The 'Pass PAI Header to UAD' option is supported only for Polycom phones.
Please note that this option is available with new Polycom firmware:
(VVX series - 6.4.2, Trio series - 7.2.0)
Set this field to a desired value
NOTE: This parameter is parsed for the caller ID validation and it is generally named 'verstat'. Other variations depend on the Trunk provider.
Set this option to 'Yes' in order for Polycom phones to perform STIR/SHAKEN Caller ID Validation
NOTE: If this option is enabled, the SIP P-Asserted-Identity Header will be passed to UAD. For more information on how Polycom phones perform validation, please refer to this Polycom document.
With STIR/SHAKEN enabled, the phone processes inbound calls based on SIP headers. If the inbound calls are suspicious based on the SIP header, the phone displays this information. Users can then decide whether to accept or reject the incoming call.
For more on the options: 'Enable Call Filtering', 'PAI Header Parameter Name', and 'Drop Calls with Verification Status', please refer to this HOWTO Configure STIR/SHAKEN.
This will only work for calls from Trunks.