The OID_WAN_HEADER_FORMAT OID requests the miniport driver to return or to set the address-header format used, as either of the following system-defined values:
Selects Ethernet-emulation format.
Selects the format native to the NdisWanMediumXxx subtype supported by the underlying driver. NDISWAN always uses Ethernet.
For a query, the miniport driver returns a list of the address formats that the NIC driver supports. For a set, the miniport driver subsequently uses the given type to format headers for this binding.
If an underlying NDIS driver does not support a header format that a protocol recognizes, that protocol's attempt to bind to the underlying driver fails. A NIC driver is not required to support both address types of header format but should if it can.