eSpace U1980 User Makes an Outgoing Call Using the PRI Trunk, and the Called Party Answers the Call But Only Hears the Busy Tone

Publication Date:  2015-07-24 Views:  209 Downloads:  0
Issue Description
Version: eSpace U1980 V100R001C01SPC100

Network: MTG300----(PRI)----U1980----(SIP)----UA5000

Fault description: An MTG300 user calls a UA5000 user successfully. However, when the UA5000 user calls the MTG300 user, the phone of the MTG300 user rings but the MTG300 user only hears the busy tone after answering the call.
Handling Process
Step 1 Use the local maintenance terminal (LMT) to obtain logs of the user service abstract module (USAM), call control module (CCM), connect module (CM), resource module (RM), PRINTTIME, and primary rate interface (PRI) modules.

Step 2 Analyze the call connection flow and find that the eSpace U1980 disconnects the call, as shown in Figure 2-1.

Figure 2-1 Call disconnected by the eSpace U1980

Step 3 Check the STATUS message repeatedly sent by the eSpace U1980 and find that the return code is "Mandatory information element is missing", as shown in Figure 2-2. Therefore, the possible cause is that the CALLPROCEEDIN message from the MTG300 has some mandatory information missing.

Figure 2-2 Analyzing the STATUS message

Step 4 Check the CALLPROCEEDING message and find the information "IE Name: Channel identification" missing, as shown in Figure 2-3.

Figure 2-3 Checking the CALLPROCEEDING message

Step 5 Modify the MTG300 configuration by adding the information "IE Name: Channel identification" in the CALLPROCEEDING message.
After the modification, the fault is rectified.


Root Cause
The call is disconnected due to a signaling exception.
When the PRI trunk is used, the "IE Name: Channel identification" information must be contained in the CALLPROCEEDING message.