4. UA (phone), gateway or other hardware/software involved:
5. Your problem:
I would like the PBX to preserve a parameter in the From uri.
For example:
Before PBX:
From: sip:123456@192.168.1.26;cd40rs=res
After PBX, I would like that cd40rs parameter is preserved.
You may be able to retrieve the parameter from the "from" header by using ARS-IN or dialplan(To PBX), and add it to the "from" header with ARS-OUT or dialplan (from PBX).
I do not know how to do that you say. How can I save the from header in ARS-IN or dialplan(To PBX) and add it to the "from" header with ARS-OUT or dialplan (from PBX)?