftCo returns an error code but does not play an announcement in an exception scenario.
          config softargu type 278 value 0
     2)  The SoftCo sends the 180 message instead of the 183 message to the PBX.
           config ims softargu isserviceofferedbyims yes (The voice service is provided by the IMS.)
           config softargu type 307 value 0

Root Cause
The 183 voice playback process on the SoftCo conflicts with the RBT playback process on the IMS platform, resulting in exceptions on the IMS platform.