The SIP Profile Settings must include the APPREF parameter, which defines a string that is referred by the TO-APPREF parameter, for example:
<parm name="APPREF" value="VoIP_SIP_settings"/>
The TO-NAPID references to the Access Point Settings must be the same as those used in the VoIP Profile Settings, for example:
<parm name="TO-NAPID" value="INTERNET"/>
For example, an additional TO-NAPID could refer to "INTERNET". This implies that any network access point can be selected with the attribute INTERNET defined, if the preferred access point could not been reached. If this is the only TO-NAPID reference, none of the network access points have predefined preference.
Having the INTERNET reference only is the recommended setting. Other examples are for the cases where certain APs are more preferred, that is, the preference is predefined and cannot be changed by the user.