NAPTR Defaulting to UDP, How to set TCP

[Karl_Yealink]

When you using the NAPTR, the transport don't up to phone.
It's up to NAPTR record.You can configure the priority, then the phone will choose TCP transport. The priority up to order parameter, the smaller parameter has higher priority.

There is another possibility, do you fill port as 0?
Please check the attach image.
If the port explicit, the phone use UDP as default transport.