I search for Kamailio source, and found that Kamailio doesnot handle the x-NAT field in SDP body.

When client use STUN, it can detect the NAT type. When client register, it contains x-NAT (0:unknown, 1: full cone, ..., 6: symmetric), which will be helpful for the server to detect NAT type.

Why doesn't Kamailio handle x-NAT? I think this is a must-have feature 
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Khoa Pham
HCMC University of Science
Faculty of Information Technology