This post is related to the issue that the call transfer from the SIP user to the POTS user fails. Below to be found the solution.
Problem description
Below there are four scenarios:
Scenario 1: The SIP user dials a Mobile/PSTN number and holds the call, then calls another SIP user and transfer the calls. (Call transfer successful).
Scenario 2: The SIP user dials a Mobile/PSTN number and holds the call, then calls a POTS/MSAG user and transfer the calls. (Call transfer fail).
Scenario 3: The SIP User dials another SIP user and holds the calls, then calls a Mobile/PSTN number and transfer the calls. (Call transfer successful).
Scenario 4: The SIP user dials a POTS/MSAG user and holds the calls, then calls a Mobile/PSTN number and transfer the calls. (Call transfer successful).
Network information
1. U1981--------SIP Trunk-------U1960----------SIP Trunk --------U1981 PSH-------PRA---Service provider.
2. U1960 ---SIP Trunk --- IAD 'U1960 also connected to IAD using SIP trunk'.
Error message
Call Transfer to 3439 Failed. <<When the SIP user tries to transfer a call to POTS, the user 'call transfer failed' >>.
Problem analysis
1. Log in to the LMT.
Right click on Device -> Add Device:
Input the Name and the IP:
Input the username and the passwords:
Go to Log Management -> Debug Log -> click on button Module Switch Configuration.
Select All Modules.
Click Start Configuration and close the module switch configuration window.
Click on the green arrow to start the log
.
.
- Repeat senario 2 'The SIP User dials a Mobile/PSTN number and holds the call, then calls a POTS/MSAG user and transfer the calls. (Call transfer fail)'.
- Then click on the pause button to stop the log .
.
Finally analyze the log.
2. After analyzing the log, we found an error message '488 Not Acceptable Here'.
Note that:
488 Not Acceptable Here indicates some aspect of the session description or the Request-URI is not acceptable, or a Codec issue.
Root cause
Found that the codec used was G722 and the IAD doesn't support it. IAD supports only three types of Codecs: G711A, G711U, G729.
Solution description
There are two solutions to resolve the issue.
1. By disabling the G722 from the IP phone:
Log in to the IP phone Web page --> Advanced --> Media --> untick the codec G722 and tick only G711A, G711U, G729 , as shown below:
2. Change the supported codec on the U19 by configuring the following command by LMT:
Log in to the LMT --> log in to the device --> command --> command tree --> insert the command below:
config system codetype g711a&g711u&g729
